CT Final Exam Questions and Answers: Radiation Dose and Safety, Exams of Nursing

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CT FINAL EXAM questions well answered to pass CT technologists must understand both the ___________ & ___________ of examinations and take steps to maximize the ________ & minimize the ____________. - correct answer ✔✔risks & benefits positive, negative What are the two components regarding radiation dose to the patient? - correct answer ✔✔1) appropriate patient selection 2)minimizing the dose to the pt w/ out compromising the diagnostic image quality CT scans provide one of the ____________ radiation doses in diagnostic radiology. *** (slide 3) - correct answer ✔✔higher --large # w/ very thin slices X-rays damage cells in _______ ways.....how? - correct answer ✔✔2; 1) Direct interaction between an x- ray photon and DNA bonds with the nucleus of the cell within the patient. 2) X-ray photon indirectly produces ion pairs in tissues as it passes through the body X-rays damage cells in two ways: - correct answer ✔✔-Direct interaction with DNA bonds. -Indirect effect caused by ionization of chemicals in the body. Direct Interaction is also known as.... - correct answer ✔✔Target Theory Gestating babies are ________ radiosensitive. - correct answer ✔✔most Radiation effects may be __________ but are more likely to be seen___________________ . - correct answer ✔✔-immediate -over a long period of time What are the effects of x-ray radiation?(4) - correct answer ✔✔-cancer -genetic effects of future generations -Long term effects (10-20 yrs) -effects of the embryo & fetus --first trimester=maximum radiosensitivity The unit of x-ray exposure in air - correct answer ✔✔Roentgen (R) Units of absorbed dose - correct answer ✔✔radiation absorbed dose=rad SI unit=Gray(Gy) 100 rad=1 Gy 1 rad= .01 Gy or 1 cGy Convert the following: 50 rad = 200 Gy = .1 rad = - correct answer ✔✔.5 Gy 20,000 rad .001 Gy or 1mGy Determine the total dose in Gy if an exam acquires 300 slices producing 2 rads per slice. - correct answer ✔✔300 slices x 2 rad/slice = 600 rad x .01 = 6 Gy Accounts for different types of ionizing radiation - correct answer ✔✔Quality factor (Q) In CT, the quality factor is ? - correct answer ✔✔1 -Filtration-bow tie -Detector efficiency -Slice width and spacing -Pitch -Scan field diameter -Radiographic technique (i.e., mAs and kVp) -Patient size and body part thickness -Repeat scans -Collimation The level of risk associated with a CT examination can be considered acceptable if: - correct answer ✔✔- The individual is aware of the risk -The individual receives some commensurate benefit -Everything reasonable has been done to reduce the risk Ped CT--General Principles - correct answer ✔✔-The patient (or the parent) should be told of the small risk involved -The procedure should be restricted to cases in which it is specifically indicated and clinical information cannot be obtained by other means -Every effort should be made to decrease the radiation dose by adjusting the kVp and mAs to a suitable level according to the size of the child being scanned. -Shielding should be used when possible (all the way around) special considerations---peds CT - correct answer ✔✔Increased sensitivity Higher effective dose Increasing use The radiosensitivity of a developing fetus is greatest from conception to 3 months' gestation because this is the time of organ and neural crest development - correct answer ✔✔.... Dose reducing strategies - correct answer ✔✔-Adjust mAs to suit the individual patient -When available, use automatic tube current modulation -Avoid increasing kVp -Increase pitch -Limit the use of thin slices -Limit repeat scans -When available, use iterative reconstruction methods -Verify the CT is clinically indicated -Customize the CT examination when possible -Shield patient Interventional CT, CT Fluoroscopy, and Cone Beam CT - correct answer ✔✔CT has proven useful for invasive interventional procedures that previously were performed using conventional fluoroscopic techniques CT Guidance of Percutaneous Procedures - ADVANTAGES - correct answer ✔✔-Provides precise 3D localization of lesions -Permits clinicians to plan an access route by showing the relationship of surrounding structures -Because the tip of the needle can be seen, interventions can be performed on small structures -Information can be gathered on materials ranging from low to high density -Contrast Media can be injected when needed -Patients can be placed in a variety of positions CT Guidance of Percutaneous Procedures - DISADVANTAGES - correct answer ✔✔Disadvantages include: a significantly higher dose to both patient and operator than normal fluoroscopy, ---making ultrasound guided techniques a viable alternative if indications allow Using CT to guide interventions improves the accuracy of the procedure and diminishes the associated risks - correct answer ✔✔........... Two different imaging techniques are used: - correct answer ✔✔Sequential CT CT fluoroscopy (CTF) Concerns exist about the radiation dose delivered from either method It is not uncommon for a single department to use both approaches, depending on the clinical problem Sequential CT - correct answer ✔✔Sequential CT takes longer to perform than CT fluoro, and may be a lengthy process because of the stop and start nature of the protocol Sequential CT - correct answer ✔✔A scan is made and the needle advanced a short distance and the process repeats until the needle or catheter is in the appropriate position CTF - correct answer ✔✔May be performed with intermittent sequential technique to allow for insertion of hands into the beam area while the beam is not on to eliminate exposure to the physician's hands Sequential CT - correct answer ✔✔Process of: a) Scan acquisition b) Adjustment of the needle c) Another scan acqusition and so forth until the needle is confirmed to be in the correct location Drawbacks of Sequential CT - correct answer ✔✔Procedure can be lengthy BB markers or wires used for mammography work well as surface skin markers Compared w/ traditional angiography, CTA has the advantages of being: - correct answer ✔✔-Less invasive -Widely available -Less expensive -Time-saving other interventional procedures may be done for treatment of vascular pathologies and utilize CT angiography techniques CTA of the Head and Neck - correct answer ✔✔Rapid, high-resolution scans are taken while contrast is in the arterial enhancement phase Goals of CTA of H&N: - correct answer ✔✔-Accurately measure stenosis of the carotid and vertebral arteries and their branches -Evaluate the circle of Willis for completeness using 3D reformation -Detect other vascular lesions What is used for the depiction of venous anatomy? - correct answer ✔✔A modification of CTA, called CT venography (CTV) High resolution 3D images can be produced to aid in treatment and surgical planning - correct answer ✔✔...... Protocols to detect PE scan in what direction? - correct answer ✔✔Caudal-to-cranial direction to minimize respiratory artifact CTA in the diagnosis of PE or Aneurysm - correct answer ✔✔Part of the technologist's role is to identify these anomalies and bring them to the attention of the radiologist CTA in the diagnosis of PE or Aneurysm - correct answer ✔✔The dose, rate, and timing of IV contrast admin are critical to the creation of diagnostic CTA exams -the use of a saline flush is recommended CTA in the diagnosis of PE or Aneurysm - correct answer ✔✔Rapid diagnosis of a pulmonary embolism can save a patient's life if drug therapy is applied in time The technologist's knowledge of pathology can bring cases of incidental findings that are of an urgent nature to the attention of practitioner who an intervene to the patient's benefit A saline flush is recommended to help eliminate streaking beam hardening artifacts from dense accumulation of contrast media in the superior vena cava that may obscure small emboliin the right main and right upper lobe pulmonary arteries Cardiac CT - correct answer ✔✔Improvement in CT detector technology and in temporal and spatial resolution have resulted in clinical results with cardiac CT that are similar to those obtainable with conventional catheter coronary angiography The technologist's understanding of the structural anatomy and the path and timing of the circulation is essential to the creation of high-quality cardiac CT images (Cardiac CT can be very useful for stent placement planning and assessment after the placement) What is done to reduce motion artifact on cardiac CTA images? - correct answer ✔✔A patient's heart rate can be temporarily lowered by the administration of beta blockers Cardiac gating attempts to use only those images acquired during periods of the lowest cardiac motion: - correct answer ✔✔-Prospective ECG triggering -Retrospective ECG gating Cardiac CT Techniques - correct answer ✔✔Most institutions also give patients nitroglycerin sublingually before coronary CT exams -The intention is to dilate vessels to improve visualization Cardiac CT - correct answer ✔✔Often considered a specialty procedure and is best done on newer machines having 256 and 320 slice capabilities to produce high quality images that can be virtually free of motion degradation w/o use of pharmaceuticals Cone Beam CT is utilized for what? - correct answer ✔✔Maxillofacial imaging, radiotherapy treatment planning, breast imaging What kind of detector does Cone Beam CT use? - correct answer ✔✔A digital flat panel detector, rather than a linear detector array Cone Beam CT - correct answer ✔✔Acquires a larger volume of information per gantry rotation Requires 3D back projection algorithm Cone Beam CT - correct answer ✔✔Cone beam CT is a relatively new entity which has found more utility in dentistry, mammography, and radiation therapy treatment simulation than in diagnostic radiography. This is mainly because it produces images that require a great deal of algorithmic manipulation to remove issues with geometric properties of x-ray beam and scatter production to provide images that are deemed acceptable for use. Further research and development will most certainly overcome these shortfalls. Flat Panel Detector - correct answer ✔✔TFT- Thin Flim Transistors - positioned within a matrix beneath the charge panel that converts light from a scintillator layer to electrons However, aligning the images was problematic PET/CT - correct answer ✔✔Without precision overlayment of images, the opportunity for errors frequently outweighs the value of the information provided. This precision can be produced when a CT and PET scan are done with the patient in the same position for one scan and then the next to accurately calibrate table position with the images and allow for good image fusion. PET/CT scanners are composed of..... - correct answer ✔✔A multidetector CT scanner in conjunction with, but separate from, a PET scanner During the study the patient passes first through......? - correct answer ✔✔The CT scanner and then into the imaging field of the PET scanner In PET/CT the strengths of the two modalities complement each other - correct answer ✔✔.... Which generation of CT scanners were the first hybrid PET/CT scanners? - correct answer ✔✔4th generation CT scanners They were used for a period of time until modern hybrid scanner design was produced Staffing Dilemma....... - correct answer ✔✔A PET/CT technologist combines the responsibilities of nuclear medicine and CT technologists, yet technologists are very rarely trained in both modalities Currently, a PET/CT technologist may have either a nuclear medicine or CT background New regulations by states as well as Medicare reimbursement are requiring that fusion scanning be done by....? - correct answer ✔✔Technologists registered in CT as well as Nuclear Medicine to ensure that quality scans are produced by qualified individuals FDG-PET Imaging - correct answer ✔✔PET creates an image from the radiation given off when positrons encounter electrons in the body How does PET work? - correct answer ✔✔by giving patients a radiopharmaceutical with a short half-life, made up of a radionuclide (in this case 18F) linked to a pharmaceutical agent (deoxy-glucose) FDG-PET imaging - correct answer ✔✔When F18 decays it gives off a positron that being positively charged seeks out nearby electrons and when encountering a free electron produces an annihilation reaction that results in 2 x-ray photons each having 511keV energy and traveling in exactly opposite directions These photons pass through the body and may be attenuated as they travel until they strike the detector ring and are registered as an event. Remember, the radionuclide produces photons within the body that are emitted. PET relies on radiation emission rather than transmission like CT does What is FDG? - correct answer ✔✔FDG is a glucose analog that is taken up by cells Many cells use glucose for energy, therefore FDG uptake is basically a map of glucose metabolism - correct answer ✔✔........ Tumor imaging with FDG is based on the fact that..... - correct answer ✔✔Malignant tumors often favor the glycolytic pathway for metabolism Glucose is use for..... - correct answer ✔✔fuel throughout the body and especially where there is high metabolic activity PET relies on this to deposit large quantities of F18 to produce high signals for detection. Since malignant tumors divide uncontrollably and require large amounts of energy to do so, they use a lot of glucose which makes an ideal situation for use of FDG FDG imaging pitfalls - correct answer ✔✔Tumor cells, however, are not the only cells that exhibit an increased uptake of FDG Because FDG maps glucose metabolism, its distribution can be altered by any physical activity Normal physiologic accumulation of FDG occurs in the brain, muscles, salivary glands, myocardium, GI tract, urinary tract, brown adipose tissue, thyroid gland, and gonadal tissues Patient preparation and management before and after FDG administration are important to get the majority of the FDG administered to deposit in the target tissues and get the least deposition possible in areas undergoing normal metabolic activity - correct answer ✔✔........... FDG Imaging Pitfalls - correct answer ✔✔It is important to recognize and understand normal variants of FDG uptake and benign disease to avoid mistaking them for pathologic processes The timing of a patient's last meal and level of hydration before a PET study can affect the PET results Patients are required to fast from 4 to 6 hours before their PET examination For insulin-dependent diabetic patients, the timing of an insulin injection may affect PET results Insulin should be given as far from the time of FDG injection as feasible FDG Imaging Pitfalls - correct answer ✔✔To avoid possible misinterpretation, any extravasation of the radiopharmaceutical should be noted by the technologist performing the examination Extravasation will show up on PET images as...... - correct answer ✔✔an extreme hot spot near the injection point FDG-PET scans are interpreted mainly by? - correct answer ✔✔Qualitative means An area of abnormality is detected by? - correct answer ✔✔comparison with background activity standard uptake value (SUV) - correct answer ✔✔used particularly when areas are judged to be equivocal by qualitative analysis alone