Biomedical subjects
S E Seltzer
Publications and source records attributed to S E Seltzer.
Academic radiology in a networked environment.
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Small (< or = 3 cm) hyperechoic renal masses: comparison of helical and convention CT for diagnosing angiomyolipoma.
OBJECTIVE: Because hyperechoic renal masses may represent angiomyolipomas or small renal cancers, CT is often used to reveal the fatty component, which allows diagnosis of angiomyolipoma in most cases. Because conventional CT can fail to reveal fat in angiomyolipomas 3 cm or smaller, we conducted a study to determine whether helical CT would improve our detection of fat and allow more of these masses to be diagnosed as angiomyolipomas. SUBJECTS AND METHODS: We used helical and conventional CT to examine 20 masses (5-29 mm in diameter) in 17 patients who had a small hyperechoic mass detected sonographically. Densitometry was performed by three readers and the mean attenuation values were compared. RESULTS: Of the 20 masses, we diagnosed angiomyolipoma in 16 masses using helical CT and in 14 masses using conventional CT. In 11 masses, we found the measured attenuation values to be more negative on helical CT scans than on conventional CT scans. In five masses, we found the opposite to be true. In the remaining four masses, we were unable to diagnose angiomyolipoma. Of the masses that we diagnosed as angiomyolipoma, the mean attenuation value when examined with helical CT (-44 H) was more negative than with conventional CT (-35 H) but not significantly so (p = .058). However, in the subset of patients with masses that were 2 cm or less in diameter (n = 14), the mean attenuation values on helical CT were significantly lower than on conventional CT (-40 H versus -30 H, p < .05). Likewise, for masses with attenuation values that differed by more than 6 H (n = 8), when imaged by the two techniques we again found that mean attenuation values on helical CT were significantly lower (-43 H versus -24 H, p < .05). CONCLUSION: Helical CT revealed angiomyolipoma across all cases as well as conventional CT did. Also, helical CT was more sensitive in revealing fat in masses less than 2 cm in diameter and in masses in which the attenuations of the two CT techniques differed by a significant amount. We preferred helical CT over conventional CT when examining hyperechoic masses for the purpose of diagnosing angiomyolipoma.
Spiral computed tomography of the liver: contrast agent pharmacokinetics and the potential for improved hepatic enhancement.
RATIONALE AND OBJECTIVES: We conducted a prospective study of 131 patients to evaluate the contrast agent dose-response relationship for liver spiral computed tomography (CT) and to test the hypothesis that spiral CT scanning provides greater enhancement than does dynamic CT scanning. METHODS: Patients were assigned to one of two control groups (dynamic CT) or to one of five experimental groups (spiral CT). Dynamic CT patients received 150 ml and spiral CT patients received either 75, 100, or 150 ml of diatrizoate meglumine. All groups had a monophasic injection rate of 2.5 ml/sec. Hepatic enhancement was compared among experimental and control groups. RESULTS: In the experimental groups, there was a linear dose-response relationship (p < .0001) among the enhancements achieved for the three dosages. The enhancement of the last slice of liver for the spiral CT versus dynamic CT groups receiving 150 ml was significantly greater (p = .002). Peak, first liver slice, and average liver enhancement values were higher with spiral CT scanning, but the difference was not statistically significant (power > .55). CONCLUSION: Using uniphasic injection rates and identical doses of contrast agent, spiral CT scanning has the advantage of improved enhancement of the last part of the liver to be imaged.
Enhanced displays of medical images: evaluation of the effectiveness of color, motion, and contour for detecting and localizing liver lesions.
RATIONALE AND OBJECTIVES: Many perceptual studies have shown that the detection of large, low-contrast targets is better either in color or in contrast-reversing presentations than in standard gray scale. We determined the value of several new display techniques for viewing liver computed tomography (CT) scans. METHODS: Eight observers (four radiologists and four nonradiologists) viewed sets of 100 liver CT images (50 with lesions and 50 without) under five display conditions on a Macintosh computer: (1) color (equiluminant color contrast); (2) color-luminance (combined luminance and chromatic contrast); (3) flicker (luminance contrast that reversed polarity at 2 Hz); (4) contour (shaded intensity mapping); and (5) control (conventional gray scale). Receiver operating characteristics (ROC) techniques were used for analysis. RESULTS: The measured ROC curve areas for the different viewing conditions were as follows: control = 0.77 +/- 0.01 (mean +/- standard error of the mean); color = 0.78 +/- 0.01; color-luminance = 0.82 +/- 0.01; flicker = 0.78 +/- 0.01; and contour = 0.76 +/- 0.01. The percentage of lesions correctly located ranged from 0.82 (color-luminance) to 0.75 (flicker). Performance under the color-luminance condition was significantly better than in the control condition (p = .01), whereas the other experimental conditions were not significantly different from the control condition (p > .21). CONCLUSION: The use of mixed color and luminance displays may have perceptual advantages for radiologists and can improve performance over that of gray-scale viewing.
Contrast material-carrying liposomes: biodistribution, clearance, and imaging characteristics.
PURPOSE: To assess the biodistribution, clearance, and computed tomographic (CT) imaging characteristics of interdigitation-fusion (IF) liposomes that carry iotrolan in their aqueous phases. MATERIALS AND METHODS: Biodistribution and clearance of liposomes containing iotrolan produced with the IF method (IF vesicles) were assessed in rats. CT scans of rats and dogs were obtained after injection of IF vesicles at 100 and 250 mg of iodine per kilogram of body weight. RESULTS: A high initial uptake (63%-96% of the injected dose) was found in the liver and spleen. Liver elimination showed half-lives to be 12.9 days at 250 mg of iodine per kilogram, 10.9 days at 100 mg, and 8.7 days at 25 mg. At 250 mg of iodine per kilogram, the rats had an average of 96 HU of hepatic and 321 HU of splenic enhancement. The dogs had 116 HU of hepatic and 65 HU of splenic enhancement. CONCLUSION: IF liposomes have favorable biodistribution, clearance, and imaging characteristics as hepatosplenic contrast agents.
Hepatic MR imaging with ferumoxides: a multicenter clinical trial of the safety and efficacy in the detection of focal hepatic lesions.
PURPOSE: To assess the safety and diagnostic efficacy of intravenous ferumoxides, a superparamagnetic iron oxide, for depiction of focal hepatic lesions on magnetic resonance (MR) images. MATERIALS AND METHODS: This open-label study included 208 patients with known or suspected focal hepatic lesions. MR images were obtained before and 45 minutes to 4 hours after intravenous infusion of ferumoxides (10 mumol/kg). The effect of ferumoxides on signal intensity of the liver was assessed with quantitative analysis. Safety was evaluated with patient monitoring and laboratory measurements. RESULTS: Mean lesion-to-liver contrast-to-noise ratio on T2-weighted images was 9.1 on unenhanced images and 12.7 on enhanced images. Signal intensity of normal liver on enhanced images decreased to 37% of that on unenhanced images. In blinded image evaluations, additional lesions were identified on 27% of enhanced images. No serious adverse events occurred. CONCLUSION: Ferumoxides is a safe and efficacious contrast agent for the detection of focal liver lesions on T2-weighted images.
Spiral CT of the chest: comparison of cine and film-based viewing.
PURPOSE: To determine radiologists' ability to find lung nodules on spiral computed tomographic (CT) scans of the chest with both rapid sequential (cine) and conventional film-based viewing. MATERIALS AND METHODS: Eight radiologists searched for lung nodules on spiral CT images (10-mm collimation, 10 mm/sec table speed) presented in two formats. Cine viewing was performed at a computer work-station; sections were viewed in 2-mm increments at frame rates up to 10 frames per second. Film-based viewing of images from a laser printer was performed with a lightbox; sections were viewed at 4-mm increments. Eight 3-5-mm-diameter simulated nodules were superimposed on each of five normal CT scans. RESULTS: Radiologists found a higher fraction of nodules with the cine presentation than with film (mean, 0.69 +/- 0.02 [standard error] versus 0.58 +/- 0.03, respectively [P = .006]). Diameter thresholds for nodule detection (50% correctly localized) were 3.3 and 3.5 mm, respectively. CONCLUSION: Cine viewing of spiral CT images of the chest improved radiologists' ability to detect nodules.
Are there clear indications for using helical, as opposed to standard, CT?
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Three-dimensional imaging and display of renal tumors using spiral CT: a potential aid to partial nephrectomy.
OBJECTIVE: A new technique for creating three-dimensional (3D) images of renal tumors using contrast-enhanced spiral computed tomography (CT) is described and preliminarily investigated. METHODS: 3D spiral CT was employed in 2 patients before radical nephrectomy and in 5 patients before partial nephrectomy. Preoperative and postoperative image analyses were conducted to evaluate the ability of the images to depict key anatomic relationships in planning partial nephrectomies. RESULTS: 3D spiral CT defined the tumor's location and relationship to the kidney surface better than the tumor's proximity to renal hilar vessels and collecting system. Negative surgical margins were obtained in all 4 patients with renal cell carcinoma, and post-operative serum creatinine remained less than 2 mg/dL in all 5 patients after partial nephrectomy. CONCLUSIONS: This early experience suggests that 3D spiral CT can help in the planning of partial nephrectomy and in attaining complete resection of renal cell carcinoma while conserving normal renal tissue.
Effects of superparamagnetic iron oxide (AMI-25) on liver and spleen imaging using spin-echo and fast spin-echo magnetic resonance pulse sequences.
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Flattening of the contrast-detail curve for large lesions on liver CT images.
This study evaluated the relative roles of physical and perceptual factors in flattening the contrast-detail (CD) curve on liver CT scans. To estimate the role of physical factors, the theoretical CD curve for a calculated theoretical observer (i.e., a nonprewhitening matched filter) was predicted using the measured noise power spectrum and measured modulation transfer function of the CT system. Another theoretical CD curve was also produced from the output of the same calculated observer after taking the human visual response function (VRF) into account. Perceptual factors were evaluated by analyzing human observers' replicated ratings of the visibility of details super-imposed on liver CT scans. The CD curve for the calculated theoretical observer was below the CD curve actually measured for nine human observers and showed no flattening. With the VRF included, flattening of the theoretical CD curves was only produced by fixed image viewing distances of less than 30 cm, a reading style not employed by the human observers. Correlated ROC analysis of observers' replicated ratings indicated that while random, intraobserver variation was present, the magnitude of this so-called observer noise was insufficient to explain the flattening of CD curves. Use of narrow display windows did not eliminate this flattening effect. The main reason for human observers' inefficient detection of large, low contrast liver lesions appears to be a consistent misuse of the image information.
Impact of positive findings at image-guided biopsy of lymphoma on patient care: evaluation of clinical history, needle size, and pathologic findings on biopsy performance.
PURPOSE: To analyze the effect of findings at image-guided biopsy of abdominal lymphoma (IGBL) on patient care and define the key determinants of clinical success. MATERIALS AND METHODS: A retrospective, bi-institutional study was performed in 102 patients with positive or suspicious IGBL findings (93 patients with non-Hodgkin and nine patients with Hodgkin lymphoma). The proportion of patients treated on the basis of IGBL findings only was calculated and correlated with 10 determinants, including history of lymphoma, biopsy technique, needle size, immunocytochemical findings, and tumor grade. RESULTS: Overall, 73 patients (72%) were treated on the basis of biopsy findings only, including 41 (91%) of 45 patients with a history of lymphoma and 32 (56%) of 57 patients with no such history (P < .01). No difference in findings existed when three needle-size groups were compared (P > .50). CONCLUSION: Whenever findings were positive, IGBL provided enough tissue to enable treatment in most patients. Fine needles were just as likely as larger needles to enable both determination of tumor grade and treatment.
Expediting the turnaround of radiology reports: use of total quality management to facilitate radiologists' report signing.
OBJECTIVE: The purpose of this study was to determine whether total quality management techniques could be used to speed radiologists' performance on the task of signing reports. SUBJECTS AND METHODS: Total quality management represents a group of tools that can be used to improve the functioning of complex processes in the workplace. The steps involved in our total quality management project were as follows: (1) commit to improving radiologists' performance, (2) commission an interdisciplinary study team, (3) propose hypotheses for the causes of signing delays, (4) identify the key issues constraining performance (Pareto analysis), (5) intervene to correct systematic problems in a test system, (6) evaluate the results of intervention on radiologists' report signing performance, and (7) hold the gains achieved by the intervention. An interdisciplinary study team identified five key obstacles to prompt signing of reports: (1) radiologists' absence from the department when reports were available for signing (e.g., nights and weekends), (2) dysfunctional hand-off between transcriptionist and radiologist, (3) requirement that a fellow or resident sign before a staff radiologist, (4) lack of a system for signing by proxy (if primary radiologist is away), (5) perceived lack of impact of signed report on clinical decision making. RESULTS: Interventions included (1) providing home computer terminals, (2) implementing a buddy system for proxy signing, (3) eliminating the requirement for a signature from a fellow or resident, (4) teaming groups of radiologists with specific transcriptionists, and (5) streamlining transcription service. When these enhancements were used in a test system, the mean time required to sign reports decreased 59% from 26.0 +/- 8.4 hr (mean +/- standard error) in the baseline period to 10.6 +/- 2.9 hr (in the enhanced period, p = .05). CONCLUSION: We conclude that total quality management methods can accelerate radiologists' signing of reports.
Design and implementation of a new radiology consultation service in a teaching hospital.
The steady increase in costs related to testing has been a major factor in the overall growth of health care expenses. Concern is substantial about the excessive number of tests ordered by physicians without measurable improvement in patients' outcomes. This is of particular concern in teaching hospitals, because in addition to the direct impact on national health care expenditures, these are the institutions in which young physicians train and formulate test-ordering practices. Proper selection of imaging tests is a complex process that requires detailed information about the patient; specific questions to be answered; and knowledge of the characteristics of the test, including sensitivity, specificity, risks, and cost. To date, no systematic method exists for combining the expertise of the radiologist with that of the referring physician before the tests are selected. Therefore, we designed a new clinical service within the radiology department that allows formal, on-the-ward consultation to assist internal medicine housestaff in the selection of radiologic tests. The goal of this study was to assess the feasibility of this formal radiology consultation service and to determine how often its imaging recommendations were implemented for patients with complicated medical conditions.
Small (< or = 3 cm) renal masses: correlation of spiral CT features and pathologic findings.
OBJECTIVE: We describe our 3-year experience using spiral CT in the evaluation of small renal masses in order to determine the usefulness of this technique for classifying the lesions and to correlate specific CT features with pathologic findings. MATERIALS AND METHODS: We retrospectively analyzed spiral CT scans and results of pathologic examinations of surgically extirpated small (< or = 3 cm) renal masses in 35 patients. The masses included 27 renal cell carcinomas, two transitional cell carcinomas, one leiomyoma, one angiomyolipoma, and four benign cysts. Several imaging features, including attenuation, pattern of contrast enhancement, presence and type of calcification, cyst wall, and septation, were correlated with pathologic findings. RESULTS: Most renal cell carcinomas had a solid growth pattern (n = 19), had attenuation values on unenhanced scans of 20 H or greater (n = 26), and had attenuation values that increased by at least 10 H with contrast enhancement (n = 26). Only three renal cell carcinomas were mostly cystic on pathologic examination. Heterogeneous enhancement correlated with the presence of acellular regions (p = .02). Of 12 cystic masses, spiral CT showed the absence of a thick or nodular fibrous capsule in seven of nine masses (specificity, 0.78) and the absence of several (or nodular) septations in six of seven masses (specificity, 0.86) but was not as sensitive in detecting these features. CONCLUSION: Spiral CT can show many of the key imaging features of small renal masses used to distinguish between benign and malignant lesions. However, despite the theoretical benefits of volumetric CT, some lesions remain indeterminate and require surgical removal for diagnosis.
'Critical paths' add value to practice guidelines.
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Predictive value of image-guided adrenal biopsy: analysis of results of 101 biopsies.
A retrospective study of 97 patients undergoing 101 image-guided adrenal biopsies (IGABs) was performed to analyze the effects of specific pathologic results on test characteristics. Three categories of pathologic results (benign adrenal tissue, malignant tissue, and nondiagnostic) were compared with outcomes. Diagnostic samples were obtained in 86% of cases. Among 72 patients with proved outcomes, IGAB had an accuracy of 96%, a sensitivity of 93%, and a negative predictive value of 91% (92% in patients with bronchogenic carcinoma). In this subset of patients, 33 had biopsy specimens that contained benign adrenal tissue. In these 33 patients, three masses (each smaller than 3 cm) proved malignant. In the 14 patients with nondiagnostic samples, two masses proved malignant. Obtaining benign adrenal tissue was highly predictive of benignity, even in the setting of lung cancer. The authors conclude that IGAB is an accurate procedure in both oncologic and nononcologic patients. However, when the biopsy specimen does not contain benign adrenal tissue or malignant cells, repeat percutaneous biopsy or surgery should be considered.