Lecture one (Radiology Principles), Exam 1 Flashcards

Question

What are embryologic effects? What is the most radiosensitive period during pregnancy?

Answer 1

* Embryologic effects – those that effect the embryo or fetus during its development * First trimester – most radiosensitive period; the most severe effects occur during the first six weeks (1st 6 weeks especially) * Sensitivity decreases during the second and third trimesters

Answer 2

1) Reduce the time of radiation exposure 2) Increase the distance from the radiation source - best 3) Provide radiation shielding between the individual and the radiation source. 4) Collimate (focus) the radiation beam. This has been shown to cut radiation in half. | 2 and 3 are most important ## Footnote Medical exposure to the patient is not counted because it is considered to be necessary for diagnostic purposes.

Answer 3

* Distance * The inverse square law: The intensity of the beam inversely proportional to the square of the distance.

Answer 4

* Shielding – lead is the metal most commonly used in diagnostic radiology for radiation protection * Shield ALL patients of childbearing age, and ALL pediatrics (if possible) * Beam restriction (another method of shielding) – the collimator is the best device for restricting the primary beam | Gold is best for shielding but too expensive

Answer 5

* Initially introduced in 1950 to limit radiation exposure of gonads and to limit potential genetic mutations * Changes in technology, automatic exposure control, and factors affecting the coverage of actual shielding led to the change

Answer 6

conceptualized as absorbed dose and effective dose. * Effective dose differs based on tissue composition for each organ * The effective dose is measured in Sieverts (Sv)

Answer 7

Background equivalent radiation time (BERT) * Compared to the background radiation to which the entire population is exposed every day from natural radioactive substances in the air, soil, and environment. Increases with altitude * A single commercial roundtrip transcontinental flight in the U.S. is associated with an effective dose of 0.05 mSv (i.e. the equivalent of 2.5 chest x-rays). | BERT AND REM ARE THE SAME

Answer 8

* Rem = convention method of radiation absorbed dose measurement (used in the US) * Sievert (Sv)= Standard International (SI) unit of measure * 1 Sv = 100 rem or 1 rem = 0.01 Sv = 10 mSv

Answer 9

1CXR = 0.01 rem or 6 days in BERT CT Abd and Pelvis CT = 1 rem * equivalent to 500 chest xrays or 4.5 years of background radiation

Answer 10

radiation workers are to keep exposures As Low As Reasonably Achievable

Answer 11

Occupational dose limits are set by the National Council on Radiation Protection * **5 rems (0.05 Sv) per year is the total dose limit for radiation workers** * 0.5 rems (0.005 Sv) per year is the total dose limit for the rest of the population

Answer 12

Thermoluminescent dosimeters * contains small chips of lithium fluoride * Change every 3 months Film Badges * piece of film similar to that of dental film within a plastic holder * Change every 4 weeks ## Footnote TLD are reusable and are more precise in low doses

Answer 13

* Roll film introduced – cellulose nitrate base coated with silver halide emulsion (Kodak) * Cellulose nitrate – highly flammable * Cellulose acetate – tended to wrinkle; gets moldy

Answer 14

* Before the radiographic film is developed, the image, which cannot yet be seen is known as the **latent image** * The actual radiographic image that is visualized after the film is processed is called the **manifest image**, or the visible image

Answer 15

* Screen film is sensitive to fluorescent light from crystals in the intensifying screens * Slow speed screens have smaller crystals, result in greater detail; commonly used for extremity work. Disadvantage: increased patient exposure * High speed screens – large crystals; therefore decreased patient exposure. Disadvantage: less detail | Low kVp+longer time= pretty picture

Answer 16

* mAs * kVp * Film-screen combination * Filtration * Tissue thickness * Processing * Fog * Artifacts

Answer 17

* Based on selective absorption of the x-ray beam * Radiopaque (radiodense) structures appear white * Radiolucent structures appear black * Other structures appear as different shades of gray based on their ability to absorb radiation

Answer 18

Mobile x-ray tube that generates a continuous, adjustable x-ray beam, allowing for real-time visualization of anatomic structures | producure you do real time

Answer 19

* Arteriograms/Venograms – Intra-arterial or intravenous contrast material used * Ingested contrast

Answer 20

Kidney function so BUN and creatinine levels

Answer 21

Intravenous

Answer 22

Includes a variety of procedures in which the vascular or GI system is imaged by x-ray during the injection or ingestion of a radiopaque water- soluble contrast material

Answer 23

iodine and barium

Answer 24

Intravascularly administered agents are iodinated, gets excreted through kidneys * Various facilities interpret ACR guidelines differently; contrast cutoff for creatinine level may range from 1.4-1.7, and may require radiologist approval

Answer 25

Iodinated contrast should be avoided for two months before administration of iodine 131 – Reduces uptake of I-131 and makes it ineffective

Answer 26

Barium Sulfate * Non-water soluble * Avoid in suspected perforations due to peritonitis Gastrografin * Water-soluble * Does not coat mucosa as well as Barium Air

Answer 27

injectable, water- soluble agents, classified as high osmolality and low osmolality agents

Answer 28

With high osmolar (ionic) contrast agents (1st generation): **Omnipaque, Isovue, Optiray**

Answer 29

Low osmolar (nonionic) contrast agents have a reduced risk of severe reactions (2nd gen): **Renografin, Hypaque Conray**

Answer 30

* the type of contrast agent chosen for injection * The reason that low-osmolality ICM have not completely replaced the older higher-osmolality ICM is their higher cost and the gaps of insurance coverage for the low osmolar compounds which are considerably more expensive.

Answer 31

* Unpredictable * Usually within 20 minutes * Independent of dose amount or rate of injection * Can occur with less than 1ml injection * Prior sensitivity testing is of no value * Symptoms can progress change from mild to severe | Allergic and didn't know

Answer 32

* Non-idiosyncratic * These can occur rapidly after injection * Usually have metallic taste in mouth and possibly nausea, vomiting * Bradycardia, hypotension and vasovagal reactions * Unattended these reactions can lead to vascular collapse and death

Answer 33

Mild * Not allergic-like response to injection including, nausea, vomiting, sensation of warmth or flushing * Usually do not require treatment; observe for 30 minutes Severe * Rare, but are rapid and progressive. Can develop into seizures, AMS, and cardiac arrest

Answer 34

Typically not life-threatening, but include urticaria, bronchospasms, angioedema, vasovagal reactions. Can progress quickly.

Answer 35

* With appropriate basic and advanced life support and monitoring equipment and drugs. * The equipment should be regularly checked.

Answer 36

steroids or anti-histamines Typical Steroid prep: * 50mg Prednisone PO 13hrs prior to exam * 50mg Prednisone PO 7hrs prior to exam * 50mg Prednisone PO 1hrs prior to exam * 50mg Benadryl PO 1hr prior to exam

Answer 37

* Preexisting renal insufficiency, diabetes, volume depletion, and severe CHF are risk factors * Prevention in high-risk patients includes IV hydration before, during, and after the study (NOT CHF) * Nonionic contrast agents may also offer a small benefit in these patients

Answer 38

* Third generation agents are available: iodixanol (Visipaque), reduces nephrotoxicity * Metformin and contrast interaction (withhold 48hrs before and after radiocontrast)

Answer 39

* Arteriography (arteriograms) * Venography(venograms)

Answer 40

* The arterial system is usually opacified by a contrast injection into a percutaneously placed small caliber catheter, usually placed into the femoral artery * Can image any major artery (e.g. carotid arteriogram, femoral arteriogram) * Angiography (arteriography) remains the “gold standard” in imaging of the arterial system

Answer 41

1. Creatinine of 1.8

Answer 42

Uses positive contrast (e.g. an iodinated contrast agent) or negative contrast (air) to demonstrate joint abnormalities that are not normally evident on plain films

Answer 43

* Advantages: Widely available, cheap, causes low dose exposure * Disadvantages: no 3D images, inferior to MRI or CT, especially in non-skeletal imaging

Answer 44

* Image is made with both the x-ray tube and the film moving at the same time * The effect is the ability to image different slices of the body, aka Body Section Radiography * X-ray source moves in one direction as the film is moved in the opposite direction, thus showing detail in a predetermined plane of tissue while blurring or eliminating detail in other planes

Answer 45

Transverse

Answer 46

* Aka Computed Axial Tomography (CAT scan) * X-ray tube and detectors move around the patient, computer provides axial tomograms of the patien

Answer 47

Helical CT scan

Answer 48

* Excellent contrast resolution * Cross-sectional images in mostly the axial plane * Excellent for imaging cortical bone | Prettier than x-ray but does the same thing

Answer 49

ct with reconstruction

Answer 50

Artifacts can be seen in conventional, computed, and direct radiography. Typical causes are: * Patient Motion * Dust particles * Foreign Bodies

Answer 51

* Do not irradiate the abdomen, pelvis, lumbar spine, or hips of a woman in the first trimester of pregnancy, unless it is clearly medically indicated * Whenever possible defer the examination or choose as alternative imaging modality (for example, ultrasound or MRI) * Limit the number of images or views obtained to those required to ensure adequate care when evaluating a pregnant woman with modalities that use ionizing radiation

Answer 52

the radiology department needs to be notified. The Radiation Safety Officer can estimate the radiation dose to the fetus

Answer 53

* Strengths: Accurate, 3D reformation ability, Ability to combine with PET * Weaknesses: Radiation exposure, Contrast reactions, Nephrotoxicity, Air embolism, Contrast extravasation

Answer 54

* Essentially always without IV contrast: Bony abnormalities, FBs, Pneumonia * Almost Always with IV contrast: Soft Tissue Trauma * Maybe: PE, Aortic Dissections, Renal Stones

Answer 55

* With IV contrast Only: Cellulitis, Mass, Infection (excluding pneumonia), Inflammation, Soft Tissue non-trauma * With oral contrast: Most Bowel abnormalities

Answer 56

* Patient is placed in a magnetic field * Radiowaves are directed into the patient * The radiowaves interact with hydrogen atoms in the patient's FAT and WATER molecules * Hydrogen atoms (protons) which are small magnets themselves, align themselves with the magnetic field. * Radiowaves are then released from the patient and detected by a receiver * A computer analyzes the data to reconstruct an image

Answer 57

* X-rays are NOT used in MRI! * The image is NOT based on selective absorption! * The terms radiopaque and radiolucent do NOT apply!

Answer 58

* The MR image is based on the strength of the radiofrequency signal emitted from the patient * A strong signal will appear white (a high signal intensity) * A weaker signal will appear gray (a low signal intensity) * No signal will appear black (no signal)

Answer 59

* With the patient placed in the magnets radio frequencies are pulsed in. When energy is then released from the body, it is digitalized and used to create the image. * The information is collected from all radii thus allowing images to be created in any plane i.e. axial, coronal or sagittal.

Answer 60

* Cardiac pacemakers * Automatic internal defibrillators * Cerebral aneurysm clips * Metal in eyes * Cochlear implants * Implanted infusion pumps * Penile prostheses * Shrapnel/foreign bodies * Tattoos with ferromagnetic dyes * Permanent cosmetics (i.e., eyeliner, lip liner, lip coloring)

Answer 61

* Orthopedic prostheses made from paramagnetic metals * Surgical hemostasis clips (delay 2 to 3 months post surgery) * Dental fillings, braces * IUD’s

Answer 62

* MRI allows for direct scanning in the coronal and sagittal planes * In T1 weighted images, white matter appears white, gray matter appears gray, CSF appears black * In T2 weighted images, CSF appears white, fatty structures appear darker (SEES MORE DETAIL)

Answer 63

T2 since fluid will light up

Answer 64

* Protons process at a frequency that is directly proportional to the strength of B0 * Varying B0 allows direct imaging in multiple slices and plains (as opposed to CT, in which imaging is dependent upon the position of the body part in the gantry) ## Footnote The B0 in MRI refers to the main static magnetic field and is measured in teslas (T).

Answer 65

* During scanning, a pulsed radio wave of a particular frequency is directed at the patient. * The hydrogen atoms are knocked out of alignment and will “echo” the radio wave back when they realign with the magnetic field

Answer 66

The time required for the atoms to realign is called the relaxation time. Two relaxation times are recognized with MR scanning: * T1 or longitudinal (spin-lattice) relaxation time. * T2 or transverse (spin-spin) relaxation time

Answer 67

* TR (repetition time) – time between pulses we send to the patient * TE (echo time) - time for signal to come back

Answer 68

* TR controls T1 weighting. The **shorter** the TR, the brighter those tissues with T1 characteristics appear * TE controls T2 weighting. The **LONGER** the TE, the brighter those tissues with T2 characteristics appear

Answer 69

* T1 weighted images (short TR): best for normal anatomy; FAT and BONE MARROW (primarily fat) appear BRIGHT * T2 weighted images (long TE): best for pathology; WATER, EDEMA, ACUTE HEMORRHAGE appear BRIGHT

Answer 70

* Proton density: FAT and WATER appear BRIGHT; good for tendon pathology

Answer 71

Tendons, ligaments, cortical bone, and air always appear black because of their lack of water content

Answer 72

* T1 weighted images: short TR; short TE * T2 weighted images: long TR; long TE * Proton Density: long TR; short TE

Answer 73

* Most are gadolinium enhanced to produce "positive" or enhanced contrast mostly on T1 weighted images. * T2 effects are negligible

Answer 74

– Extracellular agents – Blood Pool agents – Hepatobiliary agents

Answer 75

Extracellular agents * Used in imaging of tumors, inflammation or magnetic resonance angiography (MRA). Gadodiamide (Omniscan) Blood Pool agents * Agent binds to albumin; used for MRA exclusively due to longer intravascular half-life. Gadofosveset trisodium (Ablavar). * Gadolinium deposit disease

Answer 76

Used in discrimination of focal hepatic lesions due to long-lasting enhancement of normal liver parenchyma at which point lesions will stand out as black spots in contrasted normal liver. Gadobenate (MultiHance)

Answer 77

Renal Impairment

Answer 78

* Presents 2-10 weeks following contrast, usually Omniscan * Thought to release most free gadolinium * Presents as acute to subacute onset of limb edema that is accompanied by cutaneous papules and plaques overlying fibrosis of the cutaneous and subcutaneous fat * Has significant mortality risks | YOU NEED TO CHECK INR AND CREATINE LEVELS (LIVER AND KIDNEY)

Answer 79

* Expensive * Takes nearly an hour per study * But does not produce ionizing radiation * Excellent at imaging soft tissues

Answer 80

MRI with contrast

Answer 81

no * same with MRI vs x-ray | ALWAYS BLACK AIR

Answer 82

Based on directing high frequency sound waves into the patient, and recording the manner in which sound is absorbed or reflected from organs and structures Echogenicity * Solid structures appear white (echogenic, or hyperechoic) * Cystic structures appear black (echolucent, hypoechoic or anechoic)

Answer 83

* Sciatic nerve (hyperechoic with stippled “honeycomb” structure) * Adipose tissue (hypoechoic) * Muscles (note the striations and hyperechoic fascial lines on muscle surfaces) * Vein (anechoic – partially collapsed under pressure to US transducer) * Popliteal artery (anechoic – pulsating) * Bone (hyperechoic rim with hypoechoic shadow below it)

Answer 84

Oneofthegreateststrengthsof ultrasound is its ability to differentiate cysts from solid lesions, making it a useful problem-solving tool for further evaluation of cystic lesions incidentally noted on CT.

Answer 85

* Clear fluid collections produce no echoes at ultrasound, and are thus anechoic (black) * Not completely clear fluids (blood, pus, debris) will appear hypoechoic (gray), or anechoic * Since vascular ultrasound does not require injected contrast material, it is well tolerated by most patients (venous doppler has pretty much replaced venography in the imaging of DVT)

Answer 86

* Towards: Red * Away: Blue

Answer 87

* Arterial duplex (for arterial occlusive disease) * Venous duplex (for DVT and venous valvular incompetence) * Color doppler, while not diagnostic in its own right, can provide valuable information with regard to flow turbulence and variance in anatomic routes

Answer 88

* If you place the doppler on the possible vein with DVT and their is no blood going away (blue) then that is a DVT

Answer 89

Usually see artery and vein next to it. If apply pressure with transducer – wall of vein is thin and is compressible. Wall of artery is not. So, identify vessels by vein collapse.

Answer 90

* Microbubble contrast agents that are smaller than RBCs. * Used rarely in cardiac perfusion studies * Enhance the Doppler signal of flowing blood * Suppress the background tissue to highlight the signal from the blood pool * Optison and Definity are the only FDA approved agents

Answer 91

* It is cheap, harmless and is widely available * Preferred initial intraabdominal study of choice in most pediatric/pregnant patients * Results vary based on technician * Limited scope for deep structure evaluation

Answer 92

Echo of posterior enhancement * Bright band extending from the posterior aspect of the weak attenuator * Distinguishes cyst vs lesion Shadowing * Decreased posterior attenuation of highly reflective surface * Helpful in stones identification

Answer 93

* Osteoporosis is the most common metabolic disease of bone. It is due to disturbances in bone remodeling that result in less bone tissue (matrix and mineral) per unit volume * Bone mineral density (BMD), the average concentration of mineral in a defined section of bone, is used to diagnose osteoporosis

Answer 94

* A BMD of the hip and spine using a central DXA machine is used to diagnose osteoporosis. Forearm is an alternative site. * The low-energy and high-energy photons are attenuated differently in bone and soft tissue, allowing BMD in g/cm2 to be estimated.

Answer 95

Results quantified statistically, using T- and Z-scores. * Osteoporosis is quantified as T-score of −2.5 or lower. * Osteopenia is defined as T-scores between −1 and −2.5 * A T-score higher than −1 is considered normal.

Answer 96

* Based on the accumulation/metabolism or “uptake” of an injected radioactive substance (radiotracer) by body tissues * Increased uptake (hots pots; appear black) or decreased uptake (cold spots; appear white)

Answer 97

* Technetium-99m (bone scan MDP), measures bone metabolism * Gallium-67 Citrate, measures inflammatory disorders (tumors) * Indium-111 Oxine WBC, for acute infections * Ceretec Labeled WBC

Answer 98

* computed tomography (CT): $51 and $1565 * x-ray and ultrasound: $55 and $410 * nuclear medicine (NM): $135 and $1138 * magnetic resonance imaging (MRI): $165 and $2048.