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Biomedical subjects

M P Mehta

Publications and source records attributed to M P Mehta.

At least 55 records · Page 3Linked to original sources
PubMed1994

Stereotactic radiosurgery for glioblastoma multiforme.

From February 1989 to August 1992, 26 patients who presented with an initial pathological diagnosis of glioblastoma multiforme underwent tumor debulking (17) or biopsy (9), stereotactic radiosurgery (SR) and standard radiation therapy (dose range 50-66 Gy) as part of their primary tumor therapy. Presenting characteristics included median age of 55 years (range 20-79), Karnofsky Performance Score (KPS) median 82.5 (20-100), and median tumor volume 18.6 cm3 (2.2-59.7). SR collimator size ranged from 2.25 to 4 cm with a central dose of 15-35 Gy. Isocenter location, collimator size and beam paths were individualized using three-dimensional software such that the maximum possible solid angle was subtended without exceeding a 20% tumor dose gradient. The mean follow-up was 10.9 months (6-19.5) with a median of 9.5 months. Statistical analysis was performed using Kaplan-Meier actuarial analysis developing predicted 12-month survival rates. There were no significant differences noted in patient survival for the parameters of biopsy versus debulking, single versus multiple isocenters, age, initial KPS, and patterns of steroid requirement. Radiographic recurrences were divided by location into central (within central SR dose) = 0, peripheral (within 1 cm of central dose) = 16, and distant (< 1 cm) = 4. Predicted 12-month survival was 24%, with a median survival of 9.5 months. These values are similar to previous results for surgery and standard radiotherapy alone [1]. The results suggest that radiosurgery, when used as a mode of primary therapy, offers little or no benefit in quality of life or survival as recurrences occur immediately outside or distant to the central SR field.

Adult↗
PubMed1993

Consensus guidelines for high dose rate remote brachytherapy in cervical, endometrial, and endobronchial tumors. Clinical Research Committee, American Endocurietherapy Society.

PURPOSE: A large number of medical centers have recently instituted the use of High Dose-Rate Afterloading Brachytherapy (HDRAB). There is wide variation in treatment regimens, techniques, and dosimetry being used and there are no national standard protocols or guidelines for optimal therapy. METHODS AND MATERIALS: The Clinical Research Committee (CRC) of the American Endocurietherapy Society (AES) met to formulate consensus guidelines for HDRAB in cervical, endometrial, and endobronchial tumors. CONCLUSION: Each center is encouraged to follow a consistent treatment policy in a controlled fashion with complete documentation of treatment parameters and outcome including efficacy and morbidity. Until further clinical data becomes available, the linear quadratic model can be used as a guideline to formulate a new HDR regimen exercising caution when changing from a Low Dose Rate (LDR) to a HDRAB regimen. The treatments should be fractionated as much as practical to minimize long term morbidity. As more clinical data becomes available, the guidelines will mature and be updated by the Clinical Research Committee of the AES.

Brachytherapy↗
PubMed1993

Inguinofemoral radiation of N0,N1 vulvar cancer may be equivalent to lymphadenectomy if proper radiation technique is used.

PURPOSE: To update a previous retrospective study that compared inguinofemoral irradiation (N = 23) to lymphadenectomy (N = 25) for N0,N1 vulvar carcinoma with more patients and longer follow-up. These results, unlike the recent randomized Gynecologic Oncology Group (GOG study), suggest that radiation is a viable alternative to groin dissection, and the differences may be explained on the basis of irradiation technique. METHODS AND MATERIALS: Based on a growing body of data supporting control of subclinical nodal disease with irradiation in vulvar cancer, the decision was made to offer patients with squamous cell carcinoma of the vulva and clinically negative groins (N0,N1), either lymphadenectomy or inguinofemoral irradiation based on clinical factors. Because of the acute skin reaction and possible underdosing of deep femoral nodes with electrons as used in the GOG study, opposed photon fields to 50 Gy were used. From 1983 to 1991, 48 patients underwent a radical vulvectomy followed by either lymphadenectomy (Group I, n = 25) or inguinofemoral irradiation (Group II, n = 23). RESULTS: The actuarial nodal control was 100% in Group I and 91% in Group II (p = 0.14). In addition, there was no difference in cause specific survival at 3 years (96% and 90%, respectively, p = 0.47). The morbidity of lymphadenectomy (Group I) included: 16% lymphedema, 16% seromas, 44% infection, and 68% wound separation. In the irradiated patients (Group II), 16% developed lymphedema and only 9% had a significant skin reaction. CONCLUSION: Based on this analysis of local control and survival with longer follow-up and more patients, irradiation of the N0, N1 inguinofemoral nodes may be a viable alternative to lymphadenectomy for squamous cell carcinoma of the vulva if proper radiation technique and dose are used. In addition, the acute and delayed morbidity of lymphadenectomy exceeds that of irradiation.

Aged↗
PubMed1993

Thoracic volume radiation sparing following endobronchial brachytherapy: a quantitative analysis.

A retrospective analysis of patients with inoperable, Stage III non-small cell lung carcinoma presenting with malignant airway occlusion and treated with endobronchial brachytherapy boost prior to radical radiotherapy is reported. Of the 102 patients treated with endobronchial brachytherapy between October 1986 and January 1991, 22 were newly diagnosed, biopsy-proven Stage IIIA (14/22) or IIIB (8/22) non-small cell carcinoma with > 80% endoscopically demonstrated airway occlusion of the carina (1/22), mainstem bronchus (10/22) or lobar bronchus (11/22). Fifteen patients had complete lung or lobar atelectasis. Poor performance status (KPS < 70% in 13/22) and/or weight loss (> 10% in 9/22) rendered these patients ineligible for multi-institutional trials. Endobronchial boost was delivered using low dose rate (20 Gy at 2 cm) or high dose rate brachytherapy (16 Gy in 4 fractions over 2 days at 2 cm). Following a 10-14 day post-endobronchial period to allow for reaeration, patients underwent additional external beam radiotherapy (60 Gy in 30 fractions). Of the 15 patients with atelectasis, 6/15 (40%) reaerated completely, 4/15 (27%) partially, and 5/15 (33%) failed to reaerate. A new method, called "sequential volume integration" was used on the pre- and post-endobronchial films to analyze sparing of thoracic volume from external beam radiation as a consequence of reaeration. Patients with complete reaeration required 47% less and those patients with partial reaeration required 25% less ipsilateral thoracic volume radiation. There was a tend toward improved survival in reaerators (36 weeks) as compared to non-reaerators (24 weeks).

Brachytherapy↗
PubMed1993

Acute changes in glucose uptake after treatment: the effects of carmustine (BCNU) on human glioblastoma multiforme.

Sequential positron emission tomographic scans with [18F]-2-fluorodeoxyglucose (PET-FDG) were performed on 6 patients with glioblastoma multiforme who were treated with adjuvant BCNU. Scans were acquired before and 24 hours after BCNU. All patients had prior brain irradiation. Ratios between the maximal tumor FDG uptake and the contralateral white matter FDG uptake, the glucose uptake ratio, were determined. Percent changes in the glucose uptake ratio between the baseline scan and the 24 hour post-treatment scan were of prognostic significance. Patients with the largest percent changes in FDG uptake had the shortest survival. In contrast, neither the baseline glucose uptake ratio nor the visual tumor grade accurately predicted length of survival.

Biological Transport, Active↗
PubMed1993

A retrospective review of nodal treatment for vulvar cancer.

From 1983 to 1990, 42 clinical N0, N1 patients with invasive squamous cell carcinoma of the vulva underwent surgery for the primary cancer, followed by nonrandomized assignment to either surgery or radiation therapy for nodal management. This is a retrospective analysis reviewing treatment outcome and complications of inguinofemoral dissection versus photon irradiation. Group I (N = 24) underwent either bilateral or unilateral inguinofemoral dissection; Group II (N = 18) underwent bilateral groin irradiation. The 3-year disease-free survival was 84.5% and 79.7% for Group I and II (p = 0.74). The nodal failure rate at 3 years was not significantly different. The postoperative complications in the surgically treated nodes were: 17% seromas, 46% wound infection, and 71% wound separation. Of those patients developing either an infection or wound separation, 41% required daily wound care for more than 2 weeks by a visiting nurse after discharge. Only 1 of 18 (6%) irradiated patients developed a clinically significant skin reaction. The median time for complete skin/wound healing was 8 weeks (range 4-24 weeks) in Group I and 2 weeks (range 2-6 weeks) in Group II. Late postoperative complications in the surgically treated patients included meralgia paresthetica (8%) and lymphedema (12%); 1 (6%) Group II patient developed lymphedema. Based on this limited retrospective review, we conclude that inguinofemoral radiation achieves reasonable local control and may represent an alternative to surgery in selected patients. The acute and delayed morbidity of lymphadenectomy exceeds that of irradiation.

Aged↗
PubMed1993

Magnetic resonance angiography: a three-dimensional database for assessing arteriovenous malformations. Technical note.

Stereotactic angiography has long been the "gold standard" in the diagnosis of patients with arteriovenous malformations (AVM's). Although orthogonal or stereoshift images may suffice in discerning the shape and location of spherical malformations, an exact analysis and assessment of most nonspherical malformations are hampered by the fact that stereotactic angiographic images compress three-dimensional (3-D) data into two-dimensional views. As a consequence, the complex 3-D shape of an AVM can never be fully and truly discerned from conventional angiography. With the recent explosion of radiosurgical techniques, more and more AVM's are being treated noninvasively. These radiosurgical techniques require 3-D visualization to maximize nidus coverage and minimize normal brain irradiation. Alternatives to stereotactic angiography are therefore desperately needed. An entire new family of pulse sequences is now available that permits visualization of the vascular system using magnetic resonance imaging. A brief technical review of magnetic resonance angiography is presented, and its potential role(s) in the assessment and radiosurgical treatment of AVM's is explored.

Humans↗
PubMed1992

Meningeal hemangiopericytoma: defining the role for radiation therapy.

Meningeal hemangiopericytoma is a rare neoplasm arising from perivascular pericytes. Accounting for < 1% of all brain tumors, these neoplasms are characterized by a high local recurrence rate and metastatic potential. Meningeal hemangiopericytoma occur most frequently during the fifth decade of life, with an almost equal sex incidence. To evaluate and define the role for primary, postoperative, or palliative radiotherapy in meningeal hemangiopericytoma, data were gathered from our own tumor registry and compiled with an extensive analysis of published series and case reports. This analysis reveals a 90%, 9 year actuarial risk for local recurrence following surgical resection only. Interestingly, less than 33% of these recurrences were noted within the first five years, which may account for the false assumption that these tumors are highly curable with surgical resection only. Radiation therapy appears to reduce this local recurrence rate, prolonging disease-free and overall survival. Radiation responses are dose dependent, with > 50 Gray providing superior long-term disease-free survival. Meningeal hemangiopericytoma are characterized by a slow, but progressive radiographic response to ionizing radiation, not unlike other radiated, highly vascular brain lesions, such as arteriovenous malformations. A retrospective review of clinical demographics, sites of meningeal origin, radiographic and pathologic findings and the role of chemotherapy is also presented.

Adolescent↗
PubMed1992

Defining the role of radiosurgery in the management of brain metastases.

The role of stereotactic radiosurgery in the management of recurrent and newly diagnosed brain metastases was evaluated prospectively. From December 1988 to March 1991, 58 lesions in 40 patients were treated with accelerator-based stereotactic radiosurgery. All patients were followed for a minimum of 6 months or to death. The primary purpose was to determine the impact of radiosurgery on local control and its subsequent effects on quality of life. An overall tumor control rate of 82% with a complete response rate of 43% were achieved. As anticipated, the response rate for smaller tumors was substantially better than that for larger tumors (78% for lesions < 2 cm3; 50% for lesions > or = 10 cm3). Although the overall in-field progression rate was 18.5%, only 1/23 (4%) complete responders subsequently recurred. The in-field failure rate is highly comparable with recently published surgical data. Progression outside the brain was noted in two-thirds of patients. One quarter of the deaths were neurologic. The median survival for this minimally selected patient population was 6.5 months. Stereotactic radiosurgery was also associated with improved quality of life as measured by Karnofsky score, neurologic function, and steroid dependence. Long-term steroid dependence was encountered in only four patients. We conclude that stereotactic radiosurgery can be used effectively in patients with brain metastases. In this series, a high tumor response rate was achieved which was associated with improved quality of life.

Adult↗
PubMed1992

Relative pre- and postjunctional effects of a new vecuronium analogue, Org 9426, at the rat neuromuscular junction.

We have studied the relative pre- and postjunctional neuromuscular blocking effects of Org 9426 in the isolated rat hemidiaphragm muscle using twitch tension and electrophysiological recording techniques. Postjunctional effects were assessed from decreases in twitch height and from end-plate current amplitude and time constant of decay. Prejunctional effects were assessed from the fade of tetanic twitch tension and end-plate current amplitude rundown. There were no significant differences between the relative pre- and postjunctional effects of Org 9426 and those of previously studied steroidal neuromuscular blocking compounds. It is concluded, therefore, that the rapid onset and short duration of Org 9426 seen in vivo is not a consequence of a strong prejunctional, relative to postjunctional, blocking effect of the compound.

Androstanols↗
PubMed1992

Accuracy of the FEF CO2 detector in the assessment of endotracheal tube placement.

The sensitivity and reliability of the FEF end-tidal CO2 detector were investigated for its suitability in the assessment of correct placement of an endotracheal tube. Sensitivity was determined by having eight blinded volunteers observe the color change in the FEF detector with the administration of different volumes and varying CO2 concentrations of gas mixture. The color change in the FEF detector was also assessed during esophageal ventilations before and after administration of carbonated beverage into the stomach of swine and during cardiopulmonary resuscitation in swine. An interpersonal variation was present among the blinded observers during the color-matching process. Different colors were observed with the same volume and CO2 concentration of gas mixture. During esophageal ventilations before or after the administration of carbonated beverage, the FEF detector was neither accurate nor rapid in identifying esophageal placement of the endotracheal tube. The "C" color was displayed during the initial six ventilations in one swine, and esophageal intubation would have been missed. The FEF detector could (by displaying a "C" color) identify one of six correctly intubated swine during cardiopulmonary resuscitation. In conclusion, the FEF CO2 detector does not have the characteristics to reliably assess the correct placement of an endotracheal tube.

Animals↗
PubMed1992

Lung cancer mortality in Wisconsin: year 2001.

Lung cancer is the major cause of cancer mortality in Wisconsin, with an estimated 2,300 deaths in 1991. The low 5-year survival rate of about 10% in lung cancer is primarily attributed to advanced inoperable stage at diagnosis, limited response to therapy, and a high incidence of metastatic spread. Since smoking is the major etiologic factor associated with lung cancer, this is a largely preventable disease. Many current smokers may already have severe bronchopulmonary dysplasia or neoplastic changes that may manifest many years later. We report on a model developed to evaluate the effect of improved therapy for lung cancer patients in the next decade. Based on this model, Wisconsin's projected lung cancer mortality is estimated at 2,117 in the year 2001, without improved treatment, resulting in nearly 25,000 "years of potential life lost." According to this model, a 10% reduction in lung cancer mortality plus a 12-month increase in palliation in the year 2001 will "regain" more years of potential life lost than the current mortality for stomach, cervical, or uterine cancer. Thus, improved cure and palliation for lung cancer patients represents an important goal for Wisconsin's medical community.

Cause of Death↗
PubMed1991

Early changes in tumor metabolism after treatment: the effects of stereotactic radiotherapy.

Four patients with intracranial neoplasms, two with malignant gliomas and two with brain metastases, were treated with stereotactic radiotherapy. Patients received between 15 and 27.5 Gray of photon irradiation to the central tumor target point; the 80% isodose line covered the periphery of the tumor as determined by contrast enhanced computed tomography. Patients underwent a sequence of three Positron Emission Tomographic scans using [18F]-fluorodeoxyglucose (PET-FDG)--a baseline scan the day before treatment, and follow-up scans 1 and 7 days after treatment. Ratios between the maximal tumor regional cerebral metabolic rate for glucose (rCMRGlu) (T*) and the contralateral remote white matter rCMRGlu (RW), that is, the glucose uptake ratio (T*/RW), were calculated. The percent change in ratios relative to each patient's baseline scan were calculated. Ratios increased 25% to 42% 1 day post-radiotherapy, then decreased to between 10% above and 12% below the baseline value 7 days post-radiotherapy. The T*/RW increased acutely after stereotactic radiotherapy in a fashion similar to that previously described following chemotherapy with a complex multi-drug regimen. A common metabolic pathway may underlie the increase in T*/RW after these different treatments.

Brain Neoplasms↗
PubMed1991

A three-dimensional volume visualization package applied to stereotactic radiosurgery treatment planning.

A comprehensive software package has been developed for visualization and analysis of 3-dimensional data sets. The system offers a variety of 2- and 3-dimensional display facilities including highly realistic volume rendered images generated directly from the data set. The package has been specifically modified and successfully used for stereotactic radiosurgery treatment planning. The stereotactic coordinate transformation is determined by finding the localization frame automatically in the CT volume. Treatment arcs are specified interactively and displayed as paths on 3-dimensional anatomical surfaces. The resulting dose distribution is displayed using traditional 2-dimensional displays or as an isodose surface composited with underlying anatomy and the target volume. Dose volume histogram analysis is an integral part of the system. This paper gives an overview of volume rendering methods and describes the application of these tools to stereotactic radiosurgery treatment planning.

Brain Diseases↗
PubMed1991

The additive contribution of nitrous oxide to isoflurane MAC in infants and children.

The purpose of this study was to determine the contribution of nitrous oxide to isoflurane MAC in pediatric patients. MAC was determined in 47 infants and small children (mean ages 16.6 +/- 6.7 months) during isoflurane and oxygen anesthesia (n = 11) and isoflurane and nitrous oxide anesthesia (25% nitrous oxide [n = 12], 50% nitrous oxide [n = 12], and 75% nitrous oxide [n = 12]). After assigning patients to one of four groups, anesthesia was induced with increasing inspired concentrations of isoflurane in oxygen. After anesthetic induction and tracheal intubation, ventilation was controlled (carbon dioxide partial pressure = 32 +/- 5 mmHg), and nitrous oxide was added to the inspired gas mixture to achieve end-expired nitrous oxide concentrations of 0, 25, 50, or 75%. Inspired and expired gas samples were obtained from a distal sampling port in the tracheal tube. The response to skin incision in each patient was assessed at a previously selected end-tidal concentration of isoflurane. The MAC of isoflurane was determined in each group using the up-and-down method described for evaluating quantal responses. The mean duration of constant end-tidal concentrations prior to skin incision was 14 +/- 7 min (range 6-46 min). The ratio of expired to inspired nitrous oxide and isoflurane concentrations during the period of constant end-tidal concentrations was 0.96 +/- 0.01 and 0.93 +/- 0.03 respectively. The MAC of isoflurane in oxygen was 1.69 +/- 0.13 vol% (mean +/- standard deviation).(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1991

Reliability of capnography in identifying esophageal intubation with carbonated beverage or antacid in the stomach.

To evaluate the reliability of capnography in identifying esophageal intubation in the presence of a carbonated beverage in the stomach, we first investigated the amount of CO2 released from different carbonated beverages and antacids in a simulated stomach; next we measured the end-expired CO2 level during esophageal ventilation with a carbonated beverage in the stomachs of six swine. CO2 levels of approximately 20% were consistently observed in all carbonated beverages. The CO2 levels obtained with sodium bicarbonate, Maalox, and sodium citrate were 19.3%, 2.0%, and 0%, respectively. CO2 waveforms were observed during esophageal ventilation in five of six animals after intragastric administration of a carbonated beverage. An end-expired CO2 level of 2.5% or more was observed in two swine. The highest end-expired CO2 level measured was 5.3%. We conclude that although capnography is convenient and effective, it lacks all the attributes of an ideal monitor for detecting esophageal intubation.

Animals↗
PubMed1991

Treatment of Wilms' tumour. Current recommendations.

Wilms' tumour (nephroblastoma, renal embryoma) is the fifth most common paediatric malignancy, arising from the embryonal tissue of kidneys and first formally described by Max Wilms in his classic 1899 monograph. Until the early part of this century, Wilms' tumour was associated with a less than 20% survival rate. The current survival rate exceeds 80%, primarily due to large multi-institutional trials such as the National Wilms' Tumor Study (NWTS). These studies have refined and defined the roles of surgery, chemotherapy, and radiation in treating Wilms' tumour, based on staging and histology. The dramatic improvement in the prognosis for children with Wilms' tumour, especially over the past 20 years, represents a landmark achievement in the history of paediatric oncology. Specific treatment recommendations are based on the current National Wilms' Tumor Study IV schema. Stages I and II favourable histology patients do not receive radiotherapy, but are treated postoperatively with 'pulsed' or 'conventional' dactinomycin and vincristine; stage III favourable histology requires postoperative abdominal radiotherapy followed by triple agent, 'conventional' or 'pulsed' chemotherapy (dactinomycin, doxorubicin and vincristine). Patients with stage IV favourable histology, stages II to IV anaplastic, clear cell or rhabdoid histology, are treated similarly with aggressive triple-agent chemotherapy, with the addition of radiotherapy to selected sites. Recurrent and adult Wilms' tumours have poor prognoses and are treated with aggressive surgery, radiotherapy and chemotherapy.

Adult↗