Open AccessStatic versus dynamic intensity-modulated radiotherapy: Profile of integral dose in carcinoma of the nasopharynx
Author(s) -
K S Jothybasu,
Amit Bahl,
V. Subramani,
G.K. Rath,
Daya Nand Sharma,
Pramod Kumar Julka
Publication year - 2009
Publication title -
journal of medical physics/journal of medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.292
H-Index - 24
eISSN - 1998-3913
pISSN - 0971-6203
DOI - 10.4103/0971-6203.51932
Subject(s) - multileaf collimator , nuclear medicine , medicine , significant difference , radiation therapy , mean difference , radiology , radiation treatment planning , confidence interval
This study is aimed to evaluate the impact of static and dynamic intensity modulated radiotherapy (IMRT) delivery techniques planned with Eclipse TPS on the integral dose to the healthy normal tissue surrounding the tumor-bearing area and to the volume receiving doses < 5 Gy in patients with carcinoma nasopharynx treated with Simultaneous Integrated Boost IMRT (SIB-IMRT). Ten patients with carcinoma nasopharynx were chosen for this dosimetric study. IMRT plans were generated with 6X using dynamic multileaf collimator (DMLC) and static multileaf collimator (SMLC) with 5, 10 and 15 intensity levels (L). Integral dose, volume receiving 5 Gy, number of monitor units (MU) is compared against DMLC. The mean difference in the MU delivered per fraction between 5, 10 and 15 L SMLC and DMLC was -13.25% (P < 0.001, with paired t test), -11.82% (P < 0.001) and -10.81% (P < 0.001), respectively. The mean difference in the integral dose with 5, 10 and 15 L compared to DMLC was -2.96% (P < 0.001), -2.67% (P = 0.016) and -0.39% (P = 0.430), respectively. However, the difference in low-dose volume (V5Gy) was statistically insignificant with mean difference of 0.60% (P = 0.23), 1.18% (P = 0.017) and 1.70% (P = 0.078), respectively for 5, 10 and 15 L compared to DMLC. Our results show that while choosing the IMRT delivery technique using conventional MLC the concerns about integral dose and volume receiving very low doses such as 5 Gy can be ignored.