To compare the dosimetry and reproducibility of set-up with monoisocentric technique (MIT) and dual isocentric technique (DIT) in adjuvant breast radiotherapy (RT).

Breast cancer patients treated with MIT or DIT were retrospectively studied. The organ-at-risk dose was compared between two groups. All patients underwent set-up verification with an electronic portal imaging device, and set-up time was recorded for each fraction. Treatment reproducibility was assessed in terms of systematic and random error.

Twenty patients were included (11 right and 9 left-sided tumours) and ten received whole breast RT, while the rest received chest wall RT. Overall, the mean heart dose was less with MIT (0.40 versus 0.79, p = <0.001) as well as in left-sided tumours (0.37 versus 0.98, p = 0.003). The maximum dose at the field junction was significantly higher with DIT (43 Gy, 107%, p = 0.003). The maximum total error was 1 cm in lateral for supraclavicular field and 8 mm in superior–inferior in tangents for both techniques. There was no difference in set-up errors between the two techniques.

MIT resulted in better dose homogeneity at the field junctions and reduced mean heart dose as compared to DIT. MIT is safe for implementation in clinical practice for breast cancer treatment.

This study is one of the few studies comparing MIT with DIT in terms of the dosimetry and the first one to compare set-up errors between the two techniques. The ease of set-up and better dosimetry with MIT was achieved.

Intraoperative radiotherapy (IORT) has gained popularity over recent years due to its impact on shortening the radiotherapy treatment time for early breast cancer. It has certainly proven effective as an exclusive treatment or when combined with whole breast irradiation (WBIR). Seroma is a common non-life-threatening complication that may delay treatment and impose challenges on radiological diagnostic follow-up.

To review and compare the occurrence of seroma in patients who received exclusive IORT or when combined with WBIR and to outline the diagnostic challenges encountered during radiological follow-up.

Based on strict selection criteria, all eligible patients who received IORT ± WBIR treatment between 2012 and 2019 in a university hospital setting were included. Demographic data, histological diagnosis, tumour size, tumour grade, lymphovascular invasion, nodal status, receptor status, treatment with neoadjuvant hormonal chemotherapy, applicator size, dose used, duration of radiotherapy treatment, timing of seroma development and duration of seroma were documented. Both clinical and radiological follow-up were exercised in all patients.

The total number of patients treated with breast conserving surgery (BCS) and IORT was 86. Age ranged between 31 and 75 years with the median age of 51 years. Patients treated exclusively with IORT were 39 (45%) while those who received the IORT as a boost were 47 (55%). Seroma was observed in 39(45%) of both IORT and IORT\WBIR patients. Those included 15(38%) of the exclusive IORT treated patients and 24 (62%) of those treated as a boost. Duration of asymptomatic seroma ranged from 6 months to 6 years. Repeated aspiration was performed in 2 (5%) patients. Postoperative seroma occurred independent of age histological diagnosis, tumour size, tumour grade, lymphovascular invasion, nodal status, receptor status, treatment with neoadjuvant hormonal\chemotherapy, applicator size, dose used or duration of radiotherapy treatment. All reviewed patients have shown increased risk of developing seroma; however, an increased incidence of seroma in the IORT + WBIR treated patients was higher than those who received exclusive IORT treatment.

Postoperative seroma is a common non-life-threatening entity that occasionally may lead to delay in the subsequent treatment plan. IORT is a safe modality with many benefits; however, it may increase the risk of seroma formation independent of the clinical parameters. Promoting the expertise in post IORT breast imaging aids in overcoming diagnostic challenges.

Head and neck cancer (HNC) is the most common malignancy in the Indian males. Most of the cases of HNC present in locally advanced stage and requires a multidisciplinary management approach. Radical or adjuvant external beam radiotherapy (EBRT) is one of the important integral components of the management of HNC.

To find the incidence of hypothyroidism (HT) in patients of HNC treated with radiotherapy with or without concurrent chemotherapy.

A prospective, single institutional longitudinal observational study conducted at the department of radiotherapy, Institute of Post Graduate Medical Education and Research, Kolkata.

In this study, data of 118 patients were analysed. The median age at presentation was 56 years. The most common primary site of malignancy was oral cavity (39%). The patients were stage I, stage II and stage III as 11, 37·3 and 51·7% respectively. The median dose of EBRT was 66 Gy. HT statistically significantly correlated with primary site of malignancy (p = 0·001), dose of EBRT (p = 0·005). At the end of follow-up of 6 months, 39·8% developed HT.

The thyroid gland is an important organ at risk while considering EBRT to neck region. The inclusion of thyroid function test in routine follow-up is mandated.

Small-cell lung cancer (SCLC) has poor prognosis owing to the high risk of distant metastasis.

To identify the prognosticators of brain metastasis from SCLC treated by whole-brain radiotherapy.

We evaluated patients diagnosed with primary brain metastasis from SCLC between 1 January 2010 and 30 September 2019. Age, sex, disease stage at the first examination, time to the diagnosis of brain metastasis, state of other lesions at the diagnosis of brain metastasis, haematological parameters, neurologic symptoms, whole-brain radiotherapy dose, imaging findings of the brain metastasis (single or multiple), and chemotherapy and radiotherapy status were investigated for correlations with survival from the diagnosis of brain metastasis.

A total of 24 participants were evaluated. After radiotherapy, the median survival period was 118·5 (22–998) days, and 21 patients died during the follow-up period. Multivariate stepwise analysis of the four parameters of lactate dehydrogenase (LDH) level (within vs. above the reference value), platelet level (continuous variable), neurologic symptoms (with versus. without), and NSE (neuron-specific enolase) level (continuous variable) identified the following significant differences: neurologic symptoms were 3·81 (95% CI 1·07–13·5, p = 0·04), and NSE was 1·01 (95% CI 1·00–1·01, p = 0·04).

NSE and neurologic symptoms are prognosticators of brain metastasis from SCLC treated by whole-brain radiotherapy.

Harnessing available knowledge and learning from our errors are prerequisites of delivering on the challenge of improving patient safety. Towards Safer Radiotherapy, published in 2008, was a response from the UK’s (UK) radiotherapy community to concerns arising from high profile errors. The report was a driver for the development of a national reporting and learning system for radiotherapy.

A literature review was conducted covering the years from 2009 to 2020. Search terms used were radiotherapy errors, patient safety, incident learning, human factors and trend analysis. A total of 10 papers reported recommendations or implementation of changes to service delivery models following systematic error analysis. None of these were from UK service providers.

Twelve years on from the publication of Towards Safer Radiotherapy, there is little evidence of impact on safety culture within the UK radiotherapy community. Although the UK has a large radiotherapy error dataset, there remain unanswered questions about the impact on the safety culture in radiotherapy.

The purpose of the present study was to assess the accuracy of radiotherapy (RT) structure volume generated by the Monaco treatment planning system (TPS) for three different computed tomography (CT) slice thicknesses. Further, this study addressed the important issue of ‘different volumes of the same RT structure shown at different places’ in the Monaco TPS. Also, the practical impact of this difference in structure volumes has been studied for brain or head and neck patients.

Objects of known volumes were scanned with different CT slice thicknesses and contoured as an RT structure in Monaco TPS and two different volumes provided by the TPS for each RT structure were noted and compared with the real volumes of these objects. In addition, correlation was also assessed between TPS provided volumes and real volumes of these objects. The study was further extended to obtain correlation of volumes in cases of organs that exist in pairs (e.g., eye) in the human body.

Monaco TPS overestimates structure volumes except for objects with sharp corners. Although, volumes shown at different places of the same structure have nearly a linear correlation, volumes under structure table are more accurate than those shown under dose–volume histogram (DVH) statistics (total volume) table. Difference in magnitude between these two volumes has no correlation if this difference is analysed for paired organs.

This study confirmed that Monaco TPS provides ‘different value at different places’ of the volume of a given contoured structure. It is recommended that this issue should be reviewed and resolved by the supplier.

Dosimetric comparison between volumetric-modulated arc therapy (VMAT) and helical tomotherapy (HT) in the treatment of bilateral breast cancer (BBC).

Ten patients treated on HT were selected retrospectively. Dose prescription was 50 Gy in 25 fractions to breast/chest wall and supraclavicular fossa (SCF) while tumour bed was simultaneously boosted to 61 Gy in 25 fractions. VMAT plans were made with four mono-isocentric partial arcs. The monitoring unit (MU) and treatment time were used to quantify the treatment efficiency. Target volumes were compared for homogeneity index (HI), conformity index (CI) while organs at risk (OARs) were compared for relevant dose volumes and integral doses (IDs).

For targets, no significant difference is observed between VMAT and HT in CI but VMAT could give better HI. The mean lung dose, V20 and V5 is 10·6 Gy versus 8·4 Gy (p-value 0·03), 12% versus 11·5% (p-value 0·5) and 78·1% versus 43·4% (p-value 0·005), respectively. The mean heart dose, V30 and V5 is 4·9 Gy versus 4·7 Gy (p-value 0·88), 0·5% versus 1·5% (p-value 0·18) and 26·2% versus 22·8% (p-value 0·4). Integral dose (ID) for the whole body and heart are comparable: 289 Gy kg versus 299 Gy kg (p-value 0·24) and 2·9 Gy kg versus 2·8 Gy kg (p-value 0·80). ID for lungs was significantly higher with VMAT: 7·9 Gy kg versus 6·3 Gy kg (p-value 0·03). There is a 53% reduction in treatment time and 78% in MU with VMAT against HT.

VMAT can generate clinically acceptable plans comparable to HT for BBC. HT shows better control over low dose spillage in lungs compared to VMAT thereby increasing ID to lungs. VMAT shows better homogeneity and efficient treatment delivery than HT.

Teamwork is a central framework in healthcare delivery. Team dynamics can impact the team as a whole and has been identified within the literature as a contributory factor to quality and safety, patient satisfaction, staff satisfaction and overall performance. Within radiation therapy (RT), teamwork is essential in the delivery of high-quality care, yet team building and team development is under-reported.

The focus of this research is to form a better understanding of what plays an impact on teams in a large urban RT cancer centre and how to better engage staff to work together, improve team dynamics and promote team building.

An electronic search of the literature was conducted to better inform debate and aid in the development of team-building sessions in a busy radiotherapy department. Abstracts were screened and relevant articles selected if they met the search criteria that included relevancy related to team building, contributory factors on team dynamics, team-based learning, team performance and implication of civility.

A total of 45 articles were included in the final analysis. The majority were from the disciplines of medicine (45%), business (22%) and nursing (18%). Only 3 of the 45 articles (7%) focused on the profession of RT. Most articles discussed more than 1 theme with team dynamics and team building being the most common themes discussed in 16 articles each (36%). Other common themes included teamwork (31%), respect and civility (20%), leadership and hierarchy (11%), medical errors (11%) and team training (11%). Only 3 of the 45 articles (7%) focused on RT.

There is a lack of longitudinal evidence to support the impact of team building sessions to improve team dynamics and promote a positive, cohesive team environment. Specifically within RT, the impact team building has on team dynamics has been under investigation.

High-quality patient care can be linked to team collaboration and cohesiveness. Changing the culture within a team and engaging in civility and respect in everyday practice has the potential to improve team dynamics, patient safety, staff and patient satisfaction.

The purpose of the study was to evaluate the impact of changes in breathing pattern inside the breath-hold window (BHW) during deep inspiration breath hold treatment for carcinoma left breast patients post-conservative surgery.

Ten patients of carcinoma left breast post-conservative surgery were prospectively selected. Three sets of CT plain images were acquired, one with 5 mm deep inspiration BHW (DIBHR) and the other one with 1 mm BHW matching the lower threshold (DIBHL) and the third one with 1 mm BHW matching the upper threshold (DIBHH) as DIBHR. For all patients, forward intensity-modulated radiotherapy (FIMRT) and volumetric modulated arc therapy (VMAT) plans were generated in the 5 mm BHW CT series and the same plan being copy and pasted in other series. Target volume doses and critical structure doses were tabulated.

Planning target volume coverage was adequate and no significant differences were found in any CT series. Significant differences noted in average left lung V5%, V10% and V18% doses between DIBHR versus DIBHH (p values = 0·0461, 0·0283 and 0·0213, respectively) and DIBHL versus DIBHH (p values = 0·0434, 0·0484 and 0·0334, respectively) for FIMRT plans and V18% doses in DIBHR versus DIBHH (p = 0·0067) in VMAT. No differences in heart and apex of heart doses were found. Left anterior descending artery (LAD) mean doses were significant in DIBHL versus DIBHR, DIBHR versus DIBHH and DIBHL versus DIBHH (p = 0·0012, 0·0444 and 0·0048, respectively) series for FIMRT plans and DIBHR versus DIBHH and DIBHL versus DIBHH (p = 0·0341, 0·0001) for VMAT plans.

The changes in the breathing pattern inside DIBH window level cause some variation in LAD doses and no other significant differences in any parameters noted, so care should be taken while treating patients with preexisting cardiac conditions.

Dosimetric advantages of volumetric-modulated arc therapy (VMAT) over three-dimensional conformal radiotherapy (3D-CRT) are not established in a head-on comparison of a uniform group of locally advanced carcinoma of the cervix (LACC). Therefore, we conducted a dosimetric comparison of these two techniques in LACC patients.

Computed tomography (CT) data of histologically proven de novo LACC, including Stage IIB–IIIB and earlier stages deemed inoperable, were included in this prospective observational dosimetric study. Planning was initially done by 3D-CRT technique (dose of 45–50·4 Gy @ 1·8–2 Gy/# was used in the actual treatment), followed by VMAT planning and appropriate dosimetric comparisons were done in 39 cases.

For planning target volume coverage, D95, D98 and D100 (p < 0·0001 for all parameters) and V95 and V100 (p = 0·002 and <0·0001, respectively) were significantly improved with VMAT. The conformity index (CI) was significantly better with VMAT (p = 0·03), while 3D-CRT had a significantly better homogeneity index (HI)(p = 0·003). Dose to the urinary bladder was significantly reduced with VMAT compared to 3D-CRT for V20–V50, except V10. The doses to the rectum and abdominal cavity were significantly reduced with VMAT compared to 3D-CRT plans for all parameters (V10–V50). The number of organs at risks (OARs) for which constraints were met was higher with VMAT plans than with 3D-CRT plans, with at least four out of the five OARs protected in 46·1 versus 5·1% and all constraints achieved in 15·4% versus none.

We conclude that in dosimetric terms, VMAT is superior to 3D-CRT for LACC.

To evaluate clinically pertinent skin dose and volume parameters for the development of toxicities following accelerated partial breast irradiation (APBI).

Three skin structures of various thicknesses inside the body (2 mm, 3 mm, 4 mm) were contoured over the treated breast retrospectively in a cohort of 62 women who underwent APBI using multi-catheter interstitial brachytherapy. The correlation statistics between the various skin structures and acute and late skin sequelae were evaluated using the Mann–Whitney U test and receiver-operating characteristic analysis. A p-value of <0·05 was considered significant.

At a median follow-up period of 54 months (range: 28–86), a significant correlation was seen between dose received by 0·2 (D0·2) cc of skin 4 mm inside the body as well as volume receiving 100% dose (V100) of skin 3 mm inside the body with cosmesis at 2 years and at last follow-up. The threshold for the two parameters for prediction of excellent or good cosmesis was 90% of the prescribed dose and 0·05 cc, respectively. No significant dosimetric or volumetric correlation was seen with other sequelae like wound dehiscence, fat necrosis, telangiectasia and atrophy.

The results of this study support the use of dose and volumetric indices of the sub-volumes of the skin for correlation with clinical endpoints. However, the same should be validated prospectively in a larger cohort of women undergoing breast brachytherapy.

This study aimed to evaluate acute and late toxicities in nasopharyngeal cancer (NPC) patients who were treated between split-field (SF) and extended-field (EF) step-and-shoot intensity-modulated radiotherapy (IMRT) techniques.

Between January 2011 and October 2011, 21 NPC patients with stage I-IVB (7th edition American Joint Committee on Cancer Staging) were randomly assigned to undergo radiotherapy with SF or EF step-and-shoot IMRT technique.

At a median follow-up time of 60 months (range 3–77), we reported the comparable acute and late toxicities between the two techniques. One patient (9%) in SF-IMRT arm developed grade 3 acute skin toxicity.

Both SF and EF step-and-shoot IMRT techniques for NPC patients did not produce any statistically significant differences in both acute and late toxicities. Although no difference in toxicity was observed, technical problems due to field matching management were the obstacles in utilisation of SF-IMRT in our routine practice.

Previous studies showed that replacing conventional flattened beams (FF) with flattening filter-free (FFF) beams improves the therapeutic ratio in lung stereotactic body radiation therapy (SBRT), but these findings could have been impacted by dose calculation uncertainties caused by the heterogeneity of the thoracic anatomy and by respiratory motion, which were particularly high for target coverage. In this study, we minimised such uncertainties by calculating doses using high-spatial-resolution Monte Carlo and four-dimensional computed tomography (4DCT) images. We aimed to evaluate more reliably the benefits of using FFF beams for lung SBRT.

For a cohort of 15 patients with early-stage lung cancer that we investigated in a previous treatment planning study, we recalculated dose distributions with Monte Carlo using 4DCT images. This included 15 FF and 15 FFF treatment plans.

Compared to Monte Carlo, the treatment planning system (TPS) over-predicted doses in low-dose regions of the planning target volume (PTV). For most patients, replacing FF beams with FFF beams improved target coverage, tumour control, and uncomplicated tumour control probabilities.

Monte Carlo tends to reveal deficiencies in target coverage compared to coverage predicted by the TPS. Our data support previously reported benefits of using FFF beams for lung SBRT.

The overall aim of this study was to evaluate the use of Virtual Environment for Radiotherapy Training Image-Guided Radiotherapy (VERT™IGRT) as a teaching and assessment tool for 3D image matching competency within the radiotherapy clinical setting and explore radiographer perceptions, experiences and integration of VERT™IGRT as an imaging tool.

A mixed-methods study was utilised to measure clinical image matching competencies in the first quantitative phase through means of a workbook and imaging assessment. Phase II used qualitative semi-structured interviews to explore radiographer perceptions.

Workbooks enabled participants to prepare for image assessments. Interview findings were highlighted in three distinctive themes: (1) The need for supervision, guidance and feedback; (2) Experience and practice leads to confidence and competence and (3) Technology supports process but not evaluation.

VERT™IGRT provides a sound platform for training therapeutic radiographer image matching skills, but needs to be delivered with continuous feedback to develop individual decision-making skills. The technology provides opportunities for staff to increase confidence in utilsing image matching technology, but analytical and evaluation skills require supervision and continuous feedback which should be embedded in any educational training programme.

We have investigated the influence in volumetric-modulated arc therapy (VMAT) plans by a sequence of increment of gantry angle (IGA) in definitive radiotherapy treatment for cervical cancer. The plans are quantitatively analysed in terms of conformity index (CI), heterogeneity index (HI), dose–gradient index (DGI), target coverage (TC) by prescription dose, monitor unit (MU) usage, control points (CPs) and dose to organs.

In this retrospective study, we selected 27 patients with cervical cancer having aged between 54 and 69. All the patients enrolled in this study were at T3N1M0 stage of cervical cancer. The prescription dose to planning target volume (PTV) was 50 Gy and was administered in 2 Gy/fraction through VMAT technique. VMAT plans were optimised by varying the parameter ‘IGA’ as 10, 20, 30 and 40°.

Homogenous dose distribution within PTV and TC by prescription dose was significantly enhanced (p < 0·05) with larger IGA. The difference between volume receiving 15 Gy (V15Gy) in bowel was up to 10% with larger IGA (30 and 40°) and V25Gy in femoral head was up to 3% with smaller IGA (10 and 20°). CPs were enhanced and MU usage was reduced with larger IGA (30 and 40°). IGA 40° had reduced the MU usage than IGA 30° but the CI and DGI were compromised due to large MLC field segments.

This study recommends that the larger IGA could yield better results when the number of sectors is even, for a cervical cancer patient. However, more data from more patients need to be obtained and analysed to make this an evidence-based hypothesis.

Conjunctival squamous cell carcinoma (SCC) is a rare tumour of the ocular region and microscopic radical surgical is difficult. There are no single guidelines for therapeutic management and the role of radiation therapy is not clearly defined although conventionally photon or electron beams are used. Proton beam radiotherapy (PBRT) is a new option for a conservative approach and allows good sparing of the organs at risk.

After surgical resection, we collected 15 cases treated at our institution with PBRT. The dose delivered was between 48 and 60 Gy relative biological effectiveness (RBE), with fractions of 12–15 Gy RBE.

After an average period of 48 months, the patients achieved excellent disease control (overall survival and disease-free survival: 86·6%), with minimal acute and late toxicity.

In this work, we present our experience on the use of PBRT technique in SCC treatment. A larger sample of patients is needed to draw conclusions about the impact of this treatment on disease recurrence and overall survival.

Malignant spinal cord compression (MSCC) is a serious condition requiring urgent palliative radiotherapy to alleviate symptoms and avoid permanent paralysis. The aim of this project was to analyse the 30-day mortality rate post-palliative radiotherapy for MSCC patients to identify if radiotherapy can be safely omitted or the fractionation reduced in the poor prognosis group (patients likely to die within 30 days) by biomarkers and performance status (PS).

A retrospective audit was performed (July–December 2019) and data on treatment duration, date of death, biomarkers (C-reactive protein (CRP), albumin) and PS were collected using hospital patient management systems.

Hundred and one patients received palliative radiotherapy for MSCC in the 6-month period. The number of patients who died within 30 days was 17, representing 16·8% mortality rate. Rising CRP levels and poor PS indicated a poorer prognosis in this patient group.

Monitoring biomarkers and PS as standard throughout patients’ treatment is recommended to assess disease progression. Worsening PS and high CRP is an indicator of poor prognosis and early death, and therefore omission of treatment or a single fraction of radiotherapy is recommended.

Prostate cancer is the most commonly diagnosed malignancy and the third leading cause of death among Canadian men. The standard treatment modalities for prostate cancer include prostatectomy, radiation therapy, hormonal therapy and chemotherapy or any combination depending on the stage of the tumour. However, several studies have reported that tobacco smoking at the time of diagnosis and during treatment can potentially impact treatment efficacy, outcome and patients quality of life after treatment.

This narrative literature review elucidates the impacts of tobacco smoking on prostate cancer progression, treatment efficacy, including its effects on prostatectomy, radiation therapy and chemotherapy, risk of cancer recurrence and mortality and quality of life after treatment. Furthermore, we discuss the importance of integrating a smoking cessation programme into the treatment regimen for prostate cancer patients in order to yield more favourable treatment outcomes, reduce risk of recurrence and mortality and increase the quality of life after treatment for prostate cancer patients.

Smoking cessation is one of the most important interventions to prevent cancer and it is also essential after the diagnosis of prostate cancer to improve clinical outcomes. All prostate cancer patients should be advised to quit tobacco use since it can potentially improve treatment response rates and survival, as well as reduce the risk of developing treatment complications and potentially improve the quality of life after treatment. There are several benefits to smoking cessation and it should become an important component of the cancer care continuum in all oncology programmes, starting from prevention of cancer through diagnosis, treatment, survivorship and palliative care. Evidence-based smoking cessation intervention should be sustainably integrated into any comprehensive cancer programme, and the information should be targeted to the specific benefits of cessation in cancer patients.

Radiotherapy is an effective and significant mode of definitive cancer treatment with well-established local tumour control success, especially in the treatment of localised tumours. Although, for metastatic disease, the role of radiotherapy has generally been limited to palliation of symptoms. In the treatment of metastatic diseases settings, the radiation therapy technique has always been confronted with the challenge of the simultaneous treatment of all of the various distant metastatic tumour sites, however, some recent evidence suggests that radiotherapy can potentially induce anticancer immune responses whose effectors potentially migrate to distant metastatic tumours to provoke their regression in cancer patients. Thus, unirradiated distant metastatic tumour sites can exhibit a delayed therapeutic response termed the abscopal effect.

This paper reports on a review of the abscopal effect, including its biological mechanism, the effect of radiation dose and fractionation regime and the timing of immunotherapy administration on radiotherapy-induced abscopal effect, the enhancement of radiotherapy-induced abscopal effects with immunotherapy, the effect of the location of the irradiated tumour and the radiotherapy of multiple tumour sites on the likelihood and effectiveness of inducing abscopal responses in the preclinical and clinical settings and also reports on some evidence of clinical observations in patients.

Although abscopal effects of radiotherapy are still relatively rare in patients, it has gained a lot of interest due to recent development and use of immunotherapy strategies incorporating combinations of targeted immunomodulators and immune checkpoint blockade with radiation therapy. The enhancement of cancer immunotherapy could potentially enable the translation of the concept of abscopal effect into the clinics as a new strategy to induce therapeutically effective anti-tumour immune responses in cancer patients. The combination of radiotherapy and immunotherapy has the potential to expand the role of radiotherapy from a purely local tumour control treatment to play a significant role in advanced and metastatic tumour control and this could likely lead to a paradigm shift in the treatment of patients with metastatic cancer.

Microcomputers play an increasingly important role in the delivery of radiation therapy. Exposure to neutron irradiation can produce undesirable effects in modern microcomputers. The objective of this study is to measure acute and cumulative effects of neutron exposure of Intel-based microcomputers in photon and proton therapy treatment environments.

Multiple computers were irradiated with neutrons produced from MEVION S250 passive scattering proton therapy and from Varian 21EX Linear Accelerator photon therapy systems. The energy of the proton beam was 232 MeV and the photon beam energies were 6 and 18 MV. Rates of fatal errors in computer processing unit (CPU) cores were measured.

Varying rates of fatal system errors due to upsets in the CPU cores were observed. Post-exposure routine stress testing revealed no permanent hardware defects in the random access memory (RAM) or hard disk drive (HDD) of any tested systems. Microchip manufacturers fit increasingly high numbers of transistors in the same volume and the susceptibility to radiation thus increases.

This work explores if the process size of a microchip is the dominant factor and also looked at the short- and long-term effects of neutron irradiation on modern microprocessors in a clinical environment. Additionally, methods of effective shielding are proposed.