ANALYSIS OF OPTIC CHIASM RADIATION DOSE FOR NASOPHARYNGEAL CANCER (NPC) PATIENTS WITH INTENSITY MODULATED RADIOTHERAPY (IMRT) TECHNIQUE BASED ON DOSE VOLUME HISTOGRAM (DVH) GRAPH FOR THERAPY USING LINAC

Motivation/Background: Radiotherapy is the standard therapy that uses ionizing rays for the treatment of malignancies. However, in some cases of nasopharyngeal cancer (NPC), the location of the tumor pushes to the base of the brain until it reaches the optic chiasma. The optic chiasm as part of a healthy organ around the target irradiation becomes a dangerous organ or a risk organ (OAR) so it needs to be considered in the case of radiation therapy for NPC. This study aims to consider dosing in patients to fulfill radiation protection. IMRT technique is believed to maximize the success of therapy in cases of NPC. Method: In this study, secondary data was used by looking at the DVH (Dose Volume Histogram) graph from the results of radiation planning for NPC patients using the IMRT (Intensity Modulated Radiotherapy) technique. Data analysis was carried out on PTV and OAR dose values NPC patients at Ken Saras Hospital on the DVH chart that was adjusted to the wishes used, namely The International Commission on Radiation Units and Measurements (ICRU) Report 62 (1999) for PTV doses and QUANTEC for doses OAR. Results: The results of the analysis showed that of the 15 patient data analyzed, there were 10 patients with a percentage of 66.67% who received radiation doses that were in accordance with the ICRU Report 62 reference (95-107%) while patients who received less than optimal doses (< 95%) there were 5 people with a percentage of 33.33% while the maximum dose received by OAR for the optic chiasm in NPC patients who had complied with QUANTEC rules overall there were 7 patients with a percentage of 46.67% while there were 8 patients who received doses exceeding the QUANTEC limit with a percentage of 53 ,33% risk of receiving radiation side effects by 7-20%.. Conclusions: there were patients who received doses exceeding QUANTEC as much as 53.33%