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Radiation Doses in CT Procedures Using Size Specific Dose Estimation

N chaudhary1 , B Rana2*, N Singh3 , S Kumar4 , A Shukla5 ,I Sandhu6 (1) M D Oswal Cancer Treatment and Research Foundation, Ludhina, Punjab, (2)Department of Radiodiagnosis,PGIMER, Chandigarh,(3) P T U, Jalandhar, Punjab, (4) S D College, Chandigarh, Chandigarh, (5) R. N. T. M. College Udaipur, Udaipur, Rajastan,(6) Chitkar University, Patiala, Punjab


(Sunday, 7/29/2018) 3:00 PM - 6:00 PM

Room: Exhibit Hall

Purpose: The purpose of the study is to estimate actual patient dose undergoing CT imaging using Size specific doses estimation (SSDE) from phantom measured computer tomography dose index (CTDI) and taking into account of patients anatomical dimensions to correlate with actual patient dose undergoing CT imaging.

Methods: The study was conducted on Light speed 16, helical CT scanner, General Electric CT scanner for imaging and dosimetry study. The dosimetry was performed with DCT-10, pencil ionisation chamber having active length 100 mm, IBA dosimetry, GmbH, Germany. Measurement of CTDI was performed on CT phantoms using body phantom (32cm), head phantom (16cm) and 10cm phantom to simulate paediatric configuration. To calculate the effective diameter of the patient, AP and Lateral dimensions of the patient were measured form CT images assuming that the patient has a circular cross section. Patient anterior posterior (AP) separation and lateral separation were measured on transverse CT images at every three cm interval. Water equivalent effective diameter of patient was calculated as recommended in AAPM report 204.

Results: All plotted data points were combined and used in the computer fit assuming logarithmic relationship between the normalised dose coefficient and effective diameter. The normalised dose coefficient with respect to 32 cm, 16 cm and 10 cm diameter phantoms were deduced. The SSDE was calculated form measured CTDI and measured patient anatomical dimension for forty patients of head, chest, pelvis and abdomen examinations.

Conclusion: The use of SSDE helps to convert CTDI data into patient size specific radiation dose value that account for patient anatomical dimensions to correlate with actual patient dose in CT. Therefore, we strongly recommend the use of SSDE for normalizing CTDI according to patient size.


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