SPECT/CT: HOW Much Radiation Dose CT Constitute
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A study was conducted on Symbia SPECT/CT T16 to find the radiation dose to the patient from CT and radio tracers.
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SPECT/CT: HOW Much Radiation Dose CT Constitute
- 1. Hybrid Imaging Shahid Younas M.Sc. Medical Physics (Surrey) UK M.Sc. Applied Physics (UET) Lahore Sr. Medical Physicist & RPA Picture courtesy of: Shahnawaz Shahid, Shazanan Shahid, Shazeen Shahid Department of Nuclear Medicine SKMCH&RC, LAHORE SPECT CT: HOW MUCH RADIATION DOSE Thanks to:
- 3. Material and Methodology Reference 1: The Mnaual of SYMBIA SPECT/CT:SIEMENS, GERMANY. We analyzed 151 patients from a dual-headed SIEMENS’ SYMBIA T-16 unit with an integrated 16-slice CT scanner. This CT portion of this system has, variable tube current (20– 345 mA), slice thickness of 0.6–10 mm, rotational speed of 0.6–1.5 secs. tube voltage up to 130 kVp.
- 4. Effective Dose Reference 2: E. J. Hall and A. J. Giaccia, Radiolobiology for the Radiologist, Lippincott Williams & Wilkins, Philadelphia, Pa, USA, 6th edition, 2005. The quantity Effective Dose can have practical value for comparing the relative doses related to the stochastic effects and comparing different technologies [2]
- 5. Radiation Dose Conversation Mechanism Reference 3: The Essential Physics of Medical Imaging, Third Edition Third, North American Edition Edition by Jerrold T. Bushberg (Author), J. Anthony Seibert , Edwin M. Leidholdt Jr. , John M. Boone Game of 10-10 sec [3]
- 6. Risk Factor Reference 2: E. J. Hall and A. J. Giaccia, Radiolobiology for the Radiologist, Lippincott Williams & Wilkins, Philadelphia, Pa, USA, 6th edition, 2005. According to ICRP, the risk of developing a lethal cancer is approximately 4% per Sievert. The lifetime risk for cancer has been shown to be greater in the younger patients.
- 7. Dose Conversion Reference 4: (AAPM, 2008), Report, Shope et al, 1981 CT dose index Volume (CTDIv) and Dose Length Product (DLP) are two basic quantities used to estimate the average absorbed dose in the organs and tissues based for the helical (volumetric) CT scanners.[4]
- 8. Dose Length Product & CT Dose Indexvolume
- 9. CT Dose Calculations Reference 5: International Commission on Radiological Protection (ICRP) Publication 53 and 80. 𝐷𝑜𝑠𝑒 𝐿𝑒𝑛𝑔𝑡ℎ 𝑃𝑟𝑜𝑑𝑢𝑐𝑡 = 𝐶𝑇𝐷𝐼𝑣 ∗ 𝑃𝑎𝑡𝑖𝑒𝑛𝑡 𝐿𝑒𝑛𝑔𝑡ℎ 𝐷𝐿𝑃 = 𝐶𝑇𝐷𝐼𝑣 ∗ 𝐿 DLP is measured in mGy*cm
- 10. CT Dose Calculations Reference 5: International Commission on Radiological Protection (ICRP) Publication 53 and 80. 𝐸𝑓𝑓𝑒𝑐𝑡𝑖𝑣𝑒 𝐷𝑜𝑠𝑒 = 𝐷𝑜𝑠𝑒 𝐿𝑒𝑛𝑔𝑡ℎ 𝑃𝑟𝑜𝑑𝑢𝑐𝑡 . 𝑐𝑜𝑛𝑣𝑒𝑟𝑠𝑖𝑜𝑛 𝐹𝑎𝑐𝑡𝑜𝑟 Effective dose is measured in mSv 𝐸 𝑒𝑓𝑓 = 𝐷𝐿𝑃 . 𝑘
- 11. CT Dose Conversion Factors Reference 5: International Commission on Radiological Protection (ICRP) Publication 53 and 80. Reference 6: Doses to Computed Tomography Examinations in the UK – 2003 Review (Table 3) Region of Body Effective Dose per DLP for adult (mSv per mGy.cm) Head & Neck 0.0031 Head 0.0021 Neck 0.0059 Chest 0.014 Abdomen & Pelvis 0.015 Trunk 0.015
- 12. Nuclear Dose Conversion Reference 7 : “Radiation dose to patients from radiopharmaceuticals ICRP Publication 53,” Annals of the ICRP, vol. 18, no. 1–4, 1987. J. Valentin, “Radiation dose to patients from radiopharmaceuticals (Addendum 2 to ICRP publication 53) ICRP publication 80 approved by the commission in September 1997,” Annals of the ICRP, vol. 28, no. 3, pp. 1–126, 1998. Effective dose per unit administered activity” conversion factors listed in the International Commission on Radiological Protection (ICRP) Publication 53 and 80.
- 13. Results Reference 8: F. A. Mettler, W. Huda, T. T. Yoshizumi, and M. Mahesh, “Effective doses in radiology and diagnostic nuclear medicine: a catalog,” Radiology, vol. 248, no. 1, pp. 254–263, 2008. Primary Scan 99mTc-MDP Bone Mean: 868 MBq Average DLP: 46.98 % increase in patient dose due to CT Component CT Dose from SPECT 8Diagnostic CT Dose NM Dose NM + CT Dose % increase w.r.t. RP Dose Chest 0.65 7 4.95 5.6 13.13 Abd & Pelvis 0.87 8-14 5.75 16.17 Trunk 10.45 8-12 15.4 211.11 Neck 0.29 3 5.24 5.85 All doses are in milli-Sievert (mSv)
- 14. Results Primary Scan 99mTc-MIBI Parathyroid Mean: 842.5 MBq Average DLP: 135 % increase in patient dose due to CT Component CT Dose from SPECT 8Diagnostic CT Dose NM Dose NM + CT Dose % increase w.r.t. RP Dose Neck 0.8 3 7.58 8.37 10.55 All doses are in milli-Sievert (mSv)
- 15. Results Primary Scan 99mTc-Thyroid Mean: 165.5 MBq Average DLP: 63.5 % increase in patient dose due to CT Component CT Dose from SPECT 8Diagnostic CT Dose NM Dose SPECT + CT Dose % increase w.r.t. NM Dose CT Region: Neck 0.01 3 2.15 2.16 0.46 All doses are in milli-Sievert (mSv)
- 16. Results Primary Scan 131I-Post-therapy Mean: 2790 MBq Average DLP: 63.5 % increase in patient dose due to CT Component CT Dose from SPECT 8Diagnostic CT Dose NM Dose NM + CT Dose % increase w.r.t. RP Dose Neck 0.43 3 2790 2790.43 0.015 All doses are in milli-Sievert (mSv)
- 17. Secret to low dose As images are not meant to be diagnostic in the SPECT mounted CT consequently Effective Dose would be expected to be lower than typical diagnostic values – This is the secret (lower mA).
- 18. Cancer Risk from SPECT In our calculations the increased risk of cancer by additional exposure of low does CT ranges from 0.01% to 0.04 %.
- 19. Cancer Risk from SPECT Although imparted CT dose is quite lower however this lower dose can be balanced by decreasing the injected radiotracer dose at the cost of increased image time.
- 20. Thanks