Imaging Radiation Doses and Associated Risks and Benefits in Subjects Participating in Breast Cancer Clinical Trials

Incidental Thoracic Findings on Routine Computed Tomography in Epithelial Ovarian Cancer

INTRODUCTION

Multidetector computed tomography (MDCT) is routinely used in the surveillance of epithelial ovarian cancer. The aim of this study was to determine the incidence of thoracic findings on routine MDCT surveillance imaging in patients with ovarian carcinoma.

MATERIALS AND METHODS

Retrospective evaluation of 100 MDCT studies of patients with a diagnosis of epithelial ovarian cancer was performed at a university teaching hospital. The cross-sectional studies were reviewed by a consultant radiologist with subspeciality training in cross-sectional imaging.

RESULTS

Intrathoracic findings were identified in 35% of patients. Pleural effusions were identified in 40%, pulmonary nodules in 37%, mediastinal adenopathy in 17%, and thyroid nodules in 6% of patients. Thirty-five (35%) patients were found to have thoracic findings on computed tomography. Pleural effusions developed in 14 (40%) of these patients. Small lung nodules (<1 cm) were present in 13 (37%) patients. Mediastinal lymphadenopathy was seen in 6 (17%) patients. Two patients (6%) had thyroid nodules of unknown significance. Pleural effusions and small lung nodules were present at a similar level to that of the general population.

CONCLUSIONS

This retrospective study supports the imaging recommendations of the European Society of Urogenital Radiology that MDCT protocols for the initial staging and evaluation of recurrent disease in epithelial ovarian carcinoma require only inclusion of the lung bases to the inguinal region reducing exposure to ionizing radiation, alleviating patient anxiety, and offering a cost-benefit to hospitals.

Virtual unenhanced phase with spectral dual-energy CT: Is it an alternative to conventional true unenhanced phase for abdominal tissues?

PURPOSE

To compare attenuation measurements and image quality of virtual unenhanced phase (VUP) images with those of conventional true unenhanced phase (TUP) images on spectral dual energy computed tomography (DECT) with dual layer detector on abdominal tissues and to assess potential reduction in radiation dose.

MATERIAL AND METHOD

A total of 295 patients (185 men, 110 women; mean age 61±17.6 [SD] years [range: 17-95 years]) who had undergone abdominal or thoraco-abdominal CT with pre- and post-contrast imaging (portal phase) with spectral DECT with dual layer detector were retrospectively analyzed. VUP images based on portal-venous phase DECT acquisition were generated. Regions of interest were defined in abdominal tissues (liver, spleen, kidney, muscle and fat) by two independent readers. Inter-technique agreement (VUP images vs. TUP images) on attenuation measurements was assessed. Signal-to noise ratio (SNR) and image quality of TUP and VUP images were compared. The radiation dose delivered to patients was compared with the radiation dose of protocols without TUP images.

RESULTS

A total of 9880 ROIs were drawn in the abdominal tissues. The difference in mean attenuation values between TUP and VUP images was less than 15 HU in 98.3% and less than 10 HU in 92.3% of all measurements. VUP images overestimated attenuation in fat comparatively to TUP images. Image quality was evaluated as good or excellent in 77% (37/48) of TUP images and 54% (26/48) of VUP images. Using VUP images instead of TUP images could decrease the radiation dose by 32%.

CONCLUSION

VUP images demonstrate good agreement with TUP images in different abdominals tissues and can be obtained with similar image quality as TUP. VUP images appear as an alternative to TUP images, resulting in reduction of radiation dose delivered to the patient.

Intensive Imaging Surveillance of Survivors of Breast Cancer May Increase Risk of Radiation-induced Malignancy

BACKGROUND

Current clinical guidelines recommend mammography as the only imaging method for surveillance in asymptomatic survivors of early breast cancer (EBC). However, non-recommended tests are commonly used. We estimated the imaging radiation-induced malignancies (IRIM) risks in survivors of EBC undergoing different imaging surveillance models.

MATERIALS AND METHODS

We built 5 theoretical models of imaging surveillance, from annual mammography only (model 1) to increasingly imaging-intensive approaches, including computed tomography (CT) scan, positron emission tomography-CT, bone scan, and multigated acquisition scan (models 2 through 5). Using the National Cancer Institute's Radiation Risk Assessment Tool, we compared the excess lifetime attributable cancer risk (LAR) for hypothetical survivors of EBC starting surveillance at the ages of 30, 60, or 75 years and ending at 81 years.

RESULTS

For all age groups analyzed, there is a statistically significant increase in LAR when comparing model 1 with more intensive models. As an example, in a patient beginning surveillance at the age of 60 years, there is a 28.5-fold increase in the IRIM risk when comparing mammography only versus a schedule with mammography plus CT scan of chest-abdomen and bone scan. We found no differences when comparing models 2 through 5. LAR is higher when surveillance starts at a younger age, although the age effect was only statistically significant in model 1.

CONCLUSION

Non-recommended imaging during EBC surveillance can be associated with a significant increase in LAR. In addition to the lack of survival benefit, additional tests may have significant IRIM risks and should be avoided.

Projected lifetime cancer risks from occupational radiation exposure among diagnostic medical radiation workers in South Korea

BACKGROUND

Timely assessment of cancer risk from current radiation exposure among medical radiation workers can contribute to the development of strategies to prevent excessive occupational radiation exposure. The purpose of the present study is to estimate the lifetime risk of cancers induced by occupational radiation exposure among medical radiation workers.

METHODS

Using estimated organ doses and the RadRAT risk assessment tool, the lifetime cancer risk was estimated among medical radiation workers who were enrolled in the Korean National Dose Registry from 1996 to 2011. Median doses were used for estimating the risk because of the skewed distribution of radiation doses. Realistic representative exposure scenarios in the study population based on sex, job start year, and occupational group were created for calculating the lifetime attributable risk (LAR) and lifetime fractional risk (LFR).

RESULTS

The mean estimated lifetime cancer risk from occupational radiation exposure varied significantly by sex and occupational group. The highest LAR was observed in male and female radiologic technologists who started work in 1991 (264.4/100,000 and 391.2/100,000, respectively). Female workers had a higher risk of radiation-related excess cancer, although they were exposed to lower radiation doses than male workers. The higher LAR among women was attributable primarily to excess breast and thyroid cancer risks. LARs among men were higher than women in most other cancer sites. With respect to organ sites, LAR of colon cancer (44.3/100,000) was the highest in male radiologic technologists, whereas LAR of thyroid cancer (222.0/100,000) was the highest in female radiologic technologists among workers who started radiologic practice in 1991. Thyroid and bladder cancers had the highest LFR among radiologic technologists.

CONCLUSIONS

Our findings provide an assessment of the potential cancer risk from occupational radiation exposure among medical radiation workers, based on current knowledge about radiation risk. Although the radiation-related risk was small in most cases, it varied widely by sex and occupational group, and the risk would be underestimated due to the use of median, rather than mean, doses. Therefore, careful monitoring is necessary to optimize radiation doses and protect medical radiation workers from potential health risks, particularly female radiologic technologists.