To investigate the performance of image registration methods for structure delineation in head and neck (H&N) cancer patients.

This retrospective study randomly recruited 22 patients who had been irradiated in the H&N region between January 2016 and February 2024. The sample group included nasopharyngeal carcinoma (NPC) and oropharyngeal cancer (OPC) patients. The treatment planning structures were delineated as images of computed tomography simulation (CTsim) and were set as the ground-truth. The latest CT diagnostic (CTdiag) image sets of these selected patients were imported into third-party software for delineation. The structures of CTdiag were delineated using an artificial intelligence method except for the target. The performance of rigid and deformable image registration methods (RIR and DIR, respectively) between these two image sets were evaluated using dice similarity coefficient (DSC) and Hausdorff distance (HD). The performance evaluation scores were also compared between NPC and OPC.

The DSC revealed a significant difference in all structures between RIR and DIR, whereas the HD showed no significant difference on the target and the larynx. In terms of a comparison of treatment regions, OPC appeared to sustain the greatest benefit from DIR.

Image registration can provide the benefit of structure delineation, particularly when employing the DIR method. Although the DIR method may not offer a high degree of performance in terms of target delineation, it could effectively serve as a delineation guideline in this process.

A small number of studies have confirmed the advantage of generalised equivalent uniform dose (gEUD) optimisation for some standard clinical scenarios; however, its performance with complicated stereotactic treatments is yet to be explored. Therefore, this study compared two planning optimisation methods, gEUD and Physical dose, in stereotactic treatments for several complex anatomical locations.

Thirty patients were selected, ten each for sites of brain, lung and spine. Two stereotactic plans were generated for each case using the gEUD objective and Physical objective cost functions. Within each of the three sites, dosimetric indices for conformity, gradient and homogeneity, along with parameters of monitor units and dose–volume histograms (DVHs), were compared for statistical significance. Additionally, patient-specific quality assurance was conducted using portal dosimetry, and the gamma passing rate between the two plans was evaluated.

Optimisation was better with a gEUD objective as compared with Physical objective, notably sparing critical organs. Overall, the differences in mean values for six critical organs at risk favoured gEUD-based over Physical-based plans (all six 2-tailed p-values were < 0·0002). Furthermore, all differences in mean values for DVH parameters favoured gEUD-based plans: GTVmean, GTVmax, PTVD100V, homogeneity index, gradient index and monitor unit (treatment time) (each 2-tailed p < 0·05).

gEUD optimisation in stereotactic treatment plans has a clear and general statistical advantage over Physical dose optimisation.

Volumetric-modulated arc therapy (VMAT) has emerged as a promising radiation treatment technique. One of the challenges in VMAT planning for lung carcinoma is the lack of consistency among different institutions with respect to what is considered an acceptable treatment plan in terms of target coverage and doses to the organs at risk (OAR). Additionally, the accuracy of dose calculations in the presence of heterogeneous medium (i.e. air) is another challenge in lung VMAT planning. Our objective is to develop an institutional criteria for non-stereotactic body radiotherapy (non-SBRT) lung treatment plans by evaluating the dosimetric impact of plan normalisation and dose calculation algorithms, including the Anisotropic Analytical Algorithm (AAA), AcurosXB (AXB) and Monte Carlo (MC) simulation, on VMAT plans for non-small cell lung cancer (NSCLC).

The CT dataset of 20 patients with NSCLC was randomly selected to ensure a spectrum of target sizes and locations. All treatment planning was accomplished with 2–3 VMAT arcs and a prescription of 60 Gy in 30 fractions. Two plan normalisation methods were employed: (i) planning target volume (PTV) V100% = 95% and (ii) PTV V95% = 95%.

All three dose calculation algorithms revealed heterogeneous and conformal plans irrespective of plan normalisations. The PTV and OARs dose–volume constraints were met using both normalisation methods. However, we observed that AAA overestimated the minimum PTV doses by 2–5% regardless of plan normalisation. The mean PTV-V100% was lower for AAA in comparison with AXB and MC algorithms.

VMAT is an effective radiotherapy technique for achieving greater target dose conformity, heterogeneity and dose fall-off from the PTV for the treatment of NSCLC. The results of this study can provide the basis for the development of local plan acceptability criteria for NSCLC VMAT plans, and the clinical implementation can be achieved with minimal or no imposition on resources and time constraints. Occasionally, plan normalisation of PTV-V95% = 95% may be required to ensure that the OAR dose tolerances are not exceeded.

This study compared dose metrics between tangent breast plans calculated with the historical standard collapsed cone (CC) and the more accurate Monte Carlo (MC) algorithms. The intention was to correlate current plan quality metrics from the currently used CC algorithm with doses calculated using the more accurate MC algorithm.

Thirteen clinically treated patients, whose plans had been calculated using the CC algorithm, were identified. These plans were copied and recalculated using the MC algorithm. Various dose metrics were compared for targets and the time necessary to perform each calculation. Special consideration was given to V105%, as this is increasingly being used as a predictor of skin toxicity and plan quality. Finally, both the CC and MC plans for 4 of the patients were delivered onto a dose measurement phantom used to analyse quality assurance (QA) pass rates. These pass rates, using various evaluation criteria, were also compared.

Metrics such as the PTVeval D95% and V95% showed a variation of 6% or less between the CC and MC plans, while the PTVeval V100% showed variation up to 20%. The PTVeval V105% showed a relative increase of up to 593% after being recalculated with MC. The time necessary to perform calculations was 76% longer on average for CC plans than for those recalculated using MC. On average, the QA pass rates using 2%2mm and 3%3mm gamma criteria for CC plans were lower (19·2% and 5·5%, respectively) than those recalculated using MC.

Our study demonstrates MC-calculated PTVeval V105% values are significantly higher than those calculated using CC. PTVeval V105% is often used as a benchmark for acceptable plan quality and a predictor of acute toxicity. We have also shown that calculation times for MC are comparable to those for CC. Therefore, what is considered acceptable PTVeval V105% criteria should be redefined based on more accurate MC calculations.

Total skin electron beam therapy is a treatment option in patients with mycosis fungoides (MF) affecting a significant amount of the body surface. For patients with involvement of soles and interdigital folds, however, this approach is ineffective, requiring alternatives such as localised radiotherapy (RT). Although electron beams are well suited for superficial lesions, on irregular surfaces it provides inadequate tumour coverage and excess dose variance, requiring photon irradiation with tissue compensation.

We present the case of a patient with extensive cutaneous MF with skin lesions spread over both lower limbs and treated on these affected areas with photon beam RT. Long sheets of paraffin gauze dressings were used to create a 0·5-cm-thick bolus. The patient received a single fraction of 8 Gy. In vivo dosimetry using Gafchromic films was performed.

After 3 months, a complete response was achieved. In this case, paraffin gauze bolus proved to be an inexpensive, convenient, effective and flexible method for irregular superficial cancer irradiations.

Paraffin gauze bolus is a suitable option for irregular contours.

Few studies claimed that dynamic jaw (DJ) mode in Helical TomoTherapy® (HT) could improve the cranio-caudal dose distribution without prolonging the treatment time in treating different types of cancer. Also, studies suggested that DJ with a wider 5 cm field width (FW) could replace fixed jaws (FJ) with 2.5 cm FW to reduce the delivery time with the sustainable plan quality. Yet, the study on breast cancer with supraclavicular fossa (SCF) nodal involvement using DJ mode in HT is limited. This study aims to evaluate the DJ mode retrospectively by comparing their dosimetric quality with normal tissue complication probability (NTCP) of organs at risk and treatment delivery time with FJ mode on treating left-side breast with SCF nodal involvement.

All post-mastectomy patients, who had been irradiated for left-side breast with SCF nodal involvement were selected retrospectively in this study. With the same dose constraint and prescription as the treated DJ2.5 plan, two extra plans using DJ mode with 5 cm FW(DJ5.0) and FJ mode with 2.5 cm FW (FJ2.5) were computed for plan comparison.

No statistical significance was found in all the parameters of PTV and OARs, except for V20 of whole lung. DJ5.0 received V20 in ipsilateral left lung than FJ2.5 and DJ2.5. However, the average delivery time of DJ5.0 was significantly lower than that of DJ2.5 and FJ2.5 by almost 40%.

No statistical significance was found in those dosimetric and radiobiological parameters among three modes while the delivery time has greatly reduced by using DJ5.0. A shorter treatment time can minimise intra-fractional error and better the patient’s experience during treatment.

This study compared the plan dosimetry between the intensity-modulated radiation therapy (IMRT) and field-in-field (FIF) technique for head-and-neck cancer using the Elekta Monaco treatment planning system (TPS).

A total of 20 head-and-neck cancer patients were selected in this study. IMRT and FIF plans for the patients were created on the Monaco TPS (ver. 5.11.02) using the 6-MV photon beam generated by the Elekta Synergy linear accelerator. The dose–volume histograms, maximum doses, minimum doses, mean doses of the target volumes and organs-at-risk (OARs), conformity index (CI), homogeneity index (HI) and monitor units (MUs) were determined for each IMRT and FIF plan. All IMRT plans passed the patient-specific quality assurance tests from the 2D diode array measurements (MatriXX Evolution System, IBA Dosimetry, Germany).

The results showed that the dose distribution to the target volumes of IMRT plans was better than FIF plans, while the dose (mean or max dose) to the OAR was significantly lower than FIF plan, respectively. IMRT and FIF resulted in planning target volume coverage with mean dose of 71·32 ± 0·76 and 73·12 ± 0·62 Gy, respectively, and HI values of 0·08 ± 0·01 (IMRT) and 0·19 ± 0·06 (FIF). The CI for IMRT was 0·98 ± 0·01 and FIF was 0·97 ± 0·01. For the spinal cord tolerance (maximum dose < 45 Gy), IMRT resulted in 39·85 ± 2·04 Gy compared to 41·37 ± 2·42 Gy for FIF. In addition, the mean doses to the parotid grand were 27·27 ± 7·48 and 48·68 ± 1·62 Gy for the IMRT and FIF plans, respectively. Significantly more MUs were required in IMRT plans than FIF plans (on average, 846 ± 100 MU in IMRT and 467 ± 41 MU in FIF).

It is concluded that the IMRT technique could provide a better plan dosimetry than the FIF technique for head-and-neck patients.

Radiation therapy has historically used margins for target volume to ensure dosimetric planning criteria. The size of margin for a given treatment site is still uncertain particularly for moving targets along with set-up variations leading to a fuzziness of target volume. In this study, we have estimated the dosimetric benefit of normal structures using biological-based optimal margins. The treatment margins are derived by knowledge-based fuzzy logic technique which is considering the radiotherapy uncertainties in treatment planning.

All treatment plans were performed using stepped increments of asymmetric margins to estimate prostate radiobiological indices such as tumour control probability (TCP) and normal tissue complication probability (NTCP). An absolute NTCP of 5% was considered to be the maximum acceptable value while TCP of 85% was considered to be the minimal acceptable limit for each volumetric modulated arc therapy (VMAT) plan of localised prostate cancer radiotherapy. Results were used to formulate rules and membership functions for Mamdani-type fuzzy inference system (FIS). In implementing the rules for the fuzzy system for ΔNTCP values above 10%, the PTV margin was not permitted to exceed 5 mm to avoid rectal complications due to margin selection. The new margins were applied in VMAT planning of prostate cancer for standard displacement errors. The dosimetric results of normal tissue predictors were estimated such as organ mean doses, rectum V60 (volume receiving 60 Gy), bladder V65 (volume receiving 65 Gy) and other clinically significant dose–volume indicators and compared with VMAT plans using current margin formulations.

Dosimetric results compared well to the results obtained by current techniques. Good agreement was obtained between proposed fuzzy model margins and currently used margins in lower error magnitude, but significant results were observed at higher error magnitude when organ toxicity concerned without compromising the target volumes.

The new margins may be helpful to estimate possible outcomes of normal tissue complications and thus may improve complication free survival particularly when organ motion errors are inevitable, case by case.

The standard treatment modalities for prostate cancer include surgery, chemotherapy, hormonal therapy and radiation therapy or any combination depending on the stage of the tumour. Radiation therapy is a common and effective treatment modality for low-intermediate-risk patients with localised prostate cancer, to treat the intact prostate and seminal vesicles or prostate bed post prostatectomy. However, for high-risk patients with lymph node involvement, treatment with radiation will usually include treatment of the whole pelvis to cover the prostate and seminal vesicles or prostate bed and the pelvic lymph nodes followed by a boost delivery dose to the prostate and seminal vesicles or prostate bed.

We retrospectively analysed the treatment plans for 179 prostate cancer patients treated at the cancer centre with the volumetric-modulated arc therapy (VMAT) technique via RapidArc using 6 MV photon beam. Patients were either treated with a total prescription dose of 78 Gy in 39 fractions for patients with intact prostate or 66 Gy in 33 fractions for post prostatectomy patients.

There were 114 (64%) patients treated with 78 Gy/39 and 65 (36%) treated with 66 Gy/34. The mean homogeneity index (HI), conformity index (CI) and uniformity index (UI) for the PTV-primary of patients treated with 78 Gy are 0.06 ± 0.01, 1.04 ± 0.01 and 0.99 ± 0.01, respectively, and the corresponding mean values for patients treated with 66 Gy are 0.06 ± 0.02, 1.05 ± 0.01 and 0.99 ± 0.01, respectively. The mean PTV-primary V95%, V100% and V105% are 99.5 ± 0.5%, 78.8 ± 12.2% and 0.1 ± 0.5%, respectively, for patients treated with 78 Gy and 99.3 ± 0.9%, 78.1 ± 10.6% and 0.1 ± 0.4%, respectively, for patients treated with 66 Gy. The rectal V50Gy, V65Gy, V66.6Gy, V70Gy, V75Gy and V80Gy are 26.8 ± 9.1%, 14.2 ± 5.3%, 13.1 ± 5.0%, 10.8 ± 4.3%, 6.9 ± 3.1% and 0.1 ± 0.1%, respectively, for patients treated with 78 Gy and 33.7 ± 8.4%, 14.1 ± 4.5%, 6.7 ± 4.5%, 0.0 ± 0.2%, 0.0% and 0.0%, respectively, for patients treated with 66 Gy.

The use of VMAT technique for radiation therapy of high-risk prostate cancer patients is an efficient and reliable method for achieving superior dose conformity, uniformity and homogeneity to the PTV and minimal doses to the organs at risk. Results from this study provide the basis for the development and implementation of consistent treatment criteria in radiotherapy programs, have the potential to establish an evaluation process to define a consistent, standardised and transparent treatment path for all patients that reduces significant variations in the acceptability of treatment plans and potentially improve patient standard of care.

Commissioning of a new planning system involves extensive data acquisition which can be onerous involving significant clinic downtime. This could be circumvented by extracting data from existing treatment planning system (TPS) to speed up the process.

In this study, commissioning beam data was obtained from a clinically commissioned TPS (Pinnacle™) using Matlab™ generated Pinnacle™ executable scripts to commission an independent 3D dose verification TPS (Eclipse™). Profiles and output factors for commissioning as required by Eclipse™ were computed on a 50 × 50 × 50 cm3 water phantom at a dose grid resolution of 2 mm3. Verification doses were computed and compared to clinical TPS dose profiles based on TG-106 guidelines. Standard patient plans from Pinnacle™ including intensity modulated radiation therapy and volumetric modulated arc therapy were re-computed on Eclipse™ TPS while maintaining the same monitor units. Computed dose was exported back to Pinnacle for comparison with the original plans. This methodology enabled us to alleviate all ambiguities that arise in such studies.

Profile analysis using in-house software showed that for all field sizes including small multi-leaf collimator-generated fields, >95% of infield and penumbra data points of Eclipse™ match Pinnacle™ generated and measured profiles with 2%/2 mm gamma criteria. Excellent agreement was observed in the penumbra regions, with >95% of the data points passing distance to agreement criteria for complex C-shaped and S-shaped profiles. Dose volume histograms and isodose lines of patient plans agreed well to within a 0·5% for target coverage.

Migration of TPS is possible without compromising accuracy or enduring the cumbersome measurement of commissioning data. Economising time for commissioning such a verification system or for migration of TPS can add great QA value and minimise downtime.

The aim of this study was to evaluate clinical efficacy and radiobiological outcome of intensity-modulated radiation therapy (IMRT) modalities using various collimator angles and non-coplanar fields for nasopharyngeal cancer (NPC).

A 70-Gy planning target volume dose was administered for 30 NPC patients referred for IMRT. Standard IMRT plans were constructed based on the target and organs at risk (OARs) volume; and dose constraints recommended by Radiation Therapy Oncology Group (RTOG). Using various collimator angles and non-coplanar fields, 11 different additional IMRT protocols were investigated. Homogeneity indexes (HIs) and conformation numbers (CNs) were calculated. Poisson and relative seriality models were utilised for estimating tumour control probability (TCP) and normal tissue complication probabilities (NTCPs), respectively.

Various collimator angles and non-coplanar fields had no significant effect on HI, CN and TCP, while significant effects were noted for some OARs, with a maximum mean dose (Dmax). No significant differences were observed among the calculated NTCPs of all the IMRT protocols. However, the protocol with 10° collimator angle (for five fields out of seven) and 8° couch angle had the lowest NTCP. Furthermore, the standard and some of non-coplanar IMRT protocols led to the reduction in OARs Dmax.

Using appropriate standard/non-coplanar IMRT protocols for NPC treatment could potentially reduce the dose to the OARs and the probability of inducing secondary cancer in patients.