Assessments and Dosimatric Evaluation of Matching Fields Technique in the Treatment Cranio-Spinal Cancers

Abstract

Radiotherapy is one of the main methods of cancer treatment (often with chemotherapy and surgery) and is generally assumed to be 50 to 60% of cancer patients will benefit from radiotherapy, where radiation therapy is done using the Linear accelerator device. medulloblastoma, a primitive tumor growing in the cerebellum, is one of the most sensitive tumors in the childhood brain to radiotherapy. The most common malignant tumor in children is cancerous tumor with an overall infection among children aged 0-19 from 16 to 20 percent of all brain tumors in hospitals. Radiotherapy is an essential means of treating these tumors and, after surgery, radiation therapy has a significant impact, This study was conducted to understand the impact of the possibilities that could occur during the process of radiotherapy through systemic and irregular errors when set-up the patient for treatment on the occurrence of cold spots and hot spots and the risk of dose at both the craniospinal at treatment. Objectives: Aim of The Work To evaluate the dosimetry homogeneity abutting junction between photon-photon fields in treatment cranio-spinal cancers. Methodology: The study included ten of patients with medulloblastoma cancer, where the radiation treatment planning do for the medulloblastoma using two adjacent beams photon-photon and take the possibility of error (0, + 1, + 2,-1,-2 mm) in area between the fields which can Occur during the treatment process and caused of overlap or gap between this beams (hot and cold areas), Statistical analysis was performed on; maximum dose percentage received by the planning target volume (PTV max dose %) and matching beams dose percentage and mean volume of the hot area and the cold area. Results and Discussion: Disclose results of radiotherapy planning technique that two matching beams Photon-Photon, the overlap by 1 mm has been causing significant change in dosage in matching area more increase than the dose prescribed by oncologist this increase up to 10% of the prescribed dose and the volume of this hot area more than 8 cubic cm, with increased fields by 2 mm in the dose has increased by 20% of the dose prescribed. The opposite happens when the fields is reduced to (-1, -2 mm) where we find that dose decrease occurring in the region and there didn’t complete coverage of the area to be treated, causing what is called a gap (the region receives a dose of less than 95%). It reveals the result of adjacent of two beams photon-electron in radiation treatment planning for patients with nasopharynx, that an electron might enable us to reduce the dose to organ at risk (OAR) such as the spinal cord but the overlap between the photon and electron by (1, 2 mm) may cause an increase Hot spot in a dose up to 130% and the volume of hot spot is big relative to the size of the PTV. As to reduce the area by (-1, -2 mm) may result in reduced hot area or may cause a gap or cause a gap with stayed the hot area while because of the use of two adjacent photon and electron