Michael C. Schell's research while affiliated with University of Rochester Medical Center and other places
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Publications (117)
Purpose:
This study aimed to determine the feasibility and maximally tolerated dose of hypofractionated, conformal radiation therapy (RT) in patients with liver metastases.
Methods and materials:
Nonsurgical patients with ≤5 liver metastases (sum of maximal diameter of all lesions ≤8 cm) were included in the study. There were 4 dose levels: 35 G...
Objectives:
All organizations seek to minimize the risks that their operations pose to public safety. This task is especially significant if they deal with complex or hazardous technologies. Five decades of research in quantitative risk analysis have generated a set of risk management frameworks and practices that extend across a range of such dom...
Background:
Percutaneous trigeminal rhizotomy or balloon compression for trigeminal neuralgia carries a potential risk for the brainstem, the carotid artery, and the basilar artery.
Objective:
To detail the relation of critical neural and vascular structures to expanded balloons used for percutaneous compression of the trigeminal ganglion.
Meth...
Background:
Optimal doses for single-fraction stereotactic radiosurgery (SRS) in the treatment of brain metastases are not well established. Our institution utilized conservative dosing compared to maximum-tolerated doses from the Radiation Therapy Oncology Group 90-05 Phase I study.
Objective:
To report individual lesion control (LC) from conse...
To report our institutional experience with five fractions of daily 8-12 Gy stereotactic body radiotherapy (SBRT) for the treatment of oligometastatic cancer to the lung.
Thirty-four consecutive patients with oligometastatic cancers to the lung were treated with image-guided SBRT between 2008 and 2011. Patient age ranged from 38 to 81 years. There...
Purpose:
To establish institutionally specific action levels for quality assurance (QA) ofintensity-modulated radiation therapy (IMRT) treatment plans based on the guidelines andstatistical principles presented by Howell et al. in 2008 for the University of Texas MD Anderson.
Methods:
A review of 3937 fields of 364 patients treatment plans was u...
Purpose:
MD Anderson Radiological Physics Center (RPC) routinely evaluates the calibration of linear accelerators using thermoluminescent dosimeters (TLDs) and more recently optically-stimulated luminescence dosimeters (OSLDs).The RPC continues to use TLDs for the annual TomoTherapy audits.In the past, an RPC measurement was 6.2% low compared to o...
Background: A previous phase III RTOG study subset analysis demonstrated improvement in overall survival (OS) with the addition of SRS to WBRT in NSCLC patients with 1 to 3 brain metastases. As both TMZ and erlotinib are known to cross the blood brain barrier (potentially providing radiosensitization), and have documented activity in NSCLC, a phase...
257
Background: This multi-institutional phase I trial was conducted to determine the maximally tolerated dose (MTD) of hypofractionated, highly conformal radiation therapy (RT) in patients (pts) with liver metastases.
Methods: Eligibility criteria included non-surgical pts with ≤ 5 liver metastases; total measurement for all lesions ≤ 8 cm. There...
Stereotactic body radiotherapy (SBRT) and stereotactic radiosurgery (SRS) for spinal metastases are emerging treatment paradigms in the multidisciplinary management of metastases located within or adjacent (paraspinal) to the vertebral bodies/spinal cord. In this review, we provide a brief overview of spine SBRT/SRS indications, technology, plannin...
Single-fraction stereotactic radiosurgery (SRS) and hypofractionated stereotactic radiotherapy (SRT) are radiation planning and delivery techniques used for the treatment of intracranial and spine/spinal cord tumors and targets. For cranial SRS and SRT, critical normal tissues/structures include the brainstem, cranial nerves, cochlea and normal bra...
Task Group 101 of the AAPM has prepared this report for medical physicists, clinicians, and therapists in order to outline the best practice guidelines for the external-beam radiation therapy technique referred to as stereotactic body radiation therapy (SBRT). The task group report includes a review of the literature to identify reported clinical f...
Purpose:IMRT and Dynamic Arc Therapy techniques conform the dose to the GTV with varying degrees of normal tissue sparing. Four dose delivery methods (TomoTherapy, RapidArc, Dynamic Conformal Arc and fixed field IMRT) are compared for dose delivery to the tumor and dose sparing of Organs At Risk. A modest cost comparison is also performed to offer...
To investigate the toxicity and outcome after moderately hypofractionated stereotactic body radiotherapy (SBRT) for central thoracic lesions.
Fifty-three patients undergoing 63 courses of SBRT for central thoracic lesions were retrospectively reviewed. Ninety-eight lesions received 30-63 Gy in 2.5-5.0 Gy fractions using the Novalis ExacTrac patient...
This retrospective study was done to better understand the conditions for which stereotactic radiosurgery (SRS) for glioblastoma may be efficacious.
Between 2000 and 2007, 33 patients with a pathological diagnosis of glioblastoma received SRS with the Novalis Shaped Beam Radiosurgery system. Eighteen patients (54%) underwent salvage SRS for recurre...
This research addresses the problem of determining the location of a pulmonary nodule in a radiograph with the aid of a pre-existing computed tomographic (CT) scan. The nodule is segmented in the radiograph using a level set segmentation method that incorporates characteristics of the nodule in a digitally reconstructed radiograph (DRR) that is cal...
To characterize oligometastases in patients enrolled on two prospective pilot studies, treating oligometastases with hypofractionated stereotactic body radiotherapy and stereotactic radiosurgery to cranial lesions.
We describe the characteristics and local control (LC) of 293 lesions in 121 patients with five or fewer metastases treated with stereo...
It is hypothesized that oligometastatic disease represents a state of potentially curable, limited metastases. Stereotactic body radiation therapy (SBRT) is an option for patients who are not amenable to or do not want resection.
From 2001 to 2006, 121 patients with < or =5 detectable metastases were enrolled in 2 prospective studies that used cura...
Purpose: To evaluate the dose calculation difference between BrainSCAN (5.31) and Eclipse (6.5) for the same IMRT plan. Method and Materials: 9 IMRT plans (3 Head/Neck, 3 Brain, and 3 prostate) were developed using BrainSCAN and exported to Varis RV system. The same patient CT scan was imported into Eclipse and the same isocenter position was selec...
Purpose: Tissue heterogeneity perturbs the electron fluence at heterogeneity interfaces. Thus, the dose delivery to lung lesions ranging from 6 mm up through 30 mm in diameter is compromised since the dimensions of the lesions are comparable to the range of the secondary electrons in lung and air. Dose perturbations are evaluated for a range of les...
To evaluate the feasibility and efficacy of hypofractionated stereotactic body radiation therapy (SBRT) for the treatment of liver metastases.
The records of 69 patients with 174 metastatic liver lesions treated with SBRT between April 2001 and October 2004 were reviewed. The most common primary tumors were colorectal (n = 20), breast (n = 16), pan...
Purpose: To implement a new non-invasive in-vivo assay to compute the dose-response relationship following radiation-induced injury to normal lung tissue, using computed tomography (CT) scans of the chest. Methods and Materials: Follow-up volumetric CT scans were acquired in patients with metastatic tumors to the lung treated using stereotactic rad...
The curative treatment of oligometastases with radiotherapy remains an area of active investigation. We hypothesise that treating oligometastases with SBRT can prolong life and potentially cure patients, while in patients with multiple lung metastases SBRT can improve quality of life. Fifty patients with lung metastases were treated on this study....
Purpose: Tissue heterogeneity changes result in a build down/build up of the recoil electron fluence at heterogeneity interfaces. The use of stereotactic radiosurgery beams on small lung lesions can compromise the dose delivery to lesions ranging from 6 mm up through 30 mm in diameter, since the dimensions of the lesions are comparable to the range...
To examine the dosimetric feasibility of a conical implantation approach to robotic-assisted prostate brachytherapy.
An in-house inverse planning software based on the genetic algorithm (GA) was used to optimize the needle angulations and the seed positions along needles that form one or two bouquets. Volume data from 20 prostate seed implant patie...
The role of radiosurgery in the treatment of patients with advanced-stage metastatic disease is currently under debate. Previous randomized studies have not consistently supported the use of radiosurgery to treat patients with numbers of brain metastases. In negative-results studies, however, intracranial tumor control was high but extracranial dis...
The role of radiosurgery in the treatment of patients with advanced-stage metastatic disease is currently under debate. Previous randomized studies have not consistently supported the use of radiosurgery to treat patients with numbers of brain metastases. In negative-results studies, however, intracranial tumor control was high but extracranial dis...
Brain metastases occur in up to 40% of all patients with systemic cancer. We aimed to assess whether stereotactic radiosurgery provided any therapeutic benefit in a randomised multi-institutional trial directed by the Radiation Therapy Oncology Group (RTOG).
Patients with one to three newly diagnosed brain metastases were randomly allocated either...
Motion compensation radiotherapy systems are currently available. Signals representing moving targets can be obtained from either real-time X-ray images of implanted markers near the target or external respiration sensors. However, a time lag exists between the motion signal acquisition and action execution (moving the robotic arm). This time lag h...
This study assesses the efficacy and neurotoxicity of radiosurgical treatment of benign intracranial tumors using a linear accelerator, with relatively low dose and homogeneous dosimetry. Between June 1998 and July 2000, 27 patients were treated for benign lesions with radiosurgery using a 6-MV linear accelerator-based X-knife system and circular c...
In this study, postimplant seed displacement errors were analyzed using a softassign point match algorithm. Seed locations in the postimplant CT image dataset were first matched with the seed positions in the treatment plan. A CT scan was taken 2.5 – 6 hours after implantation in four testing cases. The average 3D displacement error was 0.34 ± 0.16...
A photogrammetry-based patient positioning system has been used instead of the conventional laser alignment technique for patient set-up in external beam radiotherapy. It tracks skin affixed reflective markers with multiple infrared cameras. The three-dimensional (3D) positions of the markers provide reference information to determine the treatment...
To perform a Phase I study to determine the safety and feasibility of using external beam radiotherapy to prevent neointimal hyperplasia in patients after surgical bypass of occluded infrainguinal arteries.
All patients undergoing operative infrainguinal bypass for chronic ischemia were eligible for enrollment, although those requiring a prosthetic...
This study assesses the efficacy and neurotoxicity of radiosur- gical treatment of benign intracranial tumors using a linear accelerator, with relatively low dose and homogeneous dosim- etry. Between June 1998 and July 2000, 27 patients were treated for benign lesions with radiosurgery using a 6-MV linear accelerator- based X-knife system and circu...
Recent advances in Stereotactic Radiosurgery/Conformal Radiotherapy have made it possible to deliver surgically precise radiation therapy to small lesions while preserving the surrounding tissue. However, because of physiologic motion, the application of conformal radiotherapy to extra-cranial tumors is, at present, geared toward slowing the progre...
To determine whether external beam irradiation delivered immediately after graft implantation can inhibit anastomotic intimal hyperplasia (IH) 1 month following polytetrafluoroethylene (PTFE) bypass in a sheep carotid artery model, 23 sheep underwent bilateral bypass of the ligated common carotid artery with 8-mm PTFE immediately followed by a sing...
Treatment planning for radiation therapy is a multi-objective optimization process. Here we present a machine intelligent scheme for treatment planning based on multi-objective decision analysis (MODA) and genetic algorithm (GA) optimization. Multi-objective ranking strategies are represented in the L(p) metric under the displaced ideal model. Goal...
Irradiation has been shown to inhibit postangioplasty intimal hyperplasia ("restenosis") in unbranched tubes. It seems likely that irradiation will similarly be able to inhibit intimal hyperplasia after a surgical anastomosis at a biochemical and cellular level, but whether it will produce a clinically relevant or even clinically detectable differe...
Interstitial brachytherapy for carcinoma of the prostate is achieved through the use of a configuration of radioactive seeds placed in a manner that delivers a customized, reasonably uniform dose to the target volume. Accurate dose delivery depends on both precise seed placement and reliable seed strength in the implanted configuration. This study...
Good clinical physics practice requires that dose rates of brachytherapy sources be checked by the institution using them, as recommended by American Association of Physicists in Medicine Task Group 56 and The American College of Radiology. For intravascular brachytherapy with catheter-based systems, AAPM Task Group 60 recommends that the dose rate...
There is now considerable evidence to suggest that technical innovations, 3D image-based planning, template guidance, computerized dosimetry analysis and improved quality assurance practice have converged in synergy in modern prostate brachytherapy, which promise to lead to increased tumor control and decreased toxicity. A substantial part of the m...
For radiosurgery of large arteriovenous malformations (AVMs), the optimal relationship of dose and volume to obliteration, complications, and hemorrhage is not well defined. Multivariate analysis was performed to assess the relationship of multiple AVM and treatment factors to the outcome of AVMs significantly larger than previously reported in the...
To demonstrate the feasibility of an intraoperative inverse planning technique with advanced optimization for prostate seed implantation.
We have implemented a method for optimized inverse planning of prostate seed implantation in the operating room (OR), based on the genetic algorithm (GA) driven Prostate Implant Planning Engine for Radiotherapy (...
From the clinical oncologic experience, fractionation of the radiation dose offers a better therapeutic window, both with respect to effectiveness and unwanted side effects. Thus, we undertook a pilot study in a rodent model, using a single dose of 15 Gy compared with fractionation schedules of 5 or 10 daily applications of 3 Gy.
Using a previously...
External beam irradiation of coronary arteries has been shown to be detrimental in an animal model for the prevention of neointimal hyperplasia in the presence of stents when orthovoltage x-ray beams are used. The present study investigated the effect of beam energy on the dose distribution in the wall of the artery in the presence of stents.
We us...
Recent preclinical and clinical studies indicate that irradiation using ionizing radiation in the
dose range of 15
to 30 Gy may reduce the occurrence of restenosis in patients who have undergone an
angioplasty. Several delivery systems of intravascular brachytherapy have been
developed to deliver radiation
doses in this
range with minimal normal ti...
One of the most controversial issues in utilizing radiation to inhibit restenosis is the importance of the location of the radiation source. The experimental results from using external forms of radiation have been contradictory and conflicting. In this study, we undertook to externally place a brachytherapy catheter source and to determine if a do...
Purpose:
The major radiobiological issue in determining the rationale for the use of radiation to inhibit vascular restenosis is the identification of the target cell(s) and/or cytokine(s) responsible for neointimal hyperplasia and vascular remodeling. The central hypothesis of this report is that the macrophage/monocyte and PDGF are key elements...
To investigate a method for the generation of digitally reconstructed radiographs directly from MR images (DRR-MRI) to guide a computerized portal verification procedure.
Several major steps were developed to perform an MR image-guided portal verification procedure. Initially, a wavelet-based multiresolution adaptive thresholding method was used to...
Stereotactic Radiosurgery demands extraordinary attention to quality assurance issues. This is related to the high accuracy needed to perform a successful procedure, accuracy demanded by the proximity of the target lesion to neighboring fragile and eloquent structures in the head and large doses delivered. The nature of the linac-based radiosurgery...
Treatment planning for stereotactic radiosurgery and fractionated radiotherapy is currently a labor intensive, operator-dependent process. Many degrees of freedom exist to make rigorous optimization intractable except by computationally intelligent techniques. The quality of a given plan is determined by an aggregate of clinical objectives, most of...
A genetic algorithm (GA) is presented for the optimization of template- and ultrasound-guided prostate implants. The end points for optimization are incorporated in an objective function of separable cardinal utility terms. As an application of the GA, the minimum 103Pd total source strength required to deliver a given dose was correlated with the...
To directly compare clinical efficacy of electronic to film portal images.
An observer study was designed to compare clinical efficacy of electronic to film portal images acquired using a liquid matrix ion-chamber electronic portal imaging device and a conventional metal screen/film system. Both images were acquired simultaneously for each treatmen...
An interlock system was developed to enhance safety in stereotactic radiosurgery procedures on a linear accelerator. This system assists in 1) avoiding any collision between the gantry and a floor-mounted radiosurgery stand, 2) leaving the field size to that which was used for a regular treatment prior to a radiosurgery procedure, and 3) preventing...
Three-dimensional treatment planning was performed to evaluate three standard coplanar irradiation techniques (two-field parallel-opposed, three-field, and 110 degrees bilateral arcs), the 330 degrees single rotational arc, and a four noncoplanar arc technique for the treatment of pituitary adenomas. We sought to identify the optimal technique for...
A fully automated system is being developed for the portal verification of tangential breast fields in radiation therapy of breast cancer. The automated verification system involves image acquisition, image feature extraction, feature correlation between reference and portal images, and quantitative evaluation of patient setup. In this study, the p...
We compare practical conformal treatment approaches to pancreatic cancer using 6 and 18 MV photons and contrast those approaches against standard techniques.
A four-field conformal technique for treating pancreas cancer has been developed using nonopposed 18 MV photons. This approach has been extended to 6 MV photon application by the addition of o...
Radiosurgery or stereotactic radiosurgery (SRS) is defined as the irradiation of intracranial lesions with a single fraction of focused small ionizing radiation beams, such as x-rays or gamma rays, eliminating the need for conventional invasive surgery. Stereotactic radiation therapy (SRT) is the treatment of intracranial lesions with the stereotac...
A technique of automating compensator design for lung inhomogeneity correction using an electron portal imaging device (EPID) has been investigated. This technique utilizes exit-radiation information as detected by an EPID to determine the thickness of the compensator desired. In this particular study, the compensator thickness is determined to pro...
The input/output characteristics of a matrix liquid ion-chamber electronic portal imaging device (EPID) are investigated to elucidate the imaging properties of EPIDs. The radiation input to the detector, represented by dose rate, and the pixel value output from the device are related by a characteristic curve. Various incident radiation intensities...
A technique is described that uses an independent, asymmetric collimator and a penumbra modifier to uniformly administer radiation over the craniospinal axis.
An isocenter is used at the junction of the cranial and the upper spinal fields. These fields are defined by a single isocenter at spinal cord depth and an independent, asymmetric collimator....
For the stereotactic irradiation of intracranial lesions with a linear accelerator, the use of a tertiary collimating system can be expected to confer several benefits in comparison to the use of the standard linac collimating jaw system. Moving the collimator closer to the patient should lead to reduced penumbra and reduced susceptibility to posit...
The dose to bone from I-125 photon interactions is expected to be approximately five times greater than the dose to soft tissue for the same photon fluence because of the dominance of the photoelectric effect. However, adverse clinical effects are not observed for I-125 implants near bone. Both the strong absorption of I-125 photons in bone and the...
The radiosensitive duodenum must be treated during IORT of human pancreatic head tumors, leading to an approximately 25% incidence of late bleeding. This study aimed to decrease the toxicity by administering WR2721 directly into the duodenal lumen. Duodenal toxicity in the canine was evaluated after intraoperative radiotherapy (IORT) with and witho...
Radiosurgery at UCSF is performed with a 6-MV linear accelerator with tertiary collimation for improved small field definition. The dose delivery to the target relative to normal tissue is influenced by the number of arcs, the arc geometry, field size, and beam energy. The impact of arc number, arc geometry, and field size on the dose distribution...
The low-energy photons of 125I deposit energy in tissues primarily by the photoelectric effect, which is strongly dependent on the atomic number Z. Thus dose distributions of 125I sources in media of different Z are not the same. LiF and CaF2 thermoluminescent dosimeters were used for relative dose distribution measurements in materials that are eq...