This is the second of two papers giving an overview of the use of Monte-Carlo techniques for radiotherapy applications.

The first paper gave an introduction and introduced some of the codes that are available to the user wishing to model the different aspects of radiotherapy treatment. It also aims to serve as a useful companion to a curated collection of papers on Monte-Carlo that have been published in this journal.

This paper focuses on the application of Monte-Carlo to specific problems in radiotherapy. These include radiotherapy and imaging beam production, brachytherapy, phantom and patient dosimetry, detector modelling and track structure calculations for micro-dosimetry, nano-dosimetry and radiobiology.

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.

Head and neck cancers (HNCs) are some of the commonest cases requiring palliative radiotherapy (PRT) in an Indian radiotherapy practice. A variety of PRT protocols have been explored with varying success.

The study objective was to evaluate the efficacy and tolerability of a short-course hypofractionated PRT schedule in HNC patients in terms of symptom relief, tumour response, acute side effects and survival and to compare results with other PRT regimens. All patients received 30 Gy in 10 fractions over 2 weeks followed by another 20 Gy in 5 fractions after a 4 weeks gap.

Seventy-five percent of patients completed both phases of treatment. Symptom relief was seen in 71% (pain) to 76% (dysphagia) of patients. Tumour response was recorded in 73% of patients. At 12 months, the mean overall survival was 10·29 months for patients who responded to PRT compared to 7·87 months for those who did not. Results were comparable to other regimens reported in the literature, but no radiobiological advantage of a higher dose was discernible.

Short-course hypofractionated PRT is effective in reducing tumour burden and relieving symptoms in HNC patients and possibly in lengthening survival. Selection of any schedule should be decided by treating oncologists based on clinical, logistic and socio-economic factors.

Stereotactic radiosurgery (SRS) has become a preferred treatment in the initial management of brain metastases (BM). This study reported treatment outcomes and identified the patient, tumour, and treatment-related factors that predict failure, survival, and brain necrosis (BN).

We retrospectively reviewed the electronic medical records of all BM patients treated with SRS. Patient, tumour characteristics and treatment details data were collected. All recurrences and BN were defined in the neurooncological tumour board.

From December 2016 to April 2020, 148 patients were analysed. The median follow-up was 14·8 months (range 6–51). At the time of analyses, 72·3% of the patients were alive. Presence of initial neurological deficit (HR; 2·71 (1·07–6·9); p = 0·036) and prior RT (HR; 2·55 (1·28–5·09); p = 0·008) is associated with worse overall survival. The local recurrence rate was 11·5 %. The distant brain metastasis rate was 53·4 %. Leptomeningeal metastasis was seen in 11 patients (7·4%). Symptomatic BN was seen in 19 patients (12·8 %). Bigger lesions (13 versus 23 mm diameter; p = 0·034) and cavity radiosurgery are associated with more BN (63·2 % versus 36·8%; p: 0·004).

Distant BM is the leading cause of CNS recurrences and, salvage SRS is possible. Due to the increasing risk of developing BN routine metastasectomy should be made with caution.

UroLift implants are a novel treatment for the obstructive lower urinary tract symptoms arising from benign prostatic hyperplasia. This case study aimed to assess their effectiveness as fiducial marker (FM) surrogates in prostate image-guided radiotherapy (IGRT).

Cone-beam CT images from a patient receiving prostate radiation therapy underwent manual alignment using UroLift implants and also prostate soft-tissue matching by five experienced therapeutic radiographers. The match values of both methods were compared using Bland–Altman analysis. All five observers were also asked to score the ease of matching using both approaches.

The 95% mean level of agreement for the UroLift matches were within a 2-mm threshold in all dimensions. Comparison of UroLift and prostate matches had 95% limit of agreement values of −0·98 to 1·78, −0·58 to 0·49 and −1·83 to 1·04 mm in the vertical, longitudinal and lateral planes, respectively. All of the UroLift matches were rated as ‘very easy’ or ‘possible with little difficulty’ by the five observers.

A small difference between the CBCT UroLift and CBCT prostate match was found. It has been shown that IGRT to the prostate with the aid of the UroLift system implants and CBCT is feasible and can eliminate the need for FM implants. Wider evaluation in a large cohort is recommended.

This study was aimed to evaluate the outcomes of patients with large (>2 cm in great diameter) vestibular schwannomas (VSs) treated with hypofractionated stereotactic radiotherapy (HFSRT) compared to small (<2 cm) ones and the impact of debulking surgery prior to radiation for large VSs.

Fifty-nine patients with VSs treated with HFSRT (25 Gy in 5 fractions) were evaluated by tumour size and surgical status. Patients were divided based on tumour size: small VSs (n = 42) and large VSs (n = 17). The large group was further divided into the groups of pre-treatment debulking surgery (n = 8) and no surgery (n = 9). Rates of tumour control, brainstem necrosis and neurologic dysfunction were assessed following treatment. Pre-surgical magnetic resonance imaging (MRI) were used to generate hypothetical HFSRT plans to compare the effect of debulking surgery on dosimetry. Normal tissue complication probability (NTCP) modelling was performed to compare toxicity probabilities with and without surgical debulking in large VSs.

There was no statistical difference of tumour control rate between small and large VSs with 100% for small tumours and 94·1% for large tumours (p = 0·12), respectively. In large VSs patient, the tumour control rate of HFSRT was 100% (8/8) for surgically debulked patients and 89% (8/9) for non-surgically debulked patients (p = 0·35). There were no patients who experienced brainstem necrosis or progression of facial and trigeminal nerve symptoms after HFSRT in the entire groups of patients. Surgical debulking large VSs did not change the maximum point dose of brainstem (p = 0·98), but significantly decreased volumes of VSs and changed the minimum dose to the hottest 0·5 cc of tumour (p = 0·016) as well as the volume receiving at least 23 Gy (p = 0·023). NTCP modelling revealed very low rates (average < 1%) of brainstem toxicity with or without surgical debulking, but there was a significant difference favoring surgery (p < 0·05).

HFSRT is a safe and effective treatment for both small and large VSs and is a viable option for patients with large VSs who cannot undergo surgery, if NTCP of pre-debulking HFSRT dosimetry is lower.

A patient experience survey was undertaken as part of the role of the Macmillan Consultant Therapy Radiographer for the bone and brain metastases patients to inform future development of the service.

A questionnaire was developed and approved by the Trust’s local Questionnaire, Interview and Survey Group to survey the experiences and satisfaction of the service including the informed consent process, radiotherapy appointments and overall experience and satisfaction. The survey used qualitative and quantitative methods, including Likert Scales and free comment boxes. The responses were analysed by counting the frequency of each response and identifying any themes in free text responses.

Most patients were satisfied with the consent process with 1/36 patients reporting a lack of understandable information and 4/36 wanting more side effect information. The option of plan and treat was a preference of 53% of patients due to travelling back and forth to the centre; however, only 6% stated that they wanted two separate appointments. Ninety-four percent of patients felt that they had complete confidence and trust in the professional who consented them and 86% did not feel fully involved in the decision-making process. Overall, the service was rated as 10/10 by 61% of patients (n = 36).

The patients surveyed were satisfied with their experience of the Palliative Radiotherapy Service; however, it needs to be developed further to meet the needs and expectations of the service users.

Patient wait time for every single fraction of every patient treated at our centre for the past year has been presented in this study. The waiting time data were analysed across different treatment sites and modalities.

Between March 2021 and March 2022, all patients and their corresponding recorded measurements of waiting time were analysed. Times recorded included check-in time (CK), scheduled time to start treatment (SC) and beam-on time for the first beam of therapy (ST). SPSS version 18 was used for statistical calculations, correlations and assessing significance.

A total of 181 patients were treated during this duration. The total number of radiotherapy (RT) sessions recorded was 3011. Out of these 3011 sessions, number of times treated by rapid arc (RA), intensity-modulated radiotherapy (IMRT), three-dimensional conformal radiotherapy (3DCRT), stereotactic body radiotherapy (SBRT), stereotactic radiosurgery and stereotactic radiotherapy (SRS/SRT) were 68.18%, 30.19%, 0.167%, 0.565% and 0.19%, respectively. The mean (± standard deviation) times for scheduled time to start treatment (SC) to check-in time (CK), SC to ST (beam-on time for the first beam of treatment), CK to ST and (CK or SC) to ST were −14 ± 48 min, 6 ± 50 min, 19 ± 24 min and −4 ± 31 min, respectively.

Patient wait times during RT were presented in this study. This study covered the daily waiting times before RT during modern-day RT treatment sessions. This vast series of consecutive patient data will be a valuable resource for the future planning and management of any modern RT department.

This study aimed to systematically review the literature to synthesise and summarise whether using knowledge-based planning (KBP) can improve the planning of stereotactic radiotherapy treatments.

A systematic literature search was carried out using Medline, Scopus and Cochrane databases to evaluate the use of KBP planning in stereotactic radiotherapy. Three hundred twenty-five potential studies were identified and screened to find 25 relevant studies.

Twenty-five studies met the inclusion criteria. Where a commercial KBP was used, 72.7% of studies reported a quality improvement, and 45.5% reported a reduction in planning time. There is evidence that when used as a quality control tool, KBP can highlight stereotactic plans that need revision. In studies that use KBP as the starting point for radiotherapy planning optimisation, the radiotherapy plans generated are typically equal to or superior to those planned manually.

There is evidence that KBP has the potential to improve the quality and speed of stereotactic radiotherapy planning. Further research is required to accurately quantify such systems’ quality improvements and time savings. Notably, there has been little research into their use for prostate, spinal or liver stereotactic radiotherapy, and research in these areas would be desirable. It is recommended that future studies use the ICRU 91 level 2 reporting format and that blinded physician review could add a qualitative assessment of KBP system performance.

This investigation quantifies the dose enhancement effect and dose distribution modifications due to the presence of high-z nanospheres in a proton beam.

Various proton pencil beams of therapeutic energies (60–226 MeV) and spatial distribution of 2·7 mm spot size diameter were simulated onto a water phantom utilising the TOPAS Monte Carlo toolkit version 3.6.1. The simulation modelled either water or nanospheres of high-z materials (gold, silver or platinum) at the location of the Bragg Peak (BP) to compare the differences of the resulting dose distributions.

The introduction of the nanospheres increases the maximum dose, narrows the BP and shifts the BP location upstream compared to the water phantom with no nanospheres.

This work shows that the local dose can be enhanced with the use of high-z nanoparticles in proton therapy, thereby increasing patient safety and decreasing side effects with the same amount of delivered radiation.

The aim of our study is to retrospectively report the radiobiological aspects for intensity-modulated proton therapy (IMPT) against intensity-modulated radiation therapy (IMRT) for patients with head and neck cancer treated at our institution. A secondary goal is to reinforce current model-based approaches to head and neck cancer patient selection for IMPT.

Eighteen patients were evaluated with prescription doses ranging from 50 to 70 Gy delivered in 2 Gy per fraction. The dose volume histograms (DVH) were used to calculate equivalent uniform dose (EUD), tumour control probability (TCP) and normal tissue complication probability (NTCP) for biophysical comparison using mechanistic mathematical dose response models. Absolute values of TCP and NTCP were then compared between IMPT and IMRT.

The dose models demonstrate a minimal radiobiological advantage for IMPT compared to IMRT in treating head and neck cancers. Absolute values of TCP were slightly higher, while absolute values of NTCP were slightly lower for IMPT versus IMRT.

Further studies are needed to determine if the radiobiological advantage indeed translates to a therapeutic advantage for patients.

This study aimed to quantify the difference in setup margin in cone beam computed tomography (CBCT) setup imaging, utilising the van Herk formula for two different image registration methods. Two alternative techniques of registration, bony landmark (BL) matching and soft tissue matching (ST) for head and neck cancer patients, were investigated.

This study included 30 head and neck cancer patients who received a simultaneous integrated boost of 54–60–66 Gy in 30 fractions, using volumetric modulated arc treatment. A total of 867 CBCT images were acquired during patient setup and further analysed for setup margin calculation. A region of interest was described using a clip box between the reference and CBCT image to calculate the patient’s positional inaccuracy in three translational directions, X, Y and Z, where X was mediolateral, Y was the cranial-caudal, and Z was the anterior-posterior direction in the patient-based coordinate system, respectively. The shifts were captured by altering the BL and ST matching, and the setup margin was calculated using the van Herk formula (=2·5Σ + 0·7σ where Σ was the systematic and σ was the random error).

The difference between bony and ST matching in most cases was observed to be 1·4 mm in all translational directions at a 95% confidence interval and <1° in all rotational directions. The rotational error was found to be below the action level (±3°); hence, no corrections related to rotational error were made. The translational setup margin for bone and ST-based registration was X (BL) = 4·6 mm, X (ST) = 4·4 mm, Y (BL) = 6·3 mm, Y (ST) = 4·7 mm, Z (BL) = 3·0 mm, Z (ST) = 3·6mm.

Two distinct registration approaches for head-neck patient setup did not yield any significant difference in the setup margin calculation. A suitable approach for CBCT and reference CT registration technique was required for the setup margin calculation. Confusion in selecting the correct image registration procedure can result in incorrect treatment execution. The compatibility of the two registration approaches was established in this study. Image fusion was neutralised before the second match (ST) to avoid hysteresis. For setup verification using CBCT for the head and neck region, both bone and ST registration were compatible for setup verification.

Adjacent radiation fields are applied in some radiotherapeutic cases. When using these radiation fields, considerable dose errors across the junction of radiation fields are possible. Therefore, it is necessary to evaluate the accuracy of the dose calculated by treatment planning system (TPS) when using the adjacent radiation fields. The present study aimed to quantify the dose calculation accuracy of ISOgray TPS for the photon-photon adjacent fields.

To assess the accuracy of dose calculations, the dose profiles were first measured by a Semiflex ionization chamber at 1, 1·5, 5 and 10 cm depths for different field sizes (6 × 6, 10 × 10 and 20 × 20 cm2), source to surface distances (SSDs) (90, 100 and 110 cm) and beam angles (0º, 15º, 30º and 45º). In the second step, the data at corresponding depths were extracted from the ISOgray TPS. Finally, the dosimetric performance of TPS was evaluated using a gamma index analysis.

The overall dose calculation accuracy of ISOgray TPS was within the acceptable range for the build-up region (with acceptance criteria of dose difference (DD) = 15% and distance to agreement (DTA) = 3 mm) and the depths after the build-up region (with acceptance criteria of DD = 5% and DTA = 3 mm). Moreover, the overall accuracy of dose calculations was not affected by the field size and the SSD. It was also shown that the accuracy of dose calculations was similar for the adjacent radiation fields with beam angles of 0º, 15 º and 30 º, while a considerable decrease in the pass rate values is obtained for the adjacent radiation field with 45 º beam angle. A more detailed analysis of the findings revealed that the accuracy of dose calculations in the match line regions of the adjacent radiation fields for 1 cm beam profiles was within the acceptable range; however, it declined for other depths.

The findings showed that the overall dose calculation accuracy of ISOgray TPS was acceptable for evaluated adjacent radiation fields. However, the accuracy of dose calculations in the match line regions of the adjacent radiation fields for the depth after build-up was not within the acceptable range.

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.

The Virtual Environment for Radiotherapy Training (VERT) is a simulator used to train radiotherapy students cost-effectively with limited risk. VERT is available as a two-dimensional (2D) and a more costly three-dimensional (3D) stereoscopic resource. This study aimed to identify the specific benefits afforded by stereoscopic visualisation for student training in skin apposition techniques.

Eight participants completed six electron skin apposition setups in both 2D and 3D views of VERT using a 7 cm × 10 cm rectangular applicator setup to 100 cm focus skin distance (FSD). The standard deviation (SD) of the mean distance from each corner of the applicator to the virtual patient’s skin surface [which we define as apposition precision (AP)] was measured along with the time taken to achieve each setup. Participants then completed a four-question Likert-style questionnaire concerning their preferences and perceptions of the 2D and 3D views.

There was little difference in mean setup times with 218·43 seconds for 2D and 211·29 seconds for 3D (3·3% difference). There was a similarly small difference in AP with a mean SD of 5·61 mm for 2D and 5·79 mm for 3D (3·2% difference) between views. The questionnaire results showed no preference for the 3D view over the 2D.

These findings suggest that the 2D and 3D views result in similar setup times and precision, with no user preference for the 3D view. It is recommended that the 2D version of VERT could be utilised in similar situations with a reduced logistical and financial impact.

Measurement of off-centre ratios (OCRs) is a requirement for the commissioning of cyberknife. The fixed source to axis distance (SAD) technique is required for the measurement of OCRs which is time-consuming and tedious. The fixed source to surface distance (SSD) technique, on the other hand, is easy to set up and requires less time. The OCRs have been measured with SAD and SSD setup and compared to assess the difference between each other.

The research is carried out on an Accuracy cyberknife M6, installed at NORI Cancer Hospital Islamabad. The OCRs are measured with Sun Nuclear ‘EDGE’ diode detector on a Sun Nuclear SNC 3D dosimetry system. The OCRs were measured for 12 cones and at three depths. Each OCR measured with the SAD setup is compared with the corresponding OCR measured with SSD setup using % dose distance and distance to agreement (2%/0·2mm).

For the within-the-beam and out-of-the beam regions, both OCRs are matching with each other. The percentage difference is in the order of less than 1% while the distance-to-agreement results in 100% matching for all cones and all depths. For the penumbra region, the percentage difference is higher than the other two regions. The maximum percentage difference is 2·96%. Generally, the percentage difference is higher for small cones and for OCRs measured at larger depths.

The OCRs on a cyberknife system measured with a fixed SSD setup and fixed SAD setup coincide within an acceptable limit and can be measured with both setups with similar accuracy.

A patient with Down’s syndrome, with dermatofibrosarcoma protuberans, was intended for adjuvant radiotherapy. The lesion was on the parietal region of the head of the patient. Given the proximity of the lesion to the brain, the curvature of the lesion, and potential complications of anaesthesia for a Down’s syndrome patient, brachytherapy was the appropriate treatment. Anaesthesia complications for patients with Down’s syndrome are airway infections, atlanto-occipital dislocation and bradycardia.

Instead of sedating the patient in order to prepare a mould applicator, a 3D-printed model of the patient’s head was used. This allowed us greater time to prepare the applicator in a more relaxed environment.

The fit of the mould applicator on the patient was satisfactory. Minimum air gaps were observed. The treatment could be completed with sedation only.

We were able to achieve an equivalent dose of 44·69 Gy in 5 sessions of brachytherapy, significantly reducing the anaesthesia sessions and the associated risks. A drawback of 3D printing is that it takes several hours to print the model.

Radiotherapy is an ever-changing field with constant technological advances. It is for this reason that risk management strategies are regularly updated in order to remain optimal.

A retrospective audit of all reported incidents and near misses in the audited department between 1 November 2020 and 30 April 2021 was performed. The root cause of each radiotherapy error (RTE), safety barrier (SB) and the causative factor (CF) would be defined by the Public Health England (PHE) coding system. The data will then be analysed to determine if there are any frequently occurring errors and if there are any existing relationships between multiple error.

670 patients were treated during the study period along with 35 reports generated. 77·1% (n = 27) were incidents, and 22·9% (n = 8) were near misses. 2·8% (n = 1) were reportable incidents. The ratio of RTEs to prescriptions was 0·052:1 (5·2%). 37% of RTEs were associated with image production. Slips and lapses were involved in 54·2%. Adherence to procedures/protocols was a factor in 48·5% (n = 17). Communication was a factor in 11·4% (n = 4).

The proportion of Level 1 incidents was higher in this department (2·8%) than in the PHE report (0·9%). Almost one-third, 31·4% (n = 11) of errors stemmed from one technical fault in image production. SB breaches were prevalent at the pre-treatment planning stage of the pathway. A relationship between slips/lapses and non-conformance to protocols was identified.

The rate of reported radiotherapy incidents in the UK is lower when compared with this department; this could be improved with the implementation of the quality improvement plan outlined above.

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.