JUSTIFICATION OF COMPUTERIZED TOMOGRAPHY JUSTIFICATION OF COMPUTERIZED TOMOGRAPHY EXAMINATIONS AND RADIATION RISKS IN EVERYDAY EXAMINATIONS AND RADIATION RISKS IN EVERYDAY

RADIOLOGICAL PRACTICERADIOLOGICAL PRACTICE

Darka R. HadnaDarka R. Hadnađev, Olivera Nikolić, Sanja Stojanovićđev, Olivera Nikolić, Sanja StojanovićCenter for radiology, Clinical Center of Vojvodina, Novi Sad, SerbiaCenter for radiology, Clinical Center of Vojvodina, Novi Sad, Serbia

Background:Background: Rapid technical developments and an expanding Rapid technical developments and an expanding

list of application have led to a dramatic increase in list of application have led to a dramatic increase in the use of body CT in medical practice since its the use of body CT in medical practice since its introduction in 1975.introduction in 1975.

A number of CT examinations has dramatically A number of CT examinations has dramatically increased, mainly for the new clinical applications increased, mainly for the new clinical applications which technically improved CT scanners and made which technically improved CT scanners and made it widely available. it widely available.

Procedure analysis:Procedure analysis: A review of the most recent literature regarding uncritical CT A review of the most recent literature regarding uncritical CT

overuse and insufficient use of alternative non-ionizing diagnostic overuse and insufficient use of alternative non-ionizing diagnostic modalities is presented.modalities is presented.

The popularity of CT imaging is high for many reasons: The popularity of CT imaging is high for many reasons: - speed and ease of use- speed and ease of use

- new imaging techniques- new imaging techniques - threat of a lawsuit- threat of a lawsuit

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

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

In Serbia, there are often uncritically In Serbia, there are often uncritically indicated control abdominal and pelvic CT indicated control abdominal and pelvic CT examinations.examinations.

Numerous multiphase CT examinations Numerous multiphase CT examinations are performed often as unnecessary, as are performed often as unnecessary, as well as the radiation dose the patient well as the radiation dose the patient receives on that occasion. receives on that occasion.

Table 2 Patient dose levels in Serbia

Courtesy of Professor Sanja Stojanovic (Personal Communications)

Table 3. Comparison of effective doses for standard CT examsTable 3. Comparison of effective doses for standard CT exams

LiteratureLiterature(eff. dose- mSv)(eff. dose- mSv)

Our studyOur study(eff. dose- mSv)(eff. dose- mSv)

CT headCT head 22 2.42.4

CT thoraxCT thorax 88 6.16.1

CT abdomen CT abdomen and pelvisand pelvis

1010 2020

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

There are three guiding principles to minimize There are three guiding principles to minimize the radiation dose levels: justification, the radiation dose levels: justification, optimization and limitation. optimization and limitation.

The examination must be medically indicated The examination must be medically indicated and it must use doses that are as low as and it must use doses that are as low as reasonably achievable (ALARA) without reasonably achievable (ALARA) without compromising the diagnostic task.compromising the diagnostic task.

A consideration of evidence-based A consideration of evidence-based recommendations for relevant clinical cases and recommendations for relevant clinical cases and an understanding of the risk of disease for each an understanding of the risk of disease for each patient patient

If patient doses are higher than the If patient doses are higher than the expected level, but not high enough to expected level, but not high enough to produce obvious signs of radiation injury, produce obvious signs of radiation injury, the problem may go undetected and the problem may go undetected and unreported, putting patients at increased unreported, putting patients at increased risk for long-term radiation effects. risk for long-term radiation effects.

Characteristics of Characteristics of deterministic deterministic effects:effects: Damage depends on absorbed doseDamage depends on absorbed dose Threshold existsThreshold exists Example: cataract, erythema, infertility etc.Example: cataract, erythema, infertility etc.

Characteristics of Characteristics of stochasticstochastic effects: effects: Severity is independent of absorbed doseSeverity is independent of absorbed dose Threshold does not exist Threshold does not exist

Probability of occurrence depends on absorbed dose Probability of occurrence depends on absorbed dose Example: radiation induced cancer, genetic effectExample: radiation induced cancer, genetic effect

Low-dose techniques are justified (e.g., Low-dose techniques are justified (e.g., CT colonography [CTC], repeat CT for CT colonography [CTC], repeat CT for renal stone disease).renal stone disease).

Unjustified exams - for which CT is not Unjustified exams - for which CT is not indicated or for which unnecessary series indicated or for which unnecessary series are acquired.are acquired.

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

CT scans are now used as a screening CT scans are now used as a screening procedure. procedure.

CT lung screening-the only one accepted CT lung screening-the only one accepted so farso far

CT colonographyCT colonography CT coronary angiography (Ca scoring)CT coronary angiography (Ca scoring)

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

Conclusion:Conclusion: By informing and educating the clinicians By informing and educating the clinicians

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

Thank you for the attention!Thank you for the attention!