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Biomedical subjects

P F van Waes

Publications and source records attributed to P F van Waes.

At least 19 recordsLinked to original sources
PubMed2001

Medullary cone movement in subjects with a normal spinal cord and in patients with a tethered spinal cord.

PURPOSE: To compare movement of the normal medullary cone when the patient has changed from a supine to prone position with that in patients with known or suspected tethered spinal cord syndrome. MATERIALS AND METHODS: Fifty-six individuals divided into three groups were examined with lumbar spine magnetic resonance (MR) imaging performed with the patient in the prone and supine positions. Group 1 consisted of 15 healthy volunteers and six patients with a herniated disk; group 2, 25 patients clinically suspected of having a tethered cord; and group 3, 10 patients who previously had undergone tethered cord surgery. RESULTS: All group 1 subjects showed distinct and statistically significant medullary cone movement (range, 21%--41%); no patient in group 3 showed movement (Wilcoxon rank sum test, P <.001). In group 2, the 20 patients in whom a definite diagnosis of tethered cord syndrome was made on the basis of initial supine MR image findings showed no movement, whereas two of five patients with normal supine MR images had abnormal and decreased cone movement at prone imaging. CONCLUSION: Prone MR imaging has no additional value when the supine MR image has clearly shown the cause of tethering or in patients who have undergone tethered cord surgery, but it can provide additional information in patients clinically suspected of having a tethered cord and in whom supine MR imaging depicted no abnormalities.

Adolescent↗
PubMed2000

Antegrade ureteral stent placement: positioning without use of a retraction string.

PURPOSE: To evaluate a simple method of antegrade ureteral stent insertion allowing optimal positioning of the stent without the use of a retraction string. PATIENTS AND METHODS: Seventeen stents were placed in sixteen patients with ureteral obstruction. Materials included a long vascular introducer sheath and radiopaque markers on the tips of both the sheath and the pusher catheter. For optimal positioning of the proximal pigtail in the renal pelvis, the distal end of the sheath was used to hold a large portion of the pigtail in the extended state prior to its deployment. RESULTS: All stent placements were successful. In one case, the tip of the proximal pigtail was caught in a lower-pole calix. In another case, repeat stent placement was necessary because of recurrent stricture several months after removal of the first stent. All stents functioned properly, as demonstrated by follow-up nephrostography 2 or 3 days after each procedure. CONCLUSION: The insertion method we describe is simple, easy to perform, and fast and avoids the risks associated with the use of a retraction string.

Adult↗
PubMed1996

Lenticular system: full-color, limited-angle, autostereoscopic alternative to holography.

The microlenticular system is a method of hard copy imaging that provides stereoscopic cues without the use of special glasses or viewing devices. Therefore, it is called an autostereoscopic technique. The microlenticular system consists of a layer of cylindric lenses combined with a photographic emulsion that carries three to seven different two-dimensional views of the same three-dimensional (3D) scene. Since each of the observer's eyes sees a different view, the resulting image is perceived as being 3D. The microlenticular system technique can be traced back to 1908 but was recently revived because of inventions that allow automatic photographic printing of this type of hard copy. The technique has been applied to visualization of medical 3D images obtained with the following modalities: computed tomography (CT), magnetic resonance imaging, single photon emission CT, ultrasound, scanning electron microscopy, laser scanning, and confocal laser microscopy. Use of this technique results in images suitable for planning complex surgery and for simplifying the communication of complex geometries in science and education.

Diagnostic Imaging↗
PubMed1996

Screening for bronchiectasis. A comparative study between chest radiography and high-resolution CT.

STUDY OBJECTIVE: The aim of our study was to investigate whether in the search for bronchiectasis a correlation exists between abnormalities on the chest radiograph and high-resolution CT (HRCT), and if HRCT has an additional value when the chest radiography is normal. SUBJECTS AND METHODS: In a prospective study, chest radiographs were compared with HRCT in 84 patients. Analysis of presence and extent of bronchiectasis were made for each bronchopulmonary lobe. RESULTS: Thirty-seven patients had a normal radiograph, from whom 32 had a normal HRCT. The other 5 had a low HRCT severity score with a mild cylindrical bronchiectasis. From the 47 patients with an abnormal radiograph, 36 had signs of bronchiectasis at HRCT; 11 patients, however, had a normal HRCT. The sensitivity for chest radiography to detect bronchiectasis appeared to be 87.8% with a specificity of 74.4%. We found a significant linear relationship between the severity of bronchiectasis at HRCT and abnormalities as seen on the chest radiograph (r=0.62, p=0.0001). CONCLUSION: A normal chest radiograph almost always excludes relevant bronchiectasis and no further investigation seems necessary. There is a significant linear relationship between the severity of bronchiectasis at HRCT and abnormalities as seen on the chest radiograph.

Adult↗
PubMed1995

Radiation exposure in standard and high-resolution chest CT scans.

It has been suggested that radiation doses due to high-resolution computed tomography (HRCT) of the chest are considerably higher than those from conventional CT. We compared the effective dose (E, mSv) in conventional chest CT (10-mm contiguous slices) and HRCT (1.5-mm slices, gap 10 mm). In our study, the effective dose from a HRCT (0.98 mSv) is about 6.5 times less than the effective dose from a standard CT scan (6.5 mSv), and only a factor 12 higher than from a conventional chest examination (0.085 mSv).

Humans↗
PubMed1994

Cerebral visual impairment in cerebral palsy: relation to structural abnormalities of the cerebrum.

In patients with cerebral palsy (CP), cerebral visual impairment (CVI) is frequently found in addition to ophthalmological disorders. Lesions in the visual areas are found in CT scans of CP patients with CVI. The aim of the present study was to determine the prevalence of these specific findings in CP patients with CVI. CT scans of 49 cerebral palsy patients were studied; CVI was diagnosed in 36 patients; in 13 patients, visual acuity was normal. In 8 patients, comparison with an MRI scan was possible (6 with CVI, 2 with normal acuity). The CT scans were scored according to the criteria used by Van Nieuwenhuizen (1987): normal, abnormalities of the white matter adjacent to the posterior horns of the lateral ventricles, abnormalities of the white matter located under the visual cortex, abnormalities of the visual cortex and abnormalities elsewhere. Abnormalities in the visual areas were found in 15% of the normal acuity group and in 53% of the CVI group. In 17 of the 19 CVI patients with abnormalities in the visual areas, the lesions were located in the white matter surrounding the posterior horns (89%). MRI imaging revealed the same abnormalities as the CT scans in 6 patients, but in one patient the abnormality was seen in more detail and in one patient the lesion in the occipital area was seen only on MRI. MRI examination seems to detect at least as many, but in some cases even more specific lesions in CVI patients compared to CT scanning, but the numbers were too small to allow any definitive conclusions to be drawn.

Adolescent↗
PubMed1993

[Selection of medical residents for medical specialist education: experiences with a structured procedure].

OBJECTIVE: Evaluation of an objective, standardised method for selection of residents for medical specialty training. DESIGN: Retrospective. SETTING: University Hospital Utrecht, department of diagnostic radiology. Utrecht University, Department of Clinical Psychology and Health Psychology. METHODS: All applicants for residency positions in 1990-1991 were requested to complete a standard application form. The applications were judged by seven staff members on six criteria. Using statistical tests the relative contribution of each criterium was calculated. A similar procedure was followed for those who were invited for an interview. RESULTS: Most of the criteria applied for the written and oral applications contributed significantly to the rank order achieved. The written and oral criteria showed some degree of overlap, whilst the criteria used for the written application were relatively independent from those used for the interview. For a balanced evaluation of the written information a selection committee of four staff members was sufficient. CONCLUSION: Structuring the selection process as described gives both staff and applicants more insight in the criteria applied, and thus allows a more objective and valid evaluation. To medical students it is beneficial to become acquainted with criteria that may be used in selection procedures for medical specialty training, so they can prepare themselves adequately.

Education, Medical↗
PubMed1990

Assessment of survey radiography and comparison with x-ray computed tomography for detection of hyperfunctioning adrenocortical tumors in dogs.

Results of abdominal survey radiography and x-ray computed tomography (CT) were compared in 13 dogs with hyperadrenocorticism histologically attributed to adrenocortical tumors. X-ray computed tomography enabled accurate localization of the tumor in all 13 dogs. Apart from 2 poorly demarcated irregular-shaped and mineralized carcinomas, there were no differences between adenoma (n = 3) and carcinoma (n = 10) on CT images. In 1 dog, invasion of the caudal vena cava by the tumor was suggested on CT images and was confirmed during surgery. Suspicion of adhesions between tumors of the right adrenal gland and the caudal vena cava on the basis of CT images was confirmed during surgery in only 2 of 6 dogs. Survey radiography allowed accurate localization of the tumor in 7 dogs (4 on the right side and 3 on the left). In 6 of these dogs, the tumor was visible as a well-demarcated soft tissue mass and, in the other dog, as a poorly demarcated mineralized mass. The smallest tumor visualized on survey radiographs had a diameter of 20 mm on CT images. Six tumors with diameter less than or equal to 20 mm were not visualized on survey radiographs. In 1 of these dogs, a mineralized nodule was found in the left adrenal region, without evidence of a mass. In a considerable number of cases, survey radiography can provide presurgical localization of adrenocortical tumors in dogs with hyperadrenocorticism; CT is redundant in these instances. In the absence of positive radiographic findings, CT is valuable for localization of adrenocortical tumors.

Adenoma↗
PubMed1989

Comparison of Telebrix Gastro and Gastrografin in abdominal computed tomography.

Palatability as well as the side effects and computed tomographic image quality associated with the oral use of Telebrix Gastro (ioxithalamate) and Gastrografin (amidotrizoate) in bowel opacification were compared in a double-blind study involving 100 patients in a 24-hour protocol. There was a tendency (p = 0.07) for Telebrix Gastro to show greater palatability. The difference between the 2 groups in terms of patient discomfort was too small to reach statistical significance (p less than 0.09). There was no statistical difference between the agents with respect to image quality. In 87% of cases in both groups bowel filling was adequate.

Contrast Media↗
PubMed1988

Computed tomography in the diagnosis of canine hyperadrenocorticism not suppressible by dexamethasone.

Computed tomography (CT) was performed in 10 dogs with hyperadrenocorticism not suppressible by dexamethasone. In 6 of these dogs, a unilateral adrenal mass was found on CT images. Specimens of the masses were obtained via retroperitoneal laparotomy; histologic examination revealed 4 carcinomas, 1 adenoma, and 1 nodular hyperplasia. In the 4 other dogs, CT revealed symmetric bilateral adrenal gland enlargement. In 2 of these dogs, contrast-enhanced CT revealed a mass in the pituitary fossa, which could be identified at necropsy as a pituitary tumor. The other 2 dogs were successfully treated with mitotane.

Adrenal Cortex Function Tests↗
PubMed1987

Pancreatic lesions and transfascial perirenal spread: computed tomographic demonstration.

Computed tomographic (CT) findings in 105 cases of pancreatitis and 107 cases of pancreatic carcinoma were analyzed retrospectively to determine the occurrence and roentgenologic signs of penetration of the anterior renal fascial planes in relation to clinical symptoms. In pancreatitis, the perirenal fat was infiltrated in 7% to variable extents by extrapancreatic fluid collections, either as asymptomatic fluid lying alongside renal fascial planes and perirenal septa (5 cases) or as well-circumscribed fluid collections causing clinical symptoms (2 cases). In pancreatic carcinoma the occurrence of retropancreatic extension to a perirenal space was rarer (3%). Distinction on CT between perirenal involvement from the pancreas and primary adrenal or renal lesions with anterior spread can prevent unnecessary surgery.

Adenocarcinoma↗
PubMed1986

Direct coronal and direct sagittal CT of abdomen and pelvis: an approach to staging malignancies.

Direct coronal and sagittal CT images are of high quality and are applicable to a majority of patients in daily practice. Because of the fact that transverse scans alone can be misleading, direct CT images in two or more different planes greatly enhance one's capability to stage neoplasms that are complex and extensive. The integrity of the margins of an organ, in the presence of tumor, is best determined by coronal or sagittal scanning. Lesions of the adrenal and kidney and retroperitoneal processes with possible extension into liver or other adjacent organs can be evaluated best using the combination of transverse and coronal or sagittal scans of the upper abdomen. Depending on the origin of pelvic lesions, the radiologist must consider in every individual case the performance of either direct coronal or sagittal sections or both. This judgment is based on the findings on the transverse scans, understanding of anatomic relationships of the pelvic viscera and knowledge of staging systems and their implications with respect to therapeutic decisions. In such a tailored approach, multiplanar CT facilitates improved presurgical evaluation. In some cases, the true extent of the lesion can only be seen in the coronal or sagittal planes. A potential new role for direct multiplanar CT is that it may be used as a sort of "gold standard" for the analysis of multiplanar ultrasound and MRI studies.

Abdominal Neoplasms↗
PubMed1985

Computed tomography in complicated acute appendicitis.

Due to the position and length of the appendix, intraabdominal abscesses after perforation in complicated acute appendicitis may occur in several different and sometimes unsuspected anatomical locations. Five patients are described with proven complicated acute appendicitis and inflammatory processes in multiple sites: anterior pararenal space, general retroperitoneum, subcutaneous fat space, intraperitoneal cavity, and small bowel mesentery. A confusing case of ileocecal carcinoid with mesenteric involvement is also presented. In all cases complicated acute appendicitis was diagnosed on CT prior to surgery, except in 1 case in which a pelvic abscess developed after intramural cecal bleeding in a patient with hemophilia B.

Abdomen↗