Everything from after midterm! Flashcards

Question

blood work-safety indicators

Answer 1

(SeCr) Creatinine overestimates GFR * due to metabolism of creatinine in muscle - _this causes creatinine levels to be higher in:_ - men vs women - younger vs older patients (age) - blacks vs whites (race) - _other considerations that affect SeCR readings:_ - malnourished patients/muscle wasting decrease SeCR - protein (consumption of cooked meat) increase SeCR * despite SeCR limitations; it remains a fast and inexpensive way to assess renal function (should be used in conjunction with GFR)

Answer 2

impossible to predict which patients will have an adverse reaction to IV contrast * iodinated contrast agents are one of the most widely used of all medications * also considered one of the safest (fatal reactions are rare) * excessive doses of contrast can be toxic: * safe dose limits * over doses can be fatal (affects the pulmonary and cardiovascular systems) * hydration can affect safe dose limits * upper limit= 64gI (grams of iodine) * pediatric patient dosages calculated by wieght: 2mL/kg * common practice is to limit the pt to 1 contrast injection per 48 hours

Answer 3

* iodinated contrast can cross the placenta and enter the fetus * studies unable to prove if risk exists

Answer 4

* contrast media can be excreted into breast milk * infant absorbed dose = 0.01% * safe to continue breastfeeding * option to abstain for 24 hrs

Answer 5

iodinated contrast reactions can be broadly categorized as: 1. subjective/normal 2. chemotoxic 3. idiosyncratic

Answer 6

**Normal** responses to injection of IV contrast (aka side effects): * feeling of heat/ warmth (voiding sensation) * mild flushing * metallic taste * nausea and/or vomiting symptoms are generally very brief * anxiety may increase probability of reactions * patients should be informed of normal responses prior to administration of contrast

Answer 7

result from physiochemical properties of the contrast media, the dose and the speed of injection * inludes hemodynamic disturbances and injuries to organs and vessels * examples: - pain at injection site - contrast induced nephropathy (CIN) 1. a condition or disease affecting the kidney 2. CIN is the 3rd leading cause of ARF (acute renal failure)

Answer 8

acute impairment of renal function resulting from the administraton of IV contrast * elevated SeCR within 24 hrs of contrast administration - may take up to 48 hrs for SeCR levels to rise - levels should return to normal within 7-10 days * incidence of CIN is: - 1-6% for low risk pts - 50% for high risk pts * may cause the need for temporary or chronic dialysis treatments * increases risk of death from non-renal causes

Answer 9

the following conditions and factors predispose pts to an increased likelihood of developing CIN: _Diabetes Mellitus:_ * considered a low risk (increase of 0.6%) * high risk if coupled with a preexisting renal impairment ( increase of 19.7%) _Volume of contrast material:_ * direct relationship * increased volume= increased risk * allow 48 hrs between procedures requiring contrast material

Answer 10

_Dehydration:_ * increases risk * affiliated with the higher incidence of CIN in pts presenting with multiple myeloma _special considerations:_ * other possible risk factors for CIN include: * age * gender (increased incidence in men) * atherosclerotic disease

Answer 11

_methods recommended for preventing CIN:_ * use of LOCM or IOCM (IOCM may be the safest contrast media to use) * hydration (all pts should be well hydrated prior to exam, high risk pts should recieve IV fluids prior to contrast administration) * dose (use the smallest amount of contrast media possible, min 48 hrs must elapse between administration) * temporarily discontinue medication (ex Metformin)

Answer 12

include all other forms of reactions * unpredictable and can occur within 1 hour of contrast administration - delayed reactions have been reported between 1 hr and 1 week following contrast media injection - most adverse reactions occur within minutes - the majority are non-life threatening events * are unrelated to dose - "allergic like" - children have a lower incidence

Answer 13

the most important method of reducing the pts risk of developing an idiosyncratic reaction to contrast media is to avoid using HOCM * patients who are at greater risk of developing a reaction should be monitored for 1 hr * premedication may also be used to decrease risk _idiosyncratic reactions are classified as:_ * mild * moderate * severe

Answer 14

are acute reactions and include the following signs and symtoms: * itchy skin * hives (uticaria), or other skin rash * nasal congestion, sneezing, watery eyes * coughing with possible laryngeal swelling * peripheral tingling * tachycardia or bradycardia ( \>100 beats/min or \< 60 beats/min) * hypotension * feeling of fullness or tightness of chest, mouth or throat * feeling of anxiety or nervousness

Answer 15

_what can you do:_ * stop the injection and the exam * calm and reassure the pt (elevate pts legs for hypotension and comfort) * apply cool compress to itchy areas * observe the pt for signs/symptoms of increased distress or changes * document details of reaction in pts electronic profile, on the requisition and in the pts chart * obtain medical assistance (consult with radiologist and or physician/nurse to determine necessary observation of pt prior to pt discharge)

Answer 16

are potentially or immediately life threatening and include the following signs/symptoms: * abrupt onset * bradycardia (less than 50 beats per min) * hypotension (decrease in BP) * severe dyspnea * cardiac arrhythmias * laryngeal swelling * possible convulsions/seizures * loss of consciousness * respiratory arrest or cardiac arrest

Answer 17

_what can you do:_ * call a code (fast response of RTs is necessary to maintain pts airway) * ensure integrity of IV site, which may be used to give medication to treat the reaction * calm and reassure the pt * prepare: oxygen, suction, crash cart * have the pts history ready and available * be ready to assist the physicians

Answer 18

If an adverse reaction occurs, the following information should be documented: * Amount & type of contrast used * Signs & symptoms of the reaction * Interventions or medications given during the reaction - Include the patients response to treatment * Final outcome - Was the patient sent home, or admitted to the hospital * Update patient information in computer system - Requisition should reflect the sensitivity

Answer 19

Some risk factors predispose pt.’s to an ↑ likelihood of developing an adverse reaction _Asthma_ * 3X more risk * In some cases, an asthma attack can be triggered by the stress on the body that a contrast injection can trigger * If the patient uses an inhaler, the patient should have the inhaler nearby in the event of an asthma attack _Allergies to food, drugs, or other substances_ (Example: Hayfever or Eczema) * 2X higher risk * Allergies to iodine containing foods or skin preps pose an equivalent risk as other food allergies Special considerations: * Beta-blockers can impair response to a contrast reaction treatment - \*They do not ↑ the risk of idiosyncratic reactions - May be considered a contra-indication

Answer 20

_Previous Contrast Reaction_ 11X greater risk * Reaction rate is higher for pt.'s with a previous contrast-reaction - \*Most important predictor of relative risk factor - Test injections are not recommended * Important to assess the severity of the prior reaction - Pt. may not be allowed to have another injection of contrast - Pt. may be given an antihistamine (e.g., Benadryl) prior to the injection of contrast to negate the risk of an allergic reaction - Your job as a tech is to bring all the relevant information to the radiologists attention so they can decide if the scan with contrast can be performed, & with which type of contrast agent, or if an alternative exam should be performed

Answer 21

***Patient has kidney disease or is in renal failure*** - IV contrast is filtered through the kidneys, therefore special consideration must be taken for patients who already have compromised kidney function * Considerations: - Blood tests can be performed to check the patients renal function prior to the CT scan to ensure the patients kidneys will be able to adequately filter the foreign molecules of the contrast - GFR - SeCR

Answer 22

_Dialysis & Contrast Media_ * Patients who are on temporary dialysis should not be given contrast media - Could lead to chronic kidney failure - In-patients may have the CT if arrangements have been made with unit/ward for the patient to go for dialysis treatment post CT scan * Patients who present with end-stage renal failure may undergo contrast media exams - Cannot increase extent of preexisting kidney damage - Contrast media can stay in the blood for prolonged periods of time - Contrast media is efficiently removed from the blood by hemodialysis & peritoneal dialysis

Answer 23

_Patient has history of diabetes & is taking Metformin_ * Diabetic patients can still have contrast-enhanced CT scans, but precautions must be taken as these patients have a predisposition for renal complications - Metformin lowers blood sugar * If renal dysfunction occurs, metformin can accumulate & cause lactic acidosis - These medications should be withheld for 48 hours post-contrast injection - They should not be resumed until a blood test indicates normal renal function * **Diabetic patients who may be fasting prior to their CT scan should be prioritized and watched to avoid diabetic shock**

Answer 24

_Patient has heart disease or hypertension_ * A bolus contrast injection causes vasodilation - These pt.’s can have weakened & narrowed blood vessels - A bolus injection can cause changes in BP & cardiac output, which is potentially dangerous for these patients * Vasodilatation can also cause a vasovagal reaction - Important to have a baseline blood pressure for patients who suffer from high BP in the event they feel unwell post injection

Answer 25

_Hyperthyroidism_ * A pt. history of hyperthyroidism must be brought to the radiologists attention prior to the exam - Patients may need to be monitored by an endocrinologist post-exam * Contrast media can ↑ thyroid hormone levels in these patients - Could result in a fatal thyroid storm - Requires CT scans to be conducted no sooner than 2 weeks prior to a nuclear medicine thyroid uptake study

Answer 26

_CNS (central nervous system) disorders_ * Iodinated contrast agents cannot cross an intact BBB (blood brain barrier) * Patients with diseases that disrupt the BBB are at an increased risk for developing seizures * Metastasis - Higher risk of seizure * Primary brain tumors - Lower risk of seizure * Risk of seizure can be reduced: - Oral dose of diazepam 30 minutes prior to contrast media administration

Answer 27

**_structures demonstrated:_** * blood vessels * solid organs * joints * spinal canal * GI studies (bowel) **_Administration:_** * injection * oral * rectal * intravenous **_Appearance on images:_** * white; positive contrast

Answer 28

**_Structures Demonstrated:_** * bowel * stomach * esophagus **_Administration:_** * oral * rectal **_Appearance on images:_** * white; positive contrast \*\* VoLumen can be considered negative contrast

Answer 29

**_Structures demonstrated:_** * bowel * stomach * joint spaces * spinal canal ***Administration:*** * injection * oral * rectal ***Appearance on images:*** * black; negative contrast

Answer 30

**_structures demonstrated:_** * bowel * stomach * joint spaces * spinal canal **_Administration:_** * injection * oral * rectal **_Appearance on Images:_** * black; negative contrast

Answer 31

**_structures demonstrated:_** * pancreas * stomach * bowel **_Administration:_** * oral **_appearance on images:_** * dark grey; negative contrast

Answer 32

Iodine is the active molecule. It has an atomic number of 53 which is heavier than the compounds of the body so it absorbs more radiation than the organs and soft tissues surrounding it in the body. Iodine is considered radiopaque

Answer 33

**Ionic** – molecules dissociate in solution, resulting in higher osmolality. This increases the risk of adverse reactions in patients. Slightly less expensive. **Non-ionic** – molecules remain intact in solution, resulting in lower osmolality. This reduces the risk of adverse reactions in patients and is favourable for injection in CT. Slightly more expensive.

Answer 34

Osmolality refers to the number of particles in solution per kg of water. Acts as a method of comparing the properties of IV contrast media with blood. Lower osmolality reduces the risk of adverse reactions.

Answer 35

Viscosity refers to the thickness or friction of a liquid as it flows. High viscosity liquids reduce flow rate. Viscosity is determined by the number of particles in solution, the size of the particles and the relationships between the particles. Agents with higher iodine concentrations are more viscous.

Answer 36

- ↑ injection pressure, flow rate, & injection time - ↑ needle bore size - Warm contrast media to body temperature to reduce the viscosity

Answer 37

* *_Benefits_** – osmolality is equal to blood, reducing the toxic effect and risk of anaphylaxis * *_Drawbacks_** – higher cost * *_Trade Name_** - Visipaque

Answer 38

Feeling of warmth (voiding sensation), flush feeling, metallic taste, nausea or vomiting, are normal. Symptoms last briefly

Answer 39

For compliance & ↓ pt. anxiety. If the patient moves, image quality will be severely degraded

Answer 40

Iodinated water-soluble contrast agents, such as Telebrix, Lactulose, or Gastografin

Answer 41

Impaired renal function reduces the patient’s ability to eliminate the contrast and could result in CIN

Answer 42

* Creatinine (SeCR) * GFR = Glomerular Filtration Rate.

Answer 43

**_Diabetes_** – predisposition to renal failure or compromised renal function **_High blood pressure / hypertension_** – injection of contrast causes vasodilation and could result in elevated blood pressure **_Previous contrast injection_** – ensure a toxic dose of contrast is not delivered. Patients should only receive 1 dose per 48 hours **_Allergies_** – risk of adverse reactions if allergic to contrast media, food & other substances (hayfever & Eczema) **_Asthma_** – predisposed to adverse reactions

Answer 44

Glucophage or Metformin (oral diabetes medication). Patients may be instructed to temporarily discontinue use prior to injection of contrast, and obtain a blood test 48 hours post injection to ensure their creatine, or GFR is within normal limits before resuming medication.

Answer 45

* Communicate with the patient, and determine severity/symptoms of prior reaction * Consult radiologist * Antihistamine could be administered prior to injection (dependent on severity of previous reaction(s) * Non-ionic or isomolar contrast may be indicated, or dose may be altered to reduce risk factors or toxicity

Answer 46

Stable IV access is necessary for contrast media administration * IV line can be established in the CT department * Or the IV line could be pre-established - Indwelling peripheral catheters - CVADs * AC or large forearm vein is preferred when using a pressure injector - Bending at the IV site may cause the injection to fail - Flow rates need to be ↓ if accessing a smaller vein and a smaller gauge is required - Flexible plastic cannulas need to be used with mechanical injections

Answer 47

When a pt. arrives in the CT department with an existing indwelling peripheral venous catheter, it must be carefully evaluated before it can be used to administer contrast media * Location * Age * Un-accessed connecting hub or port - Okay if accessed by saline or dextrose in water * No redness, blanching or swelling in the surrounding skin

Answer 48

Designed to deliver medications & fluids directly into the SVC (superior vena cava), IVC (inferior vena cava), or RA (right atrium) * Used for days, weeks, months, or years * Durable - Not as easily blocked or infected * May contain 1-3 lumens - Each should be used as an independent catheter port - Prevents mixing of meds - Catheters can have open or closed ends

Answer 49

PICC’s (peripherally inserted central catheter) * Are open ended catheters * Must be clamped when not in use * Should be flushed with heparinized saline to maintain the catheters patency between uses Close ended catheters: * Contain a valve that controls fluid flow & prevents reflux of blood into the catheter * Only requires a saline flush to maintain patency

Answer 50

Only specially designed PICCs can handle a mechanical injection * Make sure you verify it can be used * If not, start a separate IV - Must establish standard peripheral IV’s for contrast admin. * Or, decrease injection rate & perform a hand injection NOT mechanical Accessing & de-accessing an implanted port requires special training & is beyond the scope of a CT tech * Example: Tunneled CVC (central venous catheters)

Answer 51

Only sterile devices or needles are used to access CVADs * Disinfect the injection caps & dry prior to use * Before administering ANY substance the patency of the central line must be verified - Demonstrate blood aspiration - Most sites use a 10mL saline syringe - Contraindications to injecting contrast media: - Inability to demonstrate blood aspiration can indicate catheter malposition or occlusion - Resistance to flushing a CVAD may cause the catheter to rupture - \*Dialysis catheters should never be used for contrast administration

Answer 52

Protocols establish proper injection parameters: * Goal is to select parameters that consistently improve images & facilitate reproducible studies 1. Volume & Concentration 2. Flow rate(s) 3. Pressure limits 4. Timing of injection & scan acquisitions Documentation is required: * Name of agent used * Dose * Flow rate(s) * Injection site

Answer 53

Method of injecting IV contrast depends on: * Vascular access * Type of exam * Exams clinical indications Can be injected via the following methods: * Drip infusion * Hand * Mechanical injector (Most common)

Answer 54

(Aka. Power Injector, Pressure Injector or Pump) * Used to deliver a bolus of contrast in a short period of time * Provide reproducible levels of contrast media enhancement **_Considerations:_** * Connection tubing must be capable of withstanding the pressure of the injection * Air bubbles in the syringes & tubing must be cleared prior to the final connection is made to the patient - Prevents possibility of potentially fatal air emboli * Patency of the established IV site must be checked with blood aspiration, resistance and saline flush prior to use

Answer 55

**_Risks:_** * _Infiltration_: contrast media leaking into surrounding tissues * _extravasation_: contrast media accidentally injected into surrounding tissue (IV becomes dislodged) **_Symptoms:_** * pain at injection site * swelling at injection site * possible hematoma **_Prevention:_** * ensure pts arm is straight and IV line is not kinked * ensure proper dose is delivered * ensure a stable vein by flushing IV with saline prior to injection * choose a large enough vein for injection (consider rate and volume) * choose a large bore IV catheter **_Management:_** * stop injection if pt complains of pain at injection site or if you notice swelling at injection site * remove needle immediately, maintain pressure on the vein to prevent hematoma * apply cold pack to help reduce pain

Answer 56

* Warming device(s) * Syringe(s) -pistons * Pressure mechanism * Control panel

Answer 57

_Warming Device:_ * Attaches to a syringe * Maintains temperature of the contrast agent at or near body temperature (37oC) - Does not heat the contrast agent - Contrast agent must be warmed prior to being drawn into the pressure injector syringe

Answer 58

_Syringes:_ * Removable, pre-sterilized & disposable * Common sizes: -150→200mL * Attaches to the top of the “pressure mechanism” * Contains the pistons for contrast loading & delivery

Answer 59

_Pressure Mechanism:_ * The ‘body’ of the system * Ceiling or floor mounted - Mobile (can be used on either side of the pt.) * Consists of an electromechanical motor - Used to drive piston movement (Controls the precise delivery of contrast) * Safety devices built-in - Programmable pressure limits - Audible alarm

Answer 60

_Control Panel:_ Enables technologist manipulation of injection parameters, such as: * Flow rate * Volume * Pressure Limit (PSI; pounds per square inch) Stores injection parameter protocols into their memory * Consistent & reproducible * Can also provide a patients injection history

Answer 61

* Timing is very important for injections, so the desired anatomy can be demonstrated - Blood flow dilutes the contrast media very quickly * Software allows the injector to be electronically connected to the imaging equipment, synchronizing the injection with image acquisition - Usually built into the software and scanning parameters

Answer 62

_Three phases:_ 1. Bolus 2. Non-equilibrium 3. Equilibrium Phases are classified by rate of contrast enhancement * Helps determine ideal time between the initial administration of contrast media & scan acquisition

Answer 63

(Aka. Arterial phase) * Immediately follows an IV bolus injection * IVC & Aorta have a difference of 30 or more HU’s * Arterial structures are filled with contrast -Venous structures are not yet enhanced * CT angiography images are taken in this phase * Usually takes 15→22 seconds to reach peak contrast enhancement - Plateau typically lasts 10→15 seconds - Imaging usually occurs during the plateau

Answer 64

Most organs have an arterial blood supply * Examples: pancreas, bowel, & bladder - Peak enhancement of these organs occurs about 5→15 seconds after peak aortic enhancement * Kidneys are an exception - They also excrete contrast - Peak enhancement is 80→120 seconds after injection - A scan delay should be used between liver and kidney scans Liver has a dual blood supply * Portal vein & hepatic artery - Portal venous scans of the liver occur 60 seconds after a bolus injection - Includes arterial & venous enhancement

Answer 65

Routine brain scanning * For metastases or primary central nervous system tumors * Enhancement is due to BBB disruptions, not the vascularity of the tissue - Injection rate is of no importance - Scan delay is an important consideration - 4 minutes or longer Non routine brain scans: * CT angiography or CT brain perfusion scans - Must follow routine contrast injection protocols

Answer 66

(Aka. Venous phase) * Follows the arterial phase (Approx. 1mins after bolus phase) * Has a 10→30 HU difference Aka. AVID (arteriovenous iodine difference) * Contrast is still brighter in the arteries than the parenchyma of organs, but venous structures are now opacified * Lasts approx. 1mins (Depends on volume & flow rate of contrast agent) * Most routine (non-angiography) images are acquired in this phase

Answer 67

(Aka. Delayed phase) * Begins 2mins after bolus phase * Contrast media is emptied from the arteries, diluted from the veins & soaked the organ parenchyma * AVID of less than 10HU * Worst phase for liver scans

Answer 68

The exact timing of the start and end of each of the three phases are affected by the following factors: * Pharmacokinetic * Patient * Equipment

Answer 69

Are controllable and include: * Contrast media: 1. Volume \*\*\*\*\* 2. Flow Rate \*\*\*\*\* 3. Flow Duration 4. Scan delay time 5. Total scan time * Contrast media characteristics 1. Osmolality 2. Viscosity 3. Concentration \*\*\*\*\* = affect peak enhancement time

Answer 70

When using a higher concentration: * Compensate with a lower injection rate & decreased volume 1. To maintain adequate enhancement 2. Higher injection rates ↑ risk of extravasation 3. Higher volumes also challenge the stability of the IV (Particularly when small catheter gauges are used) * Good for CT angiography studies * Viscosity is higher * Streak artifacts are more likely to appear

Answer 71

Depict effects of aortic & hepatic enhancement - Aortic enhancement effects are more pronounced * For constant injection rates: 1. ↑ contrast volume = ↑ peak enhancement & ↑ time to reach peak 2. Overall level of enhancement is also maintained longer * For constant volumes/doses of contrast: 1. ↑ flow rate = ↓ time to peak enhancement 2. Scan delay should be adjusted to flow rate - Flow rates are typically uniphasic - Can be manipulated to change characteristics of the time-density curve (aka. **Bolus Shaping**) - Prolongs peak enhancement, ↓ need for precise scan timing

Answer 72

The following patient factors affect contrast enhancement: * age * gender * weight * height * cardiovascular status (cardiac output) * renal function * presence of disease Injection parameters can be adjusted to compensate for enhancement effects caused by patient factors

Answer 73

CT Scanner capabilities affect scan timing & contrast administration * Faster scanners: - Delay between injection of contrast media & scan acquisition must be increased (Ensures scanning will occur during peak enhancement) - ↓ scan time = ↑ scan delay - May enable the use of a smaller volume of contrast media - However, if volume is ↓ peak enhancement will also ↓ (Injection rate or concentration must be increased to compensate)

Answer 74

Two methods: 1. Test Bolus 2. Bolus Triggering * Useful for vascular studies * Ensures imaging during peak enhancement regardless of patient: 1. Age 2. Disease 3. Cardiac output

Answer 75

Injection of a 10→20mL IV bolus of contrast media * Test injection is delivered at the same rate as the diagnostic scan * Trial “scans” are performed (Using the lowest mA setting possible) - 2 second intervals are common @ the same anatomical location - 10→15 scan slices acquired - Determines the length of time from injection to peak enhancement - Identifies ideal duration of delay between injection & scan acquisition - Better imaging results if 3 seconds are added to this calculated delay

Answer 76

Aka. Bolus tracking, or Automated triggering More efficient than Test Bolus technique * Uses the contrast bolus itself to initiate scan acquisition A single cross-sectional slice is used to place an ROI * Uses a series of low-dose “scans” to monitor contrast bolus progression over the selected ROI (Aka. “Monitor scans”) * Once the desired HU is achieved (computer automatically triggers or the technologist) will manually trigger the scan acquisition -Table needs time to move the patient into the appropriate “start” position (Can cause a 3→9 second delay)

Answer 77

Limitations/Special Considerations: * Delay between last monitor scan & the start of scanning may ↓ accuracy of imaging during peak aortic enhancement - Compensate for delay by triggering scan acquisition early * Technologist is not able to stay in the room with the patient during contrast administration - ↑ risk of extravasation - A test injection with saline should be performed prior to contrast administration - Bolus Triggering should only be used for vascular studies

Answer 78

_Quality Assurance_ is a management program used to ensure excellence in healthcare * A systematic collection & evaluation of data * QA focuses on **preventing** defects or deficiencies * emphasis on human factors that lead to variation in quality pt care _Quality Control_ is part of the QA program that deals with techniques used in monitoring and maintaining the technical elements of the systems that affect the quality of the image * QC deals with instrumentation and equipment * Focuses on **detecting** deficiencies and defects

Answer 79

The part of the QA program that tests the performance of the CT scanner against an industry or machine standard * The goal of QC is to ensure all acquired images are diagnostic with minimal dose to the patient - QC is an important part of radiation protection _Purpose:_ To maintain high performance standards for patients * Regulatory bodies demand a standard be maintained due to the potential harm to patients and the public from x-rays

Answer 80

* QC ensures a scanners performance and accuracy * Image quality issues can be solved faster by evaluating the QC results * QC tests are also valuable for service engineers as the problems are often apparent in the results

Answer 81

For a QC program to run smoothly: * QC tests need to be performed on a regular basis - May be required to be performed daily, weekly, monthly or yearly * Results need to be recorded & maintained - Log all test results * Results must be interpreted promptly - Comparing QC results to both the specifications of the scanner and previous results - Results can demonstrate if the scanners performance is degrading (Analysis of results designate required response)

Answer 82

**_1. Acceptance testing:_** (Usually done by a physicist) * Ensures the scanner was delivered as ordered * Tests the stability, integrity & safety of the scanner Acceptance tests include: * Slice thickness verification * CT number linearity * Spatial and contrast resolution * Noise * Dose output **_2. Routine Performance Evaluation:_** (Can be performed by the technologist and/or the physicist) * Can be done daily, weekly, monthly and yearly * Monitors the components of a CT scanner that affect image quality and dose **_3. Error Correction:_** * If the values of the QC tests are outside the acceptance or tolerance limits, the scanner needs to be serviced

Answer 83

* Authorities such as the American College or Radiology (ACR), the International Atomic Energy Agency (IAEA), and **Health Canada** determine which QC procedures are to be performed by the technologist, and which will be performed by medical physicists * The manufacturer of the scanner may also recommend evaluative procedures

Answer 84

More advanced QC tests: * Less important more time consuming tests are usually performed less frequently - Monthly * The most complex tests are usually performed semi-annually or annually - These tests are usually performed by a physicist and may require the use of QC phantoms QC tests and their acceptance limits are also outlined in the Canadian SC 35

Answer 85

Must be performed on a regular basis * Schedule of QC testing is a compromise between pros & cons - Scanner downtime, regulatory requirements & expected benefits * Prompt interpretation of measurements - Must recognize when the CT scanner is not operating within acceptable limits * Consistent & accurate record keeping - Results should be maintained for as long as the CT scanner is active (about 10yrs)

Answer 86

Perhaps more important than the actual value of the measured variable is a change in the variable between measurements * Two performance standards for QC test results: _1. Acceptable (essential)_ * Indicates that performance must be within certain tolerances * If not, the equipment should not be used _2. Achievable (desirable_) * Indicates the level of performance that should be attained under favorable circumstances * The level at which a facility should work if feasible

Answer 87

Phantoms are regularly used in QC testing Types of phantoms: 1. _Image performance_: (image quality, subjective ex contast and spatial resolution) 2. _Geometric_: (ensure object shape, size, and positions are being represented accurately) 3. _Dosimetry_: (ensures ALARA principles are being adhered to) 4. _Quantitative_: (objective, statistical measurements)

Answer 88

(Aka. American College of Radiology Phantom) Allows for testing of: * Positioning and alignment * CT number accuracy * Slice thickness * Low contrast detectability * Image uniformity * Spatial resolution * Inter and intra place distance measurement accuracy

Answer 89

Depends on the type of CT scanner and the test being performed Suggestions when choosing technique combinations: * Select one or two representative techniques * Use techniques that match a frequently used clinical technique * Head or body technique * Technique should remain the same for a specific test from day to day

Answer 90

Test priority classifications: 1. Essential 2. Desirable Test frequency considerations: * Replacement of major components, equipment service or adjustments - Requires immediate testing * If used for accurately localizing tissue (biopsies & radiation therapy treatment) - ↑ frequency of appropriate tests * Complexity of tests - ↓ frequency of test completion

Answer 91

Daily QC tests (as outlined by the Canadian SC 35) include: * Equipment Warm Up (Usually a predefined protocol built into the scanner as per the manufacturers specifications) * Meter Operation * Equipment Conditions * Visual inspection of electronic display devices - Ensures the integrity of radiation protection considerations are maintained - Frequency depends on regulatory body - ACR states monthly, IAEA states performance by physicist, CAMRT states daily technologist responsibility

Answer 92

_Equipment Warm-up:_ * There is a warm up period before the system performs optimally - Systems that have no “downtime” still require warm-up every 24hours - Must be consistent, occurring at the same time of day * May include the boot-up of the system and operating system * Warms up the x-ray tube * Calibrates the detectors

Answer 93

A visual inspection may include the following: * Checking the integrity of cables & wires * Checking the WW & WL display * Checking for appropriate warning labels & service records * Room cleanliness/safety concerns * Checking to ensure all equipment is functioning Examples: * Table height & position indicators * Gantry angulation indicators * Laser localization lights * Intercom system

Answer 94

* CT number accuracy * visual inspection of cleanliness * noise * CT uniformity

Answer 95

* calibration of CT numbers * electronic display performance * CT number linearity * CT slice thickness

Answer 96

* CT pt support movement * low contrast detectability * spatial resolution * interlocks

Answer 97

* accuracy of gantry tilt * patient dose * CT accuracy of automatic positioning of tomographic plane

Answer 98

* radiation dose profile * protective equiptment integrity * general preventative maintenance * electronic display device performance * radiation dose * scout image * CT number dependence on phantom position

Answer 99

_equipment needed:_ * uniform water phantom _How is the test done:_ * conditions of a typical axial head and a typical axial body scan _What is the purpose:_ * evaluate the accuracy of the CT number of water _SC35 Acceptance limits:_ * must be in the range of 0 (plus or minus 4HU) (ex -4 to 4)

Answer 100

_Equipment needed:_ * uniform phantom _How is the test done:_ 1. scan phantom 2. measure variation in CT numbers from mean value 3. perform again under condition of head scan and body scan _What is the purpose:_ * measures noise, variation in HU * noise is calculated by the variation of CT numbers from a mean value in a defined area in the image of the phantom * its magnitude is equal to the SD of the CT number values within the ROI * SD within ROI must be plus or minus 10% _SC 35 acceptance limits:_ * plus or minus 10% of 0.2HU from baseline (whichever is larger) * the baseline must not deviate from the manufacturers specifications by more than plus or minus 15% (of the linear attenuation coefficient of water)

Answer 101

_Equipment needed:_ * CT machine * body phantom * head phantom _How is the test done:_ * Calculated by the mean CT number in the center of the image subtracting the mean CT number at the periphery of the image _What is the purpose:_ * to check the consistency of the CT number of an image of a homogenous material across the scan field _SC 35 Acceptance limits:_ * the difference between the mean CT number at the center of the phantom and the periphery must not exceed 2HU from the established baseline values * the basline uniformity of CT number for water must not be greater than plus or minus 5HU from the center of the phantom to the periphery \***Capping**: high value in center, low in the edges \***Cupping**: high at the edges, low in the center (they have to do with CT uniformity)

Answer 102

_Equiptment needed:_ * cleaning supplies (dust rag) _How is the test done:_ * inspect for dust or dirt on or near image reception area _What is the purpose:_ * so the dust and dirt do not negatively affect image quality _SC 35 acceptance limits:_ * clean off dust and dirt or anything that comes in contact with the IR (subjective)

Answer 103

_Equipment needed:_ * test device containing ramps, thin disks or beads _How is the test done:_ * using a test device containing one or two ramps positioned at an angle to the scan plane _What is the purpose:_ * evaluation of the tomographic section thickness _SC 35 Acceptance limits:_ * 2mm or more slice thickness: plus or minus 1mm * 2mm-1mm slice thickness: plus or minus 50% * \<1mm slice thickness: plus or minus 0.5mm

Answer 104

_Equipment needed:_ * water filled uniform phantom _How is the test done:_ * the mean CT number and standard deviation should be calculated for a 2-3cm sqaured area of water and air in the reconstructed image * the mean CT number and SD should be measured at all clinically used voltage settings _What is the purpose:_ * to measure the mean CT number and standard deviation _SC 35 Acceptance limits:_ * CT number for water must be 0 (plus or minus 4HU) * CT number for air must be -1000 (plus or minus 10HU)

Answer 105

_Equipment needed:_ * test pattern generator * laser film printer _How is the test done:_ * using a test pattern such as the SMPTE or TG18 test pattern _What is the purpose:_ * evaluating the performance of electronic display devices used to view images _SC 35 acceptance limits:_ * subjective

Answer 106

_Equipment needed:_ * quantitive phantom containing uniform objects of known materials with a wide range of CT numbers _How is the test done:_ * perform scan of phantom, compare numbers obtained with CT numbers provided by phantom manufacturer and with previously measured values _What is the purpose:_ * ensures the CT scanners CT numbers are within established limits (set by manufacturer) _SC35 acceptance limits:_ * CT numbers checked over the CT range of -1000 to 1000 * acceptable limits acieved when values "form a straight line"

Answer 107

_Equipment needed:_ * phantom, table/gantry _How is the test done:_ * phantom is placed on couch and is moved in and out of gantry * test is performed using an even weight load of no more than 135kg * table is moved a distace of 30cm (maximum scan increment) and returned to start position, must not exceed 1mm _What is the purpose:_ * ensure scan interval = the scan width to image the entire volume of the pt (for contiguous scans) _SC35 acceptance limits:_ * plus or minus 1mm of intended movement of pt in and out of gantry

Answer 108

_Equipment needed:_ * high contrast wire (2mm in diameter or less) in a tube of minimally attenuating material * bar pattern test device * test device with repeating pattern holes _How is the test done:_ * with MTF curves, visual assessment of bars or lines, using region of interest measurements _What is the purpose:_ * evaluating spatial resolution _SC35 Acceptance limits:_ * MTF curve must be within 0.5 lp/cm or plus or minus 15% of established baseline value * visual assessment has a limiting high contrast resolution of 5 lp/cm or more or spacing of 1mm or less

Answer 109

_Equipment needed:_ * CT spatial resolution test device * a phantom of objects of varying size _How is the test done:_ * done using a phantom with \<1% or (10HU) difference to surrounding material * subjective test _What is the purpose:_ * evaluate low-contrast resolution _SC35 acceptance limits:_ * proper phantom * subjective acceptance limit * value determined as the smallest sized object seen at a specified contrast level to the background when imaged under specific conditions

Answer 110

_Equipment needed:_ * scout localizer image _How is the test done:_ * the location of the actual scan plane is compard with the scanned projection radiograph scout localization _What is the purpose:_ * evaluating accuracy of the automatic position of the tomographic plane * assess scout images, ensures accuracy of localizer with the digital display location _SC35 acceptable limits:_ * reference lines indicating tomographic sections must not differ from true position by more than 2mm with the gantry in vertical position (the scan projection radiograph must be plus or minus 2mm of the actual scan plane)

Answer 111

_equipment needed:_ * pre-packaged film * protractor _How is the test done:_ * expose film * place upright and parallel to sagittal laser at various gantry tilt angles * at least 3 irradiations need to be made on the film: no tilt, 2 extreme angles * angles measured should be plus or minus 3 degrees of computer display _What is the purpose:_ * ensures physical tilt of gantry corresponds to tilt angle indicated on display _SC35 acceptable limits:_ * plus or minus 3 degrees of computer display

Answer 112

_equipment needed:_ * dosimetry phantom (head and body) * dosimeter * CT dose probes _How is test done:_ * dosimetry phantom placed on pt table without any additional attenuating material _what is the purpose:_ * evaluating patient dose _SC35 evaluation criteria:_ * must be within plus or minus 20% of the established baseline values

Answer 113

_equipment needed:_ * 1mm pin * pencil * film _how is test done:_ * **Axial:** using a needle to puncture holes in film at the positions of the laser lights and exposing the film using the smallest available scan width. The difference between the exposed areas on the film and the locations of the pin pricks must be _less than plus or minus 2mm_ * **Sagittal/coronal:** place a thin absorber (pencil) centered in the tomographic plane at the intersection of the sagittal and coronal positioning light fields. The intersection localization lights must indicate the center of the FOV. The midline of the table should be coincident with the sagittal scan alignment light. The results must be within the manufacturers recommended values and tolerances. _A limit of plus or minus 5mm should be achievable_ _What is the purpose:_ * **axial:** ensures the location of the radiation beam relative to anatomy is correct * **Sagittal and coronal:** centers the anatomic structures in the SFOV _SC35 acceptable limits:_ * underlined them for both

Answer 114

_Equipment needed:_ * water filled phantom _how is the test done:_ * scan the water filled phantom in varied clinically relevant positions on the pt support _What is the purpose:_ * to ensure HU accuracy for vaired patient positions within the gantry _SC35 acceptable limits:_ * plus or minus 5HU

Answer 115

_Equipment needed:_ * scanning microdensitometer * pre-packaged film _How is the test done:_ * measuring the value either by the density profile of the resultant film or computed from the digital image _What is the purpose:_ * variation of the intensity of the x-ray beam in the Z-plane (section thickness), to ensure collimation does not exceed prescribed scan width _SC35 acceptable limits:_ * should not exceed prescibed scan width by more than manufacturers specifications * scan width: full width half maximum of radiation dose profile

Answer 116

_equipment needed:_ * x-ray equipment and accessories _How is the test done:_ * inspection for structural integrity, cleanliness, ease of movement for all components and any other procedures recommended by the manufacturers _What is the purpose:_ * to prolong the life of the equipment _SC35 acceptable limits:_ * N/A

Answer 117

_equipment needed:_ * radiographic equipment _How is the test done:_ * take an x-ray of equipment _What is the purpose:_ * looking for defective areas of equipment _SC35 acceptable limits:_ * defective area greater than 670mm squared is NOT acceptable (lead apron) * defective area greater than 5mm diameter circle is NOT acceptable (thyroid/reproductive shielding)

Answer 118

_Equipment needed:_ * dosimeter * CT dosimetry phantom * (head and body phantoms) * CT dose probes _How is test done:_ * take a scout image of the phantom and record dose recieved _What is the purpose:_ * evaluate dose patient recieves _SC35 acceptance limits:_ * plus or minus 20% of the nominal value

Answer 119

basically verifies compliance, that is, whether the CT equipment meets manufacturers specifications (usually as outlined in the hospital request proposal to purchase a CT scanner) and ensuring that it operates efficiently in terms of various outputs, such as image quality requirements and dose output * generally includes that the features ordered are delivered and there is mechanical and electrical integrity, stability, safety of various components (ex interlocks and power drives) and CT dose and imaging performance

Answer 120

* verification of slice thickness * CT number linearity * uniformity * spatial and contrast resolution * noise * dose output

Answer 121

* qualified medical physicists * others with a firm knowledge of how CT scanners work

Answer 122

* equipment warm up * meters operation * equipment conditions * overall visual assessment of electronic display devices

Answer 123

* image performance * geometric * dosimetry * quantitive

Answer 124

based on solid water construction to ensure stability and reproducibility of QC tests conducted over time * an important feature of this phantom is that it consists of 4 modules which are designed to measure positioning accuracy, CT number accuracy, slice thickness, light accuracy alignment, low contrast resolution, CT number uniformity, and high contrast resolution

Answer 125

* CT number accuracy * low contrast resolution * slice thickness * light accuracy alignment * CT number uniformity * high contrast resolution (spatial resolution) * CT number linearity * radiation dose *

Answer 126

* light accuracy alignment: **semi-annual** * CT spatial resolution: **quarterly** * CT low contrast: **quarterly** * image uniformity: **weekly** * noise: **weekly** * CT number accuracy: **weekly** * slice thickness: **monthly** * CT linearity: **monthly**

Answer 127

* light accuracy alignment: **within 2mm** * CT spatial resolution: **0.5 lp/cm or plus or minus 15% of baseline** * CT low contrast: **\<1%or 10HU contrast to surrounding material** * image uniformity: **plus or minus 2HU from the center ROI to any at periphery** * noise: **SD within the ROI must be plus or minus 10% or 0.2HU** * CT number accuracy: **water = 0 (plus or minus 4HU)** * slice thickness: **AST \> or equal to 2mm; IT should not vary plus or minus 1mm. AST 2 to 1mm; IT should not vary plus or minus 50%. AST \< 1mm; IT should not vary plus or minus 0.5mm** * CT linearity: **-1000 to 1000 CT numbers checked out of this range**

Answer 128

Health canada

Answer 129

ensure timely diagnosis and treatment at minimum dose to pts and staff

Answer 130

inspection by regulatory bodies

Answer 131

verify compliance with performance specifications of the CT scanner

Answer 132

equipment warm up

Answer 133

standard deviation

Answer 134

a homogenous material across the scan field

Answer 135

plus or minus 2HU

Answer 136

ramps or step wedge

Answer 137

-1000 plus or minus 10HU

Answer 138

linear attenuation coefficients

Answer 139

contains objects with a wide range of CT numbers

Answer 140

straight line up or down graph

Answer 141

x-rays are unable to be emitted if the door is open

Answer 142

high contrast resolution

Answer 143

both a technologist and a physicist

Answer 144

* modulated transfer function * line pairs/cm * repeating patterns of holes * bars or lines

Answer 145

1% or 10HU

Answer 146

both inside and outside of the gantry

Answer 147

medical physicist

Answer 148

CT imaging produces higher doses vs. general x-ray procedures * Quantum Mottle compromises image quality: - Small objects are harder to image - Thinner slices require more photons - Low-contrast resolution The decision to perform a CT must be calculated via Risk vs. Benefit (Benefit must outweigh the risk) * Patient’s must be aware of the risk * ALARA principles must be maintained

Answer 149

1. **Exposure:** the amount of radiation the patient is exposed to 2. **Absorbed Dose:** the amount of radiation that is absorbed by the patient 3. **Effective Dose:** used to measure the risk of partial body exposure from the equivalent whole body dose -Effective dose takes into account the type of radiation and the exposed tissues

Answer 150

* Absorbed dose (Gy) is used to determine at what threshold a deterministic effect **will** occur * Effective dose (Sv) is used when considering the **probability** that a stochastic effect may occur

Answer 151

* These effects occur by chance * The probability of an adverse effect increases with an increase in dose * There is no dose threshold * The severity of the adverse effect is not dependent on the dose (adverse effects can still happen at low doses) * Usually appear years after exposure * Examples include cancer and genetic effects * measured using LNT dose response model (linear-non threshold radiation dose)

Answer 152

* There is a dose threshold after which an adverse effect will happen * The severity of the adverse effect is related to the dose (increases in dose increase the severity of the effect) * Because there is a dose threshold, radiation protection methods are put into place to reduce the risk to patients as well as radiation workers * Examples include skin erythema, necrosis, epilation and cataracts

Answer 153

In CT the dose distribution is more uniform * Dose spread becomes less uniform as the patient thickness increases (and the SFOV) - Entrance skin dose is greater than dose at the center of the patient - Caused by: Partial Shielding

Answer 154

Factors are directly controlled by the technologist, or inherently built into the scanner -Balance between Image Quality & Dose _Factors you should understand:_ * Technique (kVp, mA) * Collimation * Pitch * Centering * Over-ranging * Beam Geometry * Repeat Scans * Filtration * Detector Efficiency * Scan Field Diameter * Localizers * Slice Width & Spacing * Patient size & part thickness

Answer 155

* The CT dose also affects image quality * ALARA principle: as low as reasonably achievable to maintain diagnostic image quality * Image quality factors that are affected by dose include: - Noise - Spatial Resolution - Contrast Resolution

Answer 156

* “AEC” for CT scanners * Optimizes the dose to the patient while maintaining image quality regardless of patient size or tissue attenuation * Automatically adapts the mA in both the “z” and “x-y” axis * Uses information from the scout image to determine the appropriate mA during the scan * A predefined level of image quality is defined by the vendor and protocolled by the users

Answer 157

Advancements such as ATCM have reduced doses to patients, however: * New technology has also increased the number of clinical applications of CT - CT Screening procedures - CT guided procedures - Pediatric imaging (Due to scan speed) * These advancements have resulted in: - More CT exams - Increased patient doses

Answer 158

Utilizing the 3 cardinal rules of radiation protection ## Footnote 1. time 2. distance 3. shielding

Answer 159

_Time:_ * Limit the number of scans * Adjust Pitch _Distance:_ * From the source of radiation (for patients) * From the patient (for technologists) - Dose is inversely proportional to the square of the distance - Overall amount of scatter radiation in CT is low, and the distance it travels is short

Answer 160

_Patient Shielding:_ * Less beneficial in CT due to the amount of scatter - Most scatter is internal & is unaffected by surface shielding _Bismuth shielding:_ Used for anterior dose-reduction * In-plane shielding - Causes problems with ATCM - Must be outside SFOV during Scout acquisition * Lead alternative _Lead shielding:_ Used to enhance perception of safety * Out-of-plane shielding - Must not be in the SFOV - No effect on image quality - Must be 360 degrees around the patient

Answer 161

_Shielding the Public & Personnel:_ As per the SC35: * Secondary shielding is required - Room walls (to protect the public) - Based on equipment not workload values * Lead shielding is required for any person who must remain in the room during scan acquisitions - **Areas of greatest radiation exposure are near the gantry aperture** - 0.35mm of lead required for kVp’s of 100→150

Answer 162

Technologists can use the following guidelines: * Appropriate patient selection - CT referrals are reviewed by the radiologist * Limit multiphase scans (i.e., with and without contrast) * Develop protocols based on the patient’s body habitus (i.e., small, medium, & large patients) - Using the lowest appropriate mAs - Adjusting the Pitch when appropriate

Answer 163

The law of Bergonie and Tribondeau states that the radiosensitivity of a tissue is dependent on its metabolic state * Pediatric patients are therefore more sensitive to radiation exposure because their cells are rapidly dividing * Children have a longer life expectancy than adults -Results in a larger window for potential adverse effects to radiation exposure

Answer 164

* Have separate protocols for pediatric CT exams - Customize the exam - Education plays an important role in reducing dose to pediatric patients * Use CT only when clinically indicated - Consider using other modalities (e.g., MRI, ultrasound) * Apply ALARA Principles - In some cases, lower resolution scans can still be diagnostic and save patient dose - Limit the need for multiphase scans (i.e., with and without contrast) - Consider patient shielding

Answer 165

_Description:_ This method can (↓) pt. dose by 50% compared to back-projection methods

Answer 166

_Description:_ This should be (↓) for smaller sized patients

Answer 167

_Description:_ Will increase dose to pediatric patients if not (↓) from an adult protocol

Answer 168

_Description:_ Moves the patient through the gantry faster, (↓) pt. dose by 33%

Answer 169

_Description:_ Creates a more uniform dose distribution

Answer 170

Are very low dose & are used to assist in (↓) total scan dose

Answer 171

_Description:_ A 180 degree arc would (↓) dose, however, a 3600 arc is typically used for (↑) image quality

Answer 172

_Description:_ Applies to helical scans & (↑) pt. dose

Answer 173

_Description:_ Beam width must be (↑) so that the penumbra extends beyond the active detectors (↑) pt. dose

Answer 174

_Description:_ Multiphase enhancement studies fall under this category, and (↑) pt. dose

Answer 175

_Description:_ Designed to absorbed low energy photons which (↓) absorbed dose & (↑) image quality

Answer 176

_Description:_ Important when using ATCM. If not perfect, image quality is compromised due to (↑) image noise

Answer 177

_Description:_ Scintillation systems have (↑) absorption efficiency, which (↓) pt. dose & improves image quality

Answer 178

_Description:_ * If the same volume of tissue was scanned: * Taking more slices would (↑) pt. dose * Overlap would (↑) pt. dose

Answer 179

All 3 factors have a direct effect on Image Quality * Noise * Contrast Resolution * Spatial Resolution

Answer 180

**_Stochastic:_** * No threshold dose * Radiation protection modeled after this belief (no safe dose) * Cause late effects (genetic & carcinogenic) **_Non-Stochastic:_** * Threshold dose * A specific amount of radiation is required to produce an ill effect * Cause early effects

Answer 181

_In-plane shielding_: Bismuth shielding that is used inside the SFOV; Must not be used during Scout acquisition as it may affect the ATCM and ↑ pt. dose _Out-of-plane shielding_: Lead shielding that is used to cover anatomical areas that are not being scanned during CT acquisition; must be wrapped around the patient in a full 3600 to be effective. _Partial shielding_: Peripheral body parts that shield more centrally located organs from (entrance) radiation exposure; smaller body parts that lack partial shielding receive higher doses during CT scanning.

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