Biomedical subjects
Publications and source records attributed to K-J Wolf.
Recent technical developments led to a change in the significance of the different imaging modalities in the whole spectrum of neuroradiology and thus also in the field of imaging of the cervical spine. The main part in diagnostic imaging of the upper cervical spine is taken by high-resolution multislice CT and MRI. Conventional X-rays serve as an initial screening technique if required.
PURPOSE: To test whether a new quantitative measure, the tumor-to-vessel ratio, obtained from late post-iron-oxide-enhanced T1-weighted images allows for differentiating hemangiomas from liver metastases or all malignant liver lesions. MATERIAL AND METHODS: Twenty-six patients (mean 57, range 33-79 years) were prospectively studied at 1.5T magnetic resonance imaging (MRI) with a T1-weighted 2D fast low-angle shot (FLASH) sequence (repetition time/echo time/flip angle; 200 ms/4.8 ms/90 degrees ) and a T2-weighted turbo spin-echo sequence (4072 ms/99 ms/180 degrees ). Imaging was carried out before and at intervals up to 18 min after IV injection of Ferucarbotran (Resovist, Schering, Germany). In 19 patients, one representative malignant lesion was analysed. Eleven hemangiomas were evaluated in 7 patients. Two readers performed a consensus reading with a signal intensity measurement in a lesion, normal liver and hepatic veins, from which ratios were computed. RESULTS: On T1-weighted iron-oxide-enhanced MRI of 30 lesions, tumor-to-vessel signal intensity ratios were distinct in hemangiomas (median 1.04, range 0.99-1.10) as opposed to either metastases (0.64, 0.33-0.77; P < 0.05) or all malignant lesions taken together (0.64, 0.33-0.98; P < 0.05), while the tumor-to-liver ratio was not. CONCLUSION: The tumor-to-vessel ratio may help to differentiate between hemangiomas and metastases. A ratio greater than 0.98 allowed differentiating hemangiomas from metastases with a wide safety margin.
PURPOSE: To propose a semi-quantitative computed tomography (CT) protocol for determining uncalcified pineal tissue (UCPT), and to evaluate its reproducibility in modification of studies showing that the degree of calcification is a potential marker of deficient melatonin production and may prove an instability marker of circadian rhythm. MATERIAL AND METHODS: Twenty-two pineal gland autopsy specimens were scanned in a skull phantom with different slice thickness twice and the uncalcified tissue visually assessed using a four-point scale. The maximum gland density was measured and its inverse graded on a non-linear four-point scale. The sum of both scores was multiplied by the gland volume to yield the UCPT. The within-subject variance of UCPT was determined and compared between scans of different slice thickness. RESULTS: The UCPT of the first measurement, in arbitrary units, was 39+/-52.5 for 1 mm slice thickness, 44+/-51.1 for 2 mm, 45+/-34.8 for 4 mm, and 84+/-58.0 for 8 mm. Significant differences of within-subject variance of UCPT were found between 1 and 4 mm, 1 and 8 mm, and 2 and 8 mm slice thicknesses (P<0.05). CONCLUSION: A superior reproducibility of the semi-quantitative CT determination of UCPT was found using 1 and 2 mm slice thicknesses. These data support the use of thin slices of 1 and 2 mm. The benefit in reproducibility from thin slices has to be carefully weighted against their considerably higher radiation exposure.
BACKGROUND AND PURPOSE: Intracerebral hemorrhages after embolization of arteriovenous malformations (AVMs) are the most dreaded complications of this well-established therapy. Apart from the known risk factors, our center noticed a high incidence of complications during postinterventional monitoring in medical intensive care units (ICUs) and stroke units. MATERIALS AND METHODS: We report 125 consecutive interventions performed on 66 patients by using flow-dependent microcatheters and n-butyl cyanoacrylate as the embolic agent. Postinterventional intensive care monitoring was performed in an interdisciplinary operative ICU, a stroke unit, or a medical ICU. Patients were compared with regard to bleeding complications, AVM morphology, embolization result, postinterventional monitoring, and demographic factors. RESULTS: Intracerebral hemorrhages occurred in 7 patients. Significant differences in outcome were found between 66 patients monitored in the interdisciplinary operative ICU from medical ICU or stroke unit. This was also true when adjusted for age and extent of AVM reduction by using exact logistic regression. A partial AVM reduction of >60% was a considerable risk factor for hemorrhage (odds ratio [OR] = 18.8; 95% confidence interval [CI] [1.341, not available]. Age was also an essential risk factor. An age difference of 10 years leads to an OR of 2.545 (95% CI [1.56, 7.35]). DISCUSSION: A considerable AVM reduction in one session appears to increase the risk of hemorrhage technically. This suggests a distribution of the interventions in many partial steps.
INTRODUCTION: Several magnetic resonance (MR) techniques designed to demonstrate the characteristic signal intensity of blood degeneration products of thrombi have been suggested, but the effect of thrombus organization on the MR display, in particular with regard to its temporal evolution, remains to be determined. It is the purpose of this study to develop a stagnation thrombus model in rabbits and to characterize thrombus at different ages with two (MR) imaging techniques, phlebography and histology. MATERIALS AND METHODS: Venous stagnation thrombi were induced in the external jugular veins of rabbits using a minimally invasive radiological technique to produce artificial embolic vascular occlusion and hypercoagulability. Twenty-five animals were divided into 5 groups of 5 animals, and each group underwent 1.5 T MR imaging at 1, 3, 5, 7 and 9 days after thrombus induction using a T1-weighted magnetization-prepared rapid gradient-echo sequence (MP-RAGE: TR 10.4 msec, TE 4.0 msec, FA 15 degrees ) and a T2-weighted fast low-angle shot sequence (FLASH: TR 54 msec, TE 18 msec, FA 15 degrees ). The thrombus length was measured on the T1-weighted images. Thrombus conspicuity, signal intensity, and heterogeneity on T2* weighted images were described using visual scales. Radiographic venography and histology served as reference methods. RESULTS: Thrombi were successfully induced in all animals. The overall thrombus length decreased from 43 +/- 9 (day 1 after induction) to 23 +/- 4 mm (day 9). On 3D-reconstructions of the T1-weighted images, the visible portion of the true thrombus length relative to the overall thrombus length was 0.16 +/- 0.3 (day 1), 0.24 +/- 0.3 (day 3), 0.38 +/- 0.5 (day 5), 0.06 +/- 0.1 (day 7) and 0.00 (day 9). Sixteen of 25 thrombi were detectable with the T2*-weighted technique. The overall thrombus signal intensity decreased with the age of the thrombus from day 1 to day 9. The histological evaluation showed that the rabbit thrombi closely resemble human thrombi morphologically. CONCLUSIONS: The thrombus model closely resembles the human venous stagnation thrombus of different organizational stages. With state-of-the-art MRI techniques, thrombi were only partially displayed with the visibility depending on thrombus age. The model may be suitable for evaluating new and potentially more effective MRI techniques for improved thrombus visualization.
PURPOSE: To assess the degree of enhancement and image quality of 16-slice multidetector CT angiography (MDCTA) of pelvic and lower limb arteries with a monophasic contrast medium injection protocol. MATERIALS AND METHODS: Fifty patients underwent a CT angiography of the pelvic and lower limb arteries using the following parameters: collimation 16 x 1.5 mm, rotation time 0.5 s, table feed 40 mm/sec, slice thickness 2 mm, reconstruction interval 1.2 mm, 100 ml Iomeprol 400 + 60 ml normal saline, flow rate 4 ml/s, bolus tracking (threshold of 250 DeltaHU in aorta). Arterial enhancement was measured in all arterial segments. Maximum intensity projections (MIP) together with axial images were reviewed by two radiologists (consensus). If the results were inconclusive for stenosis, additional curved multiplanar reformations (MPR) were performed. RESULTS: The mean arterial enhancement values were aorta: 314 +/- 69, pelvis: 342 +/- 105, thigh: 347 +/- 139, calf: 231 +/- 109 DeltaHU. The image quality was judged as excellent in 346 (77.6 %), adequate in 76 (17 %), and inadequate in 24 (5.4 %, all but one in calf and foot) of 446 arterial territories. An override of the contrast bolus below the knee occurred in 2 patients rendering the calf arteries nondiagnostic. Venous enhancement occurred in 13 patients but this compromised the diagnostic assessment in only one case. Additional MPRs were required accurately to assess stenoses in 22 of 200 arterial levels in 16 patients with marked arterial calcifications. CONCLUSION: 16-slice MDCTA with a monophasic contrast bolus of Iomeprol 400 provided good arterial enhancement and diagnostic image quality in 94.6 % of the depicted arterial segments. The majority (67 %) of nondiagnostic segments were below the ankle. MPRs were required in patients with marked calcification for accurate assessment of stenosis.
In patients with known or suspected malignancy, ultrasonography (US) is often the first choice for liver imaging because of its widespread availability and low cost. Compared with contrast-enhanced computed tomography (CT) and magnetic resonance imaging (MRI), the sensitivity of conventional US for detecting hepatic metastases is relatively poor. The advent of microbubble contrast agents changed this situation. Sensitivity and specificity increased substantially with the use of these contrast agents and contrast-specific imaging modes in recent years. Currently, numerous US imaging methods exist, based on Doppler techniques or harmonic imaging. They exploit the complex nonlinear behavior of microbubbles in a sound field to achieve marked augmentation of the US signal. Although microbubble contrast agents are essentially blood pool agents, some have a hepatosplenic specific late phase. Imaging during this late phase is particularly useful for improving the detection of malignant liver lesions and allows US to perform similarly to spiral CT as shown by recent studies. In addition, this late phase imaging is very helpful for lesion characterization. Low mechanical index imaging with the newer perfluor agents permits real-time imaging of the dynamic contrast behavior during the arterial, portal venous, and late phases and is particularly helpful for lesion characterization. The use of US for hemodynamic studies of the liver transit time may detect blood flow changes induced by micrometastases even before they become visible on imaging. In this field of functional imaging, further research is required to achieve conclusive results, which are not yet available.
PURPOSE: Comparison of metric analysis of spinal structures, exemplarily of the ligamentum flavum, obtained with computed tomography (CT) (soft tissue window and bone window) and magnetic resonance imaging (MRI) (T1 and T2 weighted images). MATERIAL AND METHODS: Forty-six lumbar ligamenta flava of 46 patients (25 women and 21 men) were examined at a Somatom Plus 4 (Siemens, Erlangen, FRG) and at a 1.5 T clinical scanner (Magnetom Vision, Siemens, Erlangen, FRG). Two independent neuroradiologists measured the thickness of the ligamenta flava in mm. Statistics included Pearson's correlation coefficient and the intra-class correlation coefficient. RESULTS: Mean values did not differ significantly. The correlation coefficients varied between 0.69 and 0.98. The best correlation occurred comparing the same techniques in different windowing and weighting (CT: r = 0.98; MRI: r = 0.95). Correlating different techniques the combination of CT bone window and T1 weighted images presented the best result (r = 0.75). CONCLUSIONS: Because of the excellent correlation between the examined techniques CT as well as MRI can equally be used to measure distances of spinal structures.
PURPOSE: To evaluate the role of routine "whole body spiral CT"in the primary work-up of polytrauma patients for injuries of the thorax, abdomen and spine, and to compare the results with those of conventional radiography of the chest and spine and abdominal ultrasound. MATERIALS AND METHODS: Fifty consecutive polytrauma patients underwent contrast-enhanced single slice spiral CT (5 mm collimation) from the vertex to the floor of the pelvis as part of the primary work-up after emergency room admission. Overlapping high resolution sections and sagittal reformations of the spine were obtained. Reports of additional chest radiographs (n=43), abdominal ultrasound examinations(n = 47) and spine radiographs (n = 36) performed in the emergency room were available for retrospective comparison. The "final diagnoses," which served as the standard of reference, were taken from the patients' records using all information that be-came available until discharge or death, such as findings from further imaging, surgery and autopsy. RESULTS: CT showed 109(97%) of 112 thoracic and abdominal soft-tissue injuries. Relevant injuries missed were an early splenic laceration and an early pelvic hematoma, both of which became clinically apparent several hours later. There were 4 false positive CT findings. Conventional chest radiography demonstrated only 20% of thoracic and sonography 22% of abdominal injuries. Chest radiography and sonography produced 2 false-positive findings each. CT showed 66 (87%) of 76 vertebral fractures including all 19 unstable ones.CT missed 5 anterior vertebral body and 5 spinous/transverse process fractures. Conventional radiography found 71 % of vertebral fractures including only 50 % of the unstable ones. CONCLUSION: Routine performance of whole body spiral CT as part of the primary work-up of polytrauma patients provides a fast and comprehensive survey and detects almost all soft tissue injuries of the chest and abdomen. It is clearly superior to chest radiography and abdominal sonography. All spinal injuries relevant for the acute management were also seen on CT, but not on conventional radiography.
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PURPOSE: To evaluate whether metabolic changes of the erector trunci muscle in patients with lumbar disc herniation can be detected with proton magnetic resonance spectroscopy ( (1)H-MRS). MATERIALS AND METHODS: In 10 patients with lumbar disc herniation and 16 healthy volunteers, proton spectra were obtained from the erector trunci muscle and analyzed for fat-water ratio. The axial images were evaluated for the degree of atrophy of the erector trunci muscle. The muscular tissue was histopathologically examined in 2 patients. RESULTS: The examination was well tolerated by all patients and volunteers and all acquired spectra could be analyzed. Patients with lumbar disc herniation have a significantly increased fat-water ratio of 0.19 compared to 0.09 in the control group, with a p-value of 0.003. This result correlates well with the bioptical findings of increased intracellular lipid deposits and lipomatous transformation of the muscle parenchyma. CONCLUSION: (1)H-MRS is a useful method to detect metabolic changes in lumbar back musculature and, as a non-invasive technique, might play a role in monitoring exercise in lumbar disc herniation. It can be expected that muscle regeneration will be shown as precisely as muscle degeneration. This hypothesis, however, remains to be proven.
Ultrasonography (US) is the first choice for screening patients with suspected liver lesions. However, due to a lack of contrast agents, US used to be less sensitive and specific compared with computed tomography (CT) and magnet resonance imaging (MRI). The advent of microbubble contrast agents increased both sensitivity and specificity dramatically. Rapid developments of the contrast agents as well as of special imaging techniques were made in recent years. Today numerous different US imaging methods exist which based either on Doppler or on harmonic imaging. They are using the particular behaviour of microbubbles in a sound field which varies depending on the energy of insonation (low/high mechanical index, MI) as well as on the properties of the agent themselves. Apart from just blood pool enhancement some agents have a hepatosplenic specific late phase. US imaging during this late phase using relatively high MI in phase inversion mode (harmonic imaging) or stimulated acoustic emission (SAE; Doppler method) markedly improves the detection of focal liver lesions and is also very helpful for lesion characterisation. With regards to detection, contrast enhanced US performs similarly to CT as shown by recent studies. Early results of studies using low MI imaging and the newer perfluor agents are also showing promising results for lesion detection. Low MI imaging with these agents has the advantage of real time imaging and is particularly helpful for characterisation of focal lesions based on their dynamic contrast behaviour. Apart from the techniques which based on the morphology of liver lesions there were some attempts for the detection of occult metastases or micrometastases by means of liver blood flow changes. Also in this field the use of US contrast agents appears to have advantages over formerly used non contrast-enhanced methods although no conclusive results are available yet.
PURPOSE: To evaluate the growth of testicles, their sonographic structure and the recovery of testicular perfusion through collateral vessels after preliminary laparoscopic laser dissection (PLLD) of the internal spermatic artery in cryptorchism. MATERIALS AND METHODS: The postoperative position, the volume increase, the structural and vascular abnormalities and the incidence of epididymal abnormalities were evaluated with ultrasound in 32 children (mean age: 6.5 +/- 1.34 years) after PLLD. The intratesticular blood flow and the flow-in anastomoses from the deferential and cremasteric arteries were assessed using colour and power Doppler US (7.5 MHz transducer). RESULTS: All testicles were permanently positioned in the scrotum and showed growth after surgical treatment. None of the testes showed sonographic signs of atrophy. There were no clear differences in intratesticular perfusion compared to the non-operated testis. A collateral blood flow in the deferential artery was found in 44 cases by colour and/or power Doppler US. A perfusion to the lower testicular pole was detected in 29 cases by power Doppler. Intraoperatively, 12 epididymal inversions were eliminated so that an elongated epididymis was sonographically visualised in three testes. CONCLUSION: Ultrasound can be used for the postoperative control of the testicular structure and the volume increase as well as detection of the flow-in anastomoses. The collateral blood supply after PLLD was sufficient for subsequent growth of testicles in all cases.