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Biomedical subjects

J Stoker

Publications and source records attributed to J Stoker.

At least 91 records · Page 5Linked to original sources
PubMed1995

Anal sphincter complex: endoanal MR imaging of normal anatomy.

PURPOSE: To determine the normal anatomy of the anal sphincter complex on magnetic resonance (MR) images. MATERIALS AND METHODS: Ten healthy volunteers (four men, six women; age range, 21-26 years) underwent MR imaging with an endoanal coil. RESULTS: The lower part of the anal canal contained the internal sphincter, the longitudinal muscle layer, and the external sphincter; the upper part comprised the internal sphincter, the longitudinal layer, and the puborectal muscle. At the upper end, the puborectal muscle was attached to the levator ani muscle. Anteriorly, the external sphincter was connected to the urogenital diaphragm; posteriorly, it was attached to the coccyx with the anococcygeal ligament. All perianal spaces were visible. The morphology of the anterior part of the external sphincter, different in men and women, was well displayed. CONCLUSION: Depiction of the anal sphincter complex on MR images is excellent.

Adipose Tissue↗
PubMed1993

Percutaneously placed Wallstent endoprosthesis in patients with malignant distal biliary obstruction.

Seventy-five patients with malignant distal biliary obstruction were treated by percutaneously placed self-expandable Wallstent endoprostheses for palliative drainage. The stent diameter was 1 cm and its length 3.5-10.5 cm. Early complications occurred in 16 patients (21 per cent); they were related to the endoprosthesis in five (7 per cent) and serious in six (8 per cent). The 30-day mortality rate was 15 per cent, with a 1 per cent procedure-related mortality rate. Sixty-five patients died 6-365 (median 87) days after stent insertion and four had recurrence of obstruction after 21-341 (median 152) days. Reobstruction was the result of tumour ingrowth in one patient, angling of the stent in one and an unestablished cause in two. Ten patients were alive without obstruction 31-383 (median 65) days after stent insertion. Percutaneous use of the Wallstent endoprosthesis allows easy insertion; reobstruction is rare.

Adult↗
PubMed1992

[Percutaneous bile duct drainage; experiences with a new type of endoprosthesis].

Self expandable stents were placed percutaneously in 105 patients with malignant biliary obstruction. Stent diameter was 1 cm; length, 3.5-10.5 cm. Of the 60 patients with common bile duct obstruction, 50 died 0.2-12 months (median 3 months) after stent insertion. Two patients developed recurrent jaundice and cholangitis after 6 and 12 months, respectively. One patient underwent reintervention. Ten patients, one after a successful reintervention, were alive without jaundice 1-8 months (median 5 months) after stent placement. Of the 45 patients with hilar lesions, 26 died 0.7-18 months (median 5 months) after stent placement, five of them with signs of cholangitis. Nineteen are alive 1-21 months (median 7 months) afterwards. Reinterventions were carried out in 13 patients (29%). The most common cause of stent malfunction was tumour overgrowth. Stent-related complications were seen in three patients.

Adult↗
PubMed1991

Malignant biliary obstruction: percutaneous use of self-expandable stents.

A total of 83 self-expandable metallic stents were placed percutaneously in 69 patients for palliation of malignant biliary obstruction. Stent diameter was 1 cm; length, 3.5-10.5 cm. Of the 41 patients with common bile duct obstruction, 27 died 0.2-12 months (median, 3.2 months) after stent insertion. Two patients developed recurrent jaundice and cholangitis after 6 and 12 months, respectively. One patient underwent reintervention. Fourteen patients were alive without jaundice 1-8 months (median, 6.3 months) after stent placement. Of the 28 patients with hilar lesions, 13 died 0.7-7.6 months (median, 4.3 months) after stent placement. Fifteen were alive 1-15.5 months (median, 8.1 months) afterward. Recurrent jaundice and cholangitis were seen in eight of the 28 patients (28%) after 1-6 months (median, 3.6 months). The cause of malfunction of the stent(s) was tumor ingrowth in one patient, tumor overgrowth at the proximal end in five patients, and overgrowth at the distal end in two patients. Reintervention was performed in five patients (18%). Stent-related complications were seen in four patients.

Adult↗
PubMed1987

Non-surgical palliative treatment of patients with malignant biliary obstruction--the place of endoscopic and percutaneous drainage.

Non-surgical methods to treat patients with inoperable malignant biliary obstruction are endoscopic retrograde biliary drainage and ultrasound guided percutaneous transhepatic biliary drainage. During a 2 year evaluation a total of 144 patients were admitted with malignant biliary obstruction: 93 with a mid- or distal common bile duct stenosis; 51 patients with a perihilar stenosis. Endoscopic biliary drainage was performed in 123 patients and ultrasound guided percutaneous biliary drainage in 57 patients. An effect on jaundice was seen in more patients after percutaneous biliary drainage (91%) than with endoscopic biliary drainage (70%). However with the percutaneous method only 63% of patients were drained internally. The site of the stenosis seemed to be an important factor. In patients with perihilar obstruction early complications after endoscopic biliary drainage occurred in 41% of drained patients compared with 3% procedure-related and 28% catheter-related complications with ultrasound guided drainage. A major complication of the endoscopic method in perihilar disease was cholangitis due to inadequate drainage.

Adenoma, Bile Duct↗
PubMedDate not supplied

Colorectal cancer screening and surveillance with CT colonography: current controversies and obstacles.

Computed tomographic (CT) colonography has been advocated as an alternative colorectal screening method because studies in populations with a high prevalence of polyps have demonstrated that sensitivity for patients with large (> or =10 mm) polyps is generally high (approximately 90%). In three recent studies in low-prevalence populations, however, these values vary from 55% to 94%. Many questions have been raised as to the cause of this remarkable variability, which hampers the implementation of CT colonography in colorectal cancer screening and surveillance. We provide an overview of some potential causes and discuss the available, often indirect, evidence. In addition, several other obstacles that may influence implementation are discussed. Many differences between the study with high sensitivity (94%) and the two studies with low sensitivity (55% and 64%) exist: the primary method to review the data (two or three dimensional), bowel preparation (with or without oral contrast agents), study design (verification method and analysis of adenomas only), reader's experience, and scanning technique (single vs. multislice, thin vs. thick sections). Additional obstacles for implementation in prevention of colorectal cancer may be controversial results concerning patient acceptance, the large-scale use of ionizing radiation, difficulties in detecting flat adenomas, and extracolonic findings. Use of primary three-dimensional review methods, addition of oral contrast agents to bowel preparation, and endoscopic verification of false-positive results on CT colonography are speculated to have a positive influence on sensitivity. Future investigations should demonstrate the influence of these potential factors on sensitivity of CT colonography. Despite a growing body of evidence, it remains uncertain to what extent patient acceptance, radiation issues, flat lesions, and extracolonic findings will be a stumbling block to using CT colonography for colorectal cancer screening.

Adenoma↗
PubMedDate not supplied

Perceptive errors in CT colonography.

Published results to date have indicated a good per patient sensitivity of computed tomographic colonography (CTC) for colorectal cancer and for polyps measuring 10 mm or more together with a very good specificity. Sensitivity and specificity for polyps in the range of 6-10 mm are moderate. These results, however, can be achieved only with meticulous attention to technique including adequate colonic distention, and acquisition of supine and prone thin-section computed tomographic (CT) images. Moreover, there is a significant learning curve involved in the interpretation of CTC studies, with performance statistics improving with operator experience. Radiologists must be comfortable in reporting directly from workstation monitors and have access to and be familiar with software for multiplanar and endoluminal reconstructions. In addition to maximize polyp detection and minimize false positive results, reporting radiologists must have a working knowledge of normal colorectal anatomy and pathology on CTC and be familiar with potential pitfalls in interpretation. Besides the description of several possible causes for perceptive errors, also a literature search of perceptive errors in CTC is included in this paper.

Algorithms↗
PubMedDate not supplied

Percutaneous metallic self-expandable endoprostheses in malignant hilar biliary obstruction.

Forty-five patients with malignant hilar obstruction were treated with a total of 68 percutaneously inserted metallic self-expandable endoprostheses (Wallstents) for palliative biliary drainage. The stent diameter was 1 cm; the length was 3.5 to 10.5 cm. Early complications occurred in seven patients (16%), including cholangitis in four patients (9%). The 30-day mortality rate was 9%, with two procedure-related deaths (4%). Of the 45 patients, 29 died between 10 and 550 days (median, 126 days) after stent insertion. Reobstruction occurred in 13 of these patients after 26 to 184 days (median, 105 days). Sixteen patients were alive 44 to 737 days (median, 305 days) after stent insertion. Reobstruction occurred in four patients after 142 to 279 days (median, 246 days). The cause of reobstruction was proximal overgrowth in seven patients; distal overgrowth in four patients; and tumor ingrowth and proximal overgrowth, tumor ingrowth, hemobilia, and angling of the stent in one patient each. The cause of reobstruction was not established in two patients. Reintervention was performed in 14 patients (31%). Because reobstruction of Wallstent endoprostheses is primarily not stent-related but rather is caused by tumor progression, and because insertion and reintervention is easier, we consider the use of the Wallstent in malignant hilar biliary obstruction advantageous in comparison with plastic stents.

Adenoma, Bile Duct↗
PubMedDate not supplied

Complications of percutaneously inserted biliary Wallstents.

PURPOSE: Complications were assessed during and after percutaneous Wallstent endoprosthesis insertion in patients with inoperable malignant biliary obstruction. PATIENTS AND METHODS: Two hundred seven Wallstents were inserted in 176 patients: 74 had hilar strictures and 102 had distal strictures. Median survival after stent placement was 95 days. RESULTS: Early complications occurred in 12 patients (7%), predominantly cholangitis and reobstruction. Thirty-day mortality was 12%; 2% of deaths (three patients) were procedure related. Late complications, predominantly reobstruction, occurred in 35 patients (20%). Obstruction recurred in 33 patients (19%) after a median period of 135 days; 27 had a hilar stricture. Tumor overgrowth was the major cause of reobstruction (n = 19), especially proximal overgrowth. Tumor ingrowth caused reobstruction in three patients. Other causes were rare. No reobstruction due to sludge occurred. Reintervention was performed in 25 patients. Nineteen of the 25 patients benefited from repeated intervention. CONCLUSION: The use of the Wallstent is preferable to use of a plastic stent, as the major complication--reobstruction--is not stent related predominantly but is caused by tumor progression.

Adult↗
PubMedDate not supplied

Dixon quantitative chemical shift MRI for bone marrow evaluation in the lumbar spine: a reproducibility study in healthy volunteers.

PURPOSE: The purpose of this work was to explore the reproducibility of fat-fraction measurements using Dixon quantitative chemical shift imaging (QCSI) in the lumbar spine (L3, L4, and L5) of healthy volunteers. METHOD: Sixteen healthy volunteers were examined at 1.5 T two times to obtain a repeated measurement in the same slice and a third time in three parallel slices. Single slice, two point Dixon SE (TR/TE 2,500/22.3) sequences were used, from which fat-fraction images were calculated. The fat-fraction results are presented as averages over regions of interest, which were derived from the contours of the vertebrae. Reproducibility measures related to repeated measurements on different days, slice position, and contour drawing were calculated. RESULTS: The mean fat fraction was 0.37 (SD 0.08). The SD due to repeated measurement was small (sigmaR = 0.013-0.032), almost all of which can be explained by slice-(re)-positioning errors. CONCLUSION: When used to evaluate the same person longitudinally in time, Dixon QCSI fat-fraction measurement has an excellent reproducibility. It is a powerful noninvasive tool in the evaluation of bone marrow composition.

Adipose Tissue↗
PubMedDate not supplied

Endoluminal MR imaging of the rectum and anus: technique, applications, and pitfalls.

Anorectal diseases (e.g., fecal incontinence, perianal and anovaginal fistulas, anorectal tumors) require imaging for proper case management. Endoluminal magnetic resonance (MR) imaging has become an important part of diagnostic work-up in such cases. Optimal endoluminal MR imaging requires careful attention to patient preparation, imaging protocols, and potential pitfalls in interpretation. Comfortable positioning and the use of an antiperistaltic drug are vital for adequate patient preparation. Selected sequences and imaging planes are used in imaging protocols tailored for specific diseases. In fecal incontinence, three-dimensional sequences allow detailed demonstration of the anal anatomy and related defects. In perianal and anovaginal fistulas, longitudinal imaging planes help determine the superior extent of the abnormality. In anorectal tumors, T1-weighted turbo spin-echo MR imaging can help detect extension into the perirectal fat and T2-weighted turbo spin-echo MR imaging is used to optimize contrast between tumor and the rectal wall. Off-axis and radial imaging planes are used in all anorectal diseases to minimize partial volume effects. Potential pitfalls include various parts of the normal anal anatomy mimicking sphincter defects, veins and hemorrhoids mimicking fistulas and abscesses, and overhanging tumor mimicking more extensive tumor. Adequate patient preparation combined with proper technique and a knowledge of potential pitfalls will allow optimal endoluminal MR imaging of the rectum and anus.

Anus Diseases↗
PubMedDate not supplied

Metal stents for malignant biliary obstruction.

The main problem in the palliative treatment of malignant biliary obstruction is recurrent jaundice and cholangitis due to clogging of the endoprostheses. Large-bore metal stents, which can be placed using small-sized delivery systems, have been recognized as an important gain. Their use has facilitated the percutaneous drainage procedure. The long-term patency rates of both endoscopically and percutaneously placed metal stents seem to be better than those of conventional stents. Although the long-term economical aspects are in favor of metal stents due ot the decreased need for readmissions and reinterventions, the high initial costs of metal stents constitute the main obstacle to their wide-spread use.

Alloys↗