The effect of pitch and collimation on radiation dose in spiral CT

The effect of pitch and collimation on radiation dose in spiral CT 1 first-author 2 1 School of Radiation Medicine and Public Health, Soochow University, Suzhou 215006, China; School of Radiation Medicine and Public Health, Soochow University, Suzhou 215006, China; Department of Physics and Materials Science, City University of Hong Kong, Hong Kong, China Department of Physics and Materials Science, City University of Hong Kong, Hong Kong, China Measurements of radiation dose to patients in spiral computed tomography (CT) were completed for various collimations, table speeds and pitch. A standard CT head dosimetry phantom and thermoluminescent dosimeters (TLD) were used for the measurement. The effect of collimation and pitch on radiation dose was studied. The results indicated that the radiation dose at the given tube current, voltage and rotation speed was inversely proportional to pitch. And the increasing times of dose were as decreasing times of pitch. This regular pattern was tenable for radiation dose at both central holes and peripheral holes of the phantom at pitch = 1, >1 and <1. The collimation had no impact on the radiation dose. The results also indicated that radiation dose at central holes was nearly equal to that at peripheral holes. There was no significant difference between them statistically. The study demonstrates that the pitch in spiral CT scans is the primary parameter and has significant impact on radiation dose. Radiation dose TLD CT dosimetry head phantom Pitch Collimation References Kalender W A , Seissler W , Klotz E et al . Radiology , 1990 , 176 : 181 - 183 Radiology Spokas J J . Med Phys , 1982 , 9 : 228 Med Phys International Electrotechnical Commission : Evaluation and routine testing in medical imaging departments, Constancy tests of X-ray equipment for computed tomography, Publication IEC 1223-2-6 , 1994 Evaluation and routine testing in medical imaging departments, Constancy tests of X-ray equipment for computed tomography, Publication IEC 1223-2-6 Tsang Cheung , Qijun Cheng , Dinghua Feng et al . Phys Med Biol , 2001 , 46 : 813 - 820 Phys Med Biol Hui Hu . Med Phy , 1999 , 26 : 5 - 18 Med Phy McNitt-Gray M F , Cagnon C H . Med Phys , 1999 , 26 : 409 - 414 Med Phys Brink J A , Heiken J P , Balfe D M et al . Radiology , 1992 , 185 : 469 - 474 Radiology R814.42 2004-05-21 2005-06-01 2021-01-19 2005 Nuclear Science and Techniques 03 16