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Biomedical subjects

J P van Schaik

Publications and source records attributed to J P van Schaik.

18 recordsLinked to original sources
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↗
PubMed1999

Curvature of the lower lumbar facet joints: variations at different levels and relationship with orientation.

The curvature of the lower lumbar facet joints in the transverse plane was measured using an innovative computed tomographic approach, and its relationship with the orientation of the joints was evaluated. Two hundred three vertebral levels were examined in 116 patients with low back pain. Reference circles were used to quantify joint curvature. The mean curvature (+/- SD) at the levels L3-L4, L4-L5, and L5-S1 conformed to circles of 27.3 mm +/- 11.5; 35.1 mm +/- 14.6; and 51.0 mm +/- 34.5 in diameter respectively. The ratio between the curvature of the facets and their orientation was 62.6% +/- 19.0; 57.8% +/- 21.6; and 64.9% +/- 48.9. From L3-L4 down to L5-S1 the curvature of the facet joints decreases. The differences between L3-L4 and L4-L5 is smaller than between L4-L5 and L5-S1. The curvatures of the joints conform to circles that are in mean approximately 40% in diameter smaller than those to which their orientations conform.

Anthropometry↗
PubMed1997

The facet orientation circle. A new parameter for facet joint angulation in the lower lumbar spine.

STUDY DESIGN: A descriptive quantitative evaluation was done of the transverse orientation of the lower lumbar facet joints as measured by computed tomography scanning. OBJECTIVES: To evaluate a new parameter for facet joint angulation in the transverse plane (the "facet orientation circle") and to obtain reference values for this new parameter. SUMMARY OF BACKGROUND DATA: In other studies, both in vitro and in vivo, the angulation of the facet joints has been measured in degrees relative to the frontal or sagittal plane. These methods have some limitations. The parameter used in the present study has not been described in the literature. METHODS: Lower lumbar facet joint orientation was measured in 212 vertebral levels of 123 consecutive patients using the facet orientation circle parameter. Patients with degenerative or developmental abnormalities of the lumbar spine were excluded, as were those with technically inadequate computed tomography studies. RESULTS: Mean facet orientation circle diameters (+/-SD) were: L3-L4, 43.7 +/- 10.5 mm; L4-L5, 63.8 +/- 26.4 mm; and L5-S1, 82.3 +/- 23.5 mm. Differences between right and left sides were: L3-L4, 6.3 +/- 7.1 mm; L4-L5, 13.9 +/- 25.3 mm; and L5-S1, 17.9 +/- 16.2 mm, intra-observer variability was 2.3%. CONCLUSIONS: Measurement of facet joint angulation using the facet orientation circle is possible and reproducible. The morphometric data presented may be useful as a reference for biomechanical and clinical research of facet joint orientation and asymmetry.

Adolescent↗
PubMed1997

Iodine-131 therapy in sporadic nontoxic goiter.

UNLABELLED: The effect of radioiodine in the treatment of nontoxic goiter is seldom evaluated quantitatively. The aim of this study was threefold: (a) to assess the effect of 131I on goiter volume, (b) to establish a relationship between CT volume reduction and the amount of radioactivity taken up by the thyroid and (b) to assess the precision of scintigraphic thyroid volume measurements. METHODS: In 27 patients with sporadic nontoxic goiter, the thyroid volume was estimated from a [99mTc]pertechnetate scintigram. Two different models (cylinder model and surface model) were applied. The 131I dosage varied between 507 and 3700 MBq. In all patients, noncontrast CT scanning of the neck was performed before therapy and 1 yr after therapy. RESULTS: The mean CT thyroid volume before therapy was 194 +/- 138 ml. A reduction was obtained in all patients and averaged 34% +/- 17%. The volume reduction measured by CT correlated well with the amount of 131I in the thyroid (r = 0.70). In thyroids larger than 200 ml, both scintigraphic volume estimation methods were imprecise. For smaller volumes, the surface model was superior. Hypothyroidism developed in 14% of the patients. No other side effects occurred. CONCLUSION: Iodine-131 therapy for volume reduction in nontoxic goiter is a safe and effective treatment. For scintigraphic estimation of thyroid gland volumes smaller than 200 ml, the surface model is preferred.

Adult↗
PubMed1996

Atherosclerotic renal artery stenosis: ostial or truncal?

PURPOSE: To evaluate a discrepancy between the location of renal artery stenoses on intraarterial digital subtraction angiographic (DSA) images and that on spiral computed tomographic (CT) angiograms. MATERIALS AND METHODS: The spiral CT angiograms and intraarterial DSA images of 40 consecutive patients with atherosclerotic renal artery stenoses were examined retrospectively. Stenoses were classified as truncal or ostial. The atherosclerotic changes in the abdominal aorta were graded. RESULTS: Fifty-eight stenoses were demonstrated. In 48 ostial stenoses, there was no discrepancy in the location of the stenoses on spiral CT angiograms and DSA images. In 10 patients, spiral CT angiography showed an ostial lesion, whereas DSA demonstrated an apparent truncal lesion. Most of these stenoses ("pseudotruncal" ostial stenoses) were in patients with severe aortic atherosclerotic disease. CONCLUSION: A renal artery stenosis at or within 10 mm of an atherosclerotic aorta at DSA may be diagnosed as an ostial stenosis.

Adult↗
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↗
PubMed1992

Pulmonary amyloidoma. Histologic proof yielded by transthoracic coaxial fine needle biopsy.

Nodular pulmonary amyloidosis was diagnosed by percutaneous transthoracic fine needle biopsy specimen in an 88-year-old woman. Congo red staining should be performed whenever band-like hyalinized material is obtained on aspiration of a solitary nodule. Dense calcifications can occur in pulmonary amyloidomas. In selected cases, fine needle biopsy appears to be preferable to transbronchial forceps biopsy since the risk of a possibly life-threatening pulmonary hemorrhage may be lower.

Aged↗
PubMed1991

[Balloon embolization of a large carotid-cavernous fistula].

A 58-year-old male patient with a giant carotid-cavernous fistula was treated by means of endovascular balloon embolisation. The fistula was closed, and good antegrade flow in the carotid artery and intracranial vessels was obtained. Based on this case history, the pathophysiology, ultrasonographic and angiographic evaluation and treatment options are reviewed.

Angiography, Digital Subtraction↗
PubMed1990

Antegrade puncture of the femoral artery: morphologic study.

To determine the optimal site for antegrade puncture of the femoral artery, the authors evaluated three cadaver specimens and computed tomographic (CT) scans of 50 patients. The relationships among the common femoral artery, the femoral artery bifurcation, the center of the femoral head, and the inguinal ligament were evaluated. CT showed that the center of the femoral head was always located caudal to the level of the inguinal ligament but cranial to the bifurcation of the common femoral artery. Therefore, the femoral head seems to provide a reliable landmark for entering the common femoral artery.

Femoral Artery↗
PubMed1985

Translumbar catheter redirection using a tip-deflector technique.

A new technique is described for reversing the direction of the catheter tip during translumbar aortography, without the need for partial withdrawal of the catheter from the aortic lumen. The method ensures optimal delivery of contrast medium at the desired level, while avoiding the risk of retroperitoneal bleeding or dislodgement during catheter manipulation.

Aortography↗
PubMedDate not supplied

Intraarterial pressure gradients after randomized angioplasty or stenting of iliac artery lesions. Dutch Iliac Stent Trial Study Group.

PURPOSE: To determine initial technical results of percutaneous transluminal angioplasty (PTA) and stent procedures in the iliac artery, mean intraarterial pressure gradients were recorded before and after each procedure. METHODS: We randomly assigned 213 patients with typical intermittent claudication to primary stent placement (n = 107) or primary PTA (n = 106), with subsequent stenting in the case of a residual mean pressure gradient of > 10 mmHg (n = 45). Eligibility criteria included angiographic iliac artery stenosis (> 50% diameter reduction) and/or a peak systolic velocity ratio > 2.5 on duplex examination. Mean intraarterial pressures were simultaneously recorded above and below the lesion, at rest and also during vasodilatation in the case of a resting gradient < or = 10 mmHg. RESULTS: Pressure gradients in the primary stent group were 14.9 +/- 10.4 mmHg before and 2.9 +/- 3.5 mmHg after stenting. Pressure gradients in the primary PTA group were 17.3 +/- 11.3 mmHg pre-PTA, 4.2 +/- 5.4 mmHg post-PTA, and 2.5 +/- 2.8 mmHg after selective stenting. Compared with primary stent placement, PTA plus selective stent placement avoided application of a stent in 63% (86/137) of cases, resulting in a considerable cost saving. CONCLUSION: Technical results of primary stenting and PTA plus selective stenting are similar in terms of residual pressure gradients.

Adult↗