COMP Report: An updated algorithm to estimate medical physics staffing levels for radiation oncology.

Purpose: Medical physics staffing models require periodic review due to the rapid evolution of technology and clinical techniques in radiation oncology. We present an update to a grid-based physics staffing algorithm for radiation oncology (originally published in 2012) that has been widely used in Canada over the last decade.

Materials And Methods: The physics staffing algorithm structure was modified to improve the clarity and consistency of input data.

Detection of opsonic antibodies against Enterococcus faecalis cell wall carbohydrates in immune globulin preparations.

Three different commercially available polyvalent immune globulins (IG) were investigated for the existence of antibodies against cell wall carbohydrates of four different E. faecalis serotypes (using a cell wall carbohydrate-enzyme-linked immunosorbent assay), and whether these antibodies mediated opsonic killing (using an opsonic-killing assay). All three IG preparations contained antibodies against all four serotypes (CPS-A to CPS-D).

Poster - Thurs Eve-21: Experience with the Velocity(TM) pre-commissioning services.

As the first Canadian users of the Velocity™ program offered by Siemens, we would like to share our experience with the program. The Velocity program involves the measurement of the commissioning data by an independent Physics consulting company at the factory test cell. The data collected was used to model the treatment beams in our planning system in parallel with the linac delivery and installation.

Hypofractionated accelerated radiotherapy using concomitant intensity-modulated radiotherapy boost technique for localized high-risk prostate cancer: acute toxicity results.

Purpose: To evaluate the acute toxicities of hypofractionated accelerated radiotherapy (RT) using a concomitant intensity-modulated RT boost in conjunction with elective pelvic nodal irradiation for high-risk prostate cancer.

Methods And Materials: This report focused on 66 patients entered into this prospective Phase I study. The eligible patients had clinically localized prostate cancer with at least one of the following high-risk features (Stage T3, Gleason score >or=8, or prostate-specific antigen level >20 ng/mL).

A multicenter randomized trial of breast intensity-modulated radiation therapy to reduce acute radiation dermatitis.

Purpose: Dermatitis is a frequent adverse effect of adjuvant breast radiotherapy. It is more likely in full-breasted women and when the radiation is distributed nonhomogeneously in the breast. Breast intensity-modulated radiation therapy (IMRT) is a technique that ensures a more homogeneous dose distribution.

A study of tumor motion management in the conformal radiotherapy of lung cancer.

Purpose: To assess the benefit derived from the reduction of planning target volumes (PTVs) afforded by tumor motion management in treatment planning for lung cancer.

Methods: We use a simple formula that combines measurements of tumor motion and set-up error for 7 patients to determine PTVs based on the following scenarios: standard uniform 15 mm margin, individualized PTVs (no gating), spirometry-based gating, and active breath-control (ABC). We compare the percent volumes of lung receiving at least 20 Gy (V20) for a standard prescription, and the maximum tolerated doses (MTDs) at fixed V20.

Prediction of lung tumour position based on spirometry and on abdominal displacement: accuracy and reproducibility.

Background And Purpose: A simulation investigating the accuracy and reproducibility of a tumour motion prediction model over clinical time frames is presented. The model is formed from surrogate and tumour motion measurements, and used to predict the future position of the tumour from surrogate measurements alone.

Patients And Methods: Data were acquired from five non-small cell lung cancer patients, on 3 days.

Inverse vs. forward breast IMRT planning.

Breast intensity-modulated radiation therapy (IMRT) improves dose distribution homogeneity within the whole breast. Previous publications report the use of inverse or forward dose optimization algorithms. Because the inverse technique is not widely available in commercial treatment planning systems, it is important to compare the 2 algorithms.

Individualized planning target volumes for intrafraction motion during hypofractionated intensity-modulated radiotherapy boost for prostate cancer.

Purpose: The objective of the study was to access toxicities of delivering a hypofractionated intensity-modulated radiotherapy (IMRT) boost with individualized intrafraction planning target volume (PTV) margins and daily online correction for prostate position.

Methods And Materials: Phase I involved delivering 42 Gy in 21 fractions using three-dimensional conformal radiotherapy, followed by a Phase II IMRT boost of 30 Gy in 10 fractions. Digital fluoroscopy was used to measure respiratory-induced motion of implanted fiducial markers within the prostate.

Correlation of lung tumor motion with external surrogate indicators of respiration.

Purpose: To assess the correlation of respiratory volume and abdominal displacement with tumor motion as seen with X-ray fluoroscopy. Measurements throughout the patient's treatment course allowed an assessment of the interfractional reproducibility of this correlation.

Methods And Materials: Data were acquired from 11 patients; 5 were studied over multiple days.

Computed tomography (CT) evaluation of breast cancer patients with osteolytic bone metastases undergoing palliative radiotherapy--a feasibility study.

Twenty-five patients with osteolytic metastases had computed tomography (CT) scans before and 3 months after palliative radiotherapy. The median % density change following single 8Gy, 20Gy/5#, 30Gy/10# were: 128 (range 98-255), 141 (79-342), and 145 (65-235), respectively. It is feasible to evaluate remineralization of osteolytic lesions with palliative radiotherapy.

Reproducibility of lung tumor position and reduction of lung mass within the planning target volume using active breathing control (ABC).

Purpose: The active breathing control (ABC) device allows for temporary immobilization of respiratory motion by implementing a breath hold at a predefined relative lung volume and air flow direction. The purpose of this study was to quantitatively evaluate the ability of the ABC device to immobilize peripheral lung tumors at a reproducible position, increase total lung volume, and thereby reduce lung mass within the planning target volume (PTV).

Materials And Methods: Ten patients with peripheral non-small-cell lung cancer tumors undergoing radiotherapy had CT scans of their thorax with and without ABC inspiration breath hold during the first 5 days of treatment.

Digital fluoroscopy to quantify lung tumor motion: potential for patient-specific planning target volumes.

Purpose: To apply digital fluoroscopy integrated with CT simulation to measure lung tumor motion and aid in the quantification of individualized planning target volumes.

Methods And Materials: A flat panel digital fluoroscopy unit was modified and integrated with a CT simulator. The stored fluoroscopy images were overlaid with digitally reconstructed radiographs, allowing measurement of the observed lung tumor motion in relation to the corresponding contours on the static digitally reconstructed radiographs.

Integration of digital fluoroscopy with CT-based radiation therapy planning of lung tumors.

Radiation dose escalation may be a means to increase the local control rate of inoperable lung tumors. Treatment plans involve the creation of a uniform planning target volume (PTV) to ensure proper coverage despite patient breathing and setup error. This may lead to unnecessary radiation of normal tissue in shallow breathers or target underdosing for patients with excess internal motion.

Phase II study assessing the effectiveness of Biafine cream as a prophylactic agent for radiation-induced acute skin toxicity to the breast in women undergoing radiotherapy with concomitant CMF chemotherapy.

Purpose: To assess the efficacy of Biafine cream in preventing Grade 2 acute radiation dermatitis, according to the National Cancer Institute of Canada skin radiation toxicity criteria in patients undergoing concomitant adjuvant chemotherapy and radiotherapy to the breast.

Methods And Materials: Sixty patients participated in this study. Patients were treated with a lumpectomy followed by concomitant chemotherapy and radiotherapy to the breast.

Deep inspiration breath hold to reduce irradiated heart volume in breast cancer patients.

Purpose: To evaluate the use of deep inspiration breath hold (DIBH) during tangential breast radiation therapy as a means of reducing irradiated cardiac volume.

Methods And Materials: The Active Breathing Control (ABC) device designed at William Beaumont Hospital, Michigan was used to quantify the potential benefit of radiation delivery during DIBH for five left-sided breast cancer patients. This device initiates a breath hold at a predefined, reproducible lung volume.

The influence of patient geometry on the selection of chest wall irradiation techniques in post-mastectomy breast cancer patients.

Background And Purpose: To evaluate three chest wall (CW) irradiation techniques: wide tangential photon beams, direct appositional electron field and electron arc therapy with regards to target coverage and normal tissue tolerance.

Materials And Methods: Thirty-two post-mastectomy breast cancer patients were planned using three CW irradiation techniques. Computed tomography (CT) simulation was done on all patients and clinical target, heart and lung volumes were contoured.

Computed tomographic simulation of craniospinal fields in pediatric patients: improved treatment accuracy and patient comfort.

Purpose: To reduce the time required for planning and simulating craniospinal fields through the use of a computed tomography (CT) simulator and virtual simulation, and to improve the accuracy of field and shielding placement.

Methods And Materials: A CT simulation planning technique was developed. Localization of critical anatomic features such as the eyes, cribriform plate region, and caudal extent of the thecal sac are enhanced by this technique.

Prediction of obliteration of arteriovenous malformations after radiosurgery: the obliteration prediction index.

Objective: To describe the response to single dose photon stereotactic radiosurgery of arteriovenous malformations (AVMs) so that the probability of success or failure of treatment may be predicted for the individual patient.

Method: The obliteration prediction index (OPI) was calculated for AVMs by dividing the marginal dose of radiation in Gray (Gy) by the lesion diameter in centimetres in cohorts of 42 patients treated with the modified linear accelerator at Toronto-Sunnybrook Regional Cancer Centre and 394 patients treated with the gamma unit at the Royal Hallamshire Hospital, Sheffield, United Kingdom. Patients were grouped into ranges by OPI and the proportion of success and failure was calculated for each group.

Calculation of x-ray spectra for radiosurgical beams.

As conformal radiosurgery using micromultileaf collimators gains feasibility, dose calculation algorithms based on Monte Carlo or convolution techniques may become necessary. These require radiosurgical x-ray spectra. The most accurate method currently available to estimate clinical radiosurgery spectra is the Monte Carlo method.

An asymmetric half-wedged field technique for the treatment of inferiorly extended head and neck cancers.

Adequate dose coverage of the target volume of head and neck cancer patients can be difficult to achieve with lateral opposing fields when the patient's neck is short and the disease involves the lower cervical region. Rotation of the couch away from the side of the gantry, such that the beams are angled towards the inferior aspect of the patient, can result in a better dose distribution. However, if the neck separation is large, unacceptable dose inhomogeneities will still exist.

Buildup region and depth of dose maximum of megavoltage x-ray beams.

The depth of dose maximum, dmax, of megavoltage x-ray beams was studied as a function of beam energy and field size for 6-, 10-, and 18-MV x-ray beams and field sizes ranging from 1 x 1 to 30 x 30 cm2. For a given beam energy, dmax increases rapidly with increasing field size at small fields, reaches a maximum around 5 x 5 cm2 and then gradually decreases with increasing field size for large fields. Monte Carlo simulations combined with measurements verified that the effect observed at small field sizes is caused by in-phantom scatter, while at large fields the effect is due to scatter contamination of the primary beam from the linac head.

A halo-ring technique for fractionated stereotactic radiotherapy.

Stereotactic radiosurgery has become established as an effective treatment modality for certain non-malignant brain diseases such as arteriovenous malformations. This paper describes an extension of our linear accelerator-based radiosurgical technique to fractionated treatment of intracranial disease. The fractionated stereotactic radiotherapy technique expands the use of the modality by sparing normal cells within the treatment volume thus improving the therapeutic ratio.

Buildup region of high-energy x-ray beams in radiosurgery.

The depths of dose maxima of radiosurgical x-ray beams increase with the field diameter in the range from 10-30 mm. Furthermore, the degree of the increase is proportional to the photon beam energy. This behavior is in contrast to that of large radiotherapeutic fields, where the depths of dose maxima decrease with increasing field size.

Cylindrical dose distributions in pseudodynamic rotation radiosurgery: an experimental study.

A linac-based radiosurgical technique is reported which produces cylindrical isodose distributions covering cylindrical targets of arbitrary orientations within the patient's head. The technique uses rectangular collimators and 4 degrees of freedom: gantry and couch rotation, as defined by a previously known dynamic rotation technique, collimator rotation, and collimator length adjustment. The relationship between the four parameters is derived and because of its complexity, the cylindrical dynamic rotation technique is introduced as a pseudodynamic technique.