Baldev Patyal

Loma Linda University Schol of Medicine, Radiation Medicine, Faculty Member

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Papers by Baldev Patyal

A phase I trial of Proton stereotactic body radiation therapy for liver metastases

Journal of Gastrointestinal Oncology, 2018

Background: A phase I trial to determine the maximum tolerated dose (MTD) of Proton stereotactic ... more Background: A phase I trial to determine the maximum tolerated dose (MTD) of Proton stereotactic body radiation therapy (SBRT) for liver metastases in anticipation of a subsequent phase II study. Methods: An institutional IRB approved phase I clinical trial was conducted. Eligible patients had 1-3 liver metastases measuring less than 5 cm, and no metastases location within 2 cm of the GI tract. Dose escalation was conducted with three dose cohorts. The low, intermediate, and high dose cohorts were planned to receive 36, 48, and 60 respectively to the internal target volume (ITV) in 3 fractions. At least 700 mL of normal liver had to receive <15. Dose-limiting toxicity (DLT) included acute grade 3 liver, intestinal or spinal cord toxicity or any grade 4 toxicity. The MTD is defined as the dose level below that which results in DLT in 2 or more of the 6 patients in the highest dose level cohort. Results: Nine patients were enrolled (6 male, 3 female): median age 64 years (range, 33-77 years); median gross tumor volume (GTV) 11.1 mL (range, 2.14-89.3 mL); most common primary site, colorectal (5 patients). Four patients had multiple tumors. No patient experienced a DLT and dose was escalated to 60 in 3 fractions without reaching MTD. The only toxicity within 90 days of completion of treatment was one patient with a grade 1 skin hyperpigmentation without tenderness or desquamation. Two patients in the low dose cohort had local recurrence and repeat SBRT was done to previously treated lesions without any toxicities. Conclusions: Biologically ablative Proton SBRT doses are well tolerated in patients with limited liver metastases with no patients experiencing any grade 2+ acute toxicity. Results from this trial provide the grounds for an ongoing phase II Proton SBRT study of 60 over 3 fractions for liver metastases.

format_quoteNo dose-limiting toxicities were encountered; grade 1 skin hyperpigmentation was the only noted toxicity, supporting safety of 60 Gy in 3 fractions.format_quote

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A comparison of proton and photon radiotherapy in reducing cardiac exposure for patients receiving radiation therapy for distal and esophagogastric junction cancer

Journal of Clinical Oncology, 2014

167 Background: Recent studies indicate that radiation exposure to heart may have a greater impac... more 167 Background: Recent studies indicate that radiation exposure to heart may have a greater impact on perioperative cardiac morbidities than do other clinical factors. The purpose of this study is to investigate dose distributions of proton and photon treatment plans in patients (pts) with distal and esophagogastric junction (GEJ) carcinoma, focusing specifically on dose reduction to cardiac structures. Methods: Ten pts between 2010 and 2013 were included in this study. Three separate plans were generated for each patient: 3D proton plan, 3D photon plan, and Intensity modulated radiotherapy (IMRT) photon plan. The clinical target volume (CTV) consisted of the pre-operative extent of tumor plus a 10mm manual expansion in all directions. The planning target volume (PTV) was generated by a further expansion on the CTV ranging from 10-15mm. A dose of 50.4Gy given in 28 fractions was delivered to the PTV. All plans were optimized to allow 90% isodose coverage of at least 95% of the PTV. ...

Protons Offer Reduced Cardiopulmonary Exposure for Patients Receiving Radiation Therapy for Esophageal Cancer

International Journal of Radiation Oncology*Biology*Physics, 2014

The purpose of this study was to construct of an artificial neural network (ANN) for prediction o... more The purpose of this study was to construct of an artificial neural network (ANN) for prediction of response and survival in the patients treated with radiation therapy for esophageal cancer and its validation. Materials/Methods: The study group consisted of 134 patients with esophageal cancer of T1-4 and Stage I-III for the construction of an ANN for prediction of survival and its validation. We investigated the correlation between the tumor response of primary tumor after radiation therapy and each of the clinical factors in regard to patients or tumors with 111 patients. We constructed and trained an ANN to predict the tumor response using these correlative factors. The relationship between the predictive value using this ANN model and actual response was examined in 111 patients. In addition, the ANN constructed by the 111 patients was applied to a different group of 23 patients for validation analysis, and the correlation between the predictive response and actual response was also tested. We estimated the correlation between the predictive response by these ANN model and the actual value in tumor response of the 23 patients for validation analysis, and divided into the two prognostic groups according to the predictive values by this ANN model and estimated prognosis values. Results: We selected the predictive factors; T stage, tumor finding type, tumor length and wall thickness of tumor region in 111 patients, which were significantly correlated with tumor response. We constructed and trained the ANN model in four predictive factors. In ROC analysis for the comparison between the predictive values by this ANN model and the actual value in tumor response, area under the curve (AUC) was 91% when the ANN constructed by the 111 patients was applied to the 111 patients. When the ANN was applied to the different set of 23 patients, AUC was 90% and accuracy was 87% (20 of 23 patients are correctly classified). 2-year overall survival (OS) of good-and poor-prognosis group were 100% and 23%. Significant difference was revealed between good-and poor-response group in OS (p Z 0.0026). Conclusions: We constructed the ANN model to be useful to predict tumor response and survival in patients with esophageal cancer treated with radiation therapy. This ANN model could be used for determination of an optimal treatment strategy for esophageal cancer.

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SU-E-T-366: Time-Resolved EPID Dosimetry for Validating ArcIMRT

Medical Physics, 2013

ABSTRACT

SU-E-T-104: Evaluation of the Dosimetric Properties of a Synthetic Single Crystal Diamond Detector in Clinical Proton Beams

Medical Physics, 2013

PURPOSE To investigate the dosimetric properties of a new synthetic single crystal diamond Schott... more PURPOSE To investigate the dosimetric properties of a new synthetic single crystal diamond Schottky diode for accurate relative dose measurements in clinical proton beams. METHODS The dosimetric properties of the synthetic single crystal diamond detector (SCDD) were assessed by comparison with a reference parallel plate ionization chamber (PTW Markus Chamber 23343) and a micro ionization chamber (Exradin A16). The diamond detector was operated at zero bias voltage at all times. Comparative dose distribution measurements were performed by means of percent depth dose curves and lateral beam profiles using the diamond detector and a reference ionization chamber in clinical proton beams of energies 155MeV and 250 MeV for a 14cm square cerrobend aperture and 126 MeV for 3cm, 2cm and 1cm diameter circular brass collimators. ICRU 78 recommended beam parameters are used to compare the percent depth dose curves and lateral profiles obtained using the SCDD and the reference ionization chamber. The warm-up/stability of the detector response, dose linearity and dose-rate dependency were also evaluated in a 250 MeV proton beam. RESULTS During warm-up/stability the diamond detector was irradiated 6 times and the maximum deviation from the average reading was less than 0.5%. The detector response shows a good linear behavior as a function of dose with observed deviations below 0.5% over a dose range of 50cGy to 500cGy. The detector response is dose rate independent, with deviations below 0.5% in the investigated dose-rates of 64cGy/min,47.5cGy/min and 17.5cGy/min. Percent depth dose curves and lateral beam profiles obtained with the diamond detector were in good agreement with those obtained using reference dosimeters. CONCLUSION The observed dosimetric properties of the SCDD indicate that its behavior is proton energy independent in the investigated energy range and it is suitable for accurate relative dosimetric measurements in large field and small field clinical proton beams.

SU-E-T-501: Immobilization System Design and Testing for Proton Therapy

Medical Physics, 2011

ABSTRACT Purpose: To evaluate the quality of new immobilization devices for our clinical proton t... more ABSTRACT Purpose: To evaluate the quality of new immobilization devices for our clinical proton treatment program. Methods: At the Loma Linda University proton treatment center, we are developing and integrating new immobilization devices (Qfix Systems, LLC) into our clinical proton treatment program. For proton therapy applications it is desirable to use devices that exhibit a very thin water equivalent thickness (WET) to minimize beam penumbra, while the immobilization device itself also needs to be uniform in nature, with the WET accurately represented in the planning CT. Device inhomogeneities or incorrect representation of the device within the treatment planning system will result in systematic range errors. An important task in commissioning this system is validating the WET uniformity of these immobilization devices, which are typically too large to be submerged into a water tank. The WET of these devices was evaluated with a new method that measures the shift in the distal edge of a proton beam using a variable thickness range shifter apparatus that attaches to the proton snout. Results: Testing has been completed on various immobilization devices with excellent WET uniformity results. For example, the head and neck device produced a WET of 2.705mm +/− 0.015mm. The measurement technique was also very reproducible with a standard deviation of 5.7×10‐4cm for multiple measurements of the same location Conclusions: The immobilization devices that have been developed and are being integrated into our proton program meet the stringent requirements of proton therapy. The method of WET evaluation developed in this work can be adapted by other centers for evaluation of their own immobilization devices prior to deployment in proton therapy applications.

SU-GG-T-481: Investigation of the Influence of Aperture Rotation on the Dose Profiles of Proton Patch Fields

Medical Physics, 2010

ABSTRACT The use of proton patch fields that are stopped on the lateral boundary of a master fiel... more ABSTRACT The use of proton patch fields that are stopped on the lateral boundary of a master field is common practice in passively delivered proton radiation therapy, as it allows for effective coverage of target volumes in close proximity to critical structures, e.g., the spinal cord. In a typical patient setup scenario, initial orthogonal radiographs are taken to align the patient in three dimensions relative to the proton beam isocenter and a beam&#39;s eye view (BEV) x‐ray image of the master field is taken to verify correct alignment and to perform final corrections. As part of these corrections, frequently an aperture rotation is required to account for rotational misalignment of the patient relative to the beam profile. Similarly, subsequent fields patching on the master field are verified with BEV x‐ray images prior to treatment and appropriate corrective moves and aperture rotations are made. To date, no studies of the influence of aperture rotations on the delivered proton treatment across various clinical configurations have been published. We are currently performing a systematic study of clinical proton patch‐field combinations using our proton treatment planning software (Odyssey, Permedics). Performing incremental rotations of both the master and patch fields in the treatment plan, will determine the effect on the DVH for both the gross tumor volume (GTV) and organs at risk (OAR). Study endpoints include deviations from the maximum, minimum and mean dose delivered to GTV and OAR prescribed by the clinician. This study covers a range of clinical scenarios, including tumors of the cervical spine, tumors of the paranasal sinus, frontal lobe gliomas, and parasacral tumors. It is expected that the results of this study will result in practical guidelines for the setup of proton patch‐field combinations.

SU-E-T-582: Evaluation of Standard Beam Delivery Devices in Proton Intracranial Radiosurgery

Medical Physics, 2014

ABSTRACT Purpose: To evaluate the use of standard apertures and range shifters for the treatment ... more

Magnetic properties and critical behavior of quasi-two-dimensional systems [C6H5(CH2)nNH3]2CuBr4 with n=1, 2, and 3

Phys Rev B, 1992

The magnetic properties and critical behavior of the quasi-two-dimensional ferromagnets [C6H5(CH2... more The magnetic properties and critical behavior of the quasi-two-dimensional ferromagnets [C6H5(CH2)nNH3]2CuBr4, with n=1, 2, and 3, have been studied. These compounds are typical of layered magnets in that they assume distorted layer perovskite structures in which copper(II) bromide layers are sheathed by the bulk organic cations. Magnetization and susceptibility measurements show strong ferromagnetic intralayer exchange of the order of 20-25 K with weak interlayer exchange coupling of less than 1 K. The magnetic anisotropies are explored through EPR-linewidth analysis. The critical exponent gamma and transition temperatures Tc were determined by the measurements of ac initial susceptibility and isothermal magnetization. By employing a static scaling law to analyze the data of isothermal magnetizations near Tc, it was found that in a certain low-field and low-temperature region the powder magnetizations are suppressed so that the scaling hypothesis no longer holds. It is shown from the scaling analysis that the powder samples of these two-dimensional (2D) layer ferromagnets cannot be classified as simple ferromagnets whose critical behavior is described by the usual 2D critical theories.

Two-dimensional Fourier tranform ESR in the slow-motional and rigid limits : SECSY-ESR

Chemical Physics Letters, 1990

Passive proton therapy vs. IMRT planning study with focal boost for prostate cancer

Radiation oncology (London, England), Jan 24, 2015

Exploiting biologic imaging, studies have been performed to boost dose to gross intraprostatic tu... more Exploiting biologic imaging, studies have been performed to boost dose to gross intraprostatic tumor volumes (GTV) while reducing dose elsewhere in the prostate. Interest in proton beams has increased due to superior normal-tissue sparing they afford. Our goal was to dosimetrically compare 3D conformal proton boost plans with intensity-modulated radiation therapy (IMRT) plans with respect to target coverage and avoiding organs at risk. Treatment planning computer tomography scans of ten patients were selected. For each patient, two hypothetical but realistic GTVs each with a fixed volume were contoured in different anatomical locations of the prostate. IMRT and proton beam plans were created with a prescribed dose of 50.4 Gy to the initial planning target volume (PTV) including the PTV of the seminal vesicles (PSV), 70.2 Gy to the PTV of the prostate (PPS), and 90 Gy to the PTV of the gross tumor volumes (PGTVs). For proton plans, uncertainties of range and patient setup were accoun...

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A Electron Paramagnetic Resonance (epr) Study of Magnetic Anisotropies in - and Two-Dimensional Copper(ii) Magnetic Insulators

The electron paramagnetic resonance (EPR) has been used as an experimental technique to investiga... more The electron paramagnetic resonance (EPR) has been used as an experimental technique to investigate the magnetic anisotropies in some low-dimensional copper(II) magnetic insulators. The compounds studied are the two -dimensional layer perovskites, (C_6H _5(CH_2)_{ rm n}NH_3] _2CuX_4 where n = 1, 2, 3 and X is Cl or Br, and bis(cyclohexylammonium)tetrabromocuprate(II); the one-dimensional alternating linear dimer chains, piperidiniumtrichlocuprate(II) and piperaziniumhexachlorodicuprate(II); and a monomer system, bis(piperidinium)tetrabromocuprate(II). The two-dimensional layer perovskites, (C _6H_5(CH_2) _{rm n}NH_3 ]_2CuCl_4, with n = 2, 3, turned out to be the first novel copper(II) compounds whose EPR linewidths showed simultaneous contributions from the anisotropic symmetric exchange, D, the anisotropic antisymmetric exchange, d, spin diffusion and from magnetically inequivalent sites in the unit cell. The main focus of this study is to calculate all these contributions from an ...

SU-E-T-251: Developing a Daily Proton Beam Monitoring System

Medical Physics, 2015

Purpose: To develop a daily monitoring system for proton beam output check and beam uniformity ch... more Purpose: To develop a daily monitoring system for proton beam output check and beam uniformity check. Methods: Designed for continuously irradiated photon and electron beams with a field size of 20 cm x 20 cm, the daily output checker (Sun Nuclear, Inc.) is not suitable for monitoring proton beams with inter-pulse beam-off and a field size smaller than 14–16 cm in diameter. To allow such proton beam monitoring, the following tests were performed. 1. Absolute dose and array calibrations which accept continuous irradiation only, were performed using photon beams. 2. Five ion chambers within the central area of 8 cm x 8 cm were utilized to check constancy of output at the center of beam modulation and at distal edge and to check beam symmetry and flatness. 3. To simplify our evaluation, the array calibration was manually modified, such that all five chambers report equal values in spite of their differences in build-up thicknesses. 4. The chamber at the lower-right corner is placed under a buildup thickness that can offer dose measurement at the distal edge. This buildup thickness was determined by proton beam range measurements, which established buildup thickness for beam output measurement at the central chamber and range measurement at the corner chamber. 5. The beam-off delay which allows receipt of pulsed irradiation was activated and optimal delay times were determined for each proton beam at 149.6, 185.6, and 249.5 MeV. Results: The above system was tested by miss-steering proton beams and altering phantom thickness by 1 mm at a time. The system reliably monitored the beam with: 3% tolerance for beam flatness, symmetry and output. The range difference of 0.5 mm could be detected at all energies by setting a tolerance of 20%. Conclusion: A quick daily proton beam monitoring system was feasible.

Radiographic film dosimetry of proton beams for depth-dose constancy check and beam profile measurement

Journal of applied clinical medical physics / American College of Medical Physics, Jan 8, 2015

Radiographic film dosimetry suffers from its energy dependence in proton dosimetry. This study so... more Radiographic film dosimetry suffers from its energy dependence in proton dosimetry. This study sought to develop a method of measuring proton beams by the film and to evaluate film response to proton beams for the constancy check of depth dose (DD). It also evaluated the film for profile measurements. To achieve this goal, from DDs measured by film and ion chamber (IC), calibration factors (ratios of dose measured by IC to film responses) as a function of depth in a phantom were obtained. These factors imply variable slopes (with proton energy and depth) of linear characteristic curves that relate film response to dose. We derived a calibration method that enables utilization of the factors for acquisition of dose from film density measured at later dates by adapting to a potentially altered processor condition. To test this model, the characteristic curve was obtained by using EDR2 film and in-phantom film dosimetry in parallel with a 149.65 MeV proton beam, using the method. An ad...

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