The intent of the review was to identify different methodological approaches used to calculate the planning target volume (PTV) margin for head and neck patients treated with volumetric arc therapy (VMAT), and whether the necessary factors to calculate the margin size with the selected formula were used.

A comprehensive, systematic search of related studies was done using the Hydi search engine and different databases: MEDLINE, PubMed, CINAHL, ProQuest (Nursing and Allied Health), Scopus, ScienceDirect and tipsRO. The literature search included studies published between January 2007 and December 2020. Eligibility screening was performed by two reviewers.

A total of seven studies were found. All the reviewed studies used the Van Herk formula to measure the PTV margin. None of the studies incorporated the systematic errors of target volume delineation in the PTV equation. Inter-fraction translational errors were assessed in all the studies, whilst intra-fraction errors were only included in the margin equation for two studies. The studies showed great heterogeneity in the key characteristics, aims and methods.

Since systemic errors from target volume delineation were not considered and not all studies assess intra-fraction errors, PTV margins may be underestimated. The recommendations are that studies need to determine the effect of target volume variance on PTV margins. It is also recommended to compare PTV margin results using various formulas.

The aim of this study was to evaluate planning target volume (PTV) margins for two different locations using an electronic portal imaging device (EPID) to ensure that the correct radiation dose is delivered to the tumour when using intensity-modulated radiation therapy (IMRT).

Setup data were collected from 40 patients treated with IMRT for head and neck cancer (HN) (20 patients) and prostate cancer (20 patients). Setup errors from 720 registration images were analysed to evaluate systematic and random errors. Thereafter, optimal PTV margins were calculated based on International Commission on Radiation Units and Measurements 62 (ICRU), Stroom and Parker formulas compared with the Van Herk’s recipe.

To calculate the margins around the PTV, several different formulas have been used. Setup margins ranged between 2–4·3, 2·2–4·6 and 2·1–4·7 mm in X, Y and Z directions, respectively, for HN cases. Similarly, for the prostate site, setup margins ranged between 3·7–8·3, 3·2–6·8 and 3·3–8·2 mm in X, Y and Z directions.

To ensure better coverage of target volume, we adopted a PTV margin of 5 mm for HN PTVs and 10 mm for prostate PTVs in our department.

This study is primarily aimed at the analysis of various dose homogeneity indices (HIs) essential for the evaluation of therapeutic plans by employing intensity-modulated radiation therapy (IMRT) on patients with cervix cancer. Also integral dose (ID) to healthy surrounding organs is computed.

Effectiveness of different HIs (A, B, C, D) was explored for IMRT plans using 15 MV photon beam. In total, 18 patients were selected at random for treatment of cervix cancer, and dose of 5,040 cGy was delivered in 28 equal fractions.

The study was undertaken to compare four HI formulas and coefficient of determination between each set of HI was known by calculating R2 value. Mean±SD of HI A, HI B, HI C and HI D were 1·12±0·02, 0·13±0·04, 0·10±0·02 and 0·99±0·03, respectively. Mean value of ID for rectum is 3·16 and for bladder is 10·3.

Our data suggested that HI calculated using four formulas provided good plan quality. The results advocate that all the studied HIs can be effectively used for assessment of uniformity inside the target volume. However, values of HI C were closest to ideal value as compared with other three formulas; hence, it is considered a better measure to compute homogeneity of dose within target volume. The ID gives satisfactory results for surrounding normal tissues such as rectum and bladder and significant critical tissue sparing was achieved by using IMRT technique.

To calculate and compare planning target volume (PTV) margins for an offline 3 mm tolerance, daily bony anatomy verification, tattoo alignment and online prostate marker matching with those currently used at our institution.

Seventy patients had offline bony anatomy megavoltage verification. 23 different patients underwent fiducial marker matching using daily online kilovoltage verification. Systematic and random errors were measured in the right–left (RL), superior–inferior (SI) and anterior–posterior (AP) directions. Geometric uncertainties from literature were used to help calculate the margins.

PTV margins (mm) were 7 RL, 12 SI and AP (3 mm tolerance offline bony), 6 RL, 11 SI and AP (daily online bony), 8 RL, 12 SI and AP (tattoo alignment) and 5 RL, 8 SI and 6 AP (online daily prostate marker correction).

Our current margins for conformal radiotherapy patients are too small for phase 2 in the SI and AP directions. Implementing online daily bony anatomy matching would not reduce the PTV margin significantly. Online daily marker correction showed current PTV71 Gy margins as excessive by (mm) 5 RL, 2 SI and 4 anterior.