High-dose-rate interstitial brachytherapy vs external beam radiation for the treatment of complex keloids.

Postoperative external beam radiation therapy (EBRT) with superficial X-rays or electrons and high-dose-rate brachytherapy (HDR BT) are both viable options for managing keloid scars. However, complex keloid scars are especially challenging to manage. We aim to compare the benefit and challenges between interstitial HDR BT and electron EBRT in treating the complex keloids.

Quantitative Medical Physics National Job Data Distribution Analysis.

Purpose: The purpose of this study was to investigate the contemporary distribution of medical physics (MP) employment opportunities across the United States.

Methods And Materials: An annual record (2018-2019) of advertised full-time MP jobs was created using publicly available information from the American Association of Physicists in Medicine and Indeed websites. Listed jobs were categorized based on position name, work experience, job function, and geographic region.

Scatter imaging during lung stereotactic body radiation therapy characterized with phantom studies.

By collecting photons scattered out of the therapy beam, scatter imaging creates images of the treated volume. Two phantoms were used to assess the possible application of scatter imaging for markerless tracking of lung tumors during stereotactic body radiation therapy (SBRT) treatment. A scatter-imaging camera was assembled with a CsI flat-panel detector and a 5 mm diameter pinhole collimator.

Compton scatter imaging: A promising modality for image guidance in lung stereotactic body radiation therapy.

Purpose: Lung stereotactic body radiation therapy (SBRT) requires delivering large radiation doses with millimeter accuracy, making image guidance essential. An approach to forming images of patient anatomy from Compton-scattered photons during lung SBRT is presented.

Methods: To investigate the potential of scatter imaging, a pinhole collimator and flat-panel detector are used for spatial localization and detection of photons scattered during external beam therapy using lung SBRT treatment conditions (6 MV FFF beam).

Characterization of Compton-scatter imaging with an analytical simulation method.

By collimating the photons scattered when a megavoltage therapy beam interacts with the patient, a Compton-scatter image may be formed without the delivery of an extra dose. To characterize and assess the potential of the technique, an analytical model for simulating scatter images was developed and validated against Monte Carlo (MC). For three phantoms, the scatter images collected during irradiation with a 6 MV flattening-filter-free therapy beam were simulated.

Dosimetric effects of saline- versus water-filled balloon applicators for IORT using the model S700 electronic brachytherapy source.

Purpose: The Xoft Axxent Electronic Brachytherapy System (Xoft, Inc., San Jose, CA) is a viable option for intraoperative radiation therapy (IORT) treatment of early-stage breast cancer. The low-energy (50-kVp) X-ray source simplifies shielding and increases relative biological effectiveness but increases dose distribution sensitivity to medium composition.

Automated survey of 8000 plan checks at eight facilities.

Purpose: To identify policy and system related weaknesses in treatment planning and plan check work-flows.

Methods: The authors' web deployed plan check automation solution, PlanCheck, which works with all major planning and record and verify systems (demonstrated here for mosaiq only), allows them to compute violation rates for a large number of plan checks across many facilities without requiring the manual data entry involved with incident filings. Workflows and failure modes are heavily influenced by the type of record and verify system used.

Reporting small bowel dose in cervix cancer high-dose-rate brachytherapy.

Small bowel (SB) is an organ at risk (OAR) that may potentially develop toxicity after radiotherapy for cervix cancer. However, its dose from brachytherapy (BT) is not systematically reported as in other OARs, even with image-guided brachytherapy (IGBT). This study aims to introduce consideration of quantified objectives for SB in BT plan optimization and to evaluate the feasibility of sparing SB while maintaining adequate target coverage.

Thermal effusivity changes as a precursor to moist desquamation.

Skin toxicity is a ubiquitous side effect in radiotherapy and can be difficult to predict. Moist desquamation in cancer patients can decrease quality of life and occasionally demand unplanned treatment breaks thus worsening outcome. In breast cancer patients, moist desquamation occurs approximately one-third of the time, and while avenues such as intensity-modulated radiation therapy exist to decrease skin side effects, they may be prohibitively expensive to distribute widely.

A simplified technique for delivering total body irradiation (TBI) with improved dose homogeneity.

Purpose: Total body irradiation (TBI) with megavoltage photon beams has been accepted as an important component of management for a number of hematologic malignancies, generally as part of bone marrow conditioning regimens. The purpose of this paper is to present and discuss the authors' TBI technique, which both simplifies the treatment process and improves the treatment quality.

Methods: An AP/PA TBI treatment technique to produce uniform dose distributions using sequential collimator reductions during each fraction was implemented, and a sample calculation worksheet is presented.

Comparison of tumor and normal tissue dose for accelerated partial breast irradiation using an electronic brachytherapy eBx source and an Iridium-192 source.

The objective of this study has been to compare treatment plans for patients treated with electronic brachytherapy (eBx) using the Axxent System as adjuvant therapy for early stage breast cancer with treatment plans prepared from the same CT image sets using an Ir-192 source. Patients were implanted with an appropriately sized Axxent balloon applicator based on tumor cavity size and shape. A CT image of the implanted balloon was utilized for developing both eBx and Ir-192 brachytherapy treatment plans.

Helical tomotherapy delivery of an IMRT boost in lieu of interstitial brachytherapy in the setting of gynecologic malignancy: feasibility and dosimetric comparison.

Interstitial brachytherapy is an important means by which to improve local control in gynecologic malignancy when intracavitary brachytherapy is untenable. Patients unable to receive brachytherapy have traditionally received conventional external beam radiation alone with modest results. We investigated the ability of Tomotherapy (Tomotherapy Inc.

Detection of electron beam energy variations using a computed radiography system.

A method to evaluate the electron beam energy constancy by employing the computed radiography (CR) system has been developed. In this method, a right triangular plastic wedge is used to produce a curve of the CR storage phosphor plate signal versus the wedge thickness. The curve, which resembles the percentage depth ionization curve of the clinical electron beams, can be used to derive the energy constancy metric EC(50).

Evaluation of four volume-based image registration algorithms.

We evaluated 4 volume-based automatic image registration algorithms from 2 commercially available treatment planning systems (Philips Syntegra and BrainScan). The algorithms based on cross correlation (CC), local correlation (LC), normalized mutual information (NMI), and BrainScan mutual information (BSMI) were evaluated with: (1) the synthetic computed tomography (CT) images, (2) the CT and magnetic resonance (MR) phantom images, and (3) the CT and MR head image pairs from 12 patients with brain tumors. For the synthetic images, the registration results were compared with known transformation parameters, and all algorithms achieved accuracy of submillimeter in translation and subdegree in rotation.

A dosimetric comparison of MammoSite and ClearPath high-dose-rate breast brachytherapy devices.

Purpose: A new form of partial breast irradiation (PBI), ClearPath (CP) breast brachytherapy, has been introduced. We present our results of a dosimetric comparison of MammoSite (MS) and CP PBI.

Methods And Materials: The dimensions of the CP device were reconstructed onto the MS planning CT scans for 15 previously treated patients.

A dosimetric comparison of Xoft Axxent Electronic Brachytherapy and iridium-192 high-dose-rate brachytherapy in the treatment of endometrial cancer.

Purpose: This analysis was undertaken to dosimetrically compare iridium-192 high-dose-rate brachytherapy (IB) and Xoft Axxent Electronic Brachytherapy (XB; Xoft Inc., Sunnyvale, CA) in the treatment of endometrial cancer.

Methods And Materials: The planning CT scans from 11 patients previously treated with IB were used to construct hypothetical treatment plans using the source characteristics of the XB device.

A dosimetric comparison of three-dimensional conformal, intensity-modulated radiation therapy, and MammoSite partial-breast irradiation.

Purpose: Limited information is available comparing target volume and normal tissue dosimetry with the different techniques of partial breast irradiation (PBI). We present results of a dosimetric comparison of single catheter, balloon-based brachytherapy using the MammoSite catheter (BRT), 3D conformal radiation therapy (3DCRT), and intensity-modulated radiation therapy (IMRT).

Methods And Materials: Fifteen patients were treated using the BRT device.

Performance of magnetic field-guided navigation system for interventional neurosurgical and cardiac procedures.

A hospital-based magnetic guidance system (MGS) was installed to assist a physician in navigating catheters and guide wires during interventional cardiac and neurosurgical procedures. The objective of this study is to examine the performance of this magnetic field-guided navigation system. Our results show that the system's radiological imaging components produce images with quality similar to that produced by other modern fluoroscopic devices.

A feasibility study of Dynamic Phantom scanner for quality assurance of photon beam profiles at various gantry angles.

The effect of gantry rotation on beam profiles of photon and electron beams is an important issue in quality assurance for radiotherapy. To address variations in the profiles of photon and electron beams at different gantry angles, a Dynamic Phantom scanner composed of a 20 x 12 x 6 cm3 scanning Lucite block was designed as a cross-beam-profile scanner. To our knowledge, differences between scanned profiles acquired at different gantry angles with a small size Lucite block and those acquired a full-size (60 x 60 x 50 cm3) water phantom have not been previously investigated.

Limited accuracy of dose calculation for large fields at deep depths using the BrainSCAN v5.21 treatment planning system.

The Varian 120 multileaf collimator (MLC) has a leaf thickness of 5 mm projected at the isocenter plane and can deliver a radiation beam of large field size (up to 30 cm) to be used in intensity-modulated radiotherapy (IMRT). Often the dose must be delivered to depths greater than 20 cm. Therefore, during the commissioning of the BrainSCAN v5.

Monte Carlo calculations of output factors for clinically shaped electron fields.

We report on the use of the EGS4/BEAM Monte Carlo technique to predict the output factors for clinically relevant, irregularly shaped inserts as they intercept a linear accelerator's electron beams. The output factor for a particular combination--energy, cone, insert, and source-to-surface distance (SSD)--is defined in accordance with AAPM TG-25 as the product of cone correction factor and insert correction factor, evaluated at the depth of maximum dose. Since cone correction factors are easily obtained, we focus our investigation on the insert correction factors (ICFs).

Dose perturbation induced by radiographic contrast inside brachytherapy balloon applicators.

Phantom measurements and Monte Carlo calculations have been performed for the purpose of characterizing the dose perturbation caused by radiographic contrast inside the MammoSite breast brachytherapy applicator. Specifically, the dose perturbation is quantified as a heterogeneity correction factor (HCF) for various balloon radii and contrast concentration levels. The dose perturbation is larger for larger balloon radii and higher contrast concentrations.

Effect of ethmoid sinus cavity on dose distribution at interface and how to correct for it: magnetic field with photon beams.

Recent work proposed the use of magnetic field as a solution to reduce the undesirable effect of air cavities on dose after the air/tissue interface. In contrast to the published work that looks into the problem with slab geometries, in this work we use actual anatomy based on CT images and the magnetic flux from a Helmholtz coil-pair configuration to investigate the problem and to evaluate the efficacy of the proposed solution. The EGS4 phantom was created using CT scans of the head at the level of the ethmoid sinus.

Design optimization of intraoperative radiotherapy cones.

Purpose: Electron intraoperative cones (EIORCs) commonly used for intraoperative radiation therapy (IORT) often generate high-dose regions at superficial depths. This study was performed to optimize the use of rings in the EIORC design that reduces the high-dose region while minimizing the loss of the treatment volume at the prescribed depth.

Methods And Materials: Monte Carlo simulations were performed to study the dosimetry properties of various EIORC designs.