CT Module 8 Flashcards
HOUNDSFIELD UNIT
A CT number that represents the attenuating properties or density of each tissue.
- Water is the reference tissue which is given a value of zero
- Tissue it’s the highest value will be white
- Tissue lower than the range will be black
WINDOW LEVEL
The CT # of the tissue of interest. Which CT # are displayed on the image
WINDOW WIDTH
It determines the gray levels to be displayed in the image.
This can be decreased or increased to produce an image
INCREASE WINDOW WIDTH
Wider range of values will be included into the grayscale,
- the image will have lower contrast
DECREASE WINDOW WIDTH
Less range of values included ,
- Image will have higher contrast
WIDE WINDOW WIDTH
More shades of gray with in the lung tissue
- Longer gray scale
Eg- Lung window WW: 1000, WL:-700
NARROW WINDOW WIDTH
Fewer shades of gray resulting into higher contrast image
Eg. Mediastinal window, soft tissue window. WW: 529, WL : 24
Lungs are completely black
PATIENT PREPARATION IN CT
- Verify patient -
- Briefly explain the procedure
- Obtain written consent for invasive procedures
- Describe to the patient how they will be positioned and table movement
- Provide time frame of procedure
- Explain what is expected of the patient for the procedure- breathing , no movement etc
- Describe the type of contrast to be used and it’s purpose
- Check for allergies if contrast is required
- Provide lead protection where appropriate
- Provide post procedural instructions
PUPOSE OF PATIENT HISTORY SHEET
- Patient safety- For contraindications
- Protocol Selection
- Clinical information - Help radiologist with diagnosis
-
BUN ( blood Urea nitrogen ) and Serum Creatinine
Used to measure patient kidney function
GFR ( glomerular filtration rate)
Normal values
120 ml/ min
Contrast will be given for a GFR greater than 30 ml/min
BUN ( blood urea nitrogen)
Normal values
7-21 mg/dl
SERUM CREATININE
NORMAL LEVEL
Male: 60-120 umol/L
Females: -100 umol/L
BLOODWORK
For Biopsy or drainage patients on warfarin
Prothrombin Time PT, Partial thromboplastin Time PTT and Platelet count will be viewed due to the increased risk of bleeding .
- patients on warfarin , heparin , plavix or aspirin may be instructed to discontinue before the procedure due increased risk of bleeding
aPURPOSE OF CONTRAST MEDIA IN CT
To distinguish adjacent structures on a CT image, creating a difference in attenuation values
- Used in CT to distinguish normal anatomy from pathology and to make various disease processes more visible
POSITIVE CONTRAST MEDIA
- Absorbs more radiation than the surrounding tissues therefore appears white or light on images
- Has high atomic number
- Positive Hounsfeild unit
- Radiopaque
- Eg Barium #56, Iodine # 53
NEGATIVE CONTRAST MEDIA
- Penetrated by X-rays more than surrounding tissues therefore appears black on images
- Low atomic number
- Radiolucent
- Negative Hounsfeild unit
- Eg, Air , CO2 and water
aGASTROINTESTINAL POSITIVE CONTRAST MEDIA IN CT
Barium Sulphate is used
- Introduce orally
- Used to distinguish the stomach, small intestine and large bowel from the surrounding soft tissue organs
- Only 1-3 % barium suspension is needed in CT due to its greater contrast resolution
- Patient drinks 450 ml of barium1-2 hours of scan and an addition of 100-200 ml is given just before the scan to fill the oesophagus, stomach and small bowel
- Contra indication- PERFORATION suspicion - this may cause peritonitis
aGASTROINTESTINAL POSITIVE CONTRAST MEDIA IN CT
WATER SOLUBLE CONTRAST MEDIA ( Gastrografin )
- Indicated for Abdo and pelvis scans when a perforation is suspected
- Has a bitter taste, often mixed with juice for palatability
- 2-5 % solutions is utilised in CT
- Patient drinks 300 ml of water mixed with 25ml of gastrografin
- Gatrografin is hypertonic thus May causes dehydration
- very dangerous when administered to elderly, infants or patients that are dehydrated,
GASTROINTESTINAL NEGATIVE CONTRAST MEDIA IN CT
WATER
- Negative contrast media/ enthral neutral
-Causes equal distension in the bowel as barium sulfate
- Use in clinical practice is increasing
GASTROINTESTINAL NEGATIVE CONTRAST MEDIA IN CT
CO 2
- Radiolucent contrast appears black on images
- Indicated for virtual colonoscopy exams
- Rectally administered
- Small flexible rectal tube is inserted and CO2 is administered via an automated insufflation system
- CO2 will distend the colon to better visualise polyps
- CO2 is absorbed in the body and excreted via the lungs
IV CONTRAST MEDIA
- Iodinated water soluble injectable contrast media eg omnipaque/ visipaque
- Indications to identify tumours, vascular structures, vascular pathology, renal function
- Two tissues must differ by at least 10 HU to be visibly different on CT scan
- Administration of contrast media May increase the attenuation difference between adjacent structures by 40-75 HU
CT MEDICAL HISTORY
Ask for the following
- Allergies history
- Chronic diseases
- Diabetes
- Renal dysfunctions
- Congestive heart failure
- patient older than 60
If yes to the above questions, patient must have a recent blood test to check Serum Creatinine levels
CONTRASTED CT
FOR PATIENTS TAKING METFORMIN
Contrast can be administered
- if eGFR is below 30mil/ min and contrast was administered, METFORMIN May be withheld 48hrs after the injection
- If renal dysfunction occurs post contrast METFORMIN could accumulate in the bloodstream and cause lactic acidosis
PROPERTIES OF IODINATED CONTRAST MEDIA
OSMOLARITY
The number of particles in solution, unit of liquid as compared to blood
- Blood osmolarity is 290mOsm/kgwater
PROPERTIES OF IODINATED CONTRAST MEDIA
HIGH OSMOLARITY CONTRAST MEDIA
Renografin. Hypaque
- Solution has 7-8 times the OSMOLARITY of plasma
PROPERTIES OF IODINATED CONTRAST MEDIA
LOW OSMOLARITY CONTRAST MEDIA
Omnipaque. Isovue
- Solution that has 2-3 times the osmolarity of plasma
PROPERTIES OF IODINATED CONTRAST MEDIA
ISO- OSMOLARITY
Solution that has equal osmolarity to plasma
Eg. Visipaque
PROPERTIES OF IODINATED CONTRAST MEDIA
aVISCOSITY
Thickness of fluid as it flows
- Viscosity of contrast media affects its injectability
- Contrast agents can be placed in a warmer to reduce its viscosity making it easier to inject
- The lose the concentration of iodine atoms within the contrast medium the less viscous the solution
PROPERTIES OF IODINATED CONTRAST MEDIA
IONICITY
- Ionic contrast media will dissociate into 2 charged particles when brought into solution
- Non ionic contrast media will not dissociate into 2 charged particles when brought into solution. THESE CONTRAST MEDIUMS USUALLY RESULT IN LOWER ADVERSE REACTIONS
- CONTRAST TODAY IS MOSTLY NON IONIC LOW OSMOLAR, DECREASING ADVERSE EFFECTS, SINCE THEY DONOT INDUCE FLUID IMBALANCE
PROPERTIES OF IODINATED CONTRAST MEDIA
CLEARANCE
- Iodinated contrast media is not metabolised, it is excreted by the kidneys via glomerularfiltration
- Half life in patients with normal renal function is 2 hours, and cleared 100% in 24 hrs
PROPERTIES OF IODINATED CONTRAST MEDIA
DOSE
- Determined by iodine concentration and volume of solution
- Contrast Media is measured in milligrams of iodine per lililiter
PROPERTIES OF IODINATED CONTRAST MEDIA
PEDIATRIC DOSE
- asked on weight
- Common formulae is 2ml per kg
BREASTFEEDING
CONTRAST
Less than 1% of contrast media given to mom will be excepted into the breast milk and absorbed by the infant
- THerefore it is SAFE to breastfeed after receiving iodinated contrast media
VASCULAR ACCESS IN CT
peripheral catheter
- 18-20 gauge Cather preferred
- Antecubital vein is the preferred site
- Patency must be confirmed with saline injection prior to hooking up IV line to the injector
VASCULAR ACCESS IN CT
PICC LINE
- Must be a purple PICC line to with stand the injector pressure
- Must flush with saline after injection
- Inserted in the cephalic or basilic vein and advanced to the SVC
- Can remain in place for weeks or months
INJECTOR PARAMETERS
- Volume and concentration of contrast
- Flow rate
- Pressure limit
- Timing between start of injection and start of scan
CT ARTERIAL PHASE
- Arterial structures are filled with contrast
- Begins immediately after injection
- AVID ( arteriovenous iodine difference) greater than 30 HU
- Application CT Angiography
NONEQUILIBRIUM ( Venous) Phase
- Venous and arterial structures are filled with contrast
- Begin around 60-70 sec post start of injection
- AVID ( arterial venous iodine difference) 10-30 H
- Application: Routine body scanning Eg appendix
EQUILIBRIUM ( Delayed ) PHASE
- Organ parenchyma opacified with contrast
- Begins around 2 min post start of injection
- AVID ( arterial venous iodine difference) less than 10 HU
- Application : kidneys
CONTRAST ENHANCEMENT FACTORS
- Injection parameters
- Condition of patient, particularly the patients cardiac output
NB: Injection protocols are designed by first determining the time during when the contrast material is likely to first arrive in the organ or vessel of interest
AUTOMATIC INJECTION TRIGGERING
Two methods
- test bolus
- Bolus triggering or tracing
TEST BOLUS
- Obtain scout image
- Determine target region, and obtain single slice
- Begin trail scans 8-15 secs after start of injection, scan every 2 sec using low. Ma
- 10-20ml of CM is injected and several trial scans are taken to determine the length of time from injection to peak contrast enhancement in the target region
- ROI on vessel
- Determine scan delay, peak enhancement via graph
- Trial scan delay + 2 x image @ peak enhancement +3 sec
BOLUS TRIGGERING
- Uses the contrast bolus itself to initiate the scan
- Obtain scout image
- Obtain single slice target region. ROI vessel
- Set trigger thresh hold or watch the graph to begin scan protocol
- Start the contrast injection, start the low radiation scans 8-10 sec later
- When the threshold is reached, start scan, the table will move to the start position and scanning begins
NB- A drawback is that a technologist cannot stay with the patient to monitor the injection site
SIDE EFFECTS OF CONTRAST MEDIA ADMINISTRATION
Common and predictable=
- Nausea
- Vomitting
- Metallic taste in the mouth
- Feeling warmth all over
- Feeling like you have peed your self ( especially4-5 sec post injection )
IDIOSYNCRATIC REACTIONS TO CONTRAST MEDIA ADMINISTRATION
These are not predictable, they are allergy like.
- They present quickly, usually within the first 5-20 min,
- High risk patients should be monitored for 1 hour after administration
- Not related to dose, can occur in small amounts being injected
CONTRAST MEDIA
RISK FACTORS
- Patients with multiple allergies to foods and or drugs
- Patients with asthma
- Patients who exhibited a reaction to previous contrast administration
CONTRAST MEDIA
PRE TREATMENT
- Un contrasted Ct must be down if possible for high risk iodine reaction patients if possible
- Pre treatment with Costicosteroids ( prednisone) and or Antihistamine diphenhydramine ( Benadryl) If CT with contrast is deemed necessary
MILD IDIOSYNCRATIC REACTIONS TO CONTRAST MEDIA
patient will begin to=
- Cough
- Sneeze
- Nasal congestion
- Exhibit a rash
- Itching
- Urticaria ( Hives)
Treatment =. Benadryl ( Diphenhydramine)
MODERATE TO SEVERE IDIOSYNCRATIC REACTIONS TO
CONTRAST MEDIA
- Dyspnea
- Wheezing
- Laryngeal Edema
- Hypertension or hypotension
Treatment =
- Oxygen for the Dyspnea
- Epinephrine for laryngeal Edema
CONTRAST INDUCED NEPHROPATHY. ( CIN)
Acute renal dysfunction that occurs after contrast media administration
NB: renal impairment is identified, continuance of the examination should be discussed with the radiologist
RISK FACTORS FOR CONTRAST INDUCED NEPHROPATHY. ( CIN)
- Pre-existing Azotemia
- Diabetic patients
- Multiple myeloma patients
- Patients over 60
- Administration of more than 200 ml of contrast media in one day
- Dehydrated patients
- Concurrent use of nephrotoxic drugs
AZOTEMIA
A medical condition in which patient has elevated levels of urea, creatinine, relating to inadequate filtering of blood by kidney
PRETREATMENT/ PREVENTION OF CONTRAST INDUCED NEPHROPATHY. ( CIN)
- Use low osmolar non ionic contrast media
- Use smallest plume possible
- Allow 48 hours between procedures requiring CM
- Prophylactic hydration ( Saline, sodium bicarbonate )
- Vasodilators
- Antihistamines ( Benadryl) , Corticosteroids ( Prednisone) to prevent mild reactions
CONTRAST MEDIA EXTRAVASATION
Contrast media accidentally flowing into the subcutaneous tissue surrounding the vascular system
- Causes swelling at the site
Common risk factors =
- Too small cannula for pressure of automatic injector
- placement of cannula in the hand or wrist area
REDUCE RISK OF CONTRAST MEDIA EXTRAVASATION
- Use 18-20 gauge cannula
- Monitor the injection site
- Warm the contrast media to reduce the viscosity
- Use Low Osmolarity Contrast Media ( LOCM)
TREATMENT OF CONTRAST MEDIA EXTRAVASATION
- Stop infusion
- Elavate the affected extremity above the heart
- Apply cold compress over the injection site for 20 min minimise bleeding
- Apply warm compress to increase circulation and encourage CM uptake
CT HEAD INDICATIONS
- Tumors
- Circulatory pathology
- Anteriovenous malformation ( AVM)
- Inflammatory or injection conditions. (Meningitis , abscess)
- Degenerative disorder ( atrophy)
- Trauma
- Congenital abnormalities
- Hydrocephalus
CT HEAD PATIENT PREP
- Without contrast: No prep
- With contrast : NPO 2 hours before exam
- pre and post contrast: NPO 2 hours before exam
CT HEAD PRE AND POST
POSITIONING
- Remove metallic items
- Patient supine on CT bed head first in the Cradle
- Gantry parallel or angled 15-20 deg to SOML
- Laser light positioned on the Nasion and EAM
Scout
- Lateral image of cranium
- Brain scanned from base to vertex
- Gangtry is angled so to step and shoot
ENHANCED CT HEAD
INDICATION
- Infections/ Abscess
- Neoplasms
- AVM ( Ateriovenous malformation)
- Aneurysm
- Headaches and seizures
-
ENHANCED CT HEAD
CONTRA INDICATEIONS
- Intracranial haemorrhage
- Early infarction ( stroke)
- Dementia
- Hydrocephalus
- Cerebral trauama
CT HEAD SCANNING PARAMETERS
- Small Scanning FOV
- Display FOV 23cm
Axial slices+
- Base to vertex
- 5x 5 mm table increment ( thinner slices can be obtained for more detail)
Windowing =
- Soft tissue: WW 80. WL: 40
- Bone: WW 2000 WL 350
Helical Scanning
0,625 x 0,625 mm
IAC, mastoids, sinuses, orbits, CTA
CT SINUSES
Indication- Sinusitis
- Scout AP and lateral
Patient positioning =
- Patient supine with head first in cradle
- Laser light on Asian and EAM
- No contrast
Scanning=
- From hard palate to 1cm above frontal sinuses
- Helical: 0,625. X 0,625 mm slices
- Bone Window , Coronal and axial reconstruction
CT FACIAL BONES
Indication:
- Trauma
Scout:
- AP and Lateral
Positioning
- Patient supine, head first
- Anatomical Landmark position on Nasion and EAM
- No contrast
Scanning
- Topmof frontal sinuses to bottom of mandible
- Helical: 0,625 mm x 0, 625 mm
- Bone window reconstruction
CT HEAD. CTA
CIRCLE OF WILLIS
Indication:
- Acute stroke
- Carotid stenosis
- Carotid dissection
Scout
- AP and Lateral
Patient position
- Patient supine, head first
- Anatomical land mark is nasion and EAM
IV Contrast
- Test Bolus, ROI on the carotid artery C2 level
- 320 at 4ml/sec
Scanning
- Just below C2 to just above vertex
- Helical
BASAL NUCLEI
This the gray matter nuclei within the white matter, located bilaterally between the Thalamus and the cortex
CAUDATE NUCLEUS
C shaped masses that runs along the lateral ventricles
LENTIFORM NUCLEUS
Large nucleus centrally located in each hemisphere, subdivided into lateral putamen and medial Globus Pallidus
- Separated from the caudate nucleus by a large tract of white matter called internal capsule
CLAUSTRUM
Layer of gray matter just lateral to the lentiform. Nucleus and deep to the cortex
DIENCEPHALON
- Located in the middle cranial fossa
- Consists of the Thalamus, hypothalamus and Pineal body
THALAMUS
- An oval structure above the midbrain
HYPOTHALAMUS
- Located below the thalamus
- Forms the floor of the third ventricle
- Connected to the hypothalamus via the infundibulum
PINEAL GLAND
- Small gland attached to the posterior portion of the roof of the third ventricle
- Often calcified
- Should be seen in the midline, any deviation may indicate a mass
MID BRAIN
- Extends from the diencephalon to the pons
- Located in the posterior cranial fossa
- Brain stem consists of the. Midbrain, pons and medulla
- Anterior portion - cerebral peduncles
- Posterior portion- corpora quadrigemona
HIND BRAIN
- Located in the posterior cranial fossa
- Consists of the pons, Medulla oblong at a and cerebellum
PONS
Lies directly above the medulla and anterior to the cerebellum
MEDULLA
- Continuation of the upper portion of the spinal cord
- Lies just superior to the foramen magnum
CEREBELLUM
- Consists of two hemispheres with the central portion called the vermis
- Situated in the inferior and posterior portion of the crainial cavity , posterior cranial fossa
- Separated from the cerebrum by a transverse fissure and a double layer membrane called tentorium cerebell
- Consists of outer gray ( folia) and inner white ( arbor vita’s)
PROTECTION OF THE BRAIN
- Cranium
- Meninges
- Spaces( Sunderland, subarachnoid ,cisterns, ventricles)
- Cerebrospinal fluid
FALX CEREBRI
- Extension of dura mater into the longitudinal fissures
- Attached anteriorly to the crista Gali on the floor of the anterior cranial fossa. Posteriorly attached to the tentorium cerebeli
FALX CEREBELLI
- Extension of the dura mater between the cerebella hemispheres
- Attached superiorly to the tentorium cerebeli and inferiorly to the foramen magnum
TENTORIUM CEREBELI
- Located in the transverse fissure, extension between the cerebrum and cerebellum
- Extends from the occipital protuberance posteriorly to the midbrain anteriorly
ARACHNOID VILLI
Micro projections in the dural venous sinuses, which returns CSF back to the bloodstream
CSF
- Clear liquid that.contains glucose, proteins, lactic acid, urea, cation, anions and lymphocytes
- Circulates around the brain and spine
- Volume 80-150 ml ( 3-5oz)
- Function is protection
- A medium of exchange of nutrients and waste products
- Formed by choroid plexus.
CHOROID PLEXUS
Capillaries in the walls of the ventricles that from CSF
Usually appear calcified on CT
VENTRICLES OF THE BRAIN
- Cavities of the brain containing CSF
- 4 in total .two lateral, one third and one fourth
INDICATIONS FOR NECK CT
- Congenital Abnormalities
- Trauma
- Infection and abscess
- Tumors of the pharynx, parotid glands and larynx
CT NECK PREP
- Unenhanced ; No prep
- With contrast: NPO 4 hours before exam, clear fluids are encouraged
IV CONTRAST
- Used to visualise vascular structures and soft tissue tumours within the neck
Smart prep: ROI in the carotids
ORALCONTRAST
- maybe administered to distinguish between the oesophagus and surrounding tissue
CT NECK POSITIONING
- Patient supine head first into the gantry
- Laser placed on the nasion and EAM
- AP and lateral scout
- Neck is scanned from base of skull ( mid orbit) to thoracic inlet
CTA
Indications=
- Acute stroke, carotid stenosis, carotid dissections
Patient positioning=
- Patient supine head first
- Landmark Nasion and EAM
Scout
- AP and Lateral
Contrast
- 80ml ( 320 at 4 ml/sec)
- Timing ( test bolus): ROI on aortic arch, scan during arterial phase
CT CHEST INDICATIONS
- Mediastinum abnormalities
- Primary lung tumours
- Metastatic diseases to the lung
- Aneurysms
- Abscess or cysts
- Cardiac and pericardial diseases
- Dissection of the aorta
- Pleural effusion
- Pneumothorax
- Pulmonary embolism
CT CHEST PATIENT PREP
- Unenhanced: No prep
- With contrast: NPO 4 hours before exam, clear fluids are encouraged
CT CHEST PT POSITIONING
- Patient supine arms elevated feet first
- Land mark- laser at the sternal notch and axilla
Scout
- AP and Lateral
Contrast
- IV contrast media is used to visualise the structures within the mediastinum
Oral
None
CT CHEST SCANNING PARAMETERS
Mediastinum pathology cases:
- Chest is scanned from Apices to diaphragm
Pulmonary Malignancies:
- Scanned from Apices to adrenals, because a number of pulmonary malignancy’s spread to the adrenals
- Scan FOV ; large. DFV- 38 cm
- Helical scanning 0,625mm
- Lung window reconstruction
Lung window
- Wide contrast scale
- WW 1500. WL - 700
Mediastinum window
- Narrow contrast scale
- WW 400 WL 40
HR CT
Indication
- Interstitial tissue. - Pulmonary fibrosis
- Brochiectasis. - Small airway disease
- Emphysema
Scout
- AP and lateral
Patient positioning
- Supine, feet first
- No contrast
Scanning
- Lung Apices to diaphragm on inspiration and expiration
- Helical slice thickness 1:25mm
- Bone window reconstruction
CT A Chest
Indications
- Dissecting aorta
Scout
- AP and Lateral
Patient positioning
- Patient supine, feet first
- IV contrast
Scanning
- Above aortic arch to below aortic bifurcation
- Helical 0,625mm
CT PE PROTOCOL
Indication
- Pulmonary Embolism
Scout
- AP and Lateral
Patient positioning
- Supine , feet first
- IV contrast
Scanning
- Timing run ( test bolus) target slice just below the carina, ROI on pulmonary artery, calculate delay, image with maximum enhancement
- PE chest series from Apices to diaphragm
INTERNAL CAROTID ARTERY
- ascends from the neck, almost in a vertical plane, to enter the base of skull through the carotid canal of the temporal bone
- The internal carotid has no branches in the neck but branches are in the head to supply blood to the orbit and brain
EXTERNAL CAROTID ARTERY
- Ascends the neck , it passes through the parotid gland to the level of the TM joint, where bifurcates into its terminal branches to supply blood to the face and neck
-At it’s lower end it more anterior and medial than the internal carotid
RIGHT COMMON CAROTID ARTERY
Arises from the brachiocephalic artery posterior to the SC joint
- Lies medial to the internal jugular vein and birurcate into the internal and external carotid arteries at approximately the level of the thyroid cartilage (C3- C4 )
LEFT COMMON CAROTID ARTERY
Arises directly from the aortic arch.
-Lies medial to the internal jugular vein and birurcate into the internal and external carotid arteries at approximately the level of the thyroid cartilage (C3- C4 )
VERTEBRAL ARTERIES
- Begin as a branch of the subclavian artery and ascend the neck through the transverse foramina of C6- C1, enter the foramen magnum and join to form the basilar artery
- Vertebral and basilar artery’s supply the posterior aspect of the brain
INTERNAL JUGULAR VEINS
- Drain blood from the brain
- Largest of the vascular structures of the neck
- Typically runs laterally to the common carotids
- Runs posterior to the internal carotids
EXTERNAL JUGULAR VEINS
- Begin near the angle of mandible and lateral to the Sternocleidomastoid muscle
- Empties into the subclavian veins
BRACHIOCEPHALIC VEINS
- The internal jugular veins commence at the jugular foramen and descend the lateral portion of the neck to unite with subclavian vein to form the brachiocephalic vein
- The left brachiocephalic vein passes anterior to the left common carotid and right brachiocephalic artery to join the right brachiocephalic vein
- Left and right brachiocephalic veins join to form the SVC
DIAPHRAGM
- A dome shaped muscle that divides the ventral cavity into the thoracic and abdominal cavity
- The central area is termed the central tendon, and the two halves are called right and left hemi diaphragms
Attachments- XIPHOID Process
- Costal cartilages of the last 6 ribs
- Lumber Vertebrea via. Crura
CRURA
- Tendons attached from the diaphragm to the lumber spine
- The right crus is longer than the left, to L3. This is due to the force necessary to move the liver down during respiration
- The shorter left crus extends to L1/ L2
OPENINGS OF THE DIAPHRAGM
- IVC - T8
- ESOPHAGUS. - T10
- Aotrta, Thoracic duct, Azygous veins. - T12
COSTODIAPHRAGMATIC RECESS
- Located at the base of each lung
- Deepest posteriorly
- Become smaller on inspiration
- Clinical significance if patient has excess fluid in the pleural cavity, it will settle in the recess
CT ABDOMEN INDICATIONS
- Suspected lesions of the liver, pancreas, kidneys or spleen
- Fatty liver
- Adrenal gland pathologic processes
- Lymph node pathologic process
- Pancreatitis
- Abscesses
- Hematomas
- Renal stones
- Hydronephrosis
- Colon pathologic processes, polyps, Crohn’s disease, ulcerative colitis
Pelvis
- Prostate ,, cervix , urinarybladder and ovarian carcinomas
- Soft tissue masses
- Abscesses
Ct ABDOMEN PRE AND POST PREP
- NPO at least 4 hours before exam, clear fluids are encouraged
- 2 hours before exam drink barium
CT KIDNEYS AND PANCREAS PREP
Pre and post
- NPO at least 4 hours before exam, clear fluids are encouraged
- 1 hour before exam drink 4 cups of water
CT KUB PREP
No prep
CT COLONOGRAPHY BOWEL PREP
- One 4 litre bottle of acolyte to clean out the bowel
- Contrast is ingested to highlight any stool left in the colon on the virtual colonoscopy images
- 250ml of Barium
- 60 ml of Gastrografin
BARIUM SULPHATE 1-3%
CT ABDO PREP
- Patient drinks 450ml of barium 1-2 hours,prior to scan
- An addition 100- 200 ml may be given just before scanning to fill the ESOPHAGUS, stomach and small intestine
GASTROGRAFIN 3-5%
CT ABDO PREP
- Patient drinks 300 ml of water mixed with 25 ml of Gastrografin 2 hours prior to the exam
CT ABDO PELVIS
PATIENT POSITIONING
- Patient supine, arms elevated above their head, feet fist
- Landmark laser localiser , placed at the level of the xiphoid process and axilla
Scout
AP AND LATERAL
SCANNING
- Scan FOV : Large. DFV: 38 cm
- For abdomen and pelvis scan from diaphragm to symphysis pubis
-
UNCONTRASTED CT ABDOMEN
Indication:
- Suspected abdominal mass, tumor staging, abscess
Scout
- AP and Lateral
Patient Positioning
- Patient supine, feet first
- Oral Contrast
Scanning
- Diaphragm to Symphysis pubis
- Helical : 0,625mm
- Coronal and axial reconstruct
ENHANCED CT ABDOMEN AND PELVIS
Indication:
- Suspected abdominal mass, tumor staging, abscess
Scout
- AP and Lateral
Patient Positioning
- Patient supine, feet first
- Oral Contrast and IV contrast
Scanning
- Diaphragm to Symphysis pubis
- Helical : 0,625mm
- Coronal and axial reconstruct
VIRTUAL COLONOSCOPY
Indication:
- Rectal Polyps, colon cancer
Scout
-AP and lateral
Patient Positioning
- Patient on
INTRAPARETONEAL ORGANS
- Liver
- Spleen
- Stomach
- Small Bowel except Duodenum
- Cecum, Transverse colon, sigmoid colon and rectum
RETROPERITONEAL ORGANS
- Duodenum
- Pancreas
- Kidneys and ureters
- Adrenal glands
- Descending aorta and IVC
- 1st apart of the duodenum
- Ascending and descending colon
INFRAPERITONEAL ORGANS
- Urinalysis bladder
- Ureters
- Lower part of the rectum
MESENTERY
Binds the small intestine to the posterior abdominal wall
MESOCOLON
Binds the large intestine to the posterior abdominal wall
GREATER OMENTUM
Fatty apron attaches to the stomach and transverse colon and drapes over the small intestine
LESSER OMENTUM
Fold that suspends the stomach and duodenum from the liver
CRURA
- Tendon that attach the diaphragm to the lumber spine
- The right Crura is longer than the left, extends to L3
- The shorter left Crura extends to the L1/L2
- Crura to the diaphragm overlaps anterior to the aorta
- At T12 the Crura separates to form aortic hiatus
ESOPHAGEAL HIATUS
Opening in the diaphragm at T10
CT VERTEBRAL COLUMN INDICATIONS
- Tumors
- Inflammatory conditions
- Degenerative disorders
- Trauma
CT C SPINE POSITIONING
- Patient supine head first
- No rotation or head tilt
- Laser at the level of the Nasion and EAM
Scout: AP and Lateral
Scanning:
- Above the base ok skull to mid T1
- FOV : Large
- DFOV: 13 cm
- No contrast
- Helical scan
- Coronal and Sagittal reconstruction
Windows:
Soft tissue : WW: 350. WL: 40. Bone Window: WW: 2000. WL 350
CT T SPINE patient positioning
- Patient supine feet first
- Arms above the head
- 45 deg sponge under the legs
- Laser at the sternal notch and axilla
Scout : AP AND LATERAL
Scanning:
- Above T1 to below T12
- SFOV : large. DSFOV: 16 cm
- Bone and soft tissue windows
- No contrast administrated
- Helical
- Coronal and Sagittal reconstruction
Windows
- Soft tissue: WW: 350. WL 40. Bone Window: WW 2000. WL: 350
