Optimization of dose distribution with multi-leaf collimator using field-in-field technique for radiotherapy of Hodgkin s lymphoma

Abstract--Purpose: A prospective study was undertaken to evaluate radiotherapy techniques for Hodgkin's lymphoma, particularly focusing on dose homogeneity in the target and normal tissue sparing capability of manual forward planning methods using MLC- optimized field-in-field technique. Methods and materials: 10 patients with Hodgkin's lymphoma were evaluated. Two plans were imulated for each patient using 6 MV X-rays: a conventional multi-leaf (MLC) parallel-opposed (AP-PA) plan , and the same plan with additional MLC subfields (field-in-field technique, FIF). For plan comparison, the minimum, the maximum and the mean dose in the PTV and in critical organs (lungs, spinal cord, heart and thyroid) were evaluated. The Inhomogeneity Coefficient (IC), the normal tissue complication probability (NTCP) and toxicity parameters were also determined. Results: the PTV coverage resulted significantly improved with the FIF technique compared to the conventional one (mean ICFIF =0.31 vs mean ICap-pa = 0.40 , p <0.05). Basically, normal tissue toxicities were significantly reduced. Conclusion: We have shown that the use of FIF technique in Hodgkin radiotherapy effectively improves PTV conformity while saving critical organs.