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Biomedical subjects

Geoffrey D Rubin

Publications and source records attributed to Geoffrey D Rubin.

At least 19 recordsLinked to original sources
PubMed2005

Vascular mapping of the leg with multi-detector row CT angiography prior to free-flap transplantation.

PURPOSE: To retrospectively evaluate multi-detector row computed tomographic (CT) angiography in determining donor- and recipient-site arterial suitability for successful vascularized free-flap transplantation. MATERIALS AND METHODS: The institutional review board granted approval; informed consent was waived, and the study was HIPAA compliant. Lower extremities of 20 (12 male, eight female; mean age, 51 years; range, 10-84 years) patients undergoing vascularized free-flap procedures were examined at multi-detector row CT angiography. In five patients, legs were assessed as potential fibular free-flap donors for mandibular, maxillary, or radial reconstruction. In 15 patients, legs were assessed as recipient sites for free flaps. Vascular maps obtained with volume rendering, maximum intensity projections, and curved planar reformations were generated, and assessment was made in the depiction of calf vessels and presence of stenosis, occlusion, and anatomic anomaly. Findings of CT angiography, physical examination, and surgery were compared, where applicable, and successful CT-based prediction of the surgical intervention was assessed. Immediate and long-term (>70 days) viability of the graft was assessed in all patients. RESULTS: CT angiography depicted the entirety of all four major calf arteries in 29 of 32 legs scanned. In three legs, external-fixation hardware obscured some segments. There were no discrepancies between CT findings and those identified at the time of surgery. Arterial abnormalities, including stenosis, occlusion, and variant anatomy, were seen in 12 lower extremities in 10 patients. Only two were suspected on the basis of physical examination findings. In five of 20 patients, CT findings resulted in changes to the surgical plan. There was a 100% immediate viability of all grafts, which remained well vascularized between 70 days and 37 months after the procedure. CONCLUSION: Multi-detector row CT angiography provides a noninvasive means of preoperatively assessing lower extremity arteries for abnormalities, which could jeopardize graft viability or pedal arterial supply after free-flap procedures.

Aged↗
PubMed2005

Quantification of intravenously administered contrast medium transit through the peripheral arteries: implications for CT angiography.

PURPOSE: To prospectively determine the range of aortopopliteal bolus transit times in patients with moderate-to-severe peripheral arterial occlusive disease (PAOD) as a guideline for developing injection strategies for computed tomographic (CT) angiography of peripheral arteries. MATERIALS AND METHODS: The study protocol was approved by the local ethics board, and informed consent was obtained. Twenty patients with PAOD referred for CT angiography of the lower extremities were categorized into two groups, Fontaine stage IIb (group 1) and stage III or IV (group 2), and demographic information was collected. In all patients, a 16-mL test bolus was injected intravenously, and single-level dynamic acquisitions were obtained at the level of the abdominal aorta. After injection of a second 16-mL test bolus, dynamic acquisitions were obtained at the level of the knee (popliteal arteries). Aortopopliteal bolus transit times were calculated by subtracting the time to peak enhancement in the popliteal arteries from that in the aorta. Aortopopliteal transit speeds also were derived. Transit times and speeds were compared graphically between clinical stage groups. The time required for the contrast medium to enhance the entire peripheral arterial tree in patients with PAOD was estimated by using linear extrapolation. RESULTS: Sixteen men and four women with a mean age of 69 years (range, 49-86 years) were included. Twelve patients were included in group 1, and eight patients, in group 2. Aortopopliteal bolus transit times ranged from 4 to 24 seconds (median, 8 seconds) in all subjects, which corresponded to bolus transit speeds of 177 and 29 mm/sec, respectively. Wide overlap of transit times and transit speeds was observed between clinical stage groups. The estimated time needed for the bolus to enhance the entire peripheral arterial tree was 6-39 seconds. CONCLUSION: Aortopopliteal bolus transit times differ widely among patients and may be substantially delayed in all patients with PAOD. Empirical injection protocols should include an injection duration of 35 seconds or more, as well as an increased scanning delay, with table speeds of more than 30 mm/sec.

Aged↗
PubMed2005

Alternative input devices for efficient navigation of large CT angiography data sets.

PURPOSE: To compare devices for the task of navigating through large computed tomographic (CT) data sets at a picture archiving and communication system workstation. MATERIALS AND METHODS: The institutional review board approved this study, and all subjects provided informed consent. Five radiologists were asked to find 25 different vascular targets in three CT angiography data sets (average number of sections, 1025) by using several devices (trackball, tablet, jog-shuttle wheel, and mouse). For each trial, the total time to acquire the targets (T1) was recorded. A secondary study in which 13 nonradiologists performed seven trials with an artificial target inserted at a random location in the same image data was also performed. For each trial, the following items were recorded: time until first target sighting (t2), time to manipulate the device after seeing the target, sections traversed during t2 (d1), time from first sight to target acquisition (t4), sections traversed during t4 (d2), and total trial time. Statistical analysis involved repeated-measures analysis of variance (ANOVA) and pairwise comparisons. RESULTS: Repeated-measures ANOVA revealed that the device used had a significant (P < .05) effect on T1. Pairwise comparisons revealed that the trackball was significantly slower than the tablet (P < .05) and marginally slower than the jog-shuttle wheel (P < .10). Further repeated-measures ANOVA for each secondary outcome measure revealed significant differences between devices for all outcome measures (P < .005). Pairwise comparisons revealed the trackball to be significantly slower than the other devices in all measures (P < .05). The trackball was significantly (P < .05) more accurate than the other devices for d1 and d2. CONCLUSION: The trackball may not be the optimal device for navigation of large CT angiography data sets; the use of other existing devices may improve the efficiency of interpretation of these sets.

Angiography↗
PubMed2004

MDCT angiography of pediatric vascular diseases of the abdomen, pelvis, and extremities.

Multi-detector-row computed tomography (MDCT) enables rapid, noninvasive, high-resolution, and three-dimensional imaging of pediatric vascular diseases. In this paper, we explore the adaptation of the MDCT angiographic principles to pediatric patients for vascular diseases of the abdomen, pelvis, and extremities. Special emphasis is placed on the practical aspects of how to perform these studies. Optimizations of scan parameters, contrast medium usage, radiation dose, and three-dimensional image processing are discussed in detail. We provide practical guidance on how to choose between MR angiography and CT angiography. Finally, we review important pediatric vascular diseases, categorized into traumatic injuries, inherited vascular diseases, congenital vascular diseases, vasculitides, and surgical planning and assessment. In each category, we discuss how CT angiography can be tailored to maximize its clinical benefits.

Adolescent↗
PubMed2004

Pulmonary nodules on multi-detector row CT scans: performance comparison of radiologists and computer-aided detection.

PURPOSE: To compare the performance of radiologists and of a computer-aided detection (CAD) algorithm for pulmonary nodule detection on thin-section thoracic computed tomographic (CT) scans. MATERIALS AND METHODS: The study was approved by the institutional review board. The requirement of informed consent was waived. Twenty outpatients (age range, 15-91 years; mean, 64 years) were examined with chest CT (multi-detector row scanner, four detector rows, 1.25-mm section thickness, and 0.6-mm interval) for pulmonary nodules. Three radiologists independently analyzed CT scans, recorded the locus of each nodule candidate, and assigned each a confidence score. A CAD algorithm with parameters chosen by using cross validation was applied to the 20 scans. The reference standard was established by two experienced thoracic radiologists in consensus, with blind review of all nodule candidates and free search for additional nodules at a dedicated workstation for three-dimensional image analysis. True-positive (TP) and false-positive (FP) results and confidence levels were used to generate free-response receiver operating characteristic (ROC) plots. Double-reading performance was determined on the basis of TP detections by either reader. RESULTS: The 20 scans showed 195 noncalcified nodules with a diameter of 3 mm or more (reference reading). Area under the alternative free-response ROC curve was 0.54, 0.48, 0.55, and 0.36 for CAD and readers 1-3, respectively. Differences between reader 3 and CAD and between readers 2 and 3 were significant (P < .05); those between CAD and readers 1 and 2 were not significant. Mean sensitivity for individual readings was 50% (range, 41%-60%); double reading resulted in increase to 63% (range, 56%-67%). With CAD used at a threshold allowing only three FP detections per CT scan, mean sensitivity was increased to 76% (range, 73%-78%). CAD complemented individual readers by detecting additional nodules more effectively than did a second reader; CAD-reader weighted kappa values were significantly lower than reader-reader weighted kappa values (Wilcoxon rank sum test, P < .05). CONCLUSION: With CAD used at a level allowing only three FP detections per CT scan, sensitivity was substantially higher than with conventional double reading.

Adolescent↗
PubMed2004

Surveillance for endoleaks: how to detect all of them.

Endovascular aneurysm repair has proven to be a valuable alternative to open repair in selected patients. This less invasive procedure, however, requires long-term surveillance for its own set of potential complications, including perigraft leakage, or endoleak. This article focuses on the detection of these leaks, first defining and classifying endoleaks and then describing various means of detecting them, including computed tomographic angiography, magnetic resonance angiography, color-flow duplex ultrasonography, and conventional angiography.

Aortic Aneurysm, Abdominal↗
PubMed2004

Surface normal overlap: a computer-aided detection algorithm with application to colonic polyps and lung nodules in helical CT.

We developed a novel computer-aided detection (CAD) algorithm called the surface normal overlap method that we applied to colonic polyp detection and lung nodule detection in helical computed tomography (CT) images. We demonstrate some of the theoretical aspects of this algorithm using a statistical shape model. The algorithm was then optimized on simulated CT data and evaluated using a per-lesion cross-validation on 8 CT colonography datasets and on 8 chest CT datasets. It is able to achieve 100% sensitivity for colonic polyps 10 mm and larger at 7.0 false positives (FPs)/dataset and 90% sensitivity for solid lung nodules 6 mm and larger at 5.6 FP/dataset.

Algorithms↗
PubMed2004

New method of measuring coronary diameter by electron-beam computed tomographic angiography using adjusted thresholds determined by calibration with aortic opacity.

BACKGROUND: In a previous study the adjusted thresholds at which the diameters of coronary arteries determined by enhanced electron-beam computed tomography (CT) scans are equal to the corresponding quantitative coronary angiography measurements were analyzed, and their correlation with maximum CT values for the vessel short axes was determined. A rapid accurate method for such measurements was sought by substituting maximum CT values for the descending aorta in the corresponding axial images for those for the short axes. METHODS AND RESULTS: In 8 patients, 179 sites were measured. Means (+/- SD) of adjusted thresholds and the maximum CT values for vessel short axes and the descending aorta in the corresponding axial images for all vessels were 108 +/-66, 227+/-80, and 363+/-75 Hounsfield Unit (HU), respectively. Adjusted thresholds correlated with the maximum CT values for the corresponding vessel short axes and the descending aorta in the corresponding axial images, with R2=0.55, 0.33, p<0.01, respectively. An abbreviated formula for use of maximum CT values for the descending aorta in the corresponding axial images was y=0.5x-75 (HU) (y= adjusted threshold, x= maximum CT value for the descending aorta in the corresponding axial image). CONCLUSIONS: The abbreviated formula provided a rapid, accurate method for measurements independent of arterial enhancement.

Aorta, Thoracic↗
PubMed2003

Curved-slab maximum intensity projection: method and evaluation.

The authors developed and evaluated a method to produce curved-slab maximum intensity projections (MIPs) through blood vessels that semiautomatically excludes soft tissue and bone. Results obtained with the algorithm were compared with those obtained with rectangular-slab MIPs by using computed tomographic (CT) data from four patients with abdominal aortic aneurysms. Curved-slab MIPs exhibited increased mean vessel-to-perivascular tissue contrast of 55.1 HU (36%), allowed a 10% increase in contrast-to-noise ratio, and decreased apparent vessel narrowing by 0.12-1.09 mm, without increasing processing time. Curved-slab MIPs may also include multiple vessels in a single image, thereby improving interpretation efficiency by reducing the number of MIPs required in these patients from eight to three.

Aged↗
PubMed2003

CT angiography of the thoracic aorta.

Nine years after its introduction, spiral or helical CTA is being embraced as an important noninvasive tool for imaging the thoracic aorta and its branches. The high degree of accessibility and ease with which the studies are performed make it a viable alternative to aortography. Once familiar with the principles of CTA, the acquisition phase of the examination can be completed in as little as 15 minutes. Nevertheless, important challenges remain for CTA. The capabilities of MDCT to acquire thinner sections in shorter scan times have resulted in a veritable explosion of imaging data for radiologists to analyze. In this environment, efficient image processing workstations and software is critical to improving our ability to efficiently interpret these volumetric CT data. Finally, helical CT technology is far from static. Every year, new advances in engineering bring better image quality, improved resolution, and faster scan times. As medical imagers, we must not become complacent but rather constantly challenge ourselves to consider how we might further improve on our utilization of CT equipment to maximize the collection of information relevant to diagnosis and therapy.

Aortic Dissection↗
PubMed2003

3-D imaging with MDCT.

Without doubt, the greatest challenge of multidetector-row CT is dealing with 'data explosion'. For our carotid/intracranial CT angiograms, we routinely have 375 images to review (300 mm coverage reconstructed every 0.8 mm); for aortic studies we have 450-500 images ( approximately 600 mm coverage reconstructed every 1.3 mm); and for a study of the lower extremity inflow and run-off, we may generate 900-1000 transverse reconstructions. While we could reconstruct fewer images for these data, experience with single-detector row CT scanners indicates that longitudinal resolution and disease detection is improved when at least 50% overlap of cross-sections is generated [Radiology 200 (1996) 312]. If we are to optimize our clinical protocols and take full advantage of these CT scanners, we will need to change the way that we interpret, transfer, and store CT data. Film is no longer a viable option. Workstation based review of transverse reconstructions for interpretation is a necessity, but the workstations must improve to provide efficient access to these data, and we must have a way of providing our clinicians with images that can be transported to clinics and the operating room. Alternative visualization and analysis using volumetric tools, including 3-D visualization must evolve from luxury to necessity. We cannot rest on historical precedent to interpret these near isotropically sampled volumetric data using transverse reconstructions alone [Radiology 173 (1989) 527]. Although the tools for volumetric analysis on 3-D workstations have evolved over recent years, they have probably not yet evolved to a level that routine interpretation can be performed as efficiently and accurately as transverse section review. Both hardware and software developments must occur. While current computer workstations and visualization software are certainly adequate for assessing these MDCT data volumetrically, the process is very time consuming. What follows are a description of current workstation capabilities and a brief discussion of where development needs to go to facilitate the complete integration of volumetric analysis into the interpretive process of CT data.

Humans↗
PubMed2003

MDCT imaging of the aorta and peripheral vessels.

Since its clinical introduction in 1991, volumetric CT scanning using spiral or helical scanners has resulted in a revolution for diagnostic imaging. Helical CT has improved over the past 8 years with faster gantry rotation, more powerful X-ray tubes, and improved interpolation algorithms, but the greatest advance has been the recent introduction of multi detector-row CT (MDCT) scanners [J. Comput. Assist. Tomogr. 23 (1999) S83]. Currently capable of acquiring four channels of helical data simultaneously, MDCT scanners have achieved the greatest incremental gain in scan speed since the development of helical CT and have profound implications for clinical CT scanning. Fundamental advantages of MDCT include substantially shorter acquisition times, retrospective creation of thinner or thicker sections from the same raw data, and improved three-dimensional (3-D) rendering with diminished helical artifacts. While these features will likely be important to many applications of CT scanning, including the characterization of focal lung and liver lesions through the creation of thin sections retrospectively, the greatest impact has been on CT angiography. The implication for CT angiography is that scans can be performed approximately three-times faster than is possible with the fastest single-detector CT scanner. For example a 1.25 mm nominal thick section (1.6 mm effective section thickness) can be acquired with a table speed of 9.4 mm/s, and a 2.5 mm nominal thick section (3.2 mm effective section thickness) can be acquired with an 18.8 mm/s table speed. The advantages of MDCT for imaging the vascular system can be broken down into three fundamental improvements over single detector-row CT scanners speed (faster), distance (longer), and section thickness (better). The focus of this article will be how multidetector-row CT technology has substantially improved aortoiliac and lower extremity arterial imaging.

Aortic Dissection↗
PubMed2003

Early experience with computed tomographic angiography in microsurgical reconstruction.

Preoperative angiography is frequently used in the planning of microsurgical reconstruction. However, several potentially devastating complications can result from angiography, including arterial occlusion and pseudoaneurysm. Computed tomographic angiography is a relatively new technique that can provide detailed information about vascular anatomy as well as soft and bony tissue without the risks of traditional angiography. In addition, three-dimensional image reconstruction uniquely demonstrates anatomical relationships among blood vessels, bones, and soft tissue. Fourteen computed tomographic angiograms were obtained in 10 patients undergoing microsurgical reconstruction of the head and neck, lower extremity, or upper extremity. The average patient age was 46.9 years (range, 22 to 67 years). Charges related to the computed tomographic procedure were compared with those of conventional preoperative imaging for microsurgical repair. At our institution, the average computed tomographic angiogram charge was 1140 US dollars, whereas the average charge for traditional arteriography was 3900 US dollars. When compared with intraoperative evaluation, computed tomographic angiograms demonstrated clinically relevant surgical anatomy. No complications were noted for the radiographic procedure or after free flap reconstruction. Computed tomographic angiography provides high-resolution, three-dimensional arterial, venous, and soft-tissue imaging without the risks of traditional angiogram and at a lower cost.

Adult↗
PubMed2003

Semiautomated segmentation of blood vessels using ellipse-overlap criteria: method and comparison to manual editing.

Two-dimensional intensity-based methods for the segmentation of blood vessels from computed-tomography-angiography data often result in spurious segments that originate from other objects whose intensity distributions overlap with those of the vessels. When segmented images include spurious segments, additional methods are required to select segments that belong to the target vessels. We describe a method that allows experts to select vessel segments from sequences of segmented images with little effort. Our method uses ellipse-overlap criteria to differentiate between segments that belong to different objects and are separated in plane but are connected in the through-plane direction. To validate our method, we used it to extract vessel regions from volumes that were segmented via analysis of isolabel-contour maps, and showed that the difference between the results of our method and manually-edited results was within inter-expert variability. Although the total editing duration for our method, which included user-interaction and computer processing, exceeded that of manual editing, the extent of user interaction required for our method was about a fifth of that required for manual editing.

Aneurysm↗
PubMed2003

Coronary artery: quantitative evaluation of normal diameter determined with electron-beam CT compared with cine coronary angiography initial experience.

Eight male heart transplant recipients underwent contrast material-enhanced electron-beam computed tomographic angiography. Coronary artery diameters measured with fixed thresholds and adaptive line density profile (LDP) methods were calculated relative to findings at quantitative coronary angiography. Variation with fixed-threshold methods was significantly greater than that with LDP methods because of variations in vessel enhancement. Thus, more accurate measurements of vessel diameter were obtained with LDP methods.

Cineangiography↗
PubMed2002

CT angiography of the arterial system.

CTA has become an important diagnostic tool in the evaluation of vascular diseases in virtually all parts of the body. Whereas CTA is able to provide images depicting exquisite anatomic detail, careful scanning technique and selection of scan parameters are critical for high quality studies. The choices to be made when prescribing a scan can seem daunting at first, but if one applies the principles outlined previously, CTA can be a relatively easy, fast, and safe diagnostic technique that is effective in the majority of patients with vascular disease.

Angiography↗