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G A de Kort

Publications and source records attributed to G A de Kort.

7 recordsLinked to original sources
PubMed2001

Reduction of patient motion artifacts in digital subtraction angiography: evaluation of a fast and fully automatic technique.

The performance of an automatic technique for the reduction of patient motion artifacts in digital subtraction angiography was evaluated. Four observers assessed the quality of 104 cerebral digital subtraction angiographic images that were processed by means of both the automatic technique and manual pixel shifting. The automatic technique resulted in better image quality and was considerably less time-consuming.

Adult↗
PubMed2000

Proton magnetic resonance spectroscopy of temporal lobe white matter in patients with histologically proven hippocampal sclerosis.

The purpose of this study was to assess temporal lobe white matter changes accompanying hippocampal sclerosis on magnetic resonance (MR) imaging using single-voxel 1H MR spectroscopy and to strengthen the hypothesis that these white matter changes are caused by myelin alterations. In 11 patients with histologically proven hippocampal sclerosis, preoperative coronal fluid-attenuated inversion recovery images were visually assessed by two experienced neuroradiologists for hippocampal signal increase and size decrease, atrophy of collateral white matter, and temporal lobe gray/white matter demarcation loss. Single-voxel 1H MR spectroscopy of the white matter of each anterior temporal lobe was also performed, excluding the amygdala and hippocampus. The N-acetyl-aspartate (NAA)/choline and NAA/creatine ratios were calculated. In 12 healthy volunteers both temporal lobes were spectroscopically examined. In all patients the excised hippocampi were histologically assessed for the presence of sclerosis, and the excised neocortical temporal lobes were examined for gray and white matter abnormalities. MRI abnormalities were found on the right in six patients, on the left in four, and one scan was normal. Hippocampal signal increase was seen in nine patients, hippocampal size decrease in ten, atrophy of collateral white matter in nine, and gray/white matter demarcation loss in six. A significant decrease in the NAA/choline ratio was found in temporal lobe white matter ipsilateral to the pathologic hippocampus (symptomatic side), compared with the contralateral, asymptomatic side (P < 0.01), and also compared with controls (P < 0.001). The ipsilateral NAA/creatine ratio was also significantly decreased (P < 0.05) compared with the contralateral side and the control subjects (P < 0.001). Histological examination showed hippocampal sclerosis to a different degree in all patients. Neither gliosis nor cortical dysplasia was found in the ipsilateral, symptomatic temporal lobe. Significant decrease in the mean of NAA/choline ratios is found in temporal lobe white matter of patients with histologically confirmed hippocampal sclerosis. As this indicates neuronal loss or dysfunction, the number of axons may be reduced, with associated decrease in myelin density.

Adult↗
PubMed1999

Relevance of temporal lobe white matter changes in hippocampal sclerosis. Magnetic resonance imaging and histology.

RATIONALE AND OBJECTIVES: To evaluate the diagnostic relevance of ipsilateral atrophy of the collateral white matter in the parahippocampal gyrus (ACWMp) and temporal lobe gray/white matter demarcation loss (GWDL) on magnetic resonance imaging in patients with histologically confirmed hippocampal sclerosis. In the second part of this investigation, histologic specimens were analyzed to find an explanation for GWDL. METHODS: Retrospective visual assessment of hippocampal signal intensity and size and of ACWMp and GWDL was performed using 4- to 5-mm coronal T2-weighted spin-echo magnetic resonance images of 80 patients with histologically proven hippocampal sclerosis and of 30 age-matched controls without epilepsy. Frequency of occurrence and likelihood ratios of ACWMp and GWDL were calculated and their contribution to the diagnosis of hippocampal sclerosis was assessed, particularly in patients with no or restricted hippocampal abnormalities (either high signal or smaller size) on magnetic resonance imaging. The second part of the study involved the morphologic histologic assessment of neocortical temporal lobe specimens of all patients. Myelin density was evaluated in specimens of a subgroup of six patients with hippocampal sclerosis and GWDL on MRI and six patients with hippocampal sclerosis without GWDL. RESULTS: ACWMp was found in 68% and GWDL in 65% of patients with hippocampal sclerosis on magnetic resonance imaging. Both features had an infinite positive likelihood ratio. Sixty-two patients (77.5%) had concomitant hippocampal signal increase and smaller size. Eighteen patients (22.5%) had no or restricted hippocampal abnormalities on magnetic resonance imaging. When using ACWMp and GWDL as additional diagnostic parameters, 13 of these 18 patients were more unambiguously diagnosed as having hippocampal sclerosis. No significant morphologic differences were found between GWDL-positive and GWDL-negative specimens. A significantly lower average myelin stain was found in the white matter of the GWDL-positive group compared to the GWDL-negative group. CONCLUSIONS: ACWMp and GWDL can improve the visual diagnosis of hippocampal sclerosis, particularly in patients with no or restricted hippocampal abnormalities. These results suggest that loss of myelin may be the underlying cause of GWDL in association with hippocampal sclerosis.

Adolescent↗
PubMed1998

Renal artery stenosis and accessory renal arteries: accuracy of detection and visualization with gadolinium-enhanced breath-hold MR angiography.

PURPOSE: To determine the accuracy of gadolinium-enhanced breath-hold magnetic resonance (MR) angiography in the diagnosis of renal artery stenosis and visualization of accessory renal arteries. MATERIALS AND METHODS: Forty-four patients suspected of having renal artery stenosis and 10 potential kidney donors, all of whom were scheduled to undergo elective intraarterial digital subtraction angiography (DSA), were studied. Three-dimensional gradient-echo gadolinium-enhanced MR angiography was performed at 1.5 T with the following parameters: repetition time, 13.5 msec; echo time, 3.5 msec; flip angle, 60 degrees; 195 x 512 matrix; 400-mm field of view; and 6-cm imaging volume consisting of 15 4-mm-thick partitions reconstructed every 2 mm. Gadopentetate dimeglumine (30 mL) was injected with a power injector. MR angiograms were assessed before the standard of reference, intraarterial DSA, was performed. RESULTS: Four MR angiograms were not evaluable because of poor image quality. MR angiography enabled visualization of all but one of the 121 arteries. In four small accessory arteries, a stenosis could not be excluded owing to inadequate spatial resolution. MR angiography enabled the correct diagnosis in 30 of the 31 arteries with a grade 2 (50%-99%) stenosis and in seven of the 10 occluded arteries. Sensitivity and specificity for correct identification of a grade 2 stenosis were 97% and 92%, respectively. CONCLUSION: Gadolinium-enhanced MR angiography is an accurate, minimally invasive method for detecting renal artery stenosis and is reliable for visualizing accessory renal arteries.

Adult↗
PubMed1997

Assessment of the preferred plane and sequence in the depiction of mesial temporal sclerosis using magnetic resonance imaging.

RATIONALE AND OBJECTIVES: Definition of optimal magnetic resonance (MR) scanning plane and conventional MR sequence for the detection of mesial temporal sclerosis (MTS). METHODS: Coronal and axial T2-weighted images and axial T2-weighted images parallel to the long axis of the hippocampus (APLAH) and coronal inversion recovery (IR) images were obtained in patients with medically intractable temporal lobe epilepsy in their phase 1 preoperative evaluation. Thirty-three consecutive MR scans were reviewed by a panel of three radiologists. Twenty-three patients had MR abnormalities consistent with MTS, and ten scans were normal. To assess the best single scanning technique, another group of three radiologists, who were masked to all patient data, individually assessed the different planes and sequences of the 33 studies presented separately in a random fashion. For each plane and sequence, the likelihood (L) ratio for the correct diagnosis was determined separately. RESULTS: For all planes considered separately, a likelihood ratio of 4.4 was optimal for the coronal T2-weighted images. The likelihood ratio of APLAH T2 was 2.2; of axial T2, 3.9; of coronal IR, indefinite because of 100% specificity. CONCLUSIONS: For the assessment of MTS, coronal T2-weighted images were considered the best single scanning technique.

Adolescent↗
PubMedDate not supplied

Duplex ultrasonography in assessing restenosis of renal artery stents.

PURPOSE: To determine the accuracy and optimal threshold values of duplex ultrasonography (US) in assessing restenosis of renal artery stents. METHODS: Twenty-four consecutive patients with 33 renal arteries that had previously been treated with placement of a Palmaz stent underwent duplex US prior to intraarterial digital subtraction angiography (DSA), which was the reference standard. Diagnostic accuracy of in-stent peak systolic velocity (PSV) and reno-aortic ratio (RAR = PSV renal stent/PSV aorta) in detecting > 50% in-stent restenosis were evaluated by the receiver operating characteristic curve. Sensitivity and specificity were determined using the optimal threshold values, and using published threshold values: RAR > 3.5 and in-stent PSV > 180 cm/sec. RESULTS: Six examinations were technically inadequate. Nine stents had residual or restenosis > 50% at DSA. The two duplex parameters were equally accurate since areas under the curves were similar (0.943). With optimal threshold values of 226 cm/sec for PSV and 2.7 for RAR, sensitivities and specificities were 100% and 90%, and 100% and 84%, respectively. Using the published duplex criteria resulted in sensitivities and specificities of 100% and 74% for PSV, and 50% and 89% for RAR. CONCLUSION: Duplex US is a sensitive modality for detecting in-stent restenosis if laboratory-specific threshold values are used.

Aged↗