Dosimetric influence of filtered and flattening filter free photon beam on rapid arc (RA) radiotherapy planning in case of cervix carcinoma

AimTo investigate the dosimetric influence of filtered and flattening filter free (FFF) photon beam of 6 and 10[[ce:hsp sp="0.25"/]]MV energies on cervix RA radiotherapy planning and to find possibilities to develop the clinically acceptable RA plans with FFFB photon beam and explore their potential benefits to cervix cancer patients.BackgroundFFF photon beams enhances the treatment delivery by increased dose rate which results in shorter treatment time, this shorter treatment time reduces intrafraction motion and enhance comfort to the patients.Materials and methodsRA plans were generated for filtered and flattening filter free photon beams of 6 and 10[[ce:hsp sp="0.25"/]]MV energies using same dose–volumes constraints. RA plans were generated to deliver a dose of 50.4[[ce:hsp sp="0.25"/]]Gy in 28 fractions, for a cohort of eleven patients reported with cervix carcinoma. RA plans were evaluated in terms of PTV coverage, dose to OAR's, CI, HI, total no. of monitor units (MUs) and NTID and low dose volume of normal tissues.ResultsClinically acceptable and similar plans were generated for filtered and flattening filter free photon beams. FFFB delivered slightly higher mean target dose (52.28[[ce:hsp sp="0.25"/]]Gy vs. 52.0[[ce:hsp sp="0.25"/]]Gy, p[[ce:hsp sp="0.25"/]]=[[ce:hsp sp="0.25"/]]0.000 for 6[[ce:hsp sp="0.25"/]]MV and 52.42[[ce:hsp sp="0.25"/]]Gy vs. 52.0[[ce:hsp sp="0.25"/]]Gy, p[[ce:hsp sp="0.25"/]]=[[ce:hsp sp="0.25"/]]0.000 for 10[[ce:hsp sp="0.25"/]]MV) less homogeneous (1.062 vs. 1.052, p[[ce:hsp sp="0.25"/]]=[[ce:hsp sp="0.25"/]]0.000 for 6[[ce:hsp sp="0.25"/]]MV and 1.066 vs. 1.051, p[[ce:hsp sp="0.25"/]]=[[ce:hsp sp="0.25"/]]0.000 for 10[[ce:hsp sp="0.25"/]]MV) and less conformal (1.007 vs. 1.004, p[[ce:hsp sp="0.25"/]]=[[ce:hsp sp="0.25"/]]0.104 for 6[[ce:hsp sp="0.25"/]]MV and 1.012 vs. 1.003, p[[ce:hsp sp="0.25"/]]=[[ce:hsp sp="0.25"/]]0.010 for 10[[ce:hsp sp="0.25"/]]MV) RA plans compared to FB. FFFB delivered more doses to the bladder and rectum, also required more numbers of MUs in comparison to FB.ConclusionsThis study concludes that FB is more beneficial for cervix RA planning in comparison to FFFB, as FB generates more conformal and homogenous rapid arc plans and offers better OAR's sparing

Dosimetric influence of photon beam energy and number of arcs on volumetric modulated arc therapy in carcinoma cervix: A planning study

AimAim of the present study was to compare the dosimetric impact of different photon beam energies and number of arcs in the treatment of carcinoma cervix.BackgroundCarcinoma cervix is a common cancer in women worldwide with a high morbidity rate. Radiotherapy is used to treat such tumours. Volumetric Modulated Arc Therapy (VMAT) is considered superior to other techniques with multiple arcs and energies.Materials and methodsTwenty patients with carcinoma cervix underwent radiotherapy in a prospective observation study conducted at our institute. Volumetric modulated arc plans with 6[[ce:hsp sp="0.25"/]]MV, 10[[ce:hsp sp="0.25"/]]MV and 15[[ce:hsp sp="0.25"/]]MV photon energies using single arc (SA) and dual arc (DA) were generated. Several physical indices for planning target volume (PTV) like V95%, V100%, V110%, D98%, D50%, D2% and total number of MUs were compared. Normal Tissue Integral Dose (NTID) and dose to a shell structure PHY2.5 and PHY5.0 were analyzed.ResultsComparable dose coverage to PTV was observed for all the energies and arcs. CI for DA6MV (1.095) was better than SA6MV (1.127), SA10MV (1.116) and SA15MV (1.116). Evaluated parameters showed significant reduction in OAR doses. Mean bladder dose for DA6MV (41.90[[ce:hsp sp="0.25"/]]Gy) was better than SA6MV (42.48[[ce:hsp sp="0.25"/]]Gy), SA10MV (42.08[[ce:hsp sp="0.25"/]]Gy) and SA15MV (41.93[[ce:hsp sp="0.25"/]]Gy). Similarly, p-value for the mean rectal dose calculated was 0.001 (SA6 vs 15), 0.013 (DA6 vs 10) and 0.003 (DA6 vs 15) and subsequently favoured DA6MV. Difference in NTID was very small.ConclusionsThe study showed no greater advantage of higher energy, and DA VMAT plan with 6[[ce:hsp sp="0.25"/]]MV photon energy was a good choice of treatment for carcinoma cervix as it delivered a highly homogeneous and conformal plan with superior target coverage and better OAR sparing