Maximum tolerated dose in a phase I trial on adaptive dose painting by numbers for head and neck cancer.

Purpose: To determine the maximum tolerated dose (MTD) in a phase I trial on adaptive dose-painting-by-numbers (DPBN) for non-metastatic head and neck cancer.

Materials And Methods: Adaptive intensity-modulated radiotherapy was based on voxel intensity of pre-treatment and per-treatment [(18)F]fluoro-2-deoxy-d-glucose positron emission tomography ((18)F-FDG-PET) scans. Dose was escalated to a median total dose of 80.

Design of and technical challenges involved in a framework for multicentric radiotherapy treatment planning studies.

This report introduces a framework for comparing radiotherapy treatment planning in multicentric in silico clinical trials. Quality assurance, data incompatibility, transfer and storage issues, and uniform analysis of results are discussed. The solutions that are given provide a useful guide for the set-up of future multicentric planning studies or public repositories of high quality data.

Adaptive dose painting by numbers for head-and-neck cancer.

Purpose: To investigate the feasibility of adaptive intensity-modulated radiation therapy (IMRT) using dose painting by numbers (DPBN) for head-and-neck cancer.

Methods And Materials: Each patient's treatment used three separate treatment plans: fractions 1-10 used a DPBN ([(18)-F]fluoro-2-deoxy-D-glucose positron emission tomography [(18)F-FDG-PET]) voxel intensity-based IMRT plan based on a pretreatment (18)F-FDG-PET/computed tomography (CT) scan; fractions 11-20 used a DPBN plan based on a (18)F-FDG-PET/CT scan acquired after the eighth fraction; and fractions 21-32 used a conventional (uniform dose) IMRT plan. In a Phase I trial, two dose prescription levels were tested: a median dose of 80.

Preliminary results on setup precision of prone-lateral patient positioning for whole breast irradiation.

Purpose: The aim of this study was to develop a rapid and reproducible technique for prone positioning and to compare dose-volume indices in prone and supine positions.

Methods And Materials: Eighteen patients underwent computed tomography imaging for radiotherapy planning in prone and supine position. Experience was gained in the first eight patients, which lead to modifications of the Horizon prone breast board (Civco Medical Solutions, Orange City, Iowa, USA) and the patient setup technique.

Measurement techniques, modeling strategies and pitfalls to avoid when implementing a mini MLC in a non dedicated planning system.

Background And Purpose: Ghent University Hospital investigated the feasibility of the Pinnacle system for planning intracranial stereotactic treatments. The aim was to perform precise dose computation using the collapsed cone engine for treatment delivery with the Moduleaf mini-MLC mounted on an Elekta accelerator.

Material And Methods: The Moduleaf was commissioned using dose rate corrected data recorded by a diamond detector and using data measured by cylindrical chambers each limited to restricted field sizes.

Comparison of 6 MV and 18 MV photons for IMRT treatment of lung cancer.

Background And Purpose: To compare 6 MV and 18 MV photon intensity modulated radiotherapy (IMRT) for non-small cell lung cancer.

Materials And Methods: Doses for a cohort of 10 patients, typical for our department, were computed with a commercially available convolution/superposition (CS) algorithm. Final dose computation was also performed with a dedicated IMRT Monte Carlo dose engine (MCDE).

Comparison of dose-volume histograms of IMRT treatment plans for ethmoid sinus cancer computed by advanced treatment planning systems including Monte Carlo.

Background And Purpose: To recompute clinical intensity-modulated treatment plans for ethmoid sinus cancer and to compare quantitatively the dose-volume histograms (DVHs) of the planning target volume (PTV) and the optic organs at risk.

Material And Methods: Ten step-and-shoot intensity-modulated treatment plans were enrolled in this study. Large natural and surgical air cavities challenged the calculation systems.

Decoupling initial electron beam parameters for Monte Carlo photon beam modelling by removing beam-modifying filters from the beam path.

A new method is presented to decouple the parameters of the incident e(-) beam hitting the target of the linear accelerator, which consists essentially in optimizing the agreement between measurements and calculations when the difference filter, which is an additional filter inserted in the linac head to obtain uniform lateral dose-profile curves for the high energy photon beam, and flattening filter are removed from the beam path. This leads to lateral dose-profile curves, which depend only on the mean energy of the incident electron beam, since the effect of the radial intensity distribution of the incident e- beam is negligible when both filters are absent. The location of the primary collimator and the thickness and density of the target are not considered as adjustable parameters, since a satisfactory working Monte Carlo model is obtained for the low energy photon beam (6 MV) of the linac using the same target and primary collimator.

Evaluation of the Sinmed Mastercouch as replacement for a standard couch.

Background And Purpose: Introducing into practice a new carbon-fibre couch necessitates its evaluation with regard to the present clinical situation.

Materials And Methods: In this study, a geometric and dosimetric evaluation has been made for the Sinmed Mastercouch as a replacement for the Elekta C-arm couch with Mylar-tennis racket combination. Geometrically, feasible gantry angles with regard to collision and beam intersection were discriminated as function of isocentric table rotation for 10 treatment isocentres.

The importance of accurate linear accelerator head modelling for IMRT Monte Carlo calculations.

Two Monte Carlo dose engines for radiotherapy treatment planning, namely a beta release of Peregrine and MCDE (Monte Carlo dose engine), were compared with Helax-TMS (collapsed cone superposition convolution) for a head and neck patient for the Elekta SLi plus linear accelerator. Deviations between the beta release of Peregrine and MCDE up to 10% were obtained in the dose volume histogram of the optical chiasm. It was illustrated that the differences are not caused by the particle transport in the patient, but by the modelling of the Elekta SLi plus accelerator head and more specifically the multileaf collimator (MLC).

Automatic generation of a plan optimization volume for tangential field breast cancer radiation therapy.

Background And Purpose: Dose homogeneity is one of the objectives during computer planning of postoperative radiotherapy of the conserved breast. For three-dimensional (3-D) optimization of the dose distribution using serial CT scan images, suitable volumes have to be delineated. The purpose of this study was to develop a computer-generated delineation of a plan optimization volume (POV) and an irradiated volume (IV) and to automate their use in a fast dose homogeneity optimization engine.

MCDE: a new Monte Carlo dose engine for IMRT.

A new accurate Monte Carlo code for IMRT dose computations, MCDE (Monte Carlo dose engine), is introduced. MCDE is based on BEAMnrc/DOSXYZnrc and consequently the accurate EGSnrc electron transport. DOSXYZnrc is reprogrammed as a component module for BEAMnrc.

Whole abdominopelvic radiotherapy (WAPRT) using intensity-modulated arc therapy (IMAT): first clinical experience.

Purpose: Whole abdominopelvic radiation therapy (WAPRT) is a treatment option in the palliation of patients with relapsed ovarian cancer. With conventional techniques, kidneys and liver are the dose- and homogeneity-limiting organs. We developed a planning strategy for intensity-modulated arc therapy (IMAT) and report on the treatment plans of the first 5 treated patients.

Monte Carlo model of the Elekta SLiplus accelerator: validation of a new MLC component module in BEAM for a 6 MV beam.

A new component module (CM), called MLCE, has been implemented in the BEAM program. The CM takes into account the particular 'tongue-and-groove' design of the Elekta multi-leaf collimator (MLC) and the air gap between the leaves. The model was validated by two series of measurements and simulations.

Dose conformation in IMRT for head and neck tumors: which solution to apply?

At Ghent University Hospital, IMRT for head and neck cancer is routinely performed. The desired dose distribution is defined upfront as a range of acceptable doses assigned to each voxel of volumes of interest. It was found important to specify the range of acceptable doses separately to areas of the PTV either in or outside the buildup zone as well as to areas which do or do not intersect with PTV-dose limiting organs at risk (OAR).

Underdosage of the upper-airway mucosa for small fields as used in intensity-modulated radiation therapy: a comparison between radiochromic film measurements, Monte Carlo simulations, and collapsed cone convolution calculations.

Head-and-neck tumors are often situated at an air-tissue interface what may result in an underdosage of part of the tumor in radiotherapy treatments using megavoltage photons, especially for small fields. In addition to effects of transient electronic disequilibrium, for these small fields, an increased lateral electron range in air will result in an important extra reduction of the central axis dose beyond the cavity. Therefore dose calculation algorithms need to model electron transport accurately.

Clinical implementation of an objective computer-aided protocol for intervention in intra-treatment correction using electronic portal imaging.

In order to test the feasibility of a protocol for intra-fractional adjustment of the patient position, during radiation therapy treatment in the pelvic region, a two-fold study is carried out. The protocol involves an objective quantitative measurement of the error in positioning starting from the comparison of a portal image with a reference image. The first part of the study applies the protocol to determine the efficacy of adjustment using subjective determination of the positioning errors by a clinician by measuring the residual errors after adjustment.

On the determination of the effective transmission factor for stainless steel ovoid shielding segments and estimation of their shielding efficacy for the clinical situation.

Commercially available ovoid tubes for gynecological applications used in conjunction with the microSelectron-HDR (Nucletron International B.V., Waardegelder 1, 3905 TH Veenendaal, The Netherlands) for 192Ir sources, allow for shielding.

Computers create new perspectives in radiotherapy.

In diagnostic radiology a revolution has taken place over the last decade with the development of computer-based imaging (CT, MR). Such technologies are now available routinely even in medium-sized radiology departments. In radiotherapy departments, however, computer applications have often been limited to calculation of dose distributions on CT images and administrative tasks.

On-line portal imaging: image quality defining parameters for pelvic fields--a clinical evaluation.

Purpose: A test of several image enhancement techniques, performed on on-line portal images in real clinical circumstances, is presented. In addition a score system enabling us to evaluate image quality on pelvic fields is proposed and validated.

Methods And Materials: Localization images (n = 546) generated by an on-line portal imaging system during the treatment of 13 patients on pelvic fields were obtained by delivering a radiation dose of 6-8 cGy by an 18 MV photon beam, and recorded with a silicon intensified target video camera with adjustable gain, kV- and black level.

Interactive use of on-line portal imaging in pelvic radiation.

We have evaluated a fluoroscopic on-line portal imaging system in routine clinical radiotherapy, involving the treatment of 566 pelvic fields on 13 patients. The image was typically generated by delivering a radiation dose of 6-8 cGy. Comparison between portal image and simulator film was done by eye and all visible errors were corrected before continuing irradiation.

Routine clinical on-line portal imaging followed by immediate field adjustment using a tele-controlled patient couch.

We have evaluated the fluoroscopic on-line portal imaging (OPI) system developed by Siemens (Beamview-1, Concord, CA, U.S.A.

[Clinico-functional data concerning chronic asthmatic bronchitis patients treated wih guacetisal].

Guacetisal was administered to a group of patients suffering from chronic asthmatic bronchitis. The drug in question was shown to possess a good fluidifying, expectorant and indirect anti-cough action, by means of an initial increase of the bronchial secretions and a subsequent progressive decrease of secretions towards the end of the treatment. The analysis of the respiratory parameters examined showed no modifications of statistical significance.