CT Exam Flashcards
Why may lab tests be required for a patient prior to a CT exam?
To determine the blood’s ability to coagulate and to generally asses liver function
What are some lab tests that may be ordered to determine blood coagulation and liver function?
Prothombin time (PT) Partial thromboplastin time (PTT) International normalized ratio (INR) D-dimer Platelet count
What the typically accepted values for PT?
10-14 seconds
What the typically accepted values for PTT?
20-40 seconds
Which lab test is used as a way to standardize the prothombin time for patients who are taking oral anticoagulant medications (Coumdain/Heparin)?
INR
A high INR level of around _____ indicates whats?
5.0, high chance of bleeding
A low INR level of around _____ indicates whats?
0.5, high chance of having a clot
What is the normal INR range for a healthy person?
0.9-1.3
Patients on anti-coagulant drugs should have an INR of:
2.0-3.0
Patients who have a high risk of clot formation should have an INR of:
2.5-3.5
Why are D-dimer tests ordered?
To help rule out, diagnose, and monitor diseases (ex. DVT/PE) and conditions that cause hypercoagulability, a tendency to clot inappropriately
What does it mean if a patient has a positive D-dimer test?
Abnormally high level of fibrin degradation products in the body
What is generally the normal values of a D-dimer?
Less than 500 micrograms/liter fibrin equivalent units
What is the range for a normal platelet count?
150K-400K mm^3
What are some lab tests that may be ordered to determine renal function prior to receiving IV contrast?
Blood urea nitrogen (BUN)
Creatinine
Glomerular filtration rate (GFR)
What kind of information does BUN provides?
The kidney’s ability to remove impurities from the blood
What is the typically accepted values for BUN range from?
5-25 mg/dl
What is the typically accepted values for creatinine range from?
0.6-1.7 mg/dl
What does the GFR determine?
The flow rate of filtered fluid through the kidney
What is the normal GFR range from?
95-120 mL/min/1.73m^2
what are some preparatory instructions may there be for a patient receiving a CT exam with contrast media?
Drinking oral contrast media
Fasting before the exam
Premedicating to minimize contrast reactions
What kind of medication should patients withhold from taking following the procedure?
Metformin (for 48 hrs)
What is the final step in the screening process of the patient?
If the patient can verify the reason for the CT exam
When might a patient be positioned in a prone fashion?
For coronal head studies
Most CT exams requiring IV contrast is usually administered at a rate of:
2-3 cc/sec (100-150 cc)
For a CT head exam, when might a scan be delayed following the completion of the injection, and for how long?
When scanning patients with metastatic lesions, MS plaques, and AIDs by 45 minutes
The localizer image in a CT head exam is usually acquired in a _____ orientation.
Lateral
“_____” slices should be positioned perpendicular to the “transverse” slices during a CT head exam.
Coronal
Why are maxillofacial studies usually performed?
Due to trauma
What kind of scan is used for a maxillofacial study?
Helical scan with overlapping reconstructed slices, contrast media is unnecessary
An oblique sagittal view is difficult to obtain on a CT study of:
The temporomandibular joint (TMJ)
What would be the best way to perform a TMJ study on a CT scanner?
Acquire the slices transversely with a helica scan, and then multi-planar reconstructions can be performed at any oblique orientation
What are some indications to a CT of the neck?
Evaluation of tumors, inflammation/infection, and developmental anomalies
What are not enhanced in the neck by the IV contrast media?
Lymph nodes
What are some indications to a CT of the spine?
Evaluate trauma, intraspinal tumors, disk herniation, spinal infection, spinal stenosis, metastatic disease and fractures
When might IV contrast be administered for a CT exam of the spine?
If a mass is suspected, for infection, or for evaluation of a post-surgical spine
In what orientation(s) should the localizer image be collected for a CT spine study?
Lateral and AP
A localizer image for the shoulder should be obtained in what orientation?
AP
What is the best view to demonstrate a scaphoid fracture?
Coronal
In a bent knee position, the foot will be imaged in a _____ plane while the ankle is being imaged in a _____ plane.
Transverse / Coronal
With the toes pointing straight up, the foot is being scanned in the _____ plane while the ankle is being scanned in the _____ plane.
Coronal / Transverse
What are CT chest exams more routinely ordered for?
Mediastinum / Lungs
For a patient having a chest CT with IV contrast, what determines how long the delay is before scanning?
Volume of contrast media
Rate at which it is injected
Patient’s blood flow rate
If a patient is receiving about 100cc of contrast at a rate of about 3 cc/sec, how long should we wait before scanning?
20-25 seconds
Where are the transverse slices collected in a chest CT?
Between the sternal notch and the adrenals
What is not administered for abdominal CTA or detection of ureteral calculi?
Oral contrast
What might be done prior to injection of IV contrast when visualizing the abdomen?
Pre-contrast scan (to compare pre-/post-contrast images)
For evaluation of possible appendicitis, how may some facilities administer the contrast?
Rectally, up to the cecum
When evaluating the stomach wall, what may some imaging facilities do post-oral contrast so that the dense contrast does not obscure the stomach wall?
Have the patient drink some water / milk
What kind of contrast is required for a pelvis exam?
Both IV and oral
Does a patient need to breath-hold in a pelvis exam?
Yes
What is the difference between CTA and regular chest CT?
CTA evaluates the vessels
What is the recommended contrast injection rate for CTA?
3-5 cc/sec
What is the most common post-processing technique used for CTA?
Maximum intensity projection (MIP)
What does CT perfusion assess for?
Strokes (flow to the brain)
During a CT brain perfusion, a high iodine concentration is recommended along with a high flow rate of:
5-8 ml/sec
Which CT exam would be beneficial for the detection of adenomatoous polyps?
CT colonography
What are three aspects to properly prepare the colon for examination?
Colon cleansing
Fecal tagging
Colon distension
How would you prepare to colon cleanse?
High fluid, low residual diet
Dedicated dietary kit beginning 1-2 days prior
Laxatives
Evacuating immediately prior to scan
How would you prepare to fecal tag?
Consumption of a fecal / fluid tagging agent with meals prior to the exam
How would you prepare for colon distension?
Administer a gaseous agent rectally
For a CT colonography, how should we position the patient?
Supine / Prone
What are some clinical applications of PET/CT?
Ovarian cancer
Hodgkin’s Lymphoma
Lung cancer
Cardiac perfusion study
