Quantitative assessment of diagnostic radiation doses in adult blunt trauma patients.

STUDY OBJECTIVE: Many emergency departments and trauma centers utilize extensive radiologic studies during the assessment of trauma patients. A point of concern arises about the possible biological effects of these cumulative radiation doses. The objective of this study is to determine the amount of ionizing radiation received by adult blunt trauma patients at a Level I trauma center during the first 24 hours of their care. METHODS: This nonconcurrent case series reviewed the first 100 consecutive adult blunt trauma patients who presented to a Level I trauma center in 2006. All patients met hospital standards for the less acute major triage criteria. Individual radiation dose reports calculated by the computed tomography (CT) scanner were used to determine the radiation doses from each CT procedure. Standardized tables were used to determine radiation dose for plain radiographs. The median effective dose of radiation (millisieverts) was calculated for the first 24 hours of hospitalization. RESULTS: A total of 100 eligible patients presented between January 1, 2006, and March 20, 2006. Eighty-six patients had complete radiologic records available. The median age was 32 years, with an intraquartile range of 23 to 46 years; the median Injury Severity Score was 14, with an intraquartile range of 9 to 29; and the median number of CT scans was 3, with an intraquartile range of 3 to 4. The median effective total dose of ionized radiation was 40.2 mSv, with an intraquartile range of 30.5 to 47.2 mSv. A dose of 40.2 mSv is the equivalent of approximately 1,005 chest radiographs. CONCLUSION: Trauma patients meeting the less acute major triage criteria are exposed to clinically important radiation doses from diagnostic radiographic imaging during the first 24 hours of their care.

Evaluation of the quantitative capability of a high-resolution positron emission tomography scanner for small animal imaging.

OBJECTIVE: The quantitative capability of a positron emission tomography scanner for small animal imaging was evaluated in this study. METHODS: The microPET P4 (Concorde Microsystems, Knoxville, TN) scanner's capability for dynamic imaging and corrections for radioactive decay, dead time, and attenuation were evaluated. Rat brain and heart studies with and without attenuation correction were compared. A calibration approach to convert the data to nanocuries per milliliter was implemented. Calibration factors were determined using calibration phantoms of 2 sizes with and without attenuation correction. Quantitation was validated using the MiniPhantom (Data Spectrum, Chapel Hill, NC) with hot features (5:1 ratio) of different sizes (4, 6.4, 8, 13, and 16 mm). RESULTS: The microPET P4 scanner's ability to acquire dynamic studies and to correct for decay, dead time, and attenuation was demonstrated. The microPET P4 scanner provided accurate quantitation to within 6% for features larger than 10 mm. Sixty percent of object contrast was retained for features as small as 4 mm. CONCLUSIONS: The microPET P4 scanner can provide accurate quantitation.

Positron emission mammography: initial clinical results.

BACKGROUND: Evaluation of high-risk mammograms represents an enormous clinical challenge. Functional breast imaging coupled with mammography (positron emission mammography [PEM]) could improve imaging of such lesions. A prospective study was performed using PEM in women scheduled for stereotactic breast biopsy. METHODS: Patients were recruited from the surgical clinic. Patients were injected with 10 mCi of 2-[18F] fluorodeoxyglucose. One hour later, patients were positioned on the stereotactic biopsy table, imaged with a PEM scanner, and a stereotactic biopsy was performed. Imaging was reviewed and compared with pathologic results. RESULTS: There were 18 lesions in 16 patients. PEM images were analyzed by drawing a region of interest at the biopsy site and comparing the count density in the region of interest with the background. A lesion-to-background ratio >2.5 appeared to be a robust indicator of malignancy and yielded a sensitivity of 86%, specificity of 91%, and overall diagnostic accuracy of 89%. No adverse events were associated with the PEM imaging. CONCLUSIONS: The data show that PEM is safe, feasible, and has an encouraging accuracy rate in this initial experience. Lesion-to-background ratios >2.5 were found to be a useful threshold value for identifying positive (malignant) results. This study supports the further development of PEM.