In-vivo EPID dosimetry for IMRT and VMAT based on through-air predicted portal dose algorithm.

We have adapted the methodology of Berry et al. (2012) for Intensity Modulated Radiotherapy (IMRT) and Volumetric Modulated Arc Therapy (VMAT) treatments at a fixed source to imager distance (SID) based on the manufacturer's through-air portal dose image prediction algorithm. In order to fix the SID a correction factor was introduced to account for the change in air gap between patient and imager.

A phase II trial of induction chemotherapy and chemo-IMRT for head and neck squamous cell cancers at risk of bilateral nodal spread: the application of a bilateral superficial lobe parotid-sparing IMRT technique and treatment outcomes.

Purpose: To determine the feasibility of induction chemotherapy and chemo-IMRT in head and neck squamous cell cancers at risk of bilateral nodal spread (midline tumours) and to evaluate whether bilateral superficial lobe parotid-sparing IMRT can reduce the incidence of ⩾G2 subjective xerostomia.

Methods: Patients with midline tumours were enrolled to a phase II trial to receive induction platinum/5-fluorouracil and concomitant platinum with combined superficial lobe parotid-sparing IMRT. The primary site and involved nodal levels received 65 Gy in 30 fractions (f) and at risk nodal levels, 54 Gy/30f.

Pulsed brachytherapy: a modelled consideration of repair parameter uncertainties and their influence on treatment duration extension and daytime-only "block-schemes".

Objectives: The radiobiological modelling of all types of protracted brachytherapy is susceptible to uncertainties in the values of tissue repair parameters. Although this effect has been explored for many aspects of pulsed brachytherapy (PB), it is usually considered within the constraint of a fixed brachytherapy treatment time. Here the impact of repair parameter uncertainty is assessed for PB treatments of variable duration.

Dose-escalated intensity-modulated radiotherapy is feasible and may improve locoregional control and laryngeal preservation in laryngo-hypopharyngeal cancers.

Purpose: To determine the safety and outcomes of induction chemotherapy followed by dose-escalated intensity-modulated radiotherapy (IMRT) with concomitant chemotherapy in locally advanced squamous cell cancer of the larynx and hypopharynx (LA-SCCL/H).

Methods And Materials: A sequential cohort Phase I/II trial design was used to evaluate moderate acceleration and dose escalation. Patients with LA-SCCL/H received IMRT at two dose levels (DL): DL1, 63 Gy/28 fractions (Fx) to planning target volume 1 (PTV1) and 51.

The IPEM code of practice for determination of the reference air kerma rate for HDR (192)Ir brachytherapy sources based on the NPL air kerma standard.

This paper contains the recommendations of the high dose rate (HDR) brachytherapy working party of the UK Institute of Physics and Engineering in Medicine (IPEM). The recommendations consist of a Code of Practice (COP) for the UK for measuring the reference air kerma rate (RAKR) of HDR (192)Ir brachytherapy sources. In 2004, the National Physical Laboratory (NPL) commissioned a primary standard for the realization of RAKR of HDR (192)Ir brachytherapy sources.

Dosimetry audit for a multi-centre IMRT head and neck trial.

Background And Purpose: PARSPORT was a multi-centre randomised trial in the UK which compared Intensity-Modulated Radiotherapy (IMRT) and conventional radiotherapy (CRT) for patients with head and neck cancer. The dosimetry audit goals were to verify the plan delivery in participating centres, ascertain what tolerances were suitable for head and neck IMRT trials and develop an IMRT credentialing program.

Materials And Methods: Centres enrolling patients underwent rigorous quality assurance before joining the trial.

Dose-volume constraints to reduce rectal side effects from prostate radiotherapy: evidence from MRC RT01 Trial ISRCTN 47772397.

Purpose: Radical radiotherapy for prostate cancer is effective but dose limited because of the proximity of normal tissues. Comprehensive dose-volume analysis of the incidence of clinically relevant late rectal toxicities could indicate how the dose to the rectum should be constrained. Previous emphasis has been on constraining the mid-to-high dose range (>/=50 Gy).

Pre-trial quality assurance processes for an intensity-modulated radiation therapy (IMRT) trial: PARSPORT, a UK multicentre Phase III trial comparing conventional radiotherapy and parotid-sparing IMRT for locally advanced head and neck cancer.

The purpose of this study was to compare conventional radiotherapy with parotid gland-sparing intensity-modulated radiation therapy (IMRT) using the PARSPORT trial. The validity of such a trial depends on the radiotherapy planning and delivery meeting a defined standard across all centres. At the outset, many of the centres had little or no experience of delivering IMRT; therefore, quality assurance processes were devised to ensure consistency and standardisation of all processes for comparison within the trial.

Intensity Modulated Radiotherapy (IMRT) in locally advanced thyroid cancer: acute toxicity results of a phase I study.

Background And Purpose: This phase 1 study was designed to determine the toxicity of accelerated fractionation IMRT in locally advanced thyroid cancer.

Methods: Patients with high risk locally advanced thyroid cancer who required post-operative EBRT were recruited. A single-phase inverse-planned-simultaneous-boost was delivered by IMRT: 58.

A versatile phantom for quality assurance in the UK Medical Research Council (MRC) RT01 trial (ISRCTN47772397) in conformal radiotherapy for prostate cancer.

Within the UK RT01 trial the MRC also funded a quality assurance (QA) programme. This included a planning and dosimetry audit at participating centres using a purpose built phantom. Geometrical setup was visually assessed via field shaping around the phantom GTV (to within the order of 1 mm).

The dose distribution of low dose rate Cs-137 in intracavitary brachytherapy: comparison of Monte Carlo simulation, treatment planning calculation and polymer gel measurement.

In this study, the dose distribution delivered by low dose rate Cs-137 brachytherapy sources was investigated using Monte Carlo (MC) techniques and polymer gel dosimetry. The results obtained were compared with a commercial treatment planning system (TPS). The 20 mm and the 30 mm diameter Selectron vaginal applicator set (Nucletron) were used for this study.

Questionnaire based quality assurance for the RT01 trial of dose escalation in conformal radiotherapy for prostate cancer (ISRCTN 47772397).

Background And Purpose: In order to ensure the validity of the outcome of the Medical Research Council's 'RTO1 trial' of dose escalation in conformal radiotherapy for prostate cancer it was considered important that the quality of treatment delivery should meet an adequate standard across all contributing centres. A questionnaire was therefore devised to ensure that all aspects of the planning and delivery process were adequately covered.

Patients And Methods: The questionnaire considered each step in the planning and delivery process and drew the attention of the participants to the specific requirements of the trial.

Implementing the UK Medical Research Council (MRC) RT01 trial (ISRCTN 47772397): methods and practicalities of a randomised controlled trial of conformal radiotherapy in men with localised prostate cancer.

Background And Purpose: Radiotherapy is the most frequently used treatment for men with localised prostate cancer. Conformal radiotherapy (CFRT) is a relatively new development. MRC RT01 was set-up to explore optimum CFRT dose.

Intensity-modulated radiotherapy improves target coverage, spinal cord sparing and allows dose escalation in patients with locally advanced cancer of the larynx.

Background And Purpose: An investigation has been carried out into the potential of intensity-modulated radiotherapy (IMRT) to improve the coverage of the targets and the sparing of the spinal cord (SC) in radiotherapy treatment of the larynx and bilateral cervical lymph nodes, in patients with advanced larynx cancer.

Patients And Methods: Conventional radiotherapy (CRT) and IMRT plans were produced for six patients to treat the larynx (PTV1) and lymph nodes (PTV2) to 50 Gy (phase 1). A second plan was created to treat the PTV1 to 65 Gy and PTV2 to 50 Gy (phases 1 and 2).

IMRT clinical implementation: prostate and pelvic node irradiation using Helios and a 120-leaf multileaf collimator.

Dynamic intensity modulated radiation therapy (IMRT) to treat prostate and pelvic nodes using the Varian 120-leaf Millennium multileaf collimator (MLC) has been implemented in our clinic. This paper describes the procedures that have been undertaken to achieve this, including some of the commissioning aspects of Helios, verification of the dynamic dose delivery, and quality assurance (QA) of the dose delivered to the patient. Commissioning of Helios included measurements of transmission through the 120-leaf MLC, which were found to be 1.

Monte Carlo calculation of output factors for circular, rectangular, and square fields of electron accelerators (6-20 MeV).

Monte Carlo (MC) techniques can be used to build a simulation model of an electron accelerator to calculate output factors for electron fields. This can be useful during commissioning of electron beams from a linac and in clinical practice where irregular fields are also encountered. The Monte Carlo code BEAM/EGS4 was used to model electron beams (6-20 MeV) from a Varian 2100C linear accelerator.

Influence of a vac-fix immobilization device on the accuracy of patient positioning during routine breast radiotherapy.

Continued use of basic planning and treatment techniques, in contrast to the improved methods implemented at many other anatomical sites, has emphasized the need for improved breast dosimetry. Any future technique delivering a superior three-dimensional dose distribution will be of maximum benefit if set-up errors are minimized. To determine the influence of vacuum moulded bag (vac-fix) immobilization on routine breast radiotherapy, 17 patients received half their radiotherapy fractions using our standard breast board technique and half using a vac-fix device positioned on the breast board.

A comparison of multileaf collimator with conformal blocks for the boost phase of dose-escalated conformal prostate radiotherapy.

A multileaf collimator (MLC) is compared with conformal blocks for delivering the boost phase of dose-escalated conformal prostate radiotherapy. When using conformal blocks, the volume of rectum irradiated to 90% (V90) is lower (1.4+/-1.

Radiological thickness measurement using a liquid ionization chamber electronic portal imaging device.

We present a method of calibrating the Portal Vision electronic portal imaging device to obtain radiological thickness maps for compensator design. In this method, coefficients are derived to describe the relationship between intensity and thickness for a set of water-equivalent blocks. The effects of four parameters were studied: (a) The dose response of the system was measured and found to be describable by a square-root function.

Comparison of a multi-leaf collimator with conformal blocks for the delivery of stereotactically guided conformal radiotherapy.

Stereotactically-guided conformal radiotherapy is a practical technique for irradiating irregular lesions in the brain. The shaping of the conformal fields may be achieved using lead alloy blocks, a conventional multi-leaf collimator (MLC) or a mini/micro-MLC. Although the former gives more precise shaping, it is labour intensive.

60 Gy isodose volumes in carcinoma of the cervix and their relation to the geometry of uterine tube and ovoids.

The International Commission on Radiation Units and Measurements recommends the use of 60 Gy isodose volumes for reporting doses in the intracavity treatment of carcinoma of the uterine cervix. This study was aimed at determining the variation in isodose volumes while using different sizes of intrauterine tubes and ovoids, with different applicator geometries. It was based on the treatment plans of 175 patients with cervical cancer, treated with low dose rate intracavitary brachytherapy with or without additional external beam radiotherapy.

Portal imaging protocol for radical dose-escalated radiotherapy treatment of prostate cancer.

Purpose: The use of escalated radiation doses to improve local control in conformal radiotherapy of prostatic cancer is becoming the focus of many centers. There are, however, increased side effects associated with increased radiotherapy doses that are believed to be dependent on the volume of normal tissue irradiated. For this reason, accurate patient positioning, CT planning with 3D reconstruction of volumes of interest, clear definition of treatment margins and verification of treatment fields are necessary components of the quality control for these procedures.

A quality assurance procedure for the Varian multi-leaf collimator.

A quick, simple set of tests has been devised to assess and record the quality assurance aspects of the Varian multi-leaf collimator (MLC) when used for clinical treatments on a regular basis. Pre-treatment, daily and weekly checks are performed by the radiographers while more detailed quality assurance is carried out at monthly and quarterly intervals by physicists.

Beam data measurements for dynamic wedges on Varian 600C (6 MV) and 2100C (6 and 10 MV) linear accelerators.

The measurement of beam data for dynamic wedge dosimetry requires the integration of radiation dose at points across the radiation field during the dose delivery. The different measurement techniques required when using a linear diode array to measure beam profiles and when using ionization chambers to measure depth doses and effective wedge factors are described. The segmented treatment tables (STTS), which specify the delivered dose as a function of jaw position, are used by the control algorithm to deliver dynamic wedge fields.