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Biomedical subjects

C F Beaulieu

Publications and source records attributed to C F Beaulieu.

At least 19 recordsLinked to original sources
PubMed2001

Volume rendering of tendon-bone relationships using unenhanced CT.

OBJECTIVE: Clinically, three-dimensional CT of the extremities is most often used to display bony anatomy. However, by combining unenhanced CT with volume-rendering computer graphics, visualization of relationships between bone and soft-tissue structures such as muscle tendon is also possible. The aims of this study were to quantify CT attenuation values of peripheral tendon, muscle, and bone on unenhanced CT and to develop custom opacity transforms on the basis of the attenuation measurements to effectively depict tendon-muscle-bone relationships. CONCLUSION: The mean attenuation of peripheral tendon ( approximately 100 H) is distinctly higher than that of muscle ( approximately 60 H) enabling high-quality volume rendering of muscle-tendon-bone relationships with unenhanced CT. High-frequency (bone) CT reconstruction algorithms commonly used for extremity CT produce approximately twofold higher image noise and inferior three-dimensional renderings compared with those based on less noisy standard or soft-tissue reconstruction algorithms. These concepts can be used to uniquely reveal tendon-muscle-bone relationships for clinical, scientific, and educational purposes.

Adult↗
PubMed2000

Aortic aneurysmal disease: assessment of stent-graft treatment-CT versus conventional angiography.

PURPOSE: To compare computed tomographic (CT) angiography and conventional angiography for determining the success of endoluminal stent-graft treatment of aortic aneurysms. MATERIALS AND METHODS: Forty patients underwent conventional angiography and CT angiography following treatment of aortoiliac aneurysms with endoluminal stent-grafts. Six additional sets of conventional angiographic-CT angiographic examinations were performed in five patients after placement of additional stent-grafts or coil embolization to treat perigraft leakage. Three faculty CT radiologists who were blinded to patient clinical data and outcome independently interpreted the CT angiograms, and three faculty angiographers, who were not involved in the stent-graft deployment, interpreted the conventional angiograms. Images were assessed for the presence of postdeployment complications. A reference standard was developed by experienced radiologists using all available images and clinical data. Sensitivities, specificities, and kappa values were calculated. RESULTS: Perigraft leakage was the most commonly identified complication. Twenty perigraft leaks were detected in the results of 46 examinations. Sensitivities and specificities for detecting perigraft leakage were 63% and 77% for conventional angiography and 92% and 90% for CT angiography, respectively. The kappa value was 0. 41 for conventional angiography and 0.81 for CT angiography. CONCLUSION: CT angiography is the preferred method for establishing the presence of perigraft leakage following treatment of aortoiliac aneurysms with stent-grafts.

Adult↗
PubMed2000

Focal liver lesions: pattern-based classification scheme for enhancement at arterial phase CT.

PURPOSE: To present our early experience with a classification scheme for categorizing focal liver lesions on the basis of the enhancement patterns that they exhibit in the arterial phase of computed tomography (CT) and to determine whether particular enhancement patterns suggest particular diagnoses. MATERIALS AND METHODS: The authors reviewed arterial phase CT images in 100 consecutive patients with focal liver lesions, excluding simple cysts. The enhancement pattern of the dominant or representative lesion in each patient was classified into one of five categories-homogeneous, abnormal internal vessels or variegated, peripheral puddles, complete ring, or incomplete ring-by three radiologists blinded to the proved diagnosis. Lesions without enhancement were recorded separately. Agreement was reached by consensus in all cases. Standards of reference included findings at histologic examination, correlative imaging, or clinical and imaging follow-up. RESULTS: Ninety-two percent of the 100 lesions demonstrated arterial phase enhancement. Patterns associated with positive predictive values of 82% or greater and specificity of 80% or greater included abnormal internal vessels or variegated (hepatocellular carcinoma), peripheral puddles (hemangioma), and complete ring (metastasis). CONCLUSION: The appearance of hepatic lesions in the arterial phase of enhancement has potential use in the determination of specific diagnoses. The classification scheme used in this study may be a useful tool for the interpretation of arterial phase CT studies.

Adult↗
PubMed2000

Automated polyp detector for CT colonography: feasibility study.

An abdominal computed tomographic scan was modified by inserting 10 simulated colonic polyps with use of methods that closely mimic the attenuation, noise, and polyp-colon wall interface of naturally occurring polyps. A shape-based polyp detector successfully located six of the 10 polyps. When settings that enhanced the edge profile of polyps were chosen, eight of 10 polyps were detected. There were no false-positive detections. Shape analysis is technically feasible and is a promising approach to automated polyp detection.

Colon↗
PubMed2000

Stair-step artifacts with single versus multiple detector-row helical CT.

PURPOSE: To compare the effects of acquisition parameters on the magnitude and appearance of artifacts between single and multiple detector-row helical computed tomography (CT). MATERIALS AND METHODS: A cylindric (12.7 x 305.0-mm) acrylic rod inclined 45 degrees relative to the z axis was scanned at the isocenter and 100 mm from the isocenter with single detector-row (single-channel) helical CT (beam width, 1-10 mm; pitch, 1.0, 2.0, or 3.0) and multiple detector-row (four-channel) helical CT (detector width, 1. 25, 2.5, 3.75, and 5 mm; pitch, 0.75 or 1.5). The SD of radius measurements along the rod (SD(r)) was used to quantify artifacts in all 72 data sets and to analyze their frequency patterns. Volume-rendered images of the data sets were ranked by six independent and blinded readers; findings were correlated with acquisition parameters and SD(r) measurements. RESULTS: SD(r) was smaller in four- than in single-channel helical CT for any given table increment (TI). In single-channel helical CT, SD(r) increased linearly with beam width and geometrically with pitch. In four-channel helical CT, SD(r) measurements were directly proportional to the TI, regardless of the detector width and pitch combination used. Off-center object position on average increased SD(r) by a factor of 1.6 for single-channel helical CT and by a factor of 2.0 for four-channel helical CT. Subjective rankings of image quality correlated excellently with SD(r) (Spearman r = 0.94, P <.001). CONCLUSION: Artifacts are quantitatively and subjectively smaller with four- compared with single-channel helical CT for any given TI.

Artifacts↗
PubMed1999

Joint motion in an open MR unit using MR tracking.

A system for active scan plane guidance during kinematic magnetic resonance (MR) examination of joint motion was developed utilizing an external tracking coil and MR tracking software. In a phantom study and during upright, weight-bearing, physiologic knee flexion, the external tracking coil maintained the scan plane through desired structures. Thus, MR tracking provides a robust method to guide the scan plane during MR imaging of active joint motion.

Biomechanical Phenomena↗
PubMed1999

Display modes for CT colonography. Part II. Blinded comparison of axial CT and virtual endoscopic and panoramic endoscopic volume-rendered studies.

PURPOSE: To determine the sensitivity of radiologist observers for detecting colonic polyps by using three different data review (display) modes for computed tomographic (CT) colonography, or "virtual colonoscopy." MATERIALS AND METHODS: CT colonographic data in a patient with a normal colon were used as base data for insertion of digitally synthesized polyps. Forty such polyps (3.5, 5, 7, and 10 mm in diameter) were randomly inserted in four copies of the base data. Axial CT studies, volume-rendered virtual endoscopic movies, and studies from a three-dimensional mode termed "panoramic endoscopy" were reviewed blindly and independently by two radiologists. RESULTS: Detection improved with increasing polyp size. Trends in sensitivity were dependent on whether all inserted lesions or only visible lesions were considered, because modes differed in how completely the colonic surface was depicted. For both reviewers and all polyps 7 mm or larger, panoramic endoscopy resulted in significantly greater sensitivity (90%) than did virtual endoscopy (68%, P = .014). For visible lesions only, the sensitivities were 85%, 81%, and 60% for one reader and 65%, 62%, and 28% for the other for virtual endoscopy, panoramic endoscopy, and axial CT, respectively. Three-dimensional displays were more sensitive than two-dimensional displays (P < .05). CONCLUSION: The sensitivity of panoramic endoscopy is higher than that of virtual endoscopy, because the former displays more of the colonic surface. Higher sensitivities for three-dimensional displays may justify the additional computation and review time.

Colonic Polyps↗
PubMed1999

Display modes for CT colonography. Part I. Synthesis and insertion of polyps into patient CT data.

PURPOSE: To develop and validate a method for the insertion of digitally synthesized polyps into computed tomographic (CT) images of the human colon for use as ground truth for evaluation of virtual colonoscopy. MATERIALS AND METHODS: Spiral CT simulator software was used to generate 10 synthetic polyps in various configurations. Additional software was developed to insert these polyps into volume CT scans. Ten polyps in eight patients were selected for comparison. Three radiologists evaluated whether two-dimensional (2D) CT images and three-dimensional (3D) volume-rendered CT images showed synthetic or real polyps. RESULTS: Edge-response profiles and noise of simulated polyps matched those of native polyps. Frequency distributions of reviewers' responses were not significantly different for synthetic versus real polyps in either 3D or 2D images. Responses were clustered around the response of "unsure" if lesions were real or synthetic. Receiver operating characteristic curves had areas of 0.54 (95% CI = 0.39, 0.68) for 3D and 0.39 (95% CI = 0.25, 0.53) for 2D images, which were not significantly different from random guessing (P = .70 and .28 for 3D and 2D images, respectively). CONCLUSION: Synthetic polyps were indistinguishable from real polyps. This method can be used to generate ground truth experimental data for comparison of CT colonographic display and detection methods.

Adult↗
PubMed1999

Glenohumeral relationships during physiologic shoulder motion and stress testing: initial experience with open MR imaging and active imaging-plane registration.

PURPOSE: To test the hypotheses that open dynamic magnetic resonance (MR) imaging can (a) be used to evaluate and define normal shoulder motion in active joint motion and muscle contraction and (b) be used in conjunction with physical examination. MATERIALS AND METHODS: With an open-configuration, 0.5-T MR imaging system and active image-plane tracking, 10 shoulders were studied in five asymptomatic subjects to establish normal patterns of glenohumeral motion during abduction and adduction and internal and external rotation. Preliminary studies of physical examination during MR imaging, in which a physician examiner applied mechanical force to the humeral head, were also performed. RESULTS: During abduction and adduction and internal and external rotation maneuvers with active subjects muscle contraction, the humeral head remained precisely centered on the glenoid fossa in all asymptomatic subjects, which is in agreement with findings of previous radiographic studies. Application of force to the humeral head by an examiner was associated with as much as 6 mm of anterior translation and 13 mm of posterior translation. CONCLUSION: Dynamic MR imaging of the glenohumeral joint is possible over a wide range of physiologic motion in vertically open systems. Use of an MR tracking coil enabled accurate tracking of the anatomy of interest. These preliminary measurements of normal glenohumeral motion patterns begin to establish normal ranges of motion and constitute a necessary first step in characterizing pathologic motion in patients with common clinical problems such as instability and impingement.

Adult↗
PubMed1998

Automated flight path planning for virtual endoscopy.

In this paper, a novel technique for rapid and automatic computation of flight paths for guiding virtual endoscopic exploration of three-dimensional medical images is described. While manually planning flight paths is a tedious and time consuming task, our algorithm is automated and fast. Our method for positioning the virtual camera is based on the medial axis transform but is much more computationally efficient. By iteratively correcting a path toward the medial axis, the necessity of evaluating simple point criteria during morphological thinning is eliminated. The virtual camera is also oriented in a stable viewing direction, avoiding sudden twists and turns. We tested our algorithm on volumetric data sets of eight colons, one aorta and one bronchial tree. The algorithm computed the flight paths in several minutes per volume on an inexpensive workstation with minimal computation time added for multiple paths through branching structures (10%-13% per extra path). The results of our algorithm are smooth, centralized paths that aid in the task of navigation in virtual endoscopic exploration of three-dimensional medical images.

Algorithms↗
PubMed1998

Anterior cruciate ligament injury: fast spin-echo MR imaging with arthroscopic correlation in 217 examinations.

OBJECTIVE: Our objective was to evaluate the accuracy of MR imaging strategy that uses primarily fast spin-echo sequences for the diagnosis of anterior cruciate ligament tears. MATERIALS AND METHODS: The original clinical interpretations of MR images of 217 examinations of the knee joint were correlated with subsequent arthroscopic results. Each MR examination included a double-echo fast spin-echo sequence as the only imaging sequence in the sagittal plane. Subsequent discordant MR and arthroscopic examinations were then subjected to reanalysis by two observers who were unaware of arthroscopic results to determine if misinterpretations were observer or image dependent. Two hundred sixteen patients who underwent MR imaging for suspected internal derangement of the knee subsequently underwent arthroscopic surgery. Two patients had both knees evaluated. One patient was excluded because he was referred for evaluation for osteomyelitis, not internal derangement. This yielded a total number of 217 MR examinations for suspected internal derangement of the knee. RESULTS: For 56 arthroscopically proven tears, the sensitivity of MR imaging was 96%. The specificity was 98%, yielding an overall accuracy rate of 98%. The positive and negative predictive values were 95% and 99%, respectively. These values are within the ranges of previously reported MR imaging strategies using conventional spin-echo sequences. CONCLUSION: Fast spin-echo MR imaging of the knee can be an alternative to conventional spin-echo imaging for the detection of anterior cruciate ligament tears.

Adolescent↗
PubMed1998

Magnetic resonance imaging of knee cartilage repair.

Cartilage injury resulting in osteoarthritis is a frequent cause of disability in young people. Osteoarthritis, based on either cartilage injury or degeneration, is a leading cause of disability in the United States. Over the last several decades, much progress has been made in understanding cartilage injury and repair. Magnetic resonance (MR) imaging, with its unique ability to noninvasively image and characterize soft tissue, has shown promise in assessment of cartilage integrity. In addition to standard MR imaging methods, MR imaging contrast mechanisms under development may reveal detailed information regarding the physiology and morphology of cartilage. MR imaging will play a crucial role in assessing the success or failure of therapies for cartilage injury and degeneration.

Cartilage, Articular↗