To use cone-beam computed tomography (CBCT) images for treatment planning, the Hounsfield unit (HU)-electron density (ED) calibration table for CBCT should be stable. The purpose of this study was to verify the stability of the HU values for the CBCT system over 1 year and to evaluate the effects of variation in HU-ED calibration curves on dose calculation.

A tissue characterisation phantom was scanned with the field of view (FOV) of size S (FOV-S) and FOV of size M (FOV-M) using the CBCT system once a month for 1 year. A single field treatment plan was constructed on digital phantom images to validate the dose distribution using mean HU-ED calibration curves and possible variations.

HU values for each material rod over the observation period varied with trend. The HU value of the cortical bone rod decreased by about 100 HU for the FOV-S and by about 300 HU for the FOV-M. Possible variation in the HU-ED calibration curves produced a ≤17·9% dose difference in the dose maximum in the treatment plan.

The CBCT system should be calibrated periodically for consistent dose calculation.

To analyse the preliminary results of CyberKnife stereotactic radiotherapy (SBRT) boost in primary head and neck cancer patients among Indian population.

A total of nine patients of primary head and neck cancer were treated with CyberKnife SBRT boost after intensity-modulated radiation therapy (IMRT). The median phase 1 IMRT dose was 54 Gy/27 fractions. Histological types included squamous cell carcinoma (n=7) and adenoid cystic carcinoma (n=2). Response was evaluated using positron emission tomography/computed tomography and detailed clinical examination.

As a preliminary analysis with median follow up of 8 months (range: 6–19 months), phase 2 median tumour volume of 16·3 cc and a median dose of 5 Gy per fraction, eight patients had loco-regionally stable disease and one had distant metastasis. With objective assessment five patients had complete response. Treatment was well tolerated with no grade 3 or more acute toxicities directly related to CyberKnife boost.

CyberKnife SBRT boost is an attractive option for primary head and neck cancers especially where disease is in close proximity to critical structures hindering radical dose delivery. Future prospective analysis and optimum assessment of total biological effective dose (BED) in a properly selected case might actually benefit the use of CyberKnife SBRT boost.

To investigate the doses given to the kidneys and the small intestines for three radiation therapy techniques [anterior–posterior (APPA) fields, three fields and volumetric-modulated arc therapy (VMAT)] for spinal cord compression (SCC) patients with metastatic disease in the lower thoracic or lumbar spine and to monitor the time spent by clinicians and dose planners.

Radiation therapy is one of the main treatment modalities for SCC. Typical palliative radiation therapy techniques have used APPA fields or a three-field technique.

However, as delivery techniques have evolved dramatically over the past decades, VMAT has gained wide acceptance. VMAT allows for a dose reduction in the organs at risk. Such a dose reduction may result in less toxicity.

The use of the VMAT technique may require more time for contouring and planning compared with the APPA and three-field techniques. Any potential dosimetric benefit of VMAT must not be outweighed by large amounts of extra time spent by clinicians and dose planners.

For 20 patients treated with radiation therapy for SCC at our hospital, we created a VMAT plan, and the more traditionally used APPA and three-field plans. The mean kidney doses and the volume of bowel, which received 20 Gy, were extracted for each plan. The correlations between parameters for three techniques were determined.

Furthermore, the time required for contouring targets for five patients; and the time required to plan five patients, was recorded.

VMAT lead to the most conformal distributions: the high-dose areas were restricted to the target volume, whereas the healthy tissue, especially the bowel, received a lower dose. In contrast, the APPA plan lead to a larger volume of bowel being irradiated, whereas the three-field technique spared the bowel at the expense of a higher dose to the kidneys.

The average contouring time was 16 minutes, the average planning time was 38 minutes.

Patients treated for SCC in the lower thoracic or lumbar region may benefit from VMAT treatment, as it reduces the dose to the bowel and kidneys compared with APPA or three-field treatments.

In this work, dosimetric properties of the PTW Octavius detector in and out of the irradiation field have been evaluated. The 2D array of ion chambers has the potential to simplify the linear accelerator QA and pre-treatment verification.

The evaluation was performed using customised written codes in Matlab and SPSS software for statistical analysis.

Experiments indicate that the reproducibility and stability of the measurements were excellent; the detector showed the same signal with a maximum deviation of <0·5% in the short and long term. Comparisons of the ion chamber with the detector showed the same results with a maximum deviation of ~0·1%. As the detector response is linear with the dose, it can be used for the measurement at regions of high-dose gradient effectively. Logarithmic regression y=0·127 ln(x)+0·729 for detector signal and field size changes yielded a coefficient of determination of 0·997. The dose value decreases with increase in source-to-surface distance, which was modelled using a binomial regression with a coefficient of determination of 0·998 that agrees with the ionisation chamber measurement within 1%.

On the basis of the measurements and comparisons performed, this system is a reliable and accurate dosimeter for quality assurance in radiotherapy.

Cholangiocarcinoma (CCA) or klatskin’s tumour involves malignant tumours at the liver hilum’s biliary confluence. Incidence of CCA results in unresectable tumours that require appropriate therapy to improve quality of life. The liver is considered as the most frequent site of tumour recurrence. Promising results of long-term survival have been established with computed tomography-guided high-dose-rate brachytherapy.

Intraluminal brachytherapy (ILBT) is performed through the percutaneous transhapatic bile duct drain tube (PTBD). The passage of the brachytherapy guide tube through the bile duct is more complex compared with oesophageal/endobronchial application.

It results in a recoiled view of the tube in the abdominal region of the computed tomography (CT) scan. Owing to inherent artefacts induced by metal stents in CT scans, intersected view is possible between the ILBT guide tube and the intra-hepatic drain tube. It would mislead the planner to track wrong passage that could result in fatal error.

In this case study, we contoured the ILBT guide tube by cross-verifying its position with a digitally reconstructed radiograph (DRR) before catheter tracking. Thus, it ensures precise simulation of source dwell positions, thereby avoiding high-dose delivery to nearby vital organs such as intestines, liver hilum and blood vessels.

Proliferating trichilemmal tumour (PTT) is a benign tumour originating from the outer root sheath of a hair follicle. In rare instances, malignant transformation has been reported, evidenced by regional or distant metastases. Malignant transformation of PTT is often confused with squamous cell carcinoma. PTT usually occur as a solitary lesion on the scalp. It was first described as a proliferating epidermoid cyst by Wilson-Jones in 1966.

A female patient presented with a growing lesion on scalp in the right parietal region. She had already undergone excision for the same 8 months ago. The cyst was surgically removed and scalp was treated with electron therapy using a field dimension of 8×8 cm in 2011. Now, the patient is disease free with good quality of life.

Oncologists can consider electron therapy in management of PTT. This can improve cosmesis and quality of life of these patients.

A systematic literature review of six computerised databases was undertaken in order to review and summarise a forward planned lung stereotactic ablative body radiotherapy (SABR) treatment planning (TP) technique as a starting point for clinical implementation in the author’s department based on current empirical research. The data were abstracted and content analysed to synthesise the findings based upon a SIGN quality checklist tool.

A four-dimensional computed tomography scan should be performed upon which the internal target volume and organs at risk (OAR) are drawn. A set-up margin of 5 mm is applied to account for inter-fraction motion. The field arrangement consists of a combination of 7–13 coplanar and non-coplanar beams all evenly spaced. Beam modifiers are used to assist in the homogeneity of the beam, although a 20% planning target volume dose homogeneity is acceptable. The recommended fractionations by the UK SABR Consortium are 54 Gy in 3 fractions (standard), 55–60 Gy in 5 fractions (conservative) and 50–60 Gy in 8–10 fractions (very conservative). Conformity indices for both the target volume and OAR will be used to assess the planned distribution.

An overview of a clinically acceptable forward planned lung SABR TP technique based on current literature as a starting point, with a view to inverse planning with support from the UK SABR Consortium mentoring scheme.

The Calypso 4D Localization System gives the possibility to track the tumour during treatment, with no additional ionising radiation delivered. To monitor the patient continuously an array is positioned above the patient during the treatment. We intend to study, for various gantry angles, the attenuation effect of the array for 6- and 10 MV and flattening filter free (FFF) 6- and FFF 10 MV photon beams.

Measurements were performed using an ion chamber placed in a slab phantom positioned at the linac isocenter for 6 MV, 10 MV, FFF 6 MV and FFF 10 MV photon beams. Measurements were performed with and without array above the phantom for 0°, 10°, 20°, 40° and 50° beam angle for a True Beam STx linac, for 5×5 and 10×10 and 15×15 cm2 field size beams to evaluate the attenuation of the array. A VMAT treatment plan was measured using an ArcCheck with and without the array in the beam path.

Attenuation measured values were up to 3%. Attenuation values were between 1 and 2% with the exception of the 30°–50° gantry angles which were up to 3.3%. The ratio values calculated in the ArcCheck for relative dose and absolute dose 10 were both 1·00.

Attenuation of the treatment beam by the Calypso array is within acceptable limits.

Sinonasal teratocarcinosarcoma (TCS) are highly aggressive and rare malignant tumours arising from the heterogeneous admixture of components of all the three germ cell layers. There are <60 cases that have been reported in the literature. In spite of aggressive therapy, the average survival is <3 years with multimodality therapy. In total, 70% of the patients who survived >1 year received regimen of combined surgery and adjuvant therapies and this suggests that aggressive therapeutic approaches may improve the treatment outcome.

We are reporting a case study of sinonasal TCS treated with initial surgery followed with concurrent chemoradiotherapy using intensity-modulated radiotherapy (IMRT) technique. The concurrent chemotherapy and adjuvant chemotherapy consisted of carboplatin and etoposide.

This aggressive treatment protocol of concurrent chemoradiation along with adjuvant chemotherapy is well tolerated and produced 5-year locoregional control and survival without any long-term morbidities.

Our treatment protocol was well tolerated and the outcome in this individual patient has been encouraging. This could justify a combined modality approach with post-operative simultaneous-integrated boost-IMRT and chemotherapy (concurrent and adjuvant) for future patient with sinonasal TCS.

Monte Carlo (MC) simulations have been used extensively for benchmarking photon dose calculations in modern radiotherapy using linear accelerators (linacs). Moreover, a major barrier to widespread clinical implementation of MC dose calculation is the difficulty in characterising the radiation source using data reported from manufacturers.

This work aims to develop a generalised full MC histogram source model of an Elekta Precise SL-25 linac (electron exit window, target, flattening filter, monitor chambers and collimators) for 6 MV photon beams used in standard therapies. The inclusion of many different probability processes such as scatter, nuclear reactions, decay, capture cross-sections and more led to more realistic dose calculations in treatment planning and quality assurance.

Two different codes, MCNPX 2·6 and EGSr-BEAM, were used for the calculation of particle transport, first in the geometry of the internal/external accelerator source, and then followed by tracking the transport and energy deposition in phantom-equivalent tissues. A full phase space file was scored directly above the upper multilayer collimator’s jaws to derive the beam characteristics such as planar fluence, angular distribution and energy spectrum. To check the quality of the generated photon beam, its depth dose curves and cross-beam profiles were calculated and compared with measured data.

In-field dose distributions calculated using the accelerator models were tuned to match measurement data with preliminary calculations performed using the accelerator information provided by the manufacturer. Field sizes of 3×3, 5×5, 10×10, 15×15 and 20×20 cm2 were analysed. Local differences between calculated and measured curve doses beneath 2% were obtained for all the studied field sizes. Higher discrepancies were obtained in the air–water interface, where measurements of dose distributions with the ionisation chamber need to be shifted for the effective point of measurement.

The agreements between MC-calculated and measured dose distributions were excellent for both codes, showing the strength and stability of the proposed model. Beam reconstruction methods as direct input to dose-calculation codes using the recorded histograms can be implemented for more accurate patient dose estimation.

Orbital metastases lead to many distressful symptoms.

A case-report of a 44-year-old woman with a melanoma metastasis in the orbital cavity, is reported. A patient presented with headache, proptosis and diplopia. The stereotactic radiotherapy of 19.5 Gy in three fractions using CyberKnife was performed. Follow-up examination 7 months later revealed satisfactory local control of the tumour, alleviation of orbital symptoms with no negative impact on visual function.

Stereotactic radiotherapy seems to be a safe and effective treatment of orbital metastases from melanoma.

Immobilisation for patients undergoing brain or head and neck radiotherapy is achieved using perspex or thermoplastic devices that require direct moulding to patient anatomy. The mould room visit can be distressing for patients and the shells do not always fit perfectly. In addition the mould room process can be time consuming. With recent developments in three-dimensional (3D) printing technologies comes the potential to generate a treatment shell directly from a computer model of a patient. Typically, a patient requiring radiotherapy treatment will have had a computed tomography (CT) scan and if a computer model of a shell could be obtained directly from the CT data it would reduce patient distress, reduce visits, obtain a close fitting shell and possibly enable the patient to start their radiotherapy treatment more quickly.

This paper focuses on the first stage of generating the front part of the shell and investigates the dosimetric properties of the materials to show the feasibility of 3D printer materials for the production of a radiotherapy treatment shell.

Computer algorithms are used to segment the surface of the patient’s head from CT and MRI datasets. After segmentation approaches are used to construct a 3D model suitable for printing on a 3D printer. To ensure that 3D printing is feasible the properties of a set of 3D printing materials are tested.

The majority of the possible candidate 3D printing materials tested result in very similar attenuation of a therapeutic radiotherapy beam as the Orfit soft-drape masks currently in use in many UK radiotherapy centres. The costs involved in 3D printing are reducing and the applications to medicine are becoming more widely adopted. In this paper we show that 3D printing of bespoke radiotherapy masks is feasible and warrants further investigation.

To evaluate the dosimetric errors associated with the effect of the collimator angle error in volumetric-modulated arc therapy (VMAT) treatments.

Four patients with different planning target volume (PTV) and localisations treated using VMAT were analysed (high-risk prostate, low-risk prostate, head and neck (H&N) and holocranial with hippocampus protection) in terms of dosimetric variations when errors in the collimator angle were introduced. Original plans underwent modifications of the planned collimator angles of ±0·5°, ±1° and ±1·5°. These modified plans were re-calculated using the same original plan fluencies, and the resulting dose–volume histograms and homogeneity index (HI-ICRU) were compared.

For the high-risk prostate case, there was a noticeable loss of PTV dose coverage for collimator angle errors larger than ±1°, with HI-ICRU relative variations up to 75% in the range analysed. The low-risk prostate case did not present significant changes in organs at risk or PTV dose coverage. For the H&N case, the spinal cord presented changes around 4% for D0·1 cc. In the holocranial case, optic lens showed dose variations up to 5% for collimator angle errors larger than ±1°.

The effect of the collimator error in VMAT increased as the PTV increased.

For selecting the position of the isocentre, one should be cautious, and whenever possible choose a position close to the geometrical centre of the PTVs in order to avoid or minimise errors from the calibration of the collimator angle.

Histiocystic sarcoma is a rare, but aggressive tumour that often involves extranodal sites. Histiocystic sarcoma is recognised by the World Health Organization as one of six subtypes of dendritic cell neoplasms. Diagnosis is difficult due to overlapping immunohistochemistry with other dendritic cell neoplasms. The optimal roles for chemotherapy, radiotherapy and surgery in the treatment of histiocytic sarcoma remain unknown.

We report a case of a patient with histiocytic sarcoma diagnosed after excisional biopsy and immunohistochemistry testing.

The patient underwent external beam radiation therapy (EBRT). After 18 Gray (Gy), the 8 cm lesion had regressed to ~5 cm in diameter. The treatments were continued to a total dose of 45 Gy with the lesion regressing to less than a centimeter by the end of treatment. Local control was maintained but the patient died of acute myelogenous leukemia 5 months after her treatment.

This case suggests that histicytic sarcomas can be controlled locally with EBRT.