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Biomedical subjects

William A Friedman

Publications and source records attributed to William A Friedman.

At least 19 recordsLinked to original sources
PubMed2006

Pontine atypical neurocytoma: case report.

OBJECTIVE AND IMPORTANCE: Neurocytomas are typically located within the supratentorial ventricular system. Extraventricular neurocytomas are very rare, and this is only the second reported case of a pontine neurocytoma. We discuss the clinical presentation, histology, and treatment of these rare tumors. CLINICAL PRESENTATION: A 58-year-old man presented with a 4-month history of headache and unilateral facial and distal extremity paresthesia. Magnetic resonance imaging (MRI) scans demonstrated a 2.6 x 2.2-cm ring-enhancing cystic mass in the right pons. INTERVENTION: MRI-guided stereotactic biopsy yielded a diagnosis of atypical neurocytoma. Because of the location and malignant histological features of the tumor, the patient was initially treated with external beam radiation therapy. Several months later, MRI scans demonstrated tumor progression. The patient then underwent three rounds of temozolomide chemotherapy, during and after which his symptoms worsened. Aggressive subtotal resection of the tumor was achieved via a right suboccipital craniectomy. CONCLUSION: Twenty-eight months postoperatively, the patient is symptom free, and MRI scans demonstrate no evidence of residual or recurrent tumor.

Brain Stem Neoplasms↗
PubMed2006

Linear accelerator radiosurgery for vestibular schwannomas.

OBJECT: Radiosurgery has become a popular treatment for small vestibular schwannomas (VSs). The aim of this study was to review an extensive, single-institution experience with linear accelerator (LINAC) radiosurgery for VSs. METHODS: Between July 1988 and August 2005, 390 patients with VSs were treated with LINAC-based radiosurgery at the authors' institution. Patient and treatment variables were prospectively maintained in a computer database. Outcomes were tracked through periodic clinical examinations and annual scanning studies. Multivariate and actuarial statistics were used to analyze rates of local tumor control and complications, including facial and trigeminal neuropathies, after treatment. One- and 2-year actuarial control rates were both 98%, and the 5-year actuarial control rate was 90%. Only four patients (1%) required surgery for tumor growth. Seventeen patients (4.4%) reported facial weakness and 14 patients (3.6%) reported facial numbness after radiosurgery. The risk of these complications rose with increasing tumor volume or increasing radiosurgical dose to the tumor periphery. Since 1994, when doses were deliberately lowered to 1250 cGy, only two patients (0.7%) have experienced facial weakness and two (0.7%) have experienced facial numbness. CONCLUSIONS: Radiosurgery provides a safe and effective therapeutic alternative to surgery for small VSs.

Adult↗
PubMed2005

A geometrically based method of step and shoot stereotactic radiosurgery with a miniature multileaf collimator.

Conventional methods of inverse planning for intensity-modulated radiotherapy (IMRT) and intensity-modulated radiosurgery (IMRS) are generally based upon optimizing a set of beam fluence profiles according to a set of dose-volume constraints specified by a human planner. This optimization is generally carried out through an iterative approach that relies upon the optimization of a score, driving the plan's ability to satisfy the user-provided constraints. Following optimization of the fluence distribution, the non-trivial problem of converting the fluence distribution into a set of deliverable, intensity-modulated beams must be solved. A novel approach to solving this IMRS total inverse problem is presented in this paper. The proposed method uses a class solution that provides an optimized dose gradient and a method of designing a conformal plan based on an existing geometrically based optimization algorithm. After developing an optimal fluence distribution, the process then arranges the fluence into a set of simple and efficient MLC beam delivery sequences. The algorithm presented here offers several potential advantages for the application of intensity modulation to radiosurgery treatment planning. The geometrically based optimization process' simplicity requires far less human user input and decision making in the specification of dose and dose-volume constraints than do conventional inverse planning algorithms. This simplicity allows the optimization process to be completed much faster than conventional inverse-planning algorithms, literally seconds compared with at least several minutes. Likewise, the fluence conversion step is a simplified process (compared to conventional IMRT planning), which takes advantage of some simplifications uniquely appropriate to the problem at hand (IMRS). The converted, deliverable IMRS beams allow superior conformity and dose gradient relative to conventional IMRS planning or 3DCRT radiosurgery planning. Another benefit is that the number of beam intensity levels is greatly reduced, from hundreds to as few as a half-dozen intensity levels. Finally, since the treatment plan optimization process is based upon proven principles applicable to optimizing radiosurgery (rather than the general problem of optimizing fractionated radiotherapy plans), the plans generated and deliverable with this method of IMRS are potentially superior to those produced by conventional inverse-planning methods of IMRT/IMRS.

Algorithms↗
PubMed2005

Radiotherapy and radiosurgery for benign neurofibromas.

The purpose of this study was to evaluate the efficacy of radiotherapy (RT) and stereotactic radiosurgery (SRS) for neurofibromas. We studied 4 patients treated with RT (3 patients) or SRS (1 patient) and followed from 1.7 to 14.8 years. The tumor remained locally controlled in all patients. No significant complications related to treatment were observed. RT and SRS are likely to locally control neurofibromas in patients who require treatment and are not good candidates for complete resection.

Adult↗
PubMed2005

Radiosurgery in the treatment of malignant gliomas: the University of Florida experience.

OBJECTIVE: To review a single-institution's 12-year experience of treating malignant gliomas with linear accelerator-based radiosurgery. METHODS: One hundred patients were treated for malignant gliomas at the University of Florida between May 1, 1989, and June 12, 2002. Patient variables were entered into a radiosurgery database in a prospective manner. The endpoint of the study was length of survival from the time of diagnosis. The minimum length of follow-up was 18 months or until death. In an attempt to control for selection bias, we used the Radiation Oncology Therapy Group's (RTOG) recursive partitioning categories to compare survival in our group of radiosurgically boosted patients with the RTOG historical database. RESULTS: Recursive partitioning analysis classification was significantly associated with survival. Compared with historical controls, this cohort of patients demonstrated a decreased survival for recursive partitioning analysis Class I and II patients, similar survival for Class III and IV patients, and increased median survival for Class V patients. Other variables demonstrating a statistically significant impact on survival were eloquent location and recurrent disease. CONCLUSION: The results of this study and those of RTOG 93-05 suggest that the reported benefit of upfront radiosurgical boost for malignant gliomas is the result of selection bias. The possibility remains that radiosurgical boost is of benefit in recurrent tumors, especially those in RTOG Class V.

Adult↗
PubMed2005

Linear accelerator surgery for meningiomas.

OBJECT: In this paper the authors review the results of a single-center experience in the use of linear accelerator (LINAC) surgery for radiosurgical treatment of meningiomas. METHODS: A retrospective analysis of all patients treated with LINAC surgery for meningiomas between May 1989 and December 2001 was performed. All patients participated in follow-up review for a minimum of 2 years, and no patients were excluded. Two hundred ten patients were treated during the study interval. The actuarial local control rate for benign tumors was 100% at both 1 and 2 years, and 96% at 5 years. The actuarial local control rate for atypical tumors was 100% at 1 year, 92% at 2 years, and 77% at 5 years; and that for malignant tumors was 100% at both 1 and 2 years, and only 19% at 5 years. Of the 210 patients 13 (6.2%) experienced temporary radiation-induced complications, and only five (2.3%) experienced permanent complications. In all patients with a permanent complication the histological characteristics of the meningioma were malignant. CONCLUSIONS: Linear accelerator surgery produced high local control rates and very low rates of permanent morbidity in patients harboring benign meningiomas.

Adult↗
PubMed2004

Management of benign skull base meningiomas: a review.

The optimal management of benign meningiomas of the skull base is reviewed. Elderly patients with small, asymptomatic tumors can be observed and treatment can be initiated if and when progression occurs. Patients with tumors that appear to be amenable to complete resection with an acceptable rate of morbidity are optimally treated with surgery. Decompression of more extensive tumors through conservative subtotal resection and preservation of the involved cranial nerves may result in improved neurological function. Either alone or after subtotal resection, radiosurgery is indicated for tumors that can be treated adequately with this modality. Larger, ill-defined tumors and those that abut radiosensitive structures such as the optic nerve(s) are optimally treated with radiotherapy. Extensive subtotal resections that sacrifice one or more cranial nerves are no more likely to enhance the probability of success of subsequent radiotherapy than more conservative procedures.

Journal Article↗
PubMed2004

Resident duty hours in American neurosurgery.

The unexpected death of Libby Zion, at New York Hospital in 1984, led to a series of investigations that recently resulted in profound changes in resident duty hours. On July 1, 2003, the Accreditation Council for Graduate Medical Education (the governing body of all residency programs in the United States) mandated the following work hours rules: no more than 80 hours per week, no more than 24 hours of continuous patient care (with an added 6-hour transition period), 1 day in 7 free of patient care responsibilities, and a minimum of 10 rest hours between duty periods. These rules are based on a considerable body of scientific study indicating that sleep loss affects cognitive performance and, possibly, patient care. The new work hours have stimulated vigorous debate, both pro and con. Those arguments are reviewed.

Adolescent↗
PubMed2004

Linear accelerator radiosurgery in the treatment of brain metastases.

OBJECTIVE: To review a 12-year experience treating metastatic brain disease with linear accelerator-based stereotactic radiosurgery (SRS). METHODS: We performed a retrospective analysis of all patients treated between 1989 and 2001 with linear accelerator radiosurgery for brain metastases. Patients were followed up both clinically and with imaging studies to document local control, regional control, and survival. Demographic data, dosing parameters, number of lesions, histology, history of whole-brain radiation therapy, and other factors were obtained prospectively. Cox proportional-hazards regression with multivariate and univariate analysis was performed with Stata 8.0 software. RESULTS: A total of 383 patients received SRS for brain metastases during the study interval. Median survival was 9 months. Patients with tumor-type melanoma or multiple metastatic lesions had decreased survival. Actuarial 1-year local control was 75%. Differences in regional control rates were not statistically significant between patients treated with SRS and whole-brain radiation therapy versus SRS alone. CONCLUSION: Radiosurgery is an effective and safe method for treating selected patients with brain metastases.

Adult↗
PubMed2004

Do the morphological characteristics of arteriovenous malformations affect the results of radiosurgery?

OBJECT: The authors sought to determine which morphological features of arteriovenous malformations (AVMs) are statistically predictive of preradiosurgical hemorrhage, postradiosurgical hemorrhage, and neuroimaging-defined failure of radiosurgical treatment. In addition, correlation between computerized tomography (CT) scanning and angiography for the identification of AVM structures was investigated. METHODS: Archived CT dosimetry and available angiographic and clinical data for 268 patients in whom AVMs were treated with linear accelerator radiosurgery were retrospectively reviewed. Many of the morphological features of AVMs, including location, volume, compact or diffuse nidus, neovascularity, ease of nidus identification, number of feeding arteries, location (deep or superficial) of feeding arteries, number of draining veins, deep or superficial venous drainage, venous stenoses, venous ectasias, and the presence of intranidal aneurysms, were analyzed. In addition, a number of patient and treatment factors, including patient age, presenting symptoms, radiation dose, repeated treatment, and radiological outcome, were subjected to multivariate analyses. Two hundred twenty-seven patients were treated with radiosurgery for the first time and 41 patients underwent repeated radiosurgery. Eighty-one patients presented with a history of AVM hemorrhage and 91 patients had AVMs in a periventricular location. Twenty-six patients (10%) experienced a hemorrhage following radiosurgery. Of the 268 patients, 81 (30%) experienced angiographically defined cures, and 37 (14%) experienced MR imaging-defined cures. Eighty-six patients (32%) experienced neuroimaging-defined treatment failure, and 64 underwent insufficiently long follow up. A larger AVM volume (odds ratio [OR] 0.349; p = 0.004) was associated with a decreased rate of pretreatment hemorrhage, whereas periventricular location (OR 6.358; p = 0.000) was associated with an increased rate of pretreatment hemorrhage. None of the analyzed factors was predictive of hemorrhage following radiosurgery. A higher radiosurgical dose was strongly correlated with neuroimaging-defined success (OR 3.743; p = 0.006), whereas a diffuse nidus structure (OR 0.246; p = 0.008) and associated neovascularity (OR 0.428; p = 0.048) were each associated with a lower neuroimaging-defined cure rate. A strong correlation between CT scanning and angiography was noted for both nidus structure (p = 0.000; Fisher exact test) and neovascularity (p = 0.002; Fisher exact test). CONCLUSIONS: Patients presenting with AVMs that are small or periventricular were at higher risk for experiencing hemorrhage. A higher radiosurgical dose correlated strongly with neuroimaging-defined success. Patients in whom the AVM had a diffuse structure or associated neovascularity were at higher risk for neuroimaging-defined failure of radiosurgery. A strong correlation between CT scanning and angiography in the assessment of AVM structure was demonstrated.

Adolescent↗
PubMed2004

Radiosurgery and radiotherapy: observations and clarifications.

OBJECT: Radiosurgery and radiation therapy represent important but unique treatment paradigms for patients with certain neoplasms, vascular lesions, or functional disorders. The authors discuss their differences. METHODS: Reviewing the authors' experiences shows how the roles of these approaches vary just as their techniques differ. The distinct differences include the method of target localization (intraoperative compared with pretreatment) and irradiation (focused compared with wide-field), their radiobiology (effects of a single high-dose compared with multiple fractions), the physicians and other health personnel involved in the conduct of these procedures (surgical team compared with radiation team), and the expectations that follow treatment. During the last decade, considerable confusion has grown regarding nomenclature, requisite physician training, and the roles of the physician and surgeon. Ten years ago, two task forces on radiosurgery were created by national organizations in neurosurgery and radiation oncology to address these issues of procedural conduct and quality-assurance requirements. At the present time these guidelines are widely ignored. Currently, many patients, payers, and regulatory agencies are bewildered. What are the differences among stereotactic radiosurgery, fractionated radiation therapy, and stereotactic radiation therapy? Radiosurgery is to radiation therapy as microsurgery is to "microtherapy." CONCLUSIONS: In this report the authors discuss terminology, training, and physician roles in this expanding field.

Brain Diseases↗
PubMed2003

A simple and reliable index for scoring rival stereotactic radiosurgery plans.

PURPOSE: A simple and robust index for ranking rival stereotactic radiosurgery plans is presented. METHODS: The radiosurgery plan score index, CGI (Conformity/Gradient Index), is an average of a conformity score and a gradient score. Computation of the CGI score is simple, requiring only three pieces of data: (1) the total volume irradiated to the prescription isodose level, (2) the volume of the target, and (3) the total volume irradiated at half of the prescription isodose level. The overall CGI Index is a simple function of these three pieces of data. RESULTS: When multiple sets of rival stereotactic radiosurgery plans were ranked with respect to this single score index, the resulting plan rankings closely matched the plan rankings according to biologic indices (calculated nontarget brain normal tissue complication probabilities). CONCLUSIONS: The CGI is a simple and fast plan evaluation tool that can assist the radiosurgery planner in evaluating and optimizing multiple candidate radiosurgery plans.

Adult↗
PubMed2003

Radiotherapy alone or after subtotal resection for benign skull base meningiomas.

BACKGROUND: The objective of the current study was to analyze the long-term local control and complications in a series of patients who were treated with radiotherapy for benign skull base meningiomas. METHODS: Between January 1984 and July 2001, 101 patients were treated with radiotherapy alone (n = 66) or after undergoing subtotal resection (n = 35). Sixty-one patients had previously untreated tumors, and 40 patients had tumors that were recurrent after prior surgery. Patients had follow-up from 0.6 years to 19 years (median, 5.1 years). The follow-up of living patients ranged from 1.3 years to 19 years (median, 5.4 years). RESULTS: The long-term local control rates were 95% at 5 years, 92% at 10 years, and 92% at 15 years. Multivariate analysis of local control revealed that none of the parameters evaluated significantly influenced this endpoint. The cause-specific survival rates were 97% at 5 years, 92% at 10 years, and 92% at 15 years; and the absolute survival rates were 86% at 5 years, 71% at 10 years, and 62% at 15 years. Multivariate analysis of cause-specific survival revealed that only gender significantly influenced this endpoint (P = 0.0185). Severe complications were observed in eight patients, and three patients experienced complications that were fatal. CONCLUSIONS: The probability of long-term progression-free survival after radiotherapy exceeded 90% and was comparable to the results of complete resection and radiosurgery. Subtotal resection was useful for decompressing the tumor if improvement in neurologic function was anticipated after surgery. Extensive subtotal resection may result in permanent neurologic deficits and did not improve long-term local control.

Adolescent↗
PubMed2003

Linear accelerator-based radiosurgery for vestibular schwannoma.

Despite major advances in skull base surgery and microsurgical techniques, surgery for vestibular schwannoma (VS) carries a risk of complications. Some are inherent to general anesthesia and surgery of any type and include myocardial infarction, pneumonia, pulmonary embolism, and infection. Some are specific to neurosurgery in this area of the brain, and include hydrocephalus, cerebrospinal fluid leak, facial nerve paralysis, facial numbness, hearing loss, ataxia, dysphagia, and major stroke. Even in the hands of very experienced acoustic surgeons, these risks cannot be eliminated. Radiosurgery provides an outpatient, noninvasive alternative for the treatment of small acoustic schwannomas. Initially radiosurgery was undertaken in "high-risk" patients, including the elderly, those with severe medical comorbidities, and those in whom tumors recurred after surgery. Additionally, a high rate of cranial nerve morbidity was reported. With improvements in dosimetry planning and dose selection, however, authors practicing at radiosurgical centers now report very low complication rates, as well as high tumor control rates. In this report the authors specifically review the results of linear accelerator-based radiosurgery for VS and compare these outcomes with the best surgical alternatives.

Hearing Disorders↗
PubMed2003

Ultrasound-guided extracranial radiosurgery: technique and application.

PURPOSE: Stereotactic radiosurgery is an effective treatment modality for many intracranial lesions, but target mobility limits its utility for extracranial applications. We have developed a new technique for extracranial radiosurgery based on optically guided three-dimensional ultrasound (3DUS). The 3DUS system provides the ability to image the target volume and critical structures in real time and determine any misregistration of the target volume with the linear accelerator. In this paper, we describe the system and its initial clinical application in the treatment of localized metastatic disease. METHODS AND MATERIALS: The extracranial stereotactic system consists of an ultrasound unit that is optically tracked and registered with the linear accelerator coordinate system. After an initial patient positioning based on computed tomographic (CT) simulation, stereotactic ultrasound images are acquired and correlated with the CT-based treatment plan to determine any soft-tissue shifts between the time of the planning CT and the actual treatment. Optical tracking is used to correct any patient offsets that are revealed by the real-time imaging. RESULTS: Preclinical testing revealed that the ultrasound-based stereotactic navigation system is accurate to within 1.5 mm in comparison with an absolute coordinate phantom. Between March 2001 and March 2002, the system was used to deliver extracranial radiosurgery to 17 metastatic lesions in 16 patients. Treatments were delivered in 1 or 2 fractions, with an average fractional dose of 16 Gy (range 12.5-24 Gy) delivered to the 80% isodose surface. Before each fraction, the target misalignment from isocenter was determined using the 3DUS system and the misalignments averaged over all patients were anteroposterior = 4.8 mm, lateral = 3.6 mm, axial = 2.1 mm, and average total 3D displacement = 7.4 mm (range = 0-21.0 mm). After correcting patient misalignment, each plan was delivered as planned using 6-11 noncoplanar fields. No acute complications were reported. CONCLUSIONS: A system for high-precision radiosurgical treatment of metastatic tumors has been developed, tested, and applied clinically. Optical tracking of the ultrasound probe provides real-time tracking of the patient anatomy and allows computation of the target displacement before treatment delivery. The patient treatments reported here suggest the feasibility and safety of the technique.

Aged↗
PubMed2003

Routine use of postoperative ICU care for elective craniotomy: a cost-benefit analysis.

OBJECTIVE: Postoperative monitoring in an intensive care unit (ICU) setting following elective craniotomy is routine at many institutions, as it is believed that this reduces the incidence and potential seriousness of early postoperative complications. This is unproven, however, and ICU resources are scarce and costly. At our institution, one surgeon began to routinely transfer elective craniotomy patients directly to the floor following an uneventful postanesthesia care unit (PACU) recovery. This study was undertaken to see whether that practice was safe and cost-effective. METHODS: A retrospective cohort of 430 consecutive, elective adult craniotomies, from February, 2000 to September, 2001 were analyzed. Variables were divided into 12 major groups: attending surgeon, age, sex, diagnosis, Current Procedural Terminology (CPT) code, length of stay, preoperative deficit, medical co-morbidities, postop floor, medical complications, neurological complications, and total hospitalization cost. RESULTS: Patients admitted to the surgical intensive care unit (SICU) did not have fewer complications than patients transferred directly to the floor. Patients admitted to the SICU did not have more preoperative neurological deficits or medical co-morbidities. Age was not a significant predictor of either medical or neurological complications. In patients without initial postop complications, only length of stay and postop floor assignment correlated with cost (p < 0.001). Immediate transfer to the floor decreased average hospitalization length by 3 days, and provided cost savings of $4,026 per patient. CONCLUSIONS: Selective, rather than routine use of postoperative ICU care in elective craniotomy patients is safe, resulting in no greater incidence of medical or neurological complications, and may provide significant reductions in average hospitalization length and cost.

Adult↗