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Biomedical subjects

L D Cohen

Publications and source records attributed to L D Cohen.

13 recordsLinked to original sources
PubMed2001

Fast extraction of minimal paths in 3D images and applications to virtual endoscopy.

The aim of this article is to build trajectories for virtual endoscopy inside 3D medical images, using the most automatic way. Usually the construction of this trajectory is left to the clinician who must define some points on the path manually using three orthogonal views. But for a complex structure such as the colon, those views give little information on the shape of the object of interest. The path construction in 3D images becomes a very tedious task and precise a priori knowledge of the structure is needed to determine a suitable trajectory. We propose a more automatic path tracking method to overcome those drawbacks: we are able to build a path, given only one or two end points and the 3D image as inputs. This work is based on previous work by Cohen and Kimmel [Int. J. Comp. Vis. 24 (1) (1997) 57] for extracting paths in 2D images using Fast Marching algorithm. Our original contribution is twofold. On the first hand, we present a general technical contribution which extends minimal paths to 3D images and gives new improvements of the approach that are relevant in 2D as well as in 3D to extract linear structures in images. It includes techniques to make the path extraction scheme faster and easier, by reducing the user interaction. We also develop a new method to extract a centered path in tubular structures. Synthetic and real medical images are used to illustrate each contribution. On the other hand, we show that our method can be efficiently applied to the problem of finding a centered path in tubular anatomical structures with minimum interactivity, and that this path can be used for virtual endoscopy. Results are shown in various anatomical regions (colon, brain vessels, arteries) with different 3D imaging protocols (CT, MR).

Algorithms↗
PubMed2001

A comparison of the effect of loperamide in oral or suppository form vs placebo in patients with ileo-anal pouches.

OBJECTIVE: The effect of the anti-diarrhoeal drug, loperamide hydrochloride, on bowel function in patients with an ileo-anal pouch was studied by means of a blinded, three-tailed, case-controlled and randomized crossover trial, using a daily dose of 12 mg in either oral (4 mg t.d.s.) or suppository (6 mg b.d.) form. PATIENTS AND METHODS: Daily stool frequency was recorded in a diary and an objective measure of pouch motor function was obtained at the end of each treatment phase. Ten subjects (seven males, three females) aged 23-50 years (median 38 years) were studied 9-48 months (median 27 months) after ileostomy closure. Eight pouches had been constructed for ulcerative colitis and two for familial adenomatous polyposis (9J, 1W). RESULTS: Mean daily stool frequency during the oral loperamide phase was lower than during both the placebo (P=0.05) and suppository (P < 0.02) phases. Stool frequency did not differ significantly between placebo and suppository phases. There was a strong inverse correlation between mean daily stool frequency and pouch capacity (r=-0.82 after both oral and suppository phases). Large isolated pouch contractions were evident in five of eight subjects studied; suppression was observed in two of the five after oral loperamide and in three of the five after loperamide suppositories. Rhythmic pouch contractions were seen in four subjects and suppression was evident after loperamide suppositories (but not after oral loperamide) in three. A daily oral dose of 12 mg loperamide significantly lowered stool frequency in pouch patients and modified some aspects of pouch contraction. Loperamide suppositories produced more prominent suppression of pouch contractions but did not lower stool frequency. CONCLUSION: This suggests that the beneficial effect of oral loperamide is primarily due to its action on intestine proximal to the pouch itself.

Clinical Trial↗
PubMed2001

A new approach of geodesic reconstruction for drusen segmentation in eye fundus images.

Segmentation of bright blobs in an image is an important problem in computer vision and particularly in biomedical imaging. In retinal angiography, segmentation of drusen, a yellowish deposit located on the retina, is a serious challenge in proper diagnosis and prevention of further complications. Drusen extraction using classic segmentation methods does not lead to good results. We present a new segmentation method based on new transformations we introduced in mathematical morphology. It is based on the search for a new class of regional maxima components of the image. These maxima correspond to the regions inside the drusen. We present experimental results for drusen extraction using images containing examples having different types and shapes of drusen. We also apply our segmentation technique to two important cases of dynamic sequences of drusen images. The first case is for tracking the average gray level of a particular drusen in a sequence of angiographic images during a fluorescein exam. The second case is for registration and matching of two angiographic images from widely spaced exams in order to characterize the evolution of drusen.

Fluorescein Angiography↗
PubMed1996

Tracking and motion analysis of the left ventricle with deformable superquadrics.

We present a new approach to analyse the deformation of the left ventricle of the heart based on a parametric model that gives a compact representation of a set of points in a 3-D image. We present a strategy for tracking surfaces in a sequence of 3-D cardiac images. Following tracking, we then infer quantitative parameters which characterize: left ventricle motion, volume of left ventricle, ejection fraction, amplitude and twist component of cardiac motion. We explain the computation of these parameters using our model. Experimental results are shown in time sequences of two modalities of medical images, nuclear medicine and X-ray computed tomography (CT). Video sequences presenting these results are on the CD-ROM.

Computer Simulation↗
PubMed1994

A comparison of J and W pouches using an isolated ileal reservoir in pigs.

A new model for studying ileal reservoirs was used to compare J and W pouches. Sixteen female piglets were operated on between 62 and 67 days of age (median = 65). An approximately 50 cm vascularized segment of terminal ileum was isolated from the faecal stream and intestinal continuity restored. The distal 40 cm of the isolated loop was opened along its antimesenteric border and the pouch constructed (J = 8, W = 8). The remaining proximal length of ileum was brought out through the abdominal wall as a mucous fistula. One piglet in the W pouch group died post-operatively and in another, spontaneous closure of the mucous fistula prevented access to the W pouch for testing leaving six W and eight J pouches for comparison. Compliance was tested at 4 weeks by measuring intrapouch pressure during continuous distension by water. The volumes instilled at pressures of 20, 40, 60 and 80 cm of water were compared using the Mann-Whitney U-Test. Volumes varied widely at all pressures within both study groups although W pouches tended to be of larger volume for any given pouch pressure (P = NS). The failure of this study to demonstrate more clearly a difference between J and W pouches may be due to the small numbers involved but the wide range of volumes seen raises doubts about the usefulness of this pouch model.

Anastomosis, Surgical↗
PubMed1990

Fractures of the osteoporotic spine.

Prior to fracture, the osteoporotic spine can be analyzed in several ways. After fracture occurs, however, a simple plain roentgenogram usually suffices to make the diagnosis of compression fracture. If severe deformity threatens, or if there is a neurologic lesion, the surgeon now has options not previously available. Open reduction, decompression, and internal fixation with polymethylmethacrylate can be carried out safely by surgeons with expertise in spinal instrumentation. Generally, symptomatic treatment is all that is required, and if this includes an orthosis, it is an individual decision which can probably be made without fear of harming the patient further. With treatment of the acute fracture undertaken, one proceeds to employ whatever pharmacologic treatment is appropriate. Last, the patient should be allowed only the briefest period of rest.

Fractures, Spontaneous↗
PubMedDate not supplied

Spontaneous transpyloric migration of a ballooned nasojejunal tube: a randomized controlled trial.

BACKGROUND: Spontaneous transpyloric migration of a simple nasojejunal tube (NJT) can be expected in only one-third of insertions. Guidance of the tube by radiologic or endoscopic maneuvers is usually required. We believed that locating a 5-mL balloon near the tip of an NJT on which natural peristalsis could act would improve the rate of spontaneous transpyloric migration and facilitate small bowel propagation. METHODS: Thirty healthy volunteers were randomly assigned to have an inflated or noninflated, ballooned NJT fashioned from a modified 9F Hickman line catheter inserted. The pH of aspirates was measured hourly and the final location of the tube assessed by gastrografin contrast abdominal x-ray (AXR) at the end of 6 hours, at which time the tube was removed. RESULTS: After 6 hours, spontaneous transpyloric migration occurred in 86.6% of the ballooned and 66.6% of the nonballooned tubes. The final disposition of the ballooned tubes was: stomach, 2 (13.3%); duodenum, 1 (6.7%); and small bowel, 12 (80%). The final disposition of the nonballooned tubes was: stomach, 5 (33%), NS; duodenum, 9 (60%), p < .05; and small bowel, 1 (6.7%), p < .05. CONCLUSIONS: Ballooned NJT have a higher rate of spontaneous transpyloric migration and are significantly more likely to achieve an optimal small bowel location.

Adolescent↗