Investigation of Dose Delivery
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2011-01-24
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Journal of Thai Society of Therapeutic Radiology and Oncology - วารสารมะเร็งวิวัฒน์
Abstract
Introduction: fi cantly increasethe dose to the patient’s normal tissues.Objective: fi xed technical setting for head and neck and pelvic scans.Materials and Methods: filters for head and pelvic area, respectively. The technical setting of 100 kV, 20 mA and 20 ms for headregion and 125 kV, 80 mA and 13 ms for pelvic were used. TLDs-100H were used for Rando phantomskin dose measurement at the point of interest for head and neck and pelvic area. Organ doses werealso measured inside Rando phantom.Results: Conclusions: The use of CBCT for treatment verifi cation provided a high dose to the patient. It isimportant to consider about the optimal protocol and amount of times to verify the patient position tokeep additional doses as low as reasonably practicable.For head and neck CBCT, The lateral surface dose was higher than anterior ( include criticalorgan such as eyes, lip, chin and neck). The peripheral organ dose at Lt. lat area dose (0.28 cGy) wasless than central dose ( 0.4 cGy), but Right lateral area such as temporal and parotid was about thesame as the central dose (brainstem). For pelvic CBCT, The lateral surface dose was not symmetrical,with Left lateral side being ~ 20% higher than Rt. Lat. The anterior (AP) surface dose was higher thanlateral especially at the pubic area (5.2 cGy). The dose at bladder, rectum and bowl were about thesame as the central dose (~ 3 cGy). The highest dose was in the left hip joint region up to 7 cGy.CBCT scans were acquired in full-fan and half-fan mode with full and half bowtieTo investigate the skin and organ dose from the CBCT system from the clinical protocolsetup, withThe Varian 23EX Clinac at Siriraj Hospital is a linear accelerator with integrated On-BoardImager (OBI) system capable of producing cone beam computed tomography (CBCT) images of thepatient in the treatment position. The increased use of CBCT for patient setup may signi
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Journal of Thai Society of Therapeutic Radiology and Oncology - วารสารมะเร็งวิวัฒน์; Vol.17 No.1 January-June 2011; 5