Biomedical subjects

E F Halpern

Publications and source records attributed to E F Halpern.

At least 19 recordsLinked to original sources

PubMed1998

Hydroxychloroquine improves airflow and lowers circulating IgE levels in subjects with moderate symptomatic asthma.

BACKGROUND: Although antiinflammatory therapy is accepted as the cornerstone of asthma treatment, available systemic immunosuppressive agents are not widely used because of justified concerns over potential toxicity. Hydroxychloroquine (HCQ) is a well-tolerated, safe immunomodulating drug, with proven efficacy in rheumatic diseases and known actions that suggest potential utility in the treatment of asthma. OBJECTIVE: We sought to assess the effectiveness of HCQ in subjects with moderate symptomatic asthma. METHODS: Symptomatic asthmatic subjects receiving stable doses of at least 6 puffs of inhaled corticosteroid per day with daily need for beta2-adrenergic agonists were studied. After baseline run-in, these subjects were randomized to 30 weeks of HCQ (n = 8) or placebo (n = 9). Objective measures included change from baseline mean FEV1, morning and evening peak flows, beta2-agonist use, IgE level, and need for rescue corticosteroids. Subjective symptom scores from bidaily diaries were also obtained. RESULTS: In the treatment group, mean FEV1 at the last 2 visits on therapy increased by 10.8% (P < .05), morning peak flows rose 16.2% (P < .03), evening peak flows rose 14.2% (P < .04), and beta2-agonist use fell 18.6% (P < .03). Mean IgE level declined 48% from 240 to 125 IU/mL. (P < .05). In the placebo group no significant change in these parameters occurred. Comparison of changes in these objective measures between the treatment and placebo groups failed to reach significance in the small population studied. Corticosteroid rescue interventions were required in 4 patients receiving placebo and 2 receiving HCQ. HCQ was well tolerated without notable side effects. CONCLUSIONS: Although the size of our sample population precludes definitive conclusions, these findings extend previous open-label observations. The late improvement in the HCQ group is consistent with its known slow onset of action. Further studies are warranted to confirm the antiasthmatic and antiallergic effects of HCQ and to investigate its potential as a disease-modifying agent.

Adolescent↗

PubMed1998

Previous breast biopsy for benign disease rarely complicates or alters interpretation on screening mammography.

OBJECTIVE: It has been suggested that breast screening leads to too many biopsies for benign disease that permanently scar the breast and confuse the interpretation of subsequent mammograms. We undertook retrospective and prospective studies to determine how often an excisional biopsy for benign breast disease complicates or alters interpretation of screening mammograms. MATERIALS AND METHODS: Retrospective review of our screening center database yielded 31,025 asymptomatic patients who had routine mammographic screening studies between 1993 and 1996. Of the 58,538 examinations of these patients, 53,510 were of patients who had no history of breast biopsy and 5028 were of patients who had a history of breast biopsy for benign disease. Recall rates were compared between the two groups. In the prospective study, radiologists reviewed the mammograms of 1997 consecutive patients presenting to the screening center, 173 of whom reported a prior breast biopsy for benign disease. The radiologist interpreting the images determined how often evidence of the biopsy site was apparent on the mammogram and how often such changes necessitated additional imaging. RESULTS: In the retrospective study, 3296 (6%) of the 53,510 studies done in patients who did not have a biopsy for benign disease and 360 (7%) of the 5028 studies done in women who had a biopsy for benign disease led to additional imaging. Eight recalls for further imaging (0.16%) among the 5028 studies in women with a prior biopsy for benign disease were related to the biopsy site. In the prospective study, 24 (14%) of the 173 women who had a biopsy for benign disease had mammographic evidence of the biopsy site. Nine (5%) of the 173 women who had previously had a biopsy for benign disease and 86 (5%) of the 1824 patients without a prior biopsy were recalled for additional imaging. No women were recalled because a previous breast biopsy for benign disease led to confusion or diagnostic concern. CONCLUSION: Changes in patients' breasts due to previous excisional biopsies for benign breast disease rarely pose a diagnostic dilemma in the interpretation of routine screening mammograms.

Biopsy↗

PubMed1998

Characterization of adrenal masses using unenhanced CT: an analysis of the CT literature.

OBJECTIVE: Unenhanced CT scanning can reliably characterize incidentally detected adrenal masses when observers use density measurements of the adrenal gland. However, controversy exists as to the optimal density threshold required to differentiate benign from malignant lesions. This study attempts to establish a consensus by performing a pooled analysis of data found in the CT literature. MATERIALS AND METHODS: Ten CT reports were analyzed, from which individual adrenal lesion density measurements were obtained for 495 adrenal lesions (272 benign lesions and 223 malignant lesions). Threshold analysis generated a range of sensitivities and specificities for lesion characterization at different density thresholds. RESULTS: Sensitivity for characterizing a lesion as benign ranged from 47% at a threshold of 2 H to 88% at a threshold of 20 H. Similarly, specificity varied from 100% at a threshold of 2 H to 84% at a threshold of 20 H. CONCLUSION: The attempt to be absolutely certain that an adrenal lesion is benign may lead to an unacceptably low sensitivity for lesion characterization. The threshold chosen will depend on the patient population and the cost-benefit approach to patient care.

Adrenal Gland Diseases↗

PubMed1997

Prognostic indicators in acute pancreatitis: CT vs APACHE II.

PURPOSE: To investigate the correlation between established contrast-enhanced computed tomography (CECT) criteria of disease severity in acute pancreatitis and the APACHE (Acute Physiology and Chronic Health Evaluation) II score and to assess the utility of each as prognostic indicators in acute pancreatitis. MATERIALS AND METHODS: Over a 1-year period, prospective, consensus interpretation of the CECTs of 35 consecutive inpatients was performed with determination of the CECT grade, degree of necrosis, and severity index. The APACHE II score was calculated within 24 h of CECT. Multiple clinical endpoints were recorded: local complications (pseudocyst, abscess, or acute fluid collections requiring urgent surgical or radiological intervention), systemic disease (intensive care unit admission), and duration of hospitalization. Statistical analysis was performed to determine correlations. RESULTS: No statistically significant correlation existed between the APACHE II score and CECT grade, the degree of necrosis, or the CECT severity index. Only the CECT grade and severity index correlated significantly with the occurrence of local complications (P = 0.0035 and 0.0048, respectively). The APACHE II score was superior to the CECT grade as a predictor of the need for ICU admission (P = 0.022 vs P = 0.035), and no other CECT criteria was a significant predictor of ICU admission. CONCLUSION: The preferred clinical and imaging prognostic measures in acute pancreatitis, the APACHE II score and CECT criteria, do not correlate with one another in the commonly encountered, mixed primary and tertiary care population. The mathematical integration of CECT criteria and the APACHE II score fails to yield a predictor of outcome superior to the use of any one measure alone. CECT criteria best define local anatomic abnormality, and are superior to the APACHE II score as predictors of local complications. The APACHE II score is superior to all CECT criteria as an indicator of systemic disease severity (reflected in the need for ICU admission). The most effective initial triage would be immediate APACHE II calculation. Further use of imaging vs clinical assessment can then be individualized.

APACHE↗

PubMed1997

Anesthesia type does not influence early graft patency or limb salvage rates of lower extremity arterial bypass.

PURPOSE: The effect of anesthesia type on 30-day graft patency and limb salvage rates was evaluated in patients who underwent femoral to distal artery bypass. METHODS: Of 423 patients randomly assigned to receive general, spinal, or epidural anesthetic, 76 did not meet protocol standards and 32 had inadequate anesthesia. A chart review of the remaining 315 patients was undertaken to obtain surgical information not recorded in the original study. All patients were monitored with radial and pulmonary artery catheters. After surgery, patients were in a monitored setting for 48 to 72 hours and had graft function assessments hourly during the first 24 hours and then every 8 hours until discharge. RESULTS: Fifty-one patients were lost to follow-up (15 general, 22 spinal, 14 epidural). Baseline clinical characteristics were similar for the three groups except prior carotid artery surgery, which was more common in the spinal group. Indications for surgery were also similar except for a higher incidence of nonhealing ulcer in the epidural group. There were no differences among groups for 30-day graft patency with or without reoperation, 30-day graft occlusion, death, amputation, or length of hospital stay. CONCLUSION: These results suggest that the type of anesthetic given for femoral to distal artery bypass does not significantly affect 30-day occlusion rate, limb salvage rate, or hospital length of stay.

Aged↗

PubMed1997

Evaluation of the accuracy and response time of STAT-mode continuous cardiac output.

OBJECTIVES: This study was conducted to compare continuous cardiac output (CCO) with bolus thermodilution cardiac output (BTD) at steady state, and to compare the response time of STAT CCO with that of trend CCO, mean arterial pressure, and mixed venous oxygen saturation [SvO2] during an acute hemodynamic change. DESIGN: Prospective study. SETTING: University hospital. PARTICIPANTS: Twenty-nine patients undergoing cardiac surgery or liver transplantation. INTERVENTIONS: STAT and trend CCO were compared with BTD cardiac output during steady state intraoperatively and postoperatively in the intensive care unit. Ten patients, who required epicardial pacing after cardiac surgery, were studied to compare the response time of STAT CCO with that of trend CCO, mean arterial pressure, and BvO2 after a 10% to 20% increase in pacing rate. MEASUREMENTS AND MAIN RESULTS: A total of 108 cardiac output data sets were analyzed at steady state. Steady state was defined as stable heart rate and mean arterial pressure (+/- 5%) and stable central venous pressure (+/- 2 mmHg) measured immediately before and after each data set. Cardiac output ranged from 2.3 to 8.5 L/min. The correlation between STAT CCO and BTD was r = 0.94, and for trend CCO and BTD was r = 0.94. The bies and precision for STAT CCO versus BTD were 0.06 L/min (Cl 95%: -0.08 to 0.18) and 0.61 L/min. The bias and precision for trend CCO versus BTD were 0.06 L/min (Cl 95%: -0.04 to 0.16) and 0.49 L/min. Eleven data sets were analyzed to study response time of STAT CCO, which was defined as the first time the percent change of the mean of each variable was significantly increased from baseline. Significant increases in mean arterial pressure and SvO2 were detected after 30 seconds (2.5%, p = 0.01) and 90 seconds (2.0%, p = 0.04), respectively. A significant increase in STAT CCO was reached at 270 seconds (4.4%, p = 0.005). Trend CCO tended to increase but did not reach statistical significance within 6 minutes. CONCLUSIONS: STAT and trend CCO are accurate and precise and show close agreement with BTD cardiac output at steady state. The faster algorithm of STAT CCO offers some advantage over trend CCO during an acute hemodynamic change. However, because of the averaging process for determining CCO, the response time of STAT CCO is slower than that of mean arterial pressure and SvO2.

Algorithms↗

PubMed1997

Relationship between pulmonary artery diameter at computed tomography and pulmonary artery pressures at right-sided heart catheterization. Massachusetts General Hospital Lung Transplantation Program.

RATIONALE AND OBJECTIVES: The purpose of the study was to determine the relationship between pulmonary artery (PA) size at computed tomography (CT) and PA pressures, to develop a noninvasive CT method of PA pressure measurement, and to determine a PA diameter that can enable differentiation of normal subjects from those with pulmonary hypertension. METHODS: PA vessel diameters in 55 candidates for lung and heart-lung transplantation were measured at CT and correlated with PA pressures with both linear and stepwise multiple regression. The multiple regression equations were then tested prospectively in 35 pretransplantation patients. RESULTS: Combined main and left main PA cross-sectional area corrected for body surface area showed the best correlation with mean PA pressure (r = .87). The multiple regression equations helped predict mean PA pressure within 5 mm Hg in 50% of patients with chronic lung disease and in only 8% of patients with pulmonary vascular disease. CONCLUSION: There was a very good correlation between main and left main PA size and mean PA pressure. At present, however, CT has not demonstrated sufficient accuracy to be used clinically.

Adolescent↗

PubMed1997

Focal hepatic lesions: effect of three-dimensional wavelet compression on detection at CT.

PURPOSE: To evaluate the effect of three-dimensional, wavelet-based compression on the detection of focal hepatic lesions at computed tomography (CT). MATERIALS AND METHODS: CT images obtained in 69 patients with focal hepatic lesions were studied (35 consecutive cases and 34 cases selected to be difficult on the basis of lesion size or contrast). Image data were compressed by means of a three-dimensional, wavelet-based algorIthm at ratios of 10:1, 15:1, and 20:1. Normal and abnormal sections (on original and compressed images) were reviewed by using an interactive workstation. Four readers rated the presence or absence of a lesion with a five-point scale. RESULTS: At receiver operating characteristic analysis, no statistically significant difference was detected for all cases considered together. Differences approached but did not reach statistical significance for the diagnostic performance of one reader with compressed images (15:1, P = .054; 20:1, P = .051). For the subset of difficult cases, a significant difference was observed with 20:1 compressed images for one reader (P = .026). Diagnostic performance of readers was less certain in normal than in abnormal cases with both original and compressed images (difference was significant for 15:1 [P = .035] and 20:1 [P < .0001] compressed images). CONCLUSION: Three-dimensional wavelet compression is satisfactory at ratios of at least 10:1. Additional studies with a larger sample would help confirm findings with higher ratios.

Cysts↗

PubMed1997

Differentiation of liver hemangiomas from metastases and hepatocellular carcinoma at MR imaging enhanced with blood-pool contrast agent Code-7227.

PURPOSE: To evaluate differentiation of liver lesions at magnetic resonance (MR) imaging enhanced with Code-7227. MATERIALS AND METHODS: Thirty-five patients with 38 proved liver lesions (15 hemangiomas, 17 metastases, six hepatocellular carcinomas [HCCs]) underwent T1-weighted gradient-echo and T2-weighted fast-spin-echo MR imaging at 1.5 T before and after intravenous administration of Code-7227 (1.1 mg iron per kilogram of body weight). RESULTS: In hemangiomas, the mean contrast-to-noise ratio on precontrast and postcontrast images, respectively, increased from -4.51 +/- 4.7 (standard deviation) to 5.19 +/- 6.3 on T1-weighted images and decreased from 14.73 +/- 7.4 to 0.64 +/- 5.1 on T2-weighted images. In comparison, metastases remained hypointense to liver on T1-weighted images (from -5.77 +/- 5.9 to -7.8 +/- 6.8) and hyperintense on T2-weighted images (from 8.73 +/- 5.4 to 12.61 +/- 6.1). Although HCC enhanced more than metastases, they also remained hypointense to liver on T1-weighted images (from -4.87 +/- 6.1 to -1.79 +/- 5.7) and hyperintense on T2-weighted images (from 10.12 +/- 7.9 to 8.7 +/- 6.4). The degree of enhancement on T1-weighted images and of signal intensity drop on T2-weighted images were significantly lower in malignant liver masses than in hemangiomas (P < .001). CONCLUSION: Distinctly different enhancement patterns with Code-7227 helped accurate differentiation of liver lesions.

Adult↗

PubMed1997

Screening mammography: effect of national guidelines on current physician practice.

PURPOSE: To evaluate the effect of national breast cancer screening guidelines on current physician attitudes toward and practice of screening mammography. MATERIALS AND METHODS: Questionnaire responses from 278 physicians were analyzed. The questionnaire had four sections: general information on physician practice and experience, current use of breast cancer screening, perceptions of screening mammography, and physician awareness of and response to the controversy in breast cancer screening. RESULTS: In women aged 40-49 years, 144 (52%) of 278 physicians performed annual clinical breast examination and screening mammography every 2 years; 57 (21%) favored annual mammography and clinical breast examination. In women aged 50 years and older, 232 (83%) physicians screened patients annually with clinical breast examination and mammography. Two hundred seventeen (78%) physicians were aware of the recommended changes in screening guidelines; 54 (19%) were not aware of the changes. Of those aware of the changes, 56 (26%) changed to the new guidelines, 150 (69%) did not change, and six (3%) modified their practice somewhat. CONCLUSION: Physician practice as regards screening mammography is influenced by national guidelines.

Adult↗

PubMed1997

Should women with implants or a history of treatment for breast cancer be excluded from mammography screening programs?

OBJECTIVE: Our objective was to determine whether it is scientifically justified to require that women with implants or a history of treatment for breast cancer be screened in a diagnostic mammography setting and that they be excluded from mammography screening programs. MATERIALS AND METHODS: The recall rates for women with breast implants or a history of treatment for breast cancer who were screened in a dedicated mammography screening program were compared with those of other women in the screening program. The computerized records for the breast screening program of the Department of Radiology at our institution for January 1, 1990, through December 31, 1995, were reviewed. The recall rates for women who had breast implants and those for women with a history of treatment for breast cancer were compared with the recall rates for the other women who underwent screening. Each recall rate included women who were called back for additional evaluation in addition to those for whom a biopsy was recommended on the basis of the screening study. RESULTS: Of 45,134 screening examinations done during the review period, 43,454 (96%) were for women who had no history of breast cancer or of breast implants; 590 (1%) were for women who had undergone mastectomy; 991 (2%) were for women who had been treated with lumpectomy and irradiation for breast cancer; and 99 (0.2%) were for women with breast implants. Among the 43,454 examinations of women with no history of breast cancer or implants, 3081 examinations (7%) led to interpretations that produced requests for the patient to return for additional evaluation. Thirty-six women who had been treated for breast cancer by mastectomy were recalled (6%). Seventy-five women who had undergone lumpectomy and irradiation for breast cancer were recalled (8%). Five women with breast implants were recalled (5%). Statistically, these rates were not significantly different. CONCLUSION: We find no scientific reason to exclude women who have been treated for breast cancer or who have breast implants from dedicated screening programs.

Breast Implants↗

PubMed1997

Enhancement of hepatic parenchyma, aorta, and portal vein in helical CT: comparison of iodixanol and iopromide.

OBJECTIVE: The purpose of this study was to determine hepatic, aortic, and portal vein enhancement with a new dimeric, nonionic, isotonic contrast medium (iodixanol) in a routinely performed helical CT protocol and compare enhancement characteristics with those of a monomeric, nonionic, low-osmolality contrast medium (iopromide). SUBJECTS AND METHODS: In 81 patients, we injected 150 ml of iodixanol (320 mg I/ml), iodixanol (300 mg I/ml), or iopromide (300 mg I/ml). Injection rate was 5 ml/sec. A dual-phase helical CT scan was obtained (first helical scan began at 30 sec. second helical scan began at 70 sec), and enhancement characteristics were assessed. Results were analyzed taking into account various intrinsic parameters of patients. RESULTS: During the second imaging phase, iodixanol at 320 mg I/ml and iodixanol at 300 mg I/ml provided significantly higher enhancement of the liver (75 H, 69 H, 62 H), aorta (144 H, 140 H, 122 H), and portal vein (147 H, 147 H, 118 H) than did iopromide at 300 mg I/ml. No significant differences were observed during the first imaging phase. CONCLUSION: The combination of higher vascular and parenchymal enhancement levels after injection of the isotonic agent may represent a different quality of tissue enhancement. Such an enhancement would be characterized more by a higher contribution of the blood pool compartment to absolute enhancement levels than by a contribution of the interstitial compartment. Further studies are needed to determine whether the use of isotonic agents effects lesion conspicuity.

Aorta, Abdominal↗

PubMed1997

Patients' opinion of mammography screening services: immediate results versus delayed results due to interpretation by two observers.

OBJECTIVE: The purpose of this study was to evaluate by random questionnaire mailings the preferences of women who have undergone mammography in our region regarding communication of mammography screening results. MATERIALS AND METHODS: Questionnaires were mailed to 400 randomly selected women who were more than 35 years old and who had been treated at our institution for medical or surgical reasons. Questions regarding use of mammography screening at our institution versus services at other locations were included. The questionnaire described two possible mammography services; either a double reading service that would provide delayed reports (DRDR) with the benefit of extra cancers detected, and a service that provides immediate reports given directly to the patient by an on-site radiologist. The presentation of the services was reversed in half the questionnaires to avoid bias. Patients' choices were collected, as were demographic data. The choice of one system over the other was evaluated using the one-sample lest for binomial probability. The chi-square test was used to determine if the order of questions on the survey or the site of patients' screening mammography affected responses. RESULTS: The response rate was 42% (n = 168). Of these, one response informed us of the death of a patient. Of the remaining 167 respondents, 75% (n = 126) preferred the DRDR system, 13% (n = 22) preferred the system providing immediate results (p < .0001), and the other 19 respondents did not select a preference. Of the 167 respondents, 156 answered the question regarding previous screening mammography experience. Of the 105 patients who had undergone screening mammography at our institution, 78% (n = 82) preferred the DRDR system. Of the 51 patients who had undergone mammography elsewhere or who had never undergone mammography, 75% (n = 38) preferred the DRDR system. We found that ordering of presentation of the systems in the questionnaire had no effect on responses. Likewise, whether a respondent had undergone mammography at our institution had no effect on responses (p = 1.0). CONCLUSION: A statistically significant number of women who responded to our questionnaire preferred the DRDR system of reporting screening mammographic results. Educational material about double reading that we included with each patient's questionnaire could account for these results. If the use of a second interpreter is feasible and is done for batch interpretation of screening mammograms, then education of patients about this process may increase acceptance of a delayed mammographic report.

Adult↗

PubMed1997

Routine addition of an automated biopsy device to fine-needle aspiration of the lung: a prospective assessment.

OBJECTIVE: The purpose of this study was to prospectively assess the usefulness of the routine addition of an automated biopsy device (ABD) to fine-needle aspiration (FNA) of the lung and to examine the complication rate of this procedure. SUBJECTS AND METHODS: Fifty biopsies were performed under CT guidance using a coaxial technique with a 19-gauge introducer needle and a 22-gauge aspirating needle followed by a 20-gauge ABD. An average of 3.5 FNA specimens and 2.5 core specimens were obtained. Cytology and histology specimens were interpreted separately by two experienced pathologists who were unaware of the other's interpretation. Final diagnoses were based on surgery, microbiology, definitive biopsy diagnosis, and clinical follow-up. All complications were recorded. RESULTS: Of 34 malignant lesions, we achieved a diagnostic accuracy of 94% for FNA and 59% for core biopsy (p < .01). Combined accuracy was 94%. Of 16 benign lesions, an accurate definitive diagnosis was made in 31% of cases using FNA and in 69% of cases using core biopsy (p = .08). Combined accuracy was 69%. In the subset of benign lesions that were not acute infections (n = 8), an accurate definitive benign diagnosis was made in 12% of cases using FNA and in 75% of cases using core biopsy (p < .05). No false-positive diagnoses of malignancy occurred. Complications included pneumothorax, nine (18%) of 50 cases; chest tube, one (2%) of 50 cases minor pulmonary hemorrhage, seven (14%) of 50 cases; and minor hemoptysis, two (4%) of 50 cases. CONCLUSION: The complication rates of FNA with the addition of an ABD are similar to those reported in the literature for FNA alone. The addition of an ABD significantly increases the diagnostic accuracy only for the subset of benign lesions that are not acute infections.

Adolescent↗

PubMed1997

Imaging of fallopian tube tumors.

OBJECTIVE: The purposes of this study were to investigate the imaging findings in patients with primary fallopian tube neoplasms and to determine whether specific imaging features favor the preoperative diagnosis of fallopian tube tumors (FTT). MATERIALS AND METHODS: Computerized search of medical records from 1984 to 1994 identified 20 patients with a discharge diagnosis of primary fallopian tube carcinoma. Medical records, imaging studies, and pathology findings were reviewed. Eleven patients had available preoperative imaging. RESULTS: Seventeen of 20 patients with primary FTT had unilateral disease. Of these 17, preoperative imaging was available in nine, showing four solid adnexal masses, four complex cystic adnexal masses, and one normal adnexa. The preoperative imaging of these nine patients included six sonographic and five CT studies. Three patients with primary FTT had bilateral tumors, and preoperative imaging was available for two patients: Two sonographic studies and one CT study showed one complex cystic adnexal mass and three normal adnexa. CONCLUSION: Primary FTT commonly presents as an adnexal mass on preoperative imaging and mimics other pelvic malignancies, especially ovarian carcinoma. Making a specific preoperative diagnosis is difficult; however, because primary FTT is unlikely to be confused with a benign process, delay in diagnosis is rare.

Adult↗

PubMed1996

Radiofrequency tissue ablation: importance of local temperature along the electrode tip exposure in determining lesion shape and size.

RATIONALE AND OBJECTIVES: We determined whether heat distribution along a radiofrequency (RF) electrode would be uniform when longer tip exposures are used and whether local temperature effects would influence the shape of induced tissue coagulation. METHODS: Thermistors were embedded within 18-gauge RF electrodes at both ends and in the middle of the exposed tip. The length of tip exposure varied from 1 to 7 cm. RF was applied in vitro to pig liver for 6 min using a constant tip temperature, which was varied in 10 degrees C increments from 60 degrees C to 110 degrees C. Experiments were performed in triplicate. The 3- and 5-cm probes were used at a 90 degrees C tip temperature to create lesions in live pig liver and muscle using similar parameters. Temperature was measured throughout the procedure. Observable coagulation necrosis was measured at the end of the treatment. Regression analysis was used to evaluate the local temperature-lesion diameter relationship. RESULTS: Temperatures were not uniform along the tip exposure for any given trial. Temperature variation increased with higher tip temperatures and longer tip exposures. The diameter of local coagulation necrosis was a function of the local mean temperature. For in vitro trials, no coagulation was seen when the local temperature was less than 50 degrees C. Temperatures above this threshold resulted in progressively greater lesion diameter, with a minimum of 1 cm of necrosis occurring at 71 degrees C. Additional increases in lesion diameter (1.4-1.6 cm) were observed at approximately 90 degrees C. Mathematical modeling demonstrated a best-fit curve: lesion diameter (in cm) = ¿1.4 + 0.03 (tip exposure)¿ ¿1 - e [-0.067(local temp - 49.5 degrees C)]¿, r2 = .986, SD = 0.14 cm for each curve. In living tissue, less uniformity in the shape of coagulation necrosis was seen around the electrodes. Local temperature-lesion diameter data fit the same logarithmic relation, but the threshold for coagulation necrosis was 8.5 degrees C higher than for in vitro specimens. CONCLUSION: Using a single-probe technique for RF-induced tissue necrosis, the diameter of tissue coagulation may be predicted by the local temperature along the exposed electrode. The uniformity of temperature decreases with increased tip exposures. This effect may be partially corrected by creating lesions at higher tip temperatures, where necrosis diameter is increased. Because effects are more pronounced in vivo, uniform volumes of tissue necrosis are limited to tip exposures of 3 cm or less.

Animals↗

PubMed1996

Evaluation of selected two-dimensional segmentation techniques for computed tomography quantitation of lymph nodes.

RATIONALE AND OBJECTIVES: As contrast agents that selectively target normal lymph nodes are undergoing development and evaluation, it has become important to accurately and reproducibly determine nodal boundaries to study the agents and determine such values as lymph node area or mean nodal contrast concentration. This study was performed to evaluate the accuracy of different two-dimensional computer segmentation methods, tested on acrylic phantoms constructed to imitate the appearance of lymph nodes surrounded by fat. METHODS: Five segmentation techniques (manual tracing, semiautomatic local criteria threshold selection, Sobel/watershed technique, interactive deformable contour algorithm and thresholding) were evaluated using phantoms. Subsequently, the first three methods were applied to the images of enhanced lymph nodes in rabbits. RESULTS: Minimum errors in phantom area measurement (< 5%) and interoperator variation (< 5%) were seen with the Sobel/watershed technique and the interactive deformable contour algorithm. These two techniques were significantly better than thresholding and semiautomated thresholding based on local properties. CONCLUSION: Methods based on Sobel edge detection offer more objective tools than thresholding methods for segmenting objects similar to lymph nodes in computed tomography images. Both methods, Sobel/watershed and interactive deformable contour algorithm, are fast and have simple user interfaces.

Algorithms↗

PubMed1996

Secondary elevation of extracellular neurotransmitter amino acids in the reperfusion phase following focal cerebral ischemia.

The purpose of this study was to evaluate amino acid neurotransmitter dynamics in the reperfusion phase after transient cerebral ischemia. In vivo microdialysis was used to measure extracellular amino acid levels in a rabbit model of focal ischemia. During 30 min of transient ischemia (n = 5), small but significant (p < 0.05) increases in glutamate, aspartate, gamma-aminobutyric acid (GABA), and taurine were noted. These elevations rapidly returned to baseline levels upon recirculation and remained constant for up to 5.5 h of reperfusion. In rabbits subjected to 2 h of transient ischemia (n = 5), two phases of amino acid release were seen. During ischemia, large (5- to 50-fold) elevations in glutamate, aspartate, GABA, and taurine occurred, as expected. These elevations rapidly normalized upon unocclusion. However, significant (p < 0.05) secondary elevations in glutamate, aspartate, and GABA occurred after 2-4 h of reperfusion. Regression analysis demonstrated significant correlations between primary (ischemic) and secondary (reperfusion) efflux. In permanent ischemia (n = 5), amino acid levels remained elevated throughout the entire experiment. Secondary elevations in excitatory amino acids may further contribute to the excitotoxic cascade during reperfusion.

Amino Acids↗