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M S van Leeuwen

Publications and source records attributed to M S van Leeuwen.

At least 19 recordsLinked to original sources
PubMed2006

Anatomic variations in the circle of Willis in patients with symptomatic carotid artery stenosis assessed with multidetector row CT angiography.

PURPOSE: To assess the presence of anterior and posterior collateral pathways in the circle of Willis in patients with symptomatic carotid artery stenosis (SCAS) and to compare this to patients without carotid artery stenosis. MATERIALS AND METHODS: Multislice CT angiography was performed in 91 patients and 91 control subjects. Using consensus reading, 2 observers evaluated the presence and diameter of the anterior communicating artery (AcomA), the A1 segments of the anterior cerebral arteries, the posterior communicating arteries (PcomA) and the P1 segments of the posterior cerebral arteries. Anterior or posterior pathways were assumed to be present if the diameter of continuous arterial segments was >1 mm; both A1 segments and AcomA anterior, and ipsilateral P1 segment and PcomA posterior. Comparison between patients and controls was performed using the chi(2) test. RESULTS: In the patients we found significantly more hypoplastic (<1 mm) or invisible A1 segments (16 and 14 vs. 4 and 1, respectively, p < 0.01). The AcomA was invisible in 4 patients versus 1 control. An isolated compromised anterior pathway and a combined compromised anterior and posterior pathway occurred more frequently in the patients as compared to the controls; 9 versus 1% (p < 0.01) and 26 versus 4% (p < 0.01). CONCLUSION: A compromised anterior collateral pathway, usually combined with a compromised posterior pathway, occurs more frequently in patients with SCAS as compared to controls, which suggests a relation between symptomatic carotid stenosis and an incomplete circle of Willis.

Adult↗
PubMed2006

Imaging and treatment of patients with colorectal liver metastases in the Netherlands: a survey.

BACKGROUND: Clinical experience has highlighted the absence of a uniform approach to the management of patients with colorectal liver metastases in the Netherlands. METHODS: A written survey on the diagnosis and treatment of patients with colorectal liver metastases was sent to all 107 chairmen of oncology committees in each hospital. Questions were asked concerning: specialists involved in decision-making, availability and existence of guidelines and meetings, factors that needed to be improved, information regarding the diagnostic work-up of liver metastases, detailed techniques of ultrasonography (US), computed tomography (CT), magnetic resonance imaging (MRI) and positron emission tomography (PET), factors influencing resectability, types of surgery performed, the use of (neo)adjuvant chemotherapy, portal vein embolisation performance, considering isolated hepatic perfusion (IHP) or local ablation as treatment options, actual performance of local ablation and the use of systemic as well as regional chemotherapy. RESULTS: Response rate was 68% (73/107). Specialists involved in the management were mostly surgeons (70), medical oncologists (66) and radiologists (42). Factors that needed to be improved, as indicated by responders, were the absence of 1) guidelines; 2) registration of patients and 3) guidelines for radiofrequency ablation (RFA). Diagnostic work-up of synchronous liver metastases occurred in 71 hospitals, (by US in 69 and by CT in 2). For the work-up of metachronous liver metastases, US was used as initial modality in 14, CT in 2 hospitals, and 57 hospitals used one or the other (mainly US). As additional modality, CT was performed (71) and to a lesser extent MRI (38) or PET (22). Diagnostic laparoscopy and biopsy were performed incidentally. The choice for an imaging modality was mostly influenced by the literature, and to a lesser extent by the availability and by costs, personnel and waiting lists. Substantial variation exists in the US, CT, MRI and PET techniques. The absence of extrahepatic disease and the clinical condition were considered as the most important factors influencing resectability. Surgery was performed in 30 hospitals; hemihepatectomy in 25, segment resection in 27, multisegment resection in 23, wedge excision in 27 and combination of resection and RF A in 18 institutions. In 52 hospitals (neo)adjuvant chemotherapy was administrated to improve surgical results, partly (35%) in trials. In nine hospitals portal vein embolisation was performed, with the volume of the remnant liver as the most important factor. Local ablative techniques were considered as a treatment option in 48 hospitals and actually performed in 16 hospitals, without clearly defined indications. Experimental IHP was considered a treatment option by 45 (62%) responders, irrespective whether this treatment was available at their centre. Patients with extensive metastases received systemic chemotherapy in all 73 hospitals and regional chemotherapy in ten hospitals. CONCLUSION: This survey shows substantial variation in the diagnostic and therapeutic work-up of patients with colorectal liver metastases. This variation reflects either under- or over-utilisation of diagnosis and treatment options. Evidence-based guidelines taking into account the available evidence, experience and availability can solve this variation.

Colorectal Neoplasms↗
PubMed2005

Level set based cerebral vasculature segmentation and diameter quantification in CT angiography.

A level set based method is presented for cerebral vascular tree segmentation from computed tomography angiography (CTA) data. The method starts with bone masking by registering a contrast enhanced scan with a low-dose mask scan in which the bone has been segmented. Then an estimate of the background and vessel intensity distributions is made based on the intensity histogram which is used to steer the level set to capture the vessel boundaries. The relevant parameters of the level set evolution are optimized using a training set. The method is validated by a diameter quantification study which is carried out on phantom data, representing ground truth, and 10 patient data sets. The results are compared to manually obtained measurements by two expert observers. In the phantom study, the method achieves similar accuracy as the observers, but is unbiased whereas the observers are biased, i.e., the results are 0.00+/-0.23 vs. -0.32+/-0.23 mm. Also, the method's reproducibility is slightly better than the inter-and intra-observer variability. In the patient study, the method is in agreement with the observers and also, the method's reproducibility -0.04+/-0.17 mm is similar to the inter-observer variability 0.06+/-0.17 mm. Since the method achieves comparable accuracy and reproducibility as the observers, and since the method achieves better performance than the observers with respect to ground truth, we conclude that the level set based vessel segmentation is a promising method for automated and accurate CTA diameter quantification.

Algorithms↗
PubMed2005

[Timing and choice of intervention in necrotising pancreatitis].

Three patients, men aged 49, 62 and 33 years, were admitted with acute abdominal symptoms due to necrotising pancreatitis. They underwent multiple interventions during a hospital stay of several months, but ultimately recovered completely. In case of infected (peri-)pancreatic necrosis, intervention is required. Good clinical judgement in the differentiation between the septic inflammatory-response syndrome, sepsis and infected necrosis as the cause of the clinical condition is important. Because of the different intervention strategies, treatment by a team comprising a radiologist, gastroenterologist, intensive care specialist and gastrointestinal surgeon is required. Randomised studies on intervention in infected pancreatic necrosis are lacking. In 2002, to improve the treatment of patients with acute (necrotising) pancreatitis via a combination of research, consultation and centralisation, the Dutch Acute Pancreatitis Study Group was formed.

Adult↗
PubMed2003

[Tumor growth during the waiting period for radiotherapy in patients with oropharyngeal carcinoma].

OBJECTIVE: To quantify the potential increase in tumour volume during the waiting time for radiotherapy in patients with oropharyngeal squamous cell carcinoma. DESIGN: Retrospective study. METHOD: The tumour volumes as assessed on the diagnostic CT scan and the planning CT scan were compared. Thirteen patients with oropharyngeal carcinoma were included in this study. Both their diagnostic CT scan (CT-1) and their planning CT scan (CT-2) were performed in the Utrecht university medical centre. Tumour volume was calculated by delineating the tumour on CT slices and multiplying the surface area by the inter-slice distance. Tumour volumes were delineated by three independent observers. Tumour growth during the waiting time was defined as the difference in tumour volume on CT-2 and CT-1, calculated as the average of three observations. RESULTS: The mean time between CT-1 and CT-2 was 33 days. The mean waiting period between the histopathological diagnosis and the start of radiotherapy was 56 days. Three groups could be distinguished: in one group the growth was less than 25% (n = 4), in one group the growth varied between 25 and 100% (n = 5), and in a third group there was growth of more than 100% (n = 4). Apart from this, in three cases the TNM stage had to be adjusted as a result of tumour progression. CONCLUSION: This study showed that the tumour volume increased by more than 50% during the waiting time for radiotherapy in 8 out of 13 patients with squamous cell carcinoma of the oropharynx.

Aged↗
PubMed2001

A rational approach to dose reduction in CT: individualized scan protocols.

The aim of this study was to demonstrate that dose reduction and constant image quality can be achieved by adjusting X-ray dose to patient size. To establish the relation between patient size, image quality and dose we scanned 19 patients with reduced dose. Image noise was measured. Four radiologists scored image quality subjectively, whereby a higher score meant less image quality. A reference patient diameter was determined for which the dose was just sufficient. Then 22 patients were scanned with the X-ray dose adjusted to their size. Again, image noise was measured and subjective image quality was scored. The dose reduction compared with the standard protocol was calculated. In the first group the measured noise was correlated to the patient diameter (rho=0.78). This correlation is lost in the second group (rho=-0.13). The correlation between patient diameter and subjective image quality scores changes from rho=0.60 (group 1) to rho=-0.69 (group 2). Compared with the standard protocol, the dose was reduced (mean 28%, range 0-76%) in 19 of 22 patients (86%). Dose reduction and constant noise can be achieved when the X-ray dose is adjusted to the patient diameter. With constant image noise the subjective image quality increases with larger patients.

Anthropometry↗
PubMed2001

Surgical anatomy of the cerebral arteries in patients with subarachnoid hemorrhage: comparison of computerized tomography angiography and digital subtraction angiography.

OBJECT: The purpose of this study was to compare computerized tomography (CT) angiography and digital subtraction (DS) angiography studies in patients with subarachnoid hemorrhage (SAH) to assess their vascular anatomy relevant to cerebral aneurysm surgery. METHODS: From a prospective series of 100 patients with SAH, the authors selected 73 patients whose CT angiography studies were of adequate quality and in whom DS angiography of both carotid arteries had been performed. Eleven patients with no DS angiographic studies of the vertebrobasilar artery were only evaluated for the anterior half of the circle of Willis. Anterior communicating arteries (ACoAs), both precommunicating anterior cerebral arteries (A1 segments), both posterior communicating arteries (PCoAs), and both precommunicating posterior cerebral arteries (P1 segments) were assessed on CT angiography and DS angiography by two independent observers. CONCLUSIONS: Computerized tomography angiography compares well with DS angiography for visualizing normal-sized arteries, and is superior for visualizing ACoAs and hypoplastic A1 and P, segments. Important preoperative aspects such as dominant A1 segments and PCoAs are equally well seen using either modality. Neither method enabled the authors to visualize more than 50% of PCoAs. Use of CT angiography can provide the required preoperative anatomical information for aneurysm surgery in most patients with SAH.

Adult↗
PubMed2000

Role of intraoperative ultrasound of the liver with improved preoperative hepatic imaging.

OBJECTIVE: To find out whether intraoperative ultrasound (IOUS) of the liver should still be considered a routine procedure for patients having hepatic resections as their preoperative investigation has become so much better with the standard use of triphasic spiral computed tomograms (CT). DESIGN: Retrospective study. SETTING: University medical centre, Utrecht, The Netherlands. PATIENTS: 26 consecutive patients undergoing liver resection. MAIN OUTCOME MEASURES: How much additional information was given by IOUS, and its influence on operative strategy; how IOUS facilitated the hepatic resection. RESULTS: IOUS revealed additional information over triphasic CT in 13/26 patients, which led to a change in the surgical procedure in 4 (15%). For all 4 patients the change in surgical approach proved to be correct as judged by histology and clinical outcome. In 12 patients IOUS facilitated the resection by providing helpful three-dimensional anatomical insight. CONCLUSION: Despite recent improvements in preoperative investigation, IOUS should still be recommended as a routine procedure in patients having hepatic resections. In addition to aiding the ultimate decision about which part to resect, it also gives insight into the hepatic anatomy.

Female↗
PubMed1999

[Analysis and treatment of pancreatic cystic diseases].

Owing to the spectacular progress in imaging techniques, cystic lesions of the pancreas are detected more often than previously, and this leads to therapeutic dilemmas. Of the cystic lesions of the pancreas, 80% are found to be pseudocysts and 10-15%, neoplastic cysts. The definition of a pseudocyst is: 'an accumulation of pancreatic juice surrounded by a wall of connective tissue or granulation tissue, developed as the result of acute pancreatitis, pancreatic injury or chronic pancreatitis'. In cases of asymptomatic pseudocyst, an expectative policy suffices; growth and symptomatic pseudocysts justify intervention. In addition to surgical internal drainage (cystojejunostomy) there are new therapeutic techniques: external drainage guided by ultrasonography or CT, and internal drainage guided by endoscopy. Endoscopic drainage is the treatment of choice, but it requires experienced hands. The cystic tumours are subdivided into two groups: serous and mucinous cystadenomas. The group of mucinous tumours is subdivided into mucinous cystadenomas and intraductal papillary mucinous tumours. The mucinous or macrocystic adenoma is potentially malignant and should be treated as a malignancy.

Adenoma↗
PubMed1999

Perimesencephalic hemorrhage. Exclusion of vertebrobasilar aneurysms with CT angiography.

BACKGROUND AND PURPOSE: It is important to recognize a perimesencephalic pattern of hemorrhage in patients with subarachnoid hemorrhage (SAH), because in 95% of these patients the cause is nonaneurysmal and the prognosis is excellent. The purpose of this study was to investigate whether CT angiography can accurately exclude vertebrobasilar aneurysms in patients with perimesencephalic patterns of hemorrhage and therefore replace digital subtraction angiography (DSA) in this setting. METHODS: In 40 patients with posterior fossa SAH as shown on unenhanced CT, 2 radiologists independently evaluated unenhanced CT for distinguishing between perimesencephalic and nonperimesencephalic pattern of hemorrhage and assessed CT angiography for detection of aneurysms. All patients subsequently underwent DSA or autopsy. RESULTS: Observers agreed in 38 of 40 patients (95%) in differentiating perimesencephalic and nonperimesencephalic patterns of hemorrhage on unenhanced CT. On the CT angiograms, both observers detected a vertebrobasilar aneurysm in 16 patients and no aneurysm in 24 patients. These findings were confirmed by DSA or autopsy. No patients with a perimesencephalic pattern of hemorrhage were found to have an aneurysm on either CT angiography or DSA. CONCLUSIONS: Good recognition of a perimesencephalic pattern of hemorrhage is possible on unenhanced CT, and CT angiography accurately excludes and detects vertebrobasilar aneurysms. DSA can be withheld in patients with a perimesencephalic pattern of hemorrhage and negative CT angiography.

Adult↗
PubMed1999

Lumen reduction measurements of the internal carotid artery before and after Levovist enhancement: reproducibility and agreement with angiography.

Our aim was to assess reproducibility of three different lumen reduction measuring methods--North American Symptomatic Carotid Endarterectomy Trial, European Carotid Surgery Trial, and common carotid--using power Doppler and color Doppler sonography before and after Levovist enhancement. We included 20 symptomatic patients with mild or severe carotid disease. North American Symptomatic Carotid Endarterectomy Trial, European Carotid Surgery Trial, and common carotid measurements on longitudinal views and European Carotid Surgery Trial measurements on transverse views were performed. Examinations were repeated and the results compared to assess reproducibility of measurements. Correlation with angiography was obtained by calculating Pearson correlation coefficients. Reproducibility was significantly better (P < 0.05) for European Carotid Surgery Trial and common carotid measurements (95% limits of agreement between -10% to 10% and -19% to 17%) as compared to North American Symptomatic Carotid Endarterectomy Trial measurements (95% limits of agreement between -11% to 21% and -21% to 23%). Variability of measurements after enhancement increased slightly (not significant) for both power and color Doppler sonography. Additionally, European Carotid Surgery Trial measurements, using nonenhanced power Doppler or color Doppler sonography, did not correlate significantly with angiography, whereas North American Symptomatic Carotid Endarterectomy Trial and common carotid measurements correlated well with angiography, particularly in power Doppler mode after enhancement (r = 0.88 and r = 0.82, respectively). We conclude that for lumen reduction measurements of the internal carotid artery with power and color Doppler sonography, the common carotid method is the only method that is reproducible and has good correlation with angiography, which slightly improves after Levovist enhancement.

Aged↗
PubMed1998

Reproducibility of measurements of intima-media thickness and distensibility in the common carotid artery.

OBJECTIVE: To assess reproducibility of ultrasonographic measurements of arterial distensibility and intima-media thickness (IMT) in the common carotid arteries. DESIGN: Prospective study. MATERIALS: Measurements of IMT and arterial distensibility were performed on-line in B-mode and M-mode, respectively. Blood pressure was assessed. From the measured variables stiffness indices were derived. METHODS: Twenty-five persons were included in the IMT study, both healthy subjects and patients with atherosclerotic disease. Distensibility was measured in a randomly selected subgroup of 10 persons. All subjects were examined by two different sonographers on the same day and were re-examined after 1 or 2 weeks. RESULTS: When data from both carotid arteries were combined, the interobserver coefficient of variation of IMT was on average 11.7%, of diastolic diameter 3.3% of distension and relative distension 11.8%, of distensibility coefficient 12.3%, and of stiffness parameter beta 19%. Intraobserver variability was slightly lower than interobserver variability. Variability for measurements in the right common carotid artery only was higher than for measurements of both carotid arteries combined. CONCLUSIONS: Our study demonstrates that reproducibility of measurements of IMT and arterial distensibility of the common carotid artery, by B-mode and M-mode ultrasonography respectively, is acceptable when used in large studies.

Aged↗
PubMed1998

Pancreatitis and agenesis of the dorsal pancreas.

We report a case of agenesis of the dorsal pancreas, complicated by pancreatitis and diabetes mellitus. A 39-year-old woman was referred for evaluation of a chronic pancreatitis. Abdominal spiral CT and ERP and MRCP demonstrated agenesis of the dorsal pancreas. The pathogenesis, clinical features and diagnosis of this very rarely reported disease are discussed.

Adult↗
PubMed1998

Subarachnoid hemorrhage: aneurysm detection and preoperative evaluation with CT angiography.

PURPOSE: To evaluate if computed tomographic (CT) angiography can replace digital subtraction angiography (DSA) for aneurysm detection and as preoperative work-up in patients with subarachnoid hemorrhage (SAH). MATERIALS AND METHODS: Prospectively, 100 patients with SAH underwent CT angiography; 80 also underwent DSA. Two observers independently evaluated CT angiographic source images and maximum intensity projection slabs. Neurosurgeons compared CT angiograms and DSA images for presurgical evaluation. RESULTS: On CT angiograms, the observers detected 73 and 70 of 75 symptomatic aneurysms; 96% of the detected aneurysms were classified as definitely present. Of 16 incidental aneurysms, 12 and 10 were detected by the observers. With adequate CT angiographic quality, parent artery side of anterior communicating aneurysms was correctly predicted in 100% (95% confidence interval [CI]: 87%, 100%). Neurosurgeons assessed CT angiography as equal or superior to DSA in 83% (95% CI: 73%, 90%) of 87 aneurysms, and in 74% (95% CI: 63%, 82%) operation might have been based on CT angiographic findings alone. CONCLUSION: CT angiography depicted 90% of all aneurysms, and 90% were classified as definitely present. CT angiography must be of high quality with adequate depiction of the aneurysm and the parent artery for surgery to be performed on the basis of CT angiographic findings alone.

Adult↗
PubMed1998

Changes over time in optimal duplex threshold for the identification of patients eligible for carotid endarterectomy.

BACKGROUND AND PURPOSE: Two surgical trials established that carotid endarterectomy is beneficial to symptomatic patients who have a severe internal carotid artery (ICA) stenosis on angiograms. Duplex ultrasonography-derived hemodynamic parameters show a good correlation with angiography and are often used for detecting severe ICA stenoses. However, duplex performance is ultrasound machine and operator dependent. Over time both may change, possibly affecting duplex performance. We compared duplex performance of 2 time periods in 1 specific vascular laboratory using angiography as the gold standard. METHODS: Consecutive patients who underwent both angiography and duplex examinations of the ICA were evaluated (first period, 60 patients; second period, 61 patients). Peak systolic velocity and several other hemodynamic parameters and ratios were analyzed by receiver operating characteristic curves in their ability to detect severe ICA stenoses. The optimal parameter and threshold were determined for each period. Subsequently, duplex test characteristics were compared after the optimal thresholds of both the first and the second periods were applied in the second period. RESULTS: In both periods peak systolic velocity of the ICA was the best test parameter; areas under the receiver operating characteristic curve were similar (0.957 and 0.954, respectively). However, the optimal threshold was different. The optimal threshold in the second period was 270 cm/s. When the optimal threshold of 210 cm/s of the first period was applied in the second period, test characteristics changed significantly. Sensitivity increased from 98% to 100%, and specificity decreased from 85% to 71% (P=0.004). CONCLUSIONS: The optimal threshold for detecting severe ICA stenoses with duplex ultrasonography in our laboratory changed over time. Individual laboratories should assess duplex accuracy regularly and adjust adopted criteria if necessary to keep diagnostic performance optimal.

Adult↗
PubMed1997

[Towards safer and parenchyma-conserving liver resections: experience with three-dimensional reconstructions of spiral CT scan].

New techniques are available for the diagnosis and treatment of liver metastases. Three patients, a male aged 52 and two females aged 70 and 47, developed liver metastases after resection of a colorectal carcinoma. Spiral CT scanning made possible detailed three dimensional imaging of the liver to determine the extension of the metastases and the site of the metastasis in relation to blood vessels and bile ducts. This enabled the surgeon preoperatively to arrive at a balanced operation strategy, with the objectives of radical resection of the metastasis and conservation of sufficient residual liver tissue with minimal morbidity and mortality. In addition, use was made of peroperative clamping of blood vessels to determine the possibility of resecting along anatomical borders. This offers the advantages that less blood is lost and a smaller resection often suffices. In the 3 patients followed respectively a wedge excision of the tumour, a wedge excision combined with a hemihepatectomy and a resection of two segments.

Adenocarcinoma↗
PubMed1997

Computed tomographic angiographic imaging of abdominal aortic aneurysms: implications for transfemoral endovascular aneurysm management.

PURPOSE: To describe anatomic features pertinent to patient selection and graft design for transfemoral endovascular aneurysm management (TEAM) of the infrarenal aorta using computed tomographic (CT) angiography. METHODS: A prospective noncomparative analysis of 102 spiral CT scans of the abdominal aorta of patients with abdominal aortic aneurysms was performed. From the original CT data set, slices were reconstructed perpendicular to the vessel axis (central lumen line) at a 10 mm interval. In these reconstructed slices, diameter measurements were performed. Vessel length was measured along the central lumen line. In each patient possibilities for TEAM were analyzed. RESULTS: Because of technical reasons, 36 scans were excluded from the analysis. Of the remaining 66 patients, 18 could potentially be treated with a bifurcated endovascular device. The infrarenal aortic diameter-to-iliac artery diameter ratio was less than 2 in most patients. The vessel segments judged to be adequate for endovascular graft anchoring had a noncylindrical shape in the majority of cases. CONCLUSION: Only a minority of patients with abdominal aortic aneurysms can at this stage be treated with an endovascular graft. The ideal endovascular graft should be a combination of rigid and flexible components. The proximal and distal attachment systems should have some flexibility with an intrinsic maximum diameter while the midsection of the graft can be relatively rigid.

Adult↗