Homogeneity Index (HI) is an objective tool to analyz the uniformity of dose distribution in the target volume. Various formulae have been described in literature for its calculation but there is paucity of data regarding the ideal formula and the factors affecting this index. This study was undertaken to analyze HI in our patients using various formulae and to find out the co-relation between HI and prescribed dose, target volume and target location. A retrospective review of 99 patients was performed. HI was calculated using five different formulae (A-E). The patients were divided in five groups each, based on prescribed dose, target volume and target location and mean HI of each group was analysed to find the co-relation between these factors and HI. When there were multiple target volumes the primary target volume was studied. The statistical calculation was done using SPSS version 16.0. Ninety nine patients were found evaluable with 75 males and 24 females. Ninety five patients were treated with radical intent and four with palliative intent. The sites treated were head and neck (46.4%), Pelvis (17.1%), brain (15.1%), abdomen (12.1%), and thorax (6.1%). The mean prescribed dose was 4304 cGy (centiGray) and the mean target volume was 476.2 cc. The mean value of HI was 1.21, 2.08, 30.13, 21.51 and 1.27 with different formulae. There was considerable agreement between HI calculated using various formulae specially the formulae considering prescribed dose (C, D). On statistical analysis, there was no significant co-relation between the location and volume of target but there was a trend toward better HI with increasing prescribed dose. Future studies with more number of patients can confirm our results.

In modern day radiotherapy, the emphasis on reduction on volume exposed to high radiotherapy doses, improving treatment precision as well as reducing radiation-related normal tissue toxicity has increased, and thus there is greater importance given to accurate position verification and correction before delivering radiotherapy. At present, several techniques that accomplish these goals impeccably have been developed, though all of them have their limitations. There is no single method available that eliminates treatment-related uncertainties without considerably adding to the cost. However, delivering “high precision radiotherapy” without periodic image guidance would do more harm than treating large volumes to compensate for setup errors. In the present review, we discuss the concept of image guidance in radiotherapy, the current techniques available, and their expected benefits and pitfalls.

Background. Median survival in patients with hepatocellular carcinoma (HCC) and portal vein tumor thrombosis (PVTT) is 2–6 months; conventionally liver transplantation is contraindicated. Methods. We studied outcomes following living donor liver transplantation (LDLT) post-PVTT downstaging (DS) with stereotactic body radiotherapy (SBRT), and tumor ablation (with transarterial chemo- or radio-embolization). Results. Of 2348 consecutive LDLTs, 451 were for HCC, including 25 with PVTT (mainly Vp1-3) after successful DS and 20 with Vp1/2 PVTT without previous treatment. DS was attempted in 43, was successful in 27 (63%), and 25 underwent LDLT. Median alpha fetoprotein (AFP) at diagnosis and pre-LDLT were 78.1 ng/mL (3-58 200) and 55 ng/mL (2-7320), respectively. Mean DS to LDLT time was 10.2 weeks (5–16). Excluding 2 postoperative deaths, 1- and 5-year overall survival (OS) and recurrence-free survival (RFS) were 82%, 57%, and 77%, 51%, respectively, comparable to survival in 382 HCC patients without PVTT undergoing upfront LDLT (5-y OS 65%, P = 0.06; RFS 66%, P = 0.33, respectively). There was a trend toward better OS in DS+LDLT versus non-DS LDLT group (5-y OS/RFS—48%/40%). OS was significantly better than in HCC-PVTT patients receiving no intervention or palliative Sorafenib alone (1-y OS of 0%) or Sorafenib with TARE/SBRT (2-y OS of 17%) at our center during the study period. Initial AFP <400 ng/mL and AFP fall (initial minus pre-LDLT) >2000 ng/mL predicted better RFS; Grade III/IV predicted worse OS in DS patients. Conclusions. HCC patients with PVTT can achieve acceptable survival with LDLT after successful DS. Low initial AFP level, a significant drop in AFP with DS and low tumor grade, favorably influence survival in these patients.

Objective: The present study evaluated the efficacy and toxicity of adaptive radiotherapy (RT) among patients with head and neck cancer. Methods: 36 patients eligible for radical RT underwent RT planning scans and were planned for 54-Gy dose to both high-risk and low-risk target volumes in Phase I. All patients underwent a second (adaptive) scan during the fifth week of RT. Phase II plans for 16 Gy to high-risk planning target volume were developed on these mid-treatment scans. The primary end point was local response. Disease-free survival (DFS), overall survival (OS) and treatment-related morbidity were secondary end points.

In advanced, intensity‐modulated external radiotherapy facility, the multileaf collimator has a decisive role in the beam modulation by creating multiple segments or dynamically varying field shapes to deliver a uniform dose distribution to the target with maximum sparing of normal tissues. The position of each MLC leaf has become more critical for intensity‐modulated delivery (step‐and‐shoot IMRT, dynamic IMRT, and VMAT) compared to 3D CRT, where it defines only field boundaries. We analyzed the impact of the MLC positional errors on the dose distribution for volumetric‐modulated arc therapy, using a 3D dosimetry system. A total of 15 VMAT cases, five each for brain, head and neck, and prostate cases, were retrospectively selected for the study. All the plans were generated in Monaco 3.0.0v TPS (Elekta Corporation, Atlanta, GA) and delivered using Elekta Synergy linear accelerator. Systematic errors of +1,+0.5,+0.3,0,−1,−0.5,−0.3 mm were introduced in the MLC bank of the linear accelerator and the impact on the dose distribution of VMAT delivery was measured using the COMPASS 3D dosimetry system. All the plans were created using single modulated arcs and the dose calculation was performed using a Monte Carlo algorithm in a grid size of 3 mm. The clinical endpoints D95%,D50%,D2%, and Dmax,D20%, D50% were taken for the evaluation of the target and critical organs doses, respectively. A significant dosimetric effect was found for many cases even with 0.5 mm of MLC positional errors. The average change of dose D95% to PTV for ±1 mm,±0.5 mm, and ±0.3 mm was 5.15%, 2.58%, and 0.96% for brain cases; 7.19%, 3.67%, and 1.56% for head and neck cases; and 8.39%, 4.5%, and 1.86% for prostate cases, respectively. The average deviation of dose Dmax was 5.4%, 2.8%, and 0.83% for brainstem in brain cases; 8.2%, 4.4%, and 1.9% for spinal cord in H&N; and 10.8%, 6.2%, and 2.1% for rectum in prostate cases, respectively. The average changes in dose followed a linear relationship with the amount of MLC positional error, as can be expected. MLC positional errors beyond ±0.3 mm showed a significant influence on the intensity‐modulated dose distributions. It is, therefore, recommended to have a cautious MLC calibration procedure to sufficiently meet the accuracy in dose delivery.PACS number: 87.56

This study supports the sparse dosimetric data regarding the quantitative tumour volume reduction, re-emphasizing the need for adaptive replanning for minimizing normal tissue toxicity without compromising local control, and adds to the existing body of literature.

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Axillary levels I and II (lower axilla) receive substantial amount of incidental radiation doses with all the three techniques; however, conformal techniques (IMRT, 3DCRT) deliver significantly lesser incidental radiation to lower axilla than ST technique.