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Sun City Center, FL, United States

Testa M.,Massachusetts General Hospital | Verburg J.M.,Massachusetts General Hospital | Verburg J.M.,TU Eindhoven | Rose M.,Sun Nuclear Corporation | And 5 more authors.
Physics in Medicine and Biology | Year: 2013

We present a proof of principle study of proton radiography and proton computed tomography (pCT) based on time-resolved dose measurements. We used a prototype, two-dimensional, diode-array detector capable of fast dose rate measurements, to acquire proton radiographic images expressed directly in water equivalent path length (WEPL). The technique is based on the time dependence of the dose distribution delivered by a proton beam traversing a range modulator wheel in passive scattering proton therapy systems. The dose rate produced in the medium by such a system is periodic and has a unique pattern in time at each point along the beam path and thus encodes the WEPL. By measuring the time dose pattern at the point of interest, the WEPL to this point can be decoded. If one measures the time-dose patterns at points on a plane behind the patient for a beam with sufficient energy to penetrate the patient, the obtained 2D distribution of the WEPL forms an image. The technique requires only a 2D dosimeter array and it uses only the clinical beam for a fraction of second with negligible dose to patient. We first evaluated the accuracy of the technique in determining the WEPL for static phantoms aiming at beam range verification of the brain fields of medulloblastoma patients. Accurate beam ranges for these fields can significantly reduce the dose to the cranial skin of the patient and thus the risk of permanent alopecia. Second, we investigated the potential features of the technique for real-time imaging of a moving phantom. Real-time tumor tracking by proton radiography could provide more accurate validations of tumor motion models due to the more sensitive dependence of proton beam on tissue density compared to x-rays. Our radiographic technique is rapid (∼100 ms) and simultaneous over the whole field, it can image mobile tumors without the problem of interplay effect inherently challenging for methods based on pencil beams. Third, we present the reconstructed pCT images of a cylindrical phantom containing inserts of different materials. As for all conventional pCT systems, the method illustrated in this work produces tomographic images that are potentially more accurate than x-ray CT in providing maps of proton relative stopping power (RSP) in the patient without the need for converting x-ray Hounsfield units to proton RSP. All phantom tests produced reasonable results, given the currently limited spatial and time resolution of the prototype detector. The dose required to produce one radiographic image, with the current settings, is ∼0.7 cGy. Finally, we discuss a series of techniques to improve the resolution and accuracy of radiographic and tomographic images for the future development of a full-scale detector. © 2013 Institute of Physics and Engineering in Medicine. Source


Yan G.,University of Florida | Lu B.,University of Florida | Kozelka J.,Sun Nuclear Corporation | Liu C.,University of Florida | Li J.G.,University of Florida
Medical Physics | Year: 2010

Purpose: The aim of this work is to develop effective calibration methods for a novel four-dimensional (4D) diode array for pretreatment verification of intensity-modulated radiation therapy (IMRT) and rotational therapy. Methods: A novel 4D diode array (ArcCHECK, Sun Nuclear, Melbourne, FL) was developed to meet the needs of appropriate and efficient quality assurance for IMRT and especially rotational radiotherapy. The diode array presents a consistent detector image in beam's eye view at arbitrary gantry angles due to isotropic arrangement of diodes in a three-dimensional (3D) cylindrical phantom. The 50 ms simultaneous update of all diodes on the detector array (fourth dimension) makes it capable of time-resolved beam delivery analysis with any rotational delivery techniques. The calibration procedure consisted of delivering and measuring a series of calibration beams with 5.8° angular spacing surrounding the cylindrical diode array. Correction factors for diode intrinsic sensitivity and directional response dependence were derived from these measurements. A real-time algorithm to derive gantry angles based on the detector signal was developed to interpolate and apply the corresponding angular correction factors. Results: The calibration was validated with ion chamber scanned beam profiles in a 3D water tank. Excellent agreement was observed between diode array measurement and treatment planning system calculation. The accuracy of the gantry angle derivation algorithm was within 1° which caused a less than 0.2% dosimetric uncertainty. Conclusions: With the proposed calibration method and the automatic gantry angle derivation algorithm, the 4D diode array achieved isotropic detector response and is suitable for both IMRT and rotational therapy pretreatment verification. © 2010 American Association of Physicists in Medicine. Source


Patent
Sun Nuclear Corporation | Date: 2013-11-15

A radiotherapy system includes a radiotherapy device, such as a LINAC, operable to direct a radiation beam from a head thereof during operation, a field detector positioned to be within the radiation beam during operation of the radiotherapy device and operable to generate a beam measurement signal, a reference detector positioned to be outside of the radiation beam during operation of the radiotherapy device and operable to generate a reference signal, and at least one computer in signal communication with the field detector and the reference detector and configured with software to normalize the beam measurement signal based on the reference signal and to output a normalized beam measurement.


Patent
Sun Nuclear Corporation | Date: 2012-08-31

A treatment safety device is operable by a computer-based treatment safety module to prevent, by at least one of an operational interlock and a warning indicator, a medical treatment unless the treatment safety module determines that predetermined treatment verification criteria are met. The treatment safety device can tie into an existing operational interlock, such as an electrical door interlock. In a radiation oncology application, the treatment safety module verification criteria can include a satisfactory correspondence between elements of a pending treatment and an intended treatment.


Patent
Sun Nuclear Corporation | Date: 2015-05-07

A radiotherapy system includes a radiotherapy device, such as a LINAC, operable to direct a radiation beam from a head thereof during operation, a field detector positioned to be within the radiation beam during operation of the radiotherapy device and operable to generate a beam measurement signal, a reference detector positioned to be outside of the radiation beam during operation of the radiotherapy device and operable to generate a reference signal, and at least one computer in signal communication with the field detector and the reference detector and configured with software to normalize the beam measurement signal based on the reference signal and to output a normalized beam measurement.

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