Objectives of present study are a) to compare the planning and delivery aspects of five different techniques, planned by a) forward, inverse planning and electronic tissue compensation methods; and b) to evaluate and verify the accuracy of the planning system using phantom to estimate the skin dose for target and contraletral breast from five techniques. In-vivo skin dosimetry is planned with TL detectors. Five different radiotherapy techniques for treatment of carcinoma breast were studied using archived computed tomography (CT) scans of 25 breast conserving surgery patients (leftsided whole breast), planned for 50 Gy in 25 fractions. Linear accelerator (Clinac 2300 CD) photon beams were used and thermoluminescent detectors (TLD) [LiF:Mg, Ti] estimated dose on humanoid phantom. Dose coverage (95%) (to PTV) and hot spot (105%) covering volumes did not show differences (p > 0.05) in all 5 plans; Electronic compensator plans are better than others. IP-IMRT plan showed the worst Homogeneity Index (HI) (p < 0.05) and needed more monitor units (MU) (437 ± 84), than other techniques. The mean doses to ipsi-lateral lung, contra-lateral breast (CB) and heart OARs (V 20 ipsi.lung , CB, V 30 Heart ,) are the least with IP-IMRT. IP-IMRT and E-COMP plans resulted in significantly lower mean dose to the superficial skin (D mean , V 40skin , 45skin , 50skin) (p < 0.05). The mean doses estimated by TLDs were comparable or higher in 3D-CRT (D) and 3D-CRT (P) for PTV and CB; less for IP-IMRT and E-COMP compared to TPS. IP-IMRT and E-COMP techniques provide good target coverage, low doses to OARs, the least doses to the skin of PTV and contra-lateral breast and less hot spots; E-COMP showed better homogeneity, fewer MUs, and the least dose in non-target zones.

For radiotherapy of para-aortic and abdominal regions in male patients, gonads are to be protected to receive less than 2% of the prescribed dose. A testicular shield was fabricated for abdominal radiotherapy with 15 MV X-rays ((Clinac 2300 CD, Varian AG) with low melting point alloy (Cerroband). The dimensions of the testicular shield were 6.5 cm diameter and 3.5 cm depth with 1.5 cm wall thickness. During treatment, this shield was held in position by a rectangular sponge and Styrofoam support. Phantom measurement was carried out with a humanoid phantom and a 0.6 cc ion chamber. The mean energy of the scattered photon was calculated for single scattering at selected distances from the beam edge and with different field dimensions. One patient received radiotherapy with an inverted Y field and gonad doses were estimated using calibrated thermo-luminescent detector (TLD) chips. Measured doses with the ion chamber were 7.1 and 3.5% of the mid-plane doses without a shield at 3 and 7.5 cm off-field respectively. These values decreased to 4.6 and 1.7% with the bottom shield alone, and to 1.7 and 0.8% with both bottom and top shields covering the ion chamber. The measured doses at the gonads during the patient’s treatment were 0.5–0.92% for the AP field (0.74 ± 0.17%, n = 5) and 0.5–1.2% for the PA field (0.88 ± 0.24%, n = 5). The dose received by the testis for the full course of treatment was 32 cGy (0.8%) for a total mid-plane dose of 40 Gy. The first-scatter energy estimated at the gonads is around 1.14 MeV for a primary beam of 15 MV for a long axis dimension of 37 cm of primary field. During the patient’s treatment, the estimated absorbed doses at the gonads were comparable with reported values in similar treatments. The testicular shield reported in this study is of light weight and could be used conveniently in treatments of abdominal fields.

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The measured dose in water at reference point in phantom is a primary parameter for planning the treatment monitor units (MU); both in conventional and intensity modulated/image guided treatments. Traceability of dose accuracy therefore still depends mainly on the calibration factor of the ion chamber/dosimeter provided by the accredited Secondary Standard Dosimetry Laboratories (SSDLs), under International Atomic Energy Agency (IAEA) network of laboratories. The data related to Nd,water calibrations, thermoluminescent dosimetry (TLD) postal dose validation, inter-comparison of different dosimeter/electrometers, and validity of Nd,water calibrations obtained from different calibration laboratories were analyzed to find out the extent of accuracy achievable. Nd,w factors in Gray/Coulomb calibrated at IBA, GmBH, Germany showed a mean variation of about 0.2% increase per year in three Farmer chambers, in three subsequent calibrations. Another ion chamber calibrated in different accredited laboratory (PTW, Germany) showed consistent Nd,w for 9 years period. The Strontium-90 beta check source response indicated long-term stability of the ion chambers within 1% for three chambers. Results of IAEA postal TL “dose intercomparison” for three photon beams, 6 MV (two) and 15 MV (one), agreed well within our reported doses, with mean deviation of 0.03% (SD 0.87%) (n = 9). All the chamber/electrometer calibrated by a single SSDL realized absorbed doses in water within 0.13% standard deviations. However, about 1-2% differences in absorbed dose estimates observed when dosimeters calibrated from different calibration laboratories are compared in solid phantoms. Our data therefore imply that the dosimetry level maintained for clinical use of linear accelerator photon beams are within recommended levels of accuracy, and uncertainties are within reported values.