Room: Exhibit Hall | Forum 1
Purpose: To compare patient doses from ventilation perfusion (V/Q) SPECT and CT pulmonary angiography (CTPA) performed on contemporary scanners, and to assess the dose-length product (DLP) method against direct organ dose measurements in a phantom.
Methods: Effective dose (ED) for a V/Q SPECT was calculated using organ doses per unit administered activity of the pharmaceuticals listed in the ICRP Publication 128. In our institution, 185 MBq of â?¹â?¹áµ?Tc-MAA is used for perfusion component and 40 MBq of â?¹â?¹áµ?Tc-Technegas is utilized for ventilation imaging. Organ doses in CT were measured using nanoDot aluminum oxide optically stimulated dosimeters (OSLD) placed within a female adult anthropomorphic phantom model ATOM 702-G. The 56 OSLDs were placed inside 18 radiosensitive organs. Absorbed organ dose was determined as a mean value of the readings from all nanoDots placed in each organ. The phantom was scanned with CTPA protocols on two 128-slice scanners including single- and dual-source CT. The ED was calculated as a sum of absorbed organ doses multiplied by the corresponding tissue weighting factors recommended by the ICRP publication 103. The doses based on the measurements were compared to the estimates obtained using DLP values corrected for the effective diameter of the phantomâ€™s thorax
Results: The V/Q SPECT resulted in ED of 2.64 mSv. The phantom CTPA dose was 7.19 mSv and 3.90 mSv for the single- and dual-source scanner respectively. The DLP method underestimated effective dose even after correction for the phantom size. The difference with the dose based on the measurements was 5.01% and 16.92% for each scanner respectively.
Conclusion: The comparison of radiation dose from two modalities used in our institution for diagnosis of pulmonary embolism suggested V/Q SPECT has a lower dose even compared with contemporary scanners and should receive serious consideration as the first imaging choice, especially for young patients.
Not Applicable / None Entered.