1. JUSTIFICATION OF COMPUTERIZED TOMOGRAPHY EXAMINATIONS AND RADIATION RISKS IN EVERYDAY RADIOLOGICAL PRACTICE Darka R. Hadnađev, Olivera Nikolić, Sanja Stojanović Center for radiology, Clinical Center of Vojvodina, Novi Sad, Serbia

2. Background:  Rapid technical developments and an expanding list of application have led to a dramatic increase in the use of body CT in medical practice since its introduction in 1975.  A number of CT examinations has dramatically increased, mainly for the new clinical applications which technically improved CT scanners and made it widely available.

3. Procedure analysis:  A review of the most recent literature regarding uncritical CT overuse and insufficient use of alternative non-ionizing diagnostic modalities is presented.  The popularity of CT imaging is high for many reasons: - speed and ease of use - new imaging techniques - new imaging techniques - threat of a lawsuit - threat of a lawsuit

4.  Abdominal and pelvic CT examinations are two major contributors to this increase in population radiation exposure because they are associated with the greatest radiation burden among all types of CT procedures.

5. Table 1 Definition of 14 standard and four special examinations frequently carried out on MSCT scanners along with the corresponding average scan parameters and dose values, as determined in a nationwide survey performed in Germany in 2002

6.  In Serbia, there are often uncritically indicated control abdominal and pelvic CT examinations.  Numerous multiphase CT examinations are performed often as unnecessary, as well as the radiation dose the patient receives on that occasion.

7. Table 2 Patient dose levels in Serbia Courtesy of Professor Sanja Stojanovic (Personal Communications)

8. Table 3. Comparison of effective doses for standard CT exams Literature (eff. dose- mSv) Our study (eff. dose- mSv) CT head 22.4 CT thorax 86.1 CT abdomen and pelvis 1020

9.  The purpose of the study is to determine the average effective dose per each CT exam and to make the introduction of patients radiation records in everyday practice.

10.  There are three guiding principles to minimize the radiation dose levels: justification, optimization and limitation.  The examination must be medically indicated and it must use doses that are as low as reasonably achievable (ALARA) without compromising the diagnostic task.  A consideration of evidence-based recommendations for relevant clinical cases and an understanding of the risk of disease for each patient

11.  If patient doses are higher than the expected level, but not high enough to produce obvious signs of radiation injury, the problem may go undetected and unreported, putting patients at increased risk for long-term radiation effects.  Characteristics of deterministic effects:  Damage depends on absorbed dose  Threshold exists  Example: cataract, erythema, infertility etc.  Characteristics of stochastic effects:  Severity is independent of absorbed dose  Threshold does not exist  Probability of occurrence depends on absorbed dose  Example: radiation induced cancer, genetic effect

12.  Low-dose techniques are justified (e.g., CT colonography [CTC], repeat CT for renal stone disease).  Unjustified exams - for which CT is not indicated or for which unnecessary series are acquired.

13.  Once the determination is made that an appropriate CT examination can benefit the patient, CT parameters should be optimized and dose reduction techniques used to perform the diagnostic task at the lowest appropriate level of radiation dose.

14.  CT scans are now used as a screening procedure.  CT lung screening-the only one accepted so far  CT colonography  CT coronary angiography (Ca scoring)

15.  The shielding of superficial radiosensitive tissues and the optimum selection of settings are some of the technical possibilities.

16. Conclusion:  By informing and educating the clinicians and radiologists primarily on the risk of radiation and strategies to minimize it during a CT exam, we can justify the examination itself and the patient radiation risk. Therefore, it is necessary to limit the exam to the region of clinical interest by which better quality would be achieved as well as significantly reduced patient’s dose.

17. Thank you for the attention!