Dosimetric Comparison of Amorphous Silicon EPID and 2D Array Detector for Pre-Treatment Verification of Intensity Modulated Radiation Therapy

Purpose: To study the dosimetric characteristics of amorphous silicon Electronic Portal Imaging Device EPID and 2D array detector for dose verification of radiotherapy treatment plans, and the quality assurance QA testing of IMRT was investigated. Materials and methods: All measurements were done with Varian IX linear accelerator, aSi-1000 EPID and 2D array detector. The dose linearity, reproducibility, output factors, dose rate, SDD and response with slap phantom thickness have been measured and compared against those measured by ion chamber. Results: The characteristics of EPID and 2D array: the response of EPID agreed with 2D array and ion chamber 0.6cc. EPID and 2D array showed short-term output reproducibility with SD = 0.1%. The dose rates of 2D array SD = ±0.7%, EPID = ±0.4% compared with a 0.6 cc SD = ±0.5%. Output factor measurements for the central chamber of the EPID and 2D array showed no considerable deviation from ion chamber measurements. Measurement of beam profiles with the EPID and 2D array matched very well with the ion chamber measurements in the water phantom. The EPID is more sensitive to lower energy photons by increasing solid water phantom thickness. The mean and standard deviation passing rates (γ%≤1) for film, 2D array and EPID for 30 IMRT fields of five patients were 95.93 ± 0.96%, 99.05 ± 0.24%, and 99.37 ± 0.12%, respectively. Conclusion: The study shows that EPID and 2D array are a reliable and accurate dosimeter and a useful tool for quality assurance. We found that the EPID was more accurate compared with both 2D array and ion chamber. The gamma criterion of 3%/3 mm is the most suitable criteria for IMRT plans of QA.

Intersphincteric Resection Is the Optimal Procedure for Very Low Rectal Cancer: Techniques, Morbidity, Oncologic and Functional Outcomes

Background: The intersphincteric resection the most extreme form of a sphincter-preserving alternative for the abdominoperineal resection. Aim of the Work: We investigated oncological, functional outcomes and morbidity after ISR. Methods: This retrospective study included 164 patients who underwent ISR with between 2010 and 2015, Male 56.1%, Female 43.9%, with a median age was 54.5 years, Median follow-up time was of 48 months, Average surgical time was 230 min, Median blood loss was 700 mL and median hospital stay was nine days. Mean tumour size was34 mm. The surgical procedure through a laparotomy (72.6%), laparoscopically (27.4%). Neoadjuvant radiotherapy 89.6% {long-course radiotherapy 74.4%, short-course radiotherapy 15.2%}, neoadjuvant chemotherapy 28.7% and adjuvant chemotherapy 70.1%. Colonic J-pouch 16.5%, Transverse coloplasty 15.9%, a side-to-end anastomosis 26.8% and straight coloanal anastomosis 40.9%. Partial-ISR 36.6%, subtotal-ISR 37.2%, total-ISR 26.2%, diverting ileostomy 6.7%. Results: Operative mortality 1.2%, morbidity 14.6% (anastomotic leakage 3.7%, anastomotic stenosis 1.8%, a recto-vaginal fistula 2.4% bowel obstruction 3%, surgical site infection 3%. Respiratory tract infection 1.2%, local 7.9%, distant recurrence 15.2%, 5-year overall 79.8%, disease-free survival 75.8%, R0 resection 95.1%. Pathologic complete response 11%. Circumferential margin involvement 2.4%. Median number of lymph nodes 17. Mean distal margin20 mm, after 12 months Median Wexner score 6. Incontinence for (flatus 11%, liquid 4.9%, solid 4.3%). Median bowel motions in a 24-h were 3. Faecal urgency 17.7%. Stool fragmentation 18.9%. Difficult evacuation 17.7%, lifestyle alteration 14.6%. Difficulty Feces/flatus discrimination 43.3%. Nocturnal soiling in 17.1%. Daytime soiling 11%. Pad wearing 23.8%. Anti-diarrhoea medication loperamide 14%. Conclusion: ISR is a feasible surgical procedure for low rectal cancer. Oncologic and functional, outcomes after are acceptable.