Kazuya Saeki RT, Presenter: Nothing to Disclose

Takuji Yamagami MD, Abstract Co-Author: Nothing to Disclose

Yutaka Misezaki, Abstract Co-Author: Nothing to Disclose

Shingo Kono RT, Abstract Co-Author: Nothing to Disclose

Minoru Ishifuro, Abstract Co-Author: Nothing to Disclose

Kazuo Awai MD, Abstract Co-Author: Research Grant, Toshiba Corporation Research Grant, Hitachi Ltd Research Grant, Bayer AG Research Consultant, DAIICHI SANKYO Group Research Grant, Eisai Co, Ltd

The dosimetry function of CareMonitor (SIEMENS Co. Bavaria, Germany) calculates the body type from the patient height and weight and measures the radiation dose to various sites based on geometric system changes. It displays the maximum skin entrance dose (MSED) in real time. We investigated the usefulness of MSED measurements.

Using a fixed patient model (height=160 cm, weight=60 kg), we calculated the MSED and entrance dose (ED) based on the dose-area product. We changed the geometry of the angiography system from the base position where the source image distance (SID)=100 cm, field of view (FOV)=20 cm, x-ray collimation=0% (no narrow down). The bed height was at the　interventional radiology reference point, the C-arm angle was right anterior oblique (RAO)=0°, cranial=0°. Geometric angiography changes were: SID=90 - 120 cm, FOV=16-, 20-, and 25 cm, x-ray collimation=0 - 70%, bed height=-10~14 cm, C-arm angle RAO=50º, left anterior oblique (LAO)=50º and 45º, caudal=30º. We performed 5 measurements and compared changes in the average MSED and ED at different SID, FOV, x-ray collimation, and bed height settings. For measurements based on the C-arm angle, we compared the average dose at the each angle.

The average MSED and ED changes were 4.1±0.0 and 4.4±0.0 mGy at SID 90-120 cm, 3.5±0.0 and 3.8±0.0 mGy at FOV 16-, 20-, or 25 cm, 1.0±0.05 and 1.4±0.08 mGy at x-ray collimation 0~70%, and 10.1±0.01 and 1.3±0.05 mGy at a bed height of -10~14 cm, respectively. The bed height had a significant effect but SID, FOV, and x-ray collimation did not. At RAO 30º, MSED and ED changes were 8.2±0.05 and 8.5±0.05 mGy; at LAO 50º they were 17.8±0.05 and 16.5±0.05 mGy, and at LAO 45º and caudal 30º they were 26.8±0.16 and 22.5±0.12 mGy, respectively. As the C-arm angle increased, so did the dose difference.

Even after bed-height and C-arm angle changes, dosimetry was more accurate with CareMonitor than was ED, suggesting that MSED calculations consider shifts in the focus-to-virtual skin surface distance based on geometric angiography system changes.

For dosimetry, CareMonitor considers changes in the focus-to-skin distance and in the point of irradiation due to changes in the X-ray tube geometry.

Saeki, K, Yamagami, T, Misezaki, Y, Kono, S, Ishifuro, M, Awai, K, Usefulness of the Max Entrance Skin Dose Measured with CareMonitor Irrespective of Changes in the Geometry of the Angiography System.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14007827.html