Test Question Flashcards
Imaging Procedures
Displayed CT images are processed to display a specific amount of anatomical data in each images. This is the
Reconstruction Slice Thickness
Averaged into each image. Thinner slices have better spatial resolution, but thicker slices have less noise.
Which phase of contrast enhancement in the abdomen peaks at 50-60 seconds after initiating intravenous (IV) injection?
Portal venous phase
Contrast enhancement through the abdomen occurs in this order 1) arterial phase at about 30 seconds, 2) portal venous phase at about 60 seconds, 3) delayed phase at about 5 minutes (or more)
Assume that all variables remain constant: compared to a 1mm reconstructed slice, a 5mm reconstructed slice will usually result in what two changes?
Decreased image noise, decrease spatial resolution
-Thicker slices result in decreased spatial resolution( not good), but also in decreased image noise (good!) changes in the reconstruction slice thickness have no effect on the pt dose. This makes sense since slices thickness can be changed after the scan is over
Increasing the reconstruction slice thickness results in:
Visualization of more anatomy with decreased SR.
-Increasing the reconstruction slice thickness adds more anatomic data to each image. As a results, this allows visualization of more anatomy. The major disadvantage of thicker slices is decreased spatial resolution. As sliced thickness increases, SR decreases
The acquisition slice thickness used during a scan is determined by the technologist. Acquisition thickness refers to?
Thickness of activated detector rows.
-the thickness of these rows can be changed by combining rows together.
What medication helps to fill the bowels with oral contrast?
Metoclopramide (Reglan)
Metoclopramide is a medication that stimulates the stomach to empty its contents into the small bowel. This is very helpful to ensure that the small bowel is filled with contrast during the scan.
What slice parameter is used for imaging the liver in multiple phases of contrast?
2.5mm
The slice thickness depends on the length of the scan and the size of the organ. At many facilities, multiphase imaging of the liver is performed with 2.5 mm slices. Thicker slices would not provide sufficient details. Thinner slices are usually unnecessary
What medication has the effect of temporarily stopping peristalsis?
Glucagon
Glucagon is a medication use during enterography to temporarily stop peristalsis. This helps to minimize the appearance of motion blur on the CT images
The appearance of inflamed tissue surrounding the appendix is called?
Stranding
What is the minimum volume of rectal contrast expected to fill most of the large bowel?
1000ml
What CT protocol is most useful in evaluating bowel disease?
CT enterography
Bowel disease, such as Crohn’s, This protocol is designed to fill the bowels full with water or some other kind of enteric contrast. IV contrast is also administered in a particular way to identify bowel disease
Which of the following data sets should be used as the source images for creating reformations through the ankle?
0.5mm thickness x 0.5 mm interval
Reformation of any joint, including the ankle, should be created from the thinnest available images. In this question, the thinnest available images are 0.5 mm thickness x 0.5 mm interval
Which of the following slice parameters is appropriate for viewing axial slices through the elbow?
2.0 mm thickness x 2.0mm interval
Axial slices through the elbow are commonly viewed with 2.0mm reconstruction thickness and the same interval. THis is the same reconstruction parameter for all extremities in all orientations.
Which image series will produce the best volume-rendered (3D) models of the bones of the wrist?
0.625mm slices in the standard alg
All volume-rendered (3D) models should be created from the thinnest available standard algorithm images. This ensure maximum spatial resolution while also reducing image noise.
What scan delay time should be used to evaluate the urinary collecting system?
5 minutes
the collecting system includes the renal pelvis, ureters, and bladder. This aspect of the urniary system can be evaluated after filling with contrast at about 5 minutes. Scanning before 5 minutes may result in decreased contrast filling in these structures. In other words, it takes about 5 minutes for the kidneys to filter the majority of contrast out of the blood.
What phase of IV contrast enhancement is used to visualize the contrast-filled collecting system?
Excretory phase
The excretory phase (delayed phase). During this time period, the kidneys have filtered contrast out of the blood in the collecting system is filled with contrast.
What is the most important phase of the contrast enhancement when evaluating the kidneys for renal calculi?
Non-contrast
Renal Calculi (renal stones)
Which of these studies is most useful in the identifying the cause of recurrent renal stones?
CT urogram protocol:
When is evaluating a patient for recurrent renal stones, it is necessary to view the collecting system filled with contrast to identify potential causes of stone formation. The CT urogram protocol accomplishes this very thing
A patient is suspected as having a tumor obstructing the valve connecting the right ureter to the bladder. This condition is best evaluated with what IV contrast scan delay time?
5 minutes
to visualize the connection between the right ureter and the bladder, the patient should be scanned during the excretory or delayed phase. This occurs at 4 or 5 minutes after injecting IV contrast. Scanning before this time will result in only minimal contrast in the collecting system.
The “delayed phase” of adrenal imaging is acquired at what scan delay time?
15 minutes
The delayed phase of adrenal scanning is significantly later than other body regions. For delayed imaging, the adrenals should be scanned at approx 15 minutes after injecting IV contrast..
The arterial phase of the IV contrast enhancement in the kidneys is also called
Corticomedullary Phase
Arterial phase(corticomedullary phase) @ 30 seconds.
Venous phase (nephrographic phase) @ 90 seconds
Excretory phase (delayed phase) @ 5 to 10 minutes.
