Computed Tomography

The mediastinum is located in the space between the two lungs and includes structures like the heart, great blood vessels, thymus, and portions of the trachea and esophagus.

3 x 3 mm is correct. The use of small slice thickness and contiguous acquisition is preferred.

The adult spinal cord ends between the vertebral levels of L1 and L2.

One of the most common complications from guided needle biopsy of the lung is pneumothorax. Pneumothorax refers to a collection of air in the pleural space.

To opacify the rectosigmoid region, a dose of 150-250 mL is sufficient. To opacify the complete large bowel, a dose of 300 - 500 mL is needed.

In a CT scan, the total length can indeed be calculated by multiplying the scan time by the aperture size, making the statement true.

The aperture size determines the slice or section thickness. Scan time has no affect on the slice thickness.

Cerebrospinal fluid contained in the posterior horn of the lateral ventricle does not enhance with the administration of contrast material. A good blood supply as found in the cranial blood vessels, choroid plexus, and dura mater enhance well during a contrast study of the brain.

Dynamic is the term used to describe a rapid scan speed with minimal interscan delays. Rapid sequence scanning allows for acquisition of data during peak contrast enhancement phase.

Fatty infiltrates greatly reduce the density of the liver. The minimal attenuation of fat results in a low CT number value in the range of -100 Hounsfield units.

High resolution CT is used to maximize detail of high spatial frequency tissue, this includes tissues of the lungs and bony structures. This specialized technique incorporates narrow section widths and a high-resolution algorithm for image reconstruction.

To increase the total volume of information used to construct the three-dimensional model, narrow overlapping sections must be used. The use of a small scan field of view in an area of the hip will cause an out-of-field artifact.

Non-ionic contrast media include iopamidol (Isovue), iohexol (Omnipaque), and iopromide (Ultravist), but not iodamide.

Contact precautions are used to protect others from potential infections that the patient may have. Strict isolation precautions are used to protect the patient from potential infections.

To combat bradycardia during a vagal reaction to contrast, Atropine is the drug of choice. Epinephrine is used as a bronchodilator and Diphenhydramine may be used to reduce allergic effects of contrast.

Platelets are part of blood responsible for clotting. Normal platelet levels range between 150,000 and 400,000 platelets/mm^3 of blood.

The ionization chamber is used to accurately measure radiation exposure. The amount of ionization within the chamber of the device is proportional to the radiation exposure. The ionization chamber is extremely accurate in quantifying radiation exposure from a CT scan.

A person can only survive for a few minutes without breathing before the risk of brain damage begins. Therefore CPR should be administered before this point if the patient stops breathing.

A decrease in scan time will reduce the mA reducing the mAs which reduces patient dose. An increase in pitch reduces dose to the patient because the anatomy is covered in fewer rotations. Reformatting eliminates the need to rescan and is an excellent way to minimize dose. A decrease in slice thickness while scanning the same anatomical area means more slices are necessary to cover the region of interest and more dose to the patient.

BUN (blood urea nitrogen) and creatinine are both tests of the patient's renal function. The PT (prothrombin time) is a test to measure the clotting time of the patient's blood. All of these tests are necessary when administering IV contrast to ensure the patient's kidneys will clear the contrast from the body and the patient will have no problems with bleeding after the IV is removed.

The table increment is determined by adding the slice thickness with the gap between the slices. 10mm + 2mm = 12mm table increment. The other information given is just that other information to distract you.

There is no universal standard set of forms for patient consent. Each facility determines their own set of practices.

The MSAD is equal to the CTDI X the ratio of the slice thickness to the table increment. With a 2mm gap and a 10mm slice the table increment will be 12mm. The MSAD = (4.5 rads) X (10mm/12mm).

When measuring the radiation dose only from x-rays, rads and rems are equivalent. The units Sv and rem measure any kind of ionizing radiation (1 Sv = 100 rem). The units rad and Gy measure specifically x-ray radiation (1 Gy = 100 rads).

The DFOV is calculated by multiplying the pixel dimension by the matrix size. In this case, 320 x 0.75 mm = 240 mm or 24 cm DFOV.

Postpatient collimation and predetector collimation are synonymous terms used to describe collimation designed to remove scatter radiation before it reaches the detectors.

Misregistration artifacts occur due to respiration being suspended at different depths during a continuous scan, resulting in a loss of anatomic information.

CT produces images exhibiting extremely small changes in tissue density and eliminates superimposition, both of which lead to greater low contrast resolution.