Computer Tomography (CT) exam Practice Tests and PDFs

Aseptic technique is a method that prevents the introduction of unwanted organisms into an environment that may cause an infection. Nosocomial infections are common in hospitals, and it is the medical staff that is responsible for lowering the incidence of hospital acquired infections. Anytime the skin is broken, a chance of infection is possible. Aseptic technique helps to prevent infection. Hand washing, gloves, sterile supplies, and proper skin preparation are all a part of utilizing an aseptic technique for peripheral IV access.

BUN and creatinine levels indicate the ability of the patient's renal systems to clear the contrast media from the blood. The BUN provides information about the ability of the kidneys to remove impurities from the blood. Elevated creatinine levels indicate an impairment of the ability of the kidneys to excrete creatinine from the blood. Renal disease impairs the ability of the kidneys to remove impurities from the blood. IV contrast media is considered an impurity and can cause a nephrotoxic effect in the patient. It is important to pre-screen most patients prior to administering IV contrast to ensure that they can clear the contrast from their blood.

Enhancement times are directly related to injection rate, volume of contrast media, velocity of blood flow, and patient cardiac output. The first phase of enhancement is the bolus phase. This is an optimal phase for CTAS. There is a significant density difference between the abdominal aorta and IVC. The second phase is the non-equilibrium phase. During this phase, the bolus disperses into the capillaries then into the veins. The two phases of enhancement within this phase are the hepatic arterial and portal venous. The non- equilibrium phase provides the best differentiation of structures in soft tissue like the liver and pancreas. The third phase is equilibrium. During this phase, the concentration of contrast in the veins and arteries are similar and soft tissue differentiation becomes diminished.

If the IV manufacturer of a .22-gauge needle is only rated for a certain rate and PSI, the technologist must adhere to those limitations. Injecting too fast through a smaller needle catheter may cause an infiltration or cause the injector to stop the injection due to pressure limiting. The type of CT exam will also determine the flow rate. A CT Angiogram will require a faster rate and a soft tissue neck will require a slower rate. A 64- slice scanner will scan much faster than a 4-slice CT scanner. The technologist may miss a particular necessary diagnosing phase if these factors are not taken into consideration while selecting a proper flow rate.

Every facility interprets the normal range somewhat differently, but these are typical normal ranges. Urea is a waste product produced in the breakdown of protein in the liver, released in the bloodstream, filtered in the kidneys, and excreted in urine. When the kidneys are not properly working, there is a rise in blood urea nitrogen. Many other things can affect BUN levels such as certain medications, high protein foods, age, sex, dehydration, and pregnancy.

CT angiograms are scanning the patient during the bolus or arterial phase of the IV contrast injection. Faster scanners also require faster injection times. Peripheral venous access with a smaller needle will not safely allow the technologist to inject the contrast at an optimal rate to catch the arterial phase. In addition to the size of the needle, the site should be anti-cubital and proximal. Certain mid-lines are rated for the contrast injection rate and PSI that are needed for a CTA injection. These specific catheters must be documented in the patient chart.

There are many variations of consent forms available that vary by state and by facility. Signed consent forms are required at some facilities prior to administering IV contrast during a CT scan. This is done to prove that the patient was informed about the risks and side effects and still agrees to have the contrast injection. There are currently no universal laws that mandate a signed informed consent.

Many patients are apprehensive about getting a CT scan. When a patient knows exactly what to expect they usually feel less anxious and are able to follow the scan instructions. Proper pre-scan preparations with oral prep, NPO instructions, and dress attire will minimize the risk for needing portions of the exam or even the entire procedure to be repeated thus reducing radiation dose to the patient and attaining the best possible images for that patient.

It is important to always ask women of child bearing age if there is any chance of pregnancy prior to any CT exam. If there is a chance, a pregnancy test needs to be negative prior to scanning the patient. All patients should be asked about allergies prior to a CT scan. The patient may have a latex allergy or a known IV contrast reaction history. Diabetes can affect a patient's renal function, so lab work may be required prior to an IV contrast injection to make sure the kidneys can excrete the contrast from the blood. Also, certain diabetic medications also affect renal function. These medications may need to be stopped before and/or after IV contrast injections until renal function tests are performed. Pre- screening questions should be asked again by the CT technologist immediately prior to the scan.

If the patient is having any kind of interventional procedure with CT guidance, lab tests to determine the blood's ability to coagulate need to be done. The imaging staff need to be sure that the patient's blood has the correct clotting ability so the patient doesn't bleed internally. Such procedures may include all types of CT guided biopsies of any area, CT guided drainages, and ablations. If the PT or PTT are abnormal, the procedure may be cancelled.