Biomedical subjects

W D Erwin

Publications and source records attributed to W D Erwin.

At least 19 recordsLinked to original sources

PubMed2001

Correlation of marrow dose estimates based on serial pretreatment radiopharmaceutical imaging and blood data with actual marrow toxicity in anti-CD20 yttrium-90 monoclonal antibody radioimmunotherapy of non-Hodgkin's B-cell lymphoma.

The purpose of this study was to investigate whether marrow radiation absorbed dose estimates predict haematotoxicity following radioimmunotherapy with an yttrium-90 labelled anti-CD20 monoclonal antibody in non-Hodgkin's B-cell lymphoma (NHL). Radiopharmaceutical data from 12 NHL radioimmunotherapy patients were analysed retrospectively using three methods of marrow radiation absorbed dose estimation based on serial pretreatment indium-111 labelled anti-CD20 monoclonal antibody activity versus time data (0-144 h): (i) lumbar spine (LS) image counts; (ii) blood clearance (BL); and (iii) whole body (WB) activity. Linear regressions were performed between the methods, and between each method and the 0-6 month post-treatment platelet and white blood cell count nadir and absolute drop in count (ADC). For the range of yttrium-90 activities (740-1547 MBq), absorbed dose estimates (mean +/- sigma) were: LS, 142+/-50 cGy (range 62-233 cGy); BL, 89+/-21 cGy (range 63-140 cGy); and WB, 54+/-10 cGy (range 36-63 cGy). The LS and BL marrow estimates differed significantly (P <0.003), with a correlation coefficient r of 0.36 (P = NS), while WB correlated significantly with both LS (r = 0.50, P < 0.05) and BL (r = 0.58, P < 0.05). The range of r with platelet nadir and ADC was -0.20 < or = r < or = 0.01, except for WB with ADC (r = 0.38) (all P = NS). Values of r for white blood cell nadir were unexpectedly positive, being 0.13 for BL and 0.29 for LS (P = NS), and 0.60 for WB (P < 0.025). Values of r for white blood cell ADC were 0.36 for BL and -0.26 for LS (P = NS), and 0.50 for WB (P < 0.05). These results indicate that different commonly employed methods of estimating marrow radiation absorbed dose may yield significantly differing results, which may not correlate with actual radiation toxicity. Therefore, caution must be exercised in relying on these results to predict haematotoxicity.

Algorithms↗

PubMed2001

Single-photon emission computed tomography in the year 2001: instrumentation and quality control.

OBJECTIVE: SPECT instrumentation is more complex than that used for whole-body and planar imaging, and requires careful quality control to ensure optimum performance. Conventional and new hybrid SPECT imaging systems (coincidence and SPECT/CT) will be discussed. New imaging detector materials such as LSO and CZT will also be discussed, along with their potential advantages. Finally, basic SPECT quality control will be reviewed. After reading this article, the nuclear medicine technologist should be able to: (a) explain the use of single and multihead gamma cameras for SPECT imaging; (b) have an understanding of the potential of new hybrid SPECT imaging systems; (c) be aware of future developments in SPECT imaging technology; (d) understand the requirements for SPECT quality control, including field uniformity and center of rotation corrections; and (e) explain the benefits of using phantoms to augment SPECT quality control.

Gamma Cameras↗

PubMed2000

Quantitative gated myocardial SPECT: effect of collimation on left-ventricular ejection fraction.

OBJECTIVE: Left-ventricular ejection fraction (LVEF) can be computed from gated myocardial perfusion SPECT studies using quantitative algorithms. The purpose of this study was to compare the LVEF obtained using the conventional high-resolution parallel-hole collimator (HRC) to the Cardiofocal collimator (CFC) (Siemens Medical Systems, Hoffman Estates, IL) using a quantitative LVEF program. METHODS: Thirty-four patients (15 men, 19 women; mean age = 62 y) had either treadmill or pharmacological stress testing with 25-30 mCi 99mTc sestamibi injected at peak stress. Conventional gated SPECT imaging was performed approximately 30 min poststress, first with the HRC collimator, then with the CFC, using the same acquisition parameters on a single-head gamma camera. Traditional (TRAD) determination of LVEF using planar gated blood pool and/or cardiac catherization also was obtained for each patient. RESULTS: The correlation in LVEF between the CFC and HRC acquisitions was excellent, r = 0.99. The correlation between CFC and TRAD LVEF was good, r = 0.95, as was the HRC and TRAD correlation, r = 0.97. The mean LVEF value for HRC was slightly less than TRAD (54% vs. 55.4%), while the CFC mean LVEF was higher (62% vs. 55.4%). Although CFC LVEF correlated well with HRC, mean LVEF value using CFC was higher than HRC. CONCLUSION: The choice of collimator may alter the LVEF obtained from gated SPECT perfusion studies.

Algorithms↗

PubMed2000

SPECT in the year 2000: basic principles.

OBJECTIVE: SPECT has become a routine procedure in most nuclear medicine departments. SPECT provides significant technical challenges for the nuclear medicine technologist, as compared with planar imaging, in the areas of SPECT acquisition, image reconstruction, and data processing. Many new advances in SPECT methodology are becoming available, such as iterative reconstruction, multimodality fusion, and advanced gated cardiac SPECT. SPECT imaging is demanding and requires careful attention to proper acquisition protocols, whether circular or noncircular orbits, and postprocessing is becoming more complex with the addition of iterative reconstruction and attenuation correction algorithms, among others. Understanding the principles of SPECT is essential not only to produce the highest quality scans but also to identify image artifacts. After reading this article, the nuclear medicine technologist should be able to: (a) describe the historical development and benefits of SPECT imaging; (b) state the impact of image matrix size, number of projections, and arc of rotation on final SPECT image quality; (c) discuss the trade-offs between image noise content and spatial and contrast resolution in SPECT reconstruction; (d) discuss SPECT filters and their impact on image quality; (e) explain the differences between filtered backprojection and iterative reconstruction; and (f) describe the impact of attenuation and scatter in SPECT imaging and the advantages and pitfalls of attenuation correction methods.

Humans↗

PubMed1999

The effect of remifentanil on biliary tract drainage into the duodenum.

UNLABELLED: Opioids cause spasm of the sphincter of Oddi. Remifentanil is metabolized enzymatically throughout the body. Its context-sensitive half-time is 3-4 min. The effect of remifentanil on the sphincter of Oddi, is unknown. We studied, in six healthy adult volunteers, the effect of remifentanil on the flow of dye from the gall bladder into the duodenum. Control hepatobiliary imaging with 5 mCi of technetium-labeled derivatives of iminodiacetic acid was performed on each volunteer. The time from IV dye (radiopharmaceutical) injection until its appearance in the duodenum was determined by continuous scanning. Two weeks later, each volunteer received remifentanil, 0.1 microg x kg(-1) x min(-1) infused for 30 min IV before the same dose of technetium-labeled derivatives of iminodiacetic acid was injected, and for the time of their control scan plus 10 min after the injection. When the dye appeared in the duodenum, the total time from injection was compared with the control value. The time from stopping the infusion until the dye appeared in the duodenum was the "recovery time." Control scan time was 20.5+/-9.9 min (mean +/- SD; range 10-33 min). Total scan time during and after the remifentanil infusion was 50.3+/-17.3 min (range 30-81 min) (P < 0002). The recovery time was 19.8+/-12.4 min (range 5-40 min). We conclude that remifentanil delays the drainage of dye from the gall bladder into the duodenum, but the delay is shorter than that reported after other studied opioids. IMPLICATIONS: Radioactive dye was injected IV into healthy volunteers to determine the time it took for the dye to appear in the duodenum. This was repeated under the influence of a short-acting narcotic analgesic, remifentanil. Remifentanil caused a much shorter delay than previously reported after morphine or meperidine.

Adult↗

PubMed1998

Lumbar spine duplication presenting as adolescent scoliosis. A case report.

STUDY DESIGN: A report of a case of lumbar spine duplication with the clinical appearance of adolescent scoliosis. OBJECTIVE: To increase knowledge about the pathogenesis and treatment of lumbar spinal duplication. SUMMARY OF BACKGROUND DATA: Although there have been other reports of lumbar spine duplication of this magnitude, these malformations typically are associated with severe neurologic abnormalities (dicephalus, myelomeningocele) or gastrointestinal abnormalities (omphalocele, neurenteric fistulas). Several investigators have recommended early surgical intervention for this abnormality because of the perceived risk of progressive neurologic abnormality from tethering of the cord. METHODS: In a 13-year-old girl who had truncal asymmetry, lumbar spine duplication was noted on plain radiographs. A magnetic resonance study was obtained, and the patient was observed with conservative treatment for 3 years. RESULTS: Although extensive abnormalities were noted on the magnetic resonance images, which were related to duplication of spinal cord and vertebral bodies, the patient was neurologically intact and remained so until skeletal maturity. CONCLUSIONS: This rare malformation typically has severe neurologic sequelae. Conservative management in the reported patient did not result in a progressive neurologic lesion at the time of skeletal maturity.

Adolescent↗

PubMed1996

Efficacy and cost considerations of intraoperative autologous transfusion in spinal fusion for idiopathic scoliosis with predeposited blood.

STUDY DESIGN: One hundred five patients with adolescent idiopathic scoliosis who underwent posterior spinal instrumentation and fusion with predeposited autologous blood, with or without intraoperative autologous transfusion, were reviewed. OBJECTIVE: To determine the benefit/nonbenefit of intraoperative autologous transfusion in diminishing the need for homologous blood and influencing post-operative hematocrit values in healthy adolescents undergoing spinal fusion for scoliosis. SUMMARY OF BACKGROUND DATA: A steady increase in the use of intraoperative autologous transfusion in recent years has occurred without guidelines regarding which procedures and patient populations would be best served. Previous studies have failed to determine the cost effectiveness and actual reduction in homologous blood exposure attributable to intraoperative autologous transfusion in adolescents who have undergone preoperative phlebotomy. METHODS: Fifty-five adolescents (intraoperative autologous transfusion group) who underwent posterior instrumentation and fusion for idiopathic scoliosis with the use of an intraoperative autologous transfusion device were compared to 50 patients (control group) who underwent the same procedure without the intraoperative autologous transfusion device. RESULTS: The average percent salvage of red blood cells by the intraoperative autologous transfusion device was 35%. The control group utilized significantly more of the predonated autologous blood than the intraoperative autologous transfusion group (1.34 units/case vs. 1.78 units/case, P < 0.05). Homologous blood usage was the same in both groups. Two patients in the intraoperative autologous transfusion group required nondirected homologous blood (total of four units), compared to three patients in the control group (total of four units) (P = 0.048). Using multiple regression analysis, the total number of transfusions was significantly correlated with the estimated blood loss and the duration of surgery in both groups. Postoperative hematocrit levels were slightly higher in the control group, but there was not a significant difference. CONCLUSIONS: The addition of intraoperative autologous transfusion to a preoperative phlebotomy program had no benefit on homologous blood exposure or post-operative hematocrit changes in this population. Blood requirements for this procedure can be met less expensively and more reliably by merely donating one's own blood.

Adolescent↗

PubMed1996

Validation of a knowledge-based boundary detection algorithm: a multicenter study.

A completely operator-independent boundary detection algorithm for multigated blood pool (MGBP) studies has been evaluated at four medical centers. The knowledge-based boundary detector (KBBD) algorithm is nondeterministic, utilizing a priori domain knowledge in the form of rule sets for the localization of cardiac chambers and image features, providing a case-by-case method for the identification and boundary definition of the left ventricle (LV). The nondeterministic algorithm employs multiple processing pathways, where KBBD rules have been designed for conventional (CONV) imaging geometries (nominal 45 degrees LAO, nonzoom) as well as for highly zoomed and/or caudally tilted (ZOOM) studies. The resultant ejection fractions (LVEF) from the KBBD program have been compared with the standard LVEF calculations in 253 total cases in four institutions, 157 utilizing CONV geometry and 96 utilizing ZOOM geometries. The criteria for success was a KBBD boundary adequately defined over the LV as judged by an experienced observer, and the correlation of KBBD LVEFs to the standard calculation of LVEFs for the institution. The overall success rate for all institutions combined was 99.2%, with an overall correlation coefficient of r=0.95 (P<0.001). The individual success rates and EF correlations (r), for CONV and ZOOM geometers were: 98%, r=0.93 (CONV) and 100%, r=0.95 (ZOOM). The KBBD algorithm can be adapted to varying clinical situations, employing automatic processing using artificial intelligence, with performance close to that of a human operator.

Algorithms↗

PubMed1996

A radioimmunoimaging and MIRD dosimetry treatment planning program for radioimmunotherapy.

A treatment planning program for radioimmunotherapy employing quantitative Anger camera imaging and the MIRD formalism has been designed and implemented on a clinical nuclear medicine computer. Radionuclide residence times are calculated from linear, mono- and bi-exponential, and cubic spline fits to regional activity versus time curves, and radiation-absorbed dose estimates for all target organs for 131I, 67Cu, and 58 other radionuclides can be calculated. This software has been successfully applied to radioimmunotherapy of B-cell malignancies and breast adenocarcinomas.

Dose-Response Relationship, Radiation↗

PubMed1996

Prediction of radiation doses from therapy using tracer studies with iodine-131-labeled antibodies.

UNLABELLED: Tracer pharmacokinetic studies are often used in treatment planning for radionuclide therapy including radioimmunotherapy. This study evaluates the validity of using tracer studies to predict radiation doses from therapy with the same radiolabeled antibody. METHODS: Quantitative imaging and blood radioactivity were used to obtain the pharmacokinetics and radiation doses that were delivered to the total body, blood, marrow, lungs, liver, kidneys, thyroid, spleen and tumors. Tracer and therapy data for eight patients with lymphoma and one patient with breast cancer were compared using linear regression statistics. Doses of 131I-labeled antibody for the tracer studies ranged from 0.1 to 0.4 GBq (2 to 10 mCi), and therapy doses ranged from 0.7 to 5.6 GBq (20 to 150 mCi). RESULTS: Radiation doses to tissues and, in particular, the bone marrow and tumors were reliably predicted from tracer studies. In this group of patients, median dose to marrow from marrow targeting, total body and blood was 9.2 cGy/GBq for tracer studies and 7.6 cGy/GBq for therapy studies with a median difference of 0.5 cGy/GBq. Median dose to tumors was 81.1 cGy/GBq for tracer studies and 70.3 cGy/GBq for therapy studies with a median difference of 5.9 cGy/GBq. CONCLUSION: In these patients, tracer studies were predictive of the radiation doses from therapy for total body, major organs and tumors. The radiation doses to marrow and tumors, which are the usual determinants of the therapeutic index, correlated well between tracer and therapy studies (r > or = 0.95).

Antibodies, Monoclonal↗

PubMed1995

Results of operative treatment of idiopathic scoliosis in adults.

We compared the results in eighty-one patients (average age, fifty-six years; range, forty-three to eighty-three years) who had had operative treatment of idiopathic scoliosis with those in thirty patients (average age, fifty-eight years; range, forty-five to seventy years) who had declined operative treatment. Seventy-six individuals (average age, forty-eight years; range, thirty-five to seventy-four years) who did not have scoliosis served as a control group. The average duration of follow-up was five years (range, two to seventeen years). The population base consisted of 454 patients who were seen between 1970 and 1985. The treated patients were drawn from a group of 160 patients for whom an operation had been recommended; 110 patients agreed to the operation and fifty refused. The remaining 294 patients had curves of insufficient severity to warrant concern about progression, had symptoms unrelated to the scoliosis, or had curves that did not necessitate any intervention. The functional status since the operation (for the treated patients), since recommendation of the operation (for the untreated patients), or within the last ten years (for the control group) was evaluated with a comprehensive questionnaire designed to elicit details regarding pain, fatigue, and any disability in the performance of twenty-six activities of daily living. At the most recent follow-up examination, the treated patients reported a significantly greater decrease in pain and fatigue and significantly more improvement in self-image and in the ability to perform physical, functional, and positional tasks than did the untreated patients (p = 0.0001).

Activities of Daily Living↗

PubMed1993

Body and blood clearance and marrow radiation dose of 131I-Lym-1 in patients with B-cell malignancies.

Fifty-eight per cent of patients with B-cell malignancies had durable responses to treatment with 131I-Lym-1. Myelosuppression manifested by peripheral blood cytopenia was the radiation dose-limiting toxicity. The mean biologic half-times were 3.3 and 31.2 h for the fast and slow phases, respectively, of the blood clearance and 33.5 h for the clearance from the total body. Nonpenetrating radiation from the blood contributed 0.18 rad and penetrating radiations from the total body contributed 0.18 rad per administered mCi to the bone marrow. The average total contribution from both of these sources was 0.36 +/- 0.14 rad mCi-1. Clearances and marrow radiation doses were remarkably constant among different patients and among different therapy doses for the same patient. These results are potentially useful as an initial approximation for other mouse monoclonal antibodies of the same isotype. While radiation to normal marrow from 'spill-over' incident to specific targeting of 131I-Lym-1 on malignant B-cells in the marrow is not addressed in this publication because it is unique for each patient, it should be considered in the case of individual patients.

Adult↗

PubMed1992

Image normalization and background subtraction in T1-201/Tc-99m parathyroid subtraction scintigraphy. Effect on lesion detection.

The authors have developed two computer algorithms for T1-201/Tc-99m parathyroid subtraction scintigraphy that was performed on patients who subsequently underwent surgical exploration of the neck. Both methods employed a region-of-interest drawn around the thyroid/parathyroid glands for image realignment. The first algorithm normalized the Tl-201 and Tc-99m images using the ratio of maximum counts over the thyroid in each image. The second computer algorithm incorporated Tl-201 image background correction and normalization by the average of the ratios of maximum counts computed over each quadrant in both images. In 10 patients with confirmed parathyroid adenomas or hyperplasia, the first method yielded a 44% sensitivity. Upon reanalysis with the second algorithm, the sensitivity improved to 100%. Subsequently, in a total of 22 patients with 30 abnormal glands analyzed with the second algorithm, a sensitivity of 80% (94% for adenoma and 62% for hyperplasia) was achieved, with a specificity of 91%, as confirmed by surgery.

Algorithms↗

PubMed1992

A new heart-sounds gating device for medical imaging.

A heart-sounds gating device has been designed and tested which identifies, individually, both the first (S1) and second (S2) heart sound from their timing relationship, providing two trigger points through the cardiac cycle for synchronizing medical images. The new heart-sounds gate utilizes dynamically varying timing windows to anticipate the occurrence of S1 and S2. The heart-sounds gate has been initially applied to nuclear imaging of the cardiac bloodpool, but may be applied to any imaging modality requiring cardiac synchronization.

Electrocardiography↗

PubMed1991

An MRI tissue equivalent lesion phantom using a novel polysaccharide material.

A new polysaccharide material, TX-150, and method is described which will potentially allow formation of stable, multi-compartment MRI phantoms constructed without intervening septa. TX-150 can be made into water based gels which are nominally tissue equivalent. Although contiguous regions of different water content are not possible, as water diffusion will occur until equilibrium is reached, TX-150 gel T1 and T2 values can be adjusted independently, while maintaining a constant water composition, by appropriate additives. Unlike paramagnetic ions and chelates, metal phthalocyanines have been found to bind tightly to TX-150, thus, permitting formation of stable contiguous regions of differing T1 relaxation properties. Phantom T2 values can be effectively modified with 2-2-diphenyl-1 picrylhydrazyl, which has little affect on gel T1 values, to form septumless lesion phantoms of varying T1 and T2.

Gels↗

PubMed1991

Hypotensive anesthesia for scoliosis surgery in Jehovah's Witnesses.

Hypotensive anesthesia has been advocated in spinal surgery for the purpose of diminishing operative blood loss. This study evaluated its effectiveness in 12 Jehovah's Witnesses undergoing Harrington instrumentation and fusion who refused transfusion. Previous series from this institute did not use deliberate hypotension because of routinely low blood loss. Compared with matched controls operated on under normotensive anesthesia, the Jehovah's Witness patients had lower absolute blood loss but also shorter operative time. Applied linear-regression analysis demonstrated that the diminished blood loss was associated with shorter operative time (P = 0.0002) rather than lower blood pressure. The majority of blood losses in spinal instrumentation with fusion occurs with decortication. This rapid bleeding occurs at venous pressures which are unaffected by arterial blood pressure manipulation. The authors conclude that spinal surgery is possible in Jehovah's Witnesses without transfusion and that operative technique is the single most important determinant of blood loss.

Adolescent↗

PubMed1991

Truncation artifact: a potential pitfall in MR imaging of the menisci of the knee.

Because truncation artifacts on magnetic resonance (MR) images may be confused with meniscal tears, measures to suppress them were investigated in a human cadaver knee and prospective and retrospective studies of patients. The artifacts were most prominent when the acquisition matrix was 128 x 256 and the 128-pixel (phase-encoded) axis was in a superoinferior (SI) orientation. An anteroposterior (AP) orientation of the 128-pixel axis or use of a 256 x 256 acquisition matrix reduced the prominence of or nearly eliminated the artifacts. A review of reports of MR imaging and arthroscopic examinations of 83 knees yielded eight menisci that were falsely interpreted at MR imaging as having tears. Retrospective review of the images suggested that the errors were due to truncation artifacts in two cases. Truncation artifacts will cause relatively little difficulty if diagnostic observers are aware of their characteristics and simple steps are taken to minimize their prominence, including acquiring images in 192 x 256 or 256 x 256 matrices or AP rather than SI orientation of the phase-encoded (128-pixel) axis of 128 x 256 matrices.

Autopsy↗

PubMed1991

Alpha 2-adrenergic model of gastroparesis: validation with renzapride, a stimulator of motility.

Motility-stimulating drugs can increase gastric antral and intestinal contractions but do not usually enhance emptying unless gastroparesis is present. An alpha 2-adrenergic agonist (SC-39585A) was used to inhibit antroduodenal motility and simulate gastroparesis in dogs. SC-39585A caused dose-related inhibition of emptying of solid and liquid meals as well as the antral and duodenal motility responses to the solid meal. The motility-enhancing agent renzapride (100 micrograms/kg iv) did not enhance emptying of the solid meal under nondelayed conditions. However, at the same dose it partially reversed the delay in solid emptying but only when antroduodenal motility was incompletely (30 micrograms/kg sc) and not totally (100 micrograms/kg sc) inhibited by SC-39585A. This was done in part by antagonizing antral but not duodenal inhibition of motility. Renzapride was also effective orally in reversing the delay in solid emptying. Similarly, renzapride reversed the delay in liquid emptying caused by SC-39585A (30 micrograms/kg sc). An alpha 2-adrenergic agonist can be used to model gastroparesis in dogs by inhibiting antroduodenal motility and can also be used to examine the actions of motor stimulants, such as renzapride, which promote gastric emptying.

Adrenergic alpha-Agonists↗