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B Hasegawa

Publications and source records attributed to B Hasegawa.

10 recordsLinked to original sources
PubMed2001

Correlation of tumor and whole-body dosimetry with tumor response and toxicity in refractory neuroblastoma treated with (131)I-MIBG.

UNLABELLED: The purpose of our study was to determine the effect of tumor-targeted radiation in neuroblastoma by correlating administered (131)I-metaiodobenzylguanidine (MIBG) activity to tumor and whole-body dosimetry, tumor volume change, overall response, and hematologic toxicity. METHODS: Eligible patients had MIBG-positive lesions and tumor-free, cryopreserved hematopoietic stem cells. Activity was administered according to body weight and protocol as part of a phase I and phase II study. The whole-body radiation dose was derived from daily 1-m exposure measurements, the tumor self-absorbed radiation dose (TSARD) was determined from scintillation-camera conjugate views, and the tumor volume was measured using CT or MRI. RESULTS: Forty-two patients with refractory neuroblastoma (16 with prior hematopoietic stem cell transplant) received a median activity of 555 MBq/kg (15 mCi/kg) (range, 93-770 MBq/kg) and a median total activity of 11,470 MBq (310 mCi) (range, 3,330-30,969 MBq). The median whole-body radiation dose was 228 cGy (range, 57-650 cGy) and the median TSARD was 3,300 cGy (range, 312-30,500 cGy). Responses among evaluable patients included 16 partial response, 3 mixed response, 14 stable disease, and 9 progressive disease. Higher TSARD values predicted better overall disease response (P < 0.01). The median decrease in tumor volume was 19%; 18 tumors decreased, 4 remained stable, and 5 increased in size. Correlation was seen between administered activity per kilogram and whole-body dose as well as hematologic toxicity (assessed by blood platelet and neutrophil count nadir) (P < 0.05). The median whole-body dose was higher in the 11 patients who required hematopoietic stem cell infusion for prolonged neutropenia versus the 31 patients who did not (323 vs. 217 cGy; P = 0.03). CONCLUSION: Despite inaccuracies inherent in dosimetry methods, (131)I-MIBG activity per kilogram correlated with whole-body radiation dose and hematologic toxicity. The TSARD by conjugate planar imaging predicted tumor volume decrease and also correlated with overall tumor response.

3-Iodobenzylguanidine↗
PubMed1998

Phase I dose escalation of 131I-metaiodobenzylguanidine with autologous bone marrow support in refractory neuroblastoma.

PURPOSE: The analogue 131I-metaiodobenzylguanidine (MIBG), which is specifically targeted to neuroblastoma cells, may provide more effective and less toxic treatment for neuroblastoma than conventional external-beam radiotherapy. We report a dose escalation study of 131I-MIBG to define dose-limiting toxicity without and with autologous bone marrow support. PATIENTS AND METHODS: Thirty patients with relapsed neuroblastoma were treated in groups of six with escalating doses of 3 to 18 mCi/kg of 131I-MIBG. After rapid escalation in the first three patients treated at 3 to 6 mCi/kg, treatment was escalated in 3-mCi/kg increments from 9 to 18 mCi/kg. Autologous tumor-free bone marrow was cryopreserved in all patients receiving 12 mCi/kg and more. Toxicity and response were assessed. RESULTS: Eighty percent of patients who received 12 mC/kg or more experienced grade 4 thrombocytopenia and/or neutropenia. Dose-limiting hematologic toxicity was reached at 15 mCi/kg, at which level two of five assessable patients required bone marrow reinfusion for absolute neutrophil count (ANC) of less than 200/microL for more than 2 weeks, and four of nine at the 18-mCi/kg level. Prolonged thrombocytopenia was common, with failure to become platelet-transfusion independent in nine patients. One patient with extensive prior treatment developed secondary leukemia and three became hypothyroid. Responses were seen in 37% of patients, with one complete response (CR), 10 partial response (PR), three mixed response, 10 stable disease, and six progressive disease. The minimum dose of 131I-MIBG for 10 of the 11 responders was 12 mCi/kg. CONCLUSION: Treatment with 131I-MIBG has mainly hematologic toxicity, which can be abrogated with bone marrow rescue. The high response rate in refractory disease suggests that this agent may be useful in combination with myeloablative chemotherapy and autologous stem-cell rescue to improve outcome in advanced neuroblastoma.

3-Iodobenzylguanidine↗
PubMed1989

Assessment of induced bronchoconstriction in anesthetized cats by the end-inflation occlusion method.

Airway occlusion during constant flow inflation allows rapid determination of frequency-dependence of pulmonary resistance by estimating its extreme values: RL,max (zero frequency) and RL,min (high frequency). RL,max represents the maximum resistance value that can be obtained with the prevailing time constant inequalities and stress relaxation, while RL,min represents the resistance that would be obtained in the absence of time constant inequalities and stress relaxation. In 5 anesthetized, tracheostomized, paralyzed, and artificially ventilated cats, RL,min, RL,max, and static pulmonary elastance (EL,st) have been measured following airway occlusion at the end of constant flow tidal inflations. Measurements were made before and during continuous infusion of increasing doses of serotonin (10-100 micrograms/kg/min IV). The development of intrinsic positive end-expiratory pressure (PEEPi) was also assessed. Cats varied greatly in their responsiveness to serotonin, but RL,min, RL,max, and EL,st increased and PEEPi developed in all cats. Increases in RL,max did not always parallel increases in RL,min but were similar to those in EL,st, suggesting that altered viscoelastic properties of the lung contributed to the increases in RL,max. We conclude that time-constant inequalities, changes in the lung periphery, and hyperinflation probably all contribute to the observed increases in RL,max and will influence conventional methods of measuring RL. Measuring RL,min potentially provides a better method for assessing the reduction in caliber of the conducting airways in isolation.

Airway Obstruction↗
PubMed1983

Videodensitometric quantitation of mean blood flow.

Standard angiography demonstrates the anatomy of arterial occlusive disease but does not define its physiological significance. However, measurement of flow in a compromised vessel at rest and following peripheral dilatation provides important physiological information. Using digital subtraction angiography, femoral arterial flows determined by the cross-correlation transit time technique were compared to measurements by electromagnetic flowmeter. Thirty-five femoral arterial flow measurements were obtained in nine dogs instrumented with an electromagnetic flow probe and balloon occluder. Renografin 76 (7 cc) was power-injected at 14 cc/sec into the distal abdominal aorta. Angiographic flow measurements correlated well with electromagnetic flowmeter measurements (r = 0.94, standard deviation of the difference (SDD) = 15 ml/min). Intravenous studies provided somewhat poorer correlation due to difficulties in defining dimensions (r = 0.72, SDD = 36). Paired contrast injections (2 injections in succession) in 11 studies increased flow from an average of 80 to 250 ml/min (a 210 +/- 100% increase), providing an estimate of a vessel's capacity to provide increased flow during peripheral dilatation. Thus, reliable angiographic flow determinations may be obtained by arterial and intravenous contrast injections, adding physiological information to anatomical definition.

Absorptiometry, Photon↗
PubMed1983

Work in progress: a correction for tissue iodine accumulation in videodensitometric measurements of left ventricular ejection fraction.

Left ventricular ejection fractions were determined following eight intravenous injections in three dogs using area/length and digital videodensitometric techniques. Ejection fractions were measured by both techniques for all beats during left ventricular opacification. Even after noniodinated background corrections, tissue iodine accumulation produced large errors in measured iodine content late in the contrast material curve. By using a model for tissue iodine accumulation, an algorithm was developed that appears to reduce these errors. The measured ejection fraction for ten beats following the peak of the contrast material curve declined an average of 1.8% following correction, compared with 14% prior to correction. Following correction for tissue iodine accumulation, correlation between area/length and video-densitometric ejection fractions was 0.94. By correcting for tissue iodine accumulation, much more of the contrast material curve provides usable data for estimating ejection fractions.

Absorptiometry, Photon↗
PubMed1982

Slow late myocardial clearance of thallium: a characteristic phenomenon in coronary artery disease.

We extended the quantitative seven-pinhole method to follow the dynamics of thallium redistribution after exercise. We observed a pattern of slow late thallium clearance that appears to be characteristic of myocardium supplied by obstructed coronary arteries. In 28 subjects, quantitative thallium scintigrams (seven-pinhole tomography, circumferential count profiles) and blood samples for thallium concentration were taken immediately, 2 hours and 4 hours after maximal treadmill exercise. Twenty subjects had coronary artery disease (CAD) and eight were normal. The rate of thallium clearance from the blood (TCB) was compared with the rate of thallium clearance from each segmental region of myocardium (TCM, derived by ratioing corresponding segments of the absolute circumferential count profiles) between the 2- and 4-hour images. In seven of the eight normal subjects, TCM exceeded TCB in all regions of all images (specificity 88%). Seventeen of the 20 CAD patients had at least one region where TCM was less than TCB (sensitivity 85%). Of the 13 patients with multivessel CAD, 11 had multiple regions with TCM less than TCB. Using this criterion, we detected 31 of 39 obstructed coronary arteries. Of the 37 regions that were abnormal by this analysis, 30 corresponded to obstructed coronary arteries. In contrast, while conventional circumferential count profile analysis also was abnormal in 17 of the 20 CAD patients, it diagnosed multivessel CAD in only five of the 13 patients that had it. These results show that slow late thallium clearance from myocardium is characteristic of regions of myocardium supplied by diseased coronary arteries and that observation of this phenomenon may improve diagnostic sensitivity for the presence of multivessel CAD.

Coronary Disease↗
PubMed1982

Digital subtraction angiography as a method of screening for coronary artery disease during peripheral vascular angiography.

Since myocardial infarction is the major cause of perioperative and postoperative death following peripheral vascular surgery, an accurate method of screening for coronary artery disease in this group of patients is needed. Digital subtraction angiography (DSA) with the use of intra-arterial aortic root injection of contrast material was evaluated as a method of screening for coronary artery disease in patients undergoing angiography for peripheral vascular disease. The feasibility of this method was demonstrated in animal experiments. Fifteen milliliters of Renografin-76 was power injected into the aortic root of seven anesthetized 20 kg mongrel dogs. Normal coronary artery anatomy was clearly demonstrated with DSA, and a series of iatrogenically created stenoses and occlusions were accurately identified. Excellent definition of patent grafts to the left anterior descending and circumflex coronary arteries was obtained in two dogs that had undergone previous coronary artery bypass grafting. A balloon occluder on one graft was used to demonstrate partial and near-total obstruction of the bypass graft. We are currently studying the use of aortic root injections using DSA to determine coronary artery disease in patients having standard angiography for peripheral vascular disease. Adequate visualization of coronary arteries and bypass grafts with only 20 ml of contrast has been obtained. The potential ability of this technique to identify and allow treatment of life-threatening coronary artery lesions in patients prior to or simultaneously with peripheral vascular surgery may result in reduced mortality.

Angiography↗
PubMed1982

Single-photon emission tomography with a 12-pinhole collimator.

To assess the advantages of more complete angular sampling and of more views in the tomographic reconstruction process, tomographic imaging with a 12-pinhole (12PH) collimator has been compared with 7-pinhole tomography (7PH). The 12PH system gives a 50% increase in sensitivity but resolution degrades more rapidly with depth. The 7PH and 12PH systems provide similar accuracy of detection of lesions in a myocardial ring phantom. The 7PH images, however, demonstrated more noise and "ripple" artifacts. The 12PH system offers a larger reconstruction volume and generates fewer artifacts when the collimator is misaligned with the myocardial long-axis, thus making patient positioning less critical than with 7PH. A disadvantage is that individual views are minified by the 12PH collimator, and a 256 X 256 image matrix should be used during image acquisition to limit digital sampling errors.

Evaluation Studies as Topic↗
PubMedDate not supplied

Scatter-glare correction using a convolution algorithm with variable weighting.

Several investigators have approximated the scatter component of digital radiographic images by applying a constant weighting factor to a convolved version of the detected image. The scatter approximation is then subtracted from the detected image. When a constant weighting factor is used, the scatter in areas of low transmission is underestimated. We have extended this technique by allowing for a spatially variable weighting factor based on the local image intensity. This technique improves the scatter estimate and should provide better results for general videodensitometric applications.

Algorithms↗