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Biomedical subjects

Cole A Giller

Publications and source records attributed to Cole A Giller.

11 recordsLinked to original sources
PubMed2005

Robotically guided radiosurgery for children.

BACKGROUND: A robotically guided linear accelerator has recently been developed which provides frameless radiosurgery with high precision. Potential advantages for the pediatric population include the avoidance of the cognitive decline associated with whole brain radiotherapy, the ability to treat young children with thin skulls unsuitable for frame-based methods, and the possible avoidance of general anesthesia. We report our experience with this system (the "Cyberknife") in the treatment of 21 children. PROCEDURES: Cyberknife radiosurgery was performed on 38 occasions for 21 patients, age ranging from 8 months to 16 years (7.0 +/- 5.1 years), with tumors considered unresectable. Three had pilocytic astrocytomas, two had anaplastic astrocytomas, three had ependymomas (two anaplastic), four had medulloblastomas, three had atypical teratoid/rhabdoid tumors, three had craniopharyngiomas, and three had other pathologies. The mean target volume was 10.7 +/- 20 cm(3), mean marginal dose was 18.8 +/- 8.1 Gy, and mean follow-up is 18 +/- 11 months. Twenty-seven (71%) of the treatments were single-shot and eight (38%) patients did not require general anesthesia. RESULTS: Local control was achieved in the patients with pilocytic and anaplastic astrocytoma, three of the patients with medulloblastoma, and the three with craniopharyngioma, but not for those with ependymoma. Two of the patients with rhabdoid tumors are alive 16 and 35 months after this diagnosis. There have been no procedure related deaths or complications. CONCLUSION: Cyberknife radiosurgery can be used to achieve local control for some children with CNS tumors without the need for rigid head fixation.

Adolescent↗
PubMed2005

New frontiers in radiosurgery for the brain and body.

Radiosurgery is defined as the use of highly focused beams of radiation to ablate a pathologic target, thus achieving a surgical objective by noninvasive means. Recent advances have allowed a wide variety of intracranial lesions to be effectively treated with radiosurgery, and radiosurgical treatment has been accepted as a standard part of the neurosurgical armamentarium. The advent of frameless radiosurgery now permits radiosurgical treatment to all parts of the body and is being actively explored by many centers. This article reviews some of the modern tools for radiosurgical treatment and discusses the current clinical practice of radiosurgery.

Journal Article↗
PubMed2005

Use of sagittal images for localization of the subthalamic nucleus. Technical note.

Direct observation of the subthalamic nucleus (STN) is not always possible, and physicians at many centers rely on indirect methods that relate the position of the STN to more easily recognized structures such as the red nucleus (RN). In this paper the authors describe an indirect method of viewing the STN based on the anatomy depicted on sagittal magnetic resonance (MR) images. A review of sagittal slices appearing in standard stereotactic atlases showed that the STN lies within the angle formed by the descending internal capsule (IC) and the substantia nigra (SN). The authors' technique consists of marking the location of the STN in this nigrocapsular angle on each sagittal MR image between the RN and the lateral border of the brainstem, and transferring these points to axial MR images to build a locus of points used to describe the STN. A point is chosen in the center of this locus as the stereotactic target. Two hundred eighty-two sagittal images obtained from 71 MR imaging studies performed in 29 patients by using a fast-spin echo inversion-recovery technique were examined for the presence of the STN, the SN, and the IC. The descending IC could be detected in 97% of the slices, the SN in 95% of the slices, and the STN in 73% of the slices. This indirect method involving sagittal anatomy can be used to refine localization of the STN.

Humans↗
PubMed2004

Feasibility of radiosurgery for malignant brain tumors in infants by use of image-guided robotic radiosurgery: preliminary report.

OBJECTIVE: The benefits of radiation therapy are generally denied to infants with malignant brain tumors because of the risk of devastating cognitive decline. Efforts to limit this morbidity with radiosurgical techniques have not been feasible for infants because of the dual requirements of rigid head fixation and high precision. We report the radiosurgical treatment of five infants by use of a robotically controlled system without rigid head fixation. METHODS: Five infants with malignant brain tumors received radiosurgical treatment with a robotically driven linear accelerator. Immobilization was aided by general anesthesia, form-fitting head supports, face masks, and body molds. The average marginal dose was 17 +/- 2 Gy, and the average treatment volume was 18 +/- 22 ml. RESULTS: X-rays obtained during treatment revealed acceptable agreement with preoperative computed tomographic scans in all patients. In one patient, the lesion did not progress, but a distant recurrence occurred 15 months after radiosurgery and also was treated with radiosurgery. In another patient, tumor in the treated region did not progress, but recurrence elsewhere led to death 7 months after treatment. Tumor enlargement occurred in Patient 3 at 3 months posttreatment, leading to death 2 months later. Tumor size was smaller in the remaining two patients at 9 and 11 months after treatment. There has been no toxicity attributed to treatment. CONCLUSION: Radiosurgery with minimal toxicity can be delivered to infants by use of a robotically controlled system that does not require rigid fixation. A formal dose-escalation trial is under way to address dose and toxicity for infants more thoroughly.

Brain Neoplasms↗
PubMed2003

Linearity and non-linearity in cerebral hemodynamics.

BACKGROUND: Transcranial Doppler ultrasound has been extensively used to study cerebral hemodynamics, and yet the basic characteristics of the input/output system of blood pressure/velocity are little known. We examine whether this system can best be considered linear or non-linear. METHODS: We assessed the adequacy of linear modeling in four ways: (1) Known properties of cerebral blood flow were reviewed and analyzed from a systems standpoint; (2) 1100 ARX & OE model types were tested with data from 29 normal subjects, with and without lowpass filtering; (3) time-frequency analysis was used to identify nonstationary behavior and markers of non-linearity (such as bifurcations, chirps, and intermittent autoregulatory impairment) in the same data sets; (4) simple computer models of autoregulation incorporating time delays and non-linear elements were tested for production of spontaneous oscillations. RESULTS: (1) Several aspects of cerebral hemodynamics are poorly described by linear models, (2) the ARX & OE models performed poorly, (3) time-frequency analysis showed non-linear and nonstationary behavior, (4) the computer models produced spontaneous oscillations similar to those observed in humans. CONCLUSIONS: There is strong evidence that the blood pressure/velocity system is non-linear.

Blood Flow Velocity↗
PubMed2003

Local electronic storage of radiological studies for radiosurgery.

OBJECTIVE: Although radiosurgical practice mandates meticulous radiological follow-up, even the most efficient radiology department can be overwhelmed by the large number of radiosurgical patients who have undergone diagnostic studies for many years at many different institutions to follow many separate lesions. Although the task of assembling these studies is theoretically possible, because they are spread out in time and space, it is often impractical. We therefore sought to construct a computer-based system that could store images from multiple sources and present them instantly for review. METHODS: We attached a flatbed film scanner to a standard desktop computer in our clinic and scanned selected sheets of film into an image database at each visit of a radiosurgical patient. "Low-tech" solutions were deliberately chosen-that is, to enhance ease and software compatibility, we used the operating system's directory structure for organization of data instead of proprietary software. Standard commercially available software was used to review studies that had been previously scanned. RESULTS: During a 2- to 3-year period, images were scanned from 1129 studies performed on 435 patients. Images could be reviewed instantly and compared with current studies, and scanning a single piece of film required approximately 30 seconds. We estimate that the current capacity of our computer memory will satisfy our needs for approximately 12 years. CONCLUSION: Assembly of an efficient and inexpensive system for image storage and retrieval suitable for radiosurgical practice is feasible and straightforward. Although our system is not a substitute for a radiology department, it obviates the constant frustration of "finding the films" and has become an essential part of our radiosurgical practice.

Brain Diseases↗
PubMed2003

Validation of a near-infrared probe for detection of thin intracranial white matter structures.

OBJECT: The authors have developed an intracranial near-infrared (NIR) probe that analyzes the scattering of light emitted from its tip to measure the optical properties of cerebral tissue. Despite its success in distinguishing graymatter from white matter in humans during stereotactic surgery, the limits of this instrument's resolution remain unclear. In this study, the authors determined the spatial resolution of this new probe by using a rodent model supplemented with phantom measurements and computer simulation. METHODS: A phantom consisting of Intralipid and gelatin was constructed to resemble a layer of white matter overlying a layer of gray matter. Near-infrared measurements were obtained as the probe was inserted through the gray-white matter transition. A computer simulation of NIR measurements through a gray-white matter transition was also performed using Monte Carlo techniques. The NIR probe was then used to study 19 tracks from the cortical surface through the corpus callosum in an in vivo rodent preparation. The animals were killed and histological sections through the tracks were obtained. Data from the phantom models and computer simulations showed that the NIR probe samples a volume of tissue extending 1 to 1.5 mm in front of the probe tip (this distance is termed the "lookthrough" distance). Measurements obtained from an NIR probe passing through a thin layer of white matter consisted of an initial segment of increasing values, a maximum (peak) value, and a trailing segment of decreasing values. The length of the initial segment is the lookthrough distance, the position of the peak indicates the location of the superficial white matter boundary, and the length of the trailing segment is the thickness of the layer. These considerations were confirmed in experiments with rodents. All tracks passed through the corpus callosum, which was demonstrated as a broad peak on each NIR graph. The position of the dorsal boundary of the corpus callosum and its width (based on histological measurements) correlated well with the peak of the NIR curve and its trailing segment, respectively. The initial segments correlated well with estimates of the lookthrough distance. Five of the tracks transected the smaller anterior commissure (diameter 0.2 mm), producing a narrow NIR peak at the correct depth. CONCLUSIONS: Data in this study confirm that the NIR probe can reliably detect and measure the thickness of layers of white matter as thin as 0.2 mm. Such resolution should be adequate to detect larger structures of interest encountered during stereotactic surgery in humans.

Animals↗
PubMed2002

Ventralis intermedius thalamotomy can succeed when ventralis intermedius thalamic stimulation fails: report of 2 cases for tremor.

In 2 patients with essential tremor, thalamotomy in the ventralis intermedius (VIM) provided lasting tremor relief after thalamic stimulation of the VIM failed. These cases illustrate that the effects of deep brain stimulation might not be those of simple inhibition, and that thalamotomy should be considered when deep brain stimulation does not succeed.

Aged↗