Virtual endoscopy combined with intraoperative neuronavigation for planning of endoscopic surgery in patients with occlusive hydrocephalus and intracranial cysts.

We assessed the clinical value of MR ventriculoscopy (virtual endoscopy, VE) combined with image-guided frameless stereotaxy for endoscopic surgery of occlusive hydrocephalus and intracranial cysts. VE was obtained in 20 patients with hydrocephalus and three with intracranial cysts. All surgical operations were endoscopic. The path of the rigid endoscope to the target point was planned using neuronavigation. VE was carried out along the same trajectory retrospectively in 20 cases and prospectively in three. The results were analysed for demonstration of anatomical landmarks and structures at risk. VE was successful in all patients. Possible obstacles to endoscopic access to the lamina terminalis and the basal cisterns and structures at risk, such as the basilar artery, were clearly shown in relation to the direction of the endoscope. However, the floor of the third ventricle and septum pellucidum were not clearly seen and possible abnormalities could therefore not be appreciated. VE can provide realistic simulation of endoscopic third ventriculostomy and cystostomy. The appropriate trepanation point and trajectory of the endoscope can be assessed with regard to the size of the foramen of Monro and the position of vulnerable structures. This simulated trajectory can be adapted to the field of operation by image-guided neuronavigation. This regime may potentially reduce the risk of damage to intracranial structures.

[Virtual endoscopy of the upper urinary tract based on contrast-enhanced MR urography data sets]. / Virtuelle Endoskopie des oberen Harntraktes auf der Basis kontrastangehobener MR-Urographie Datensätze.

PURPOSE: To investigate the feasibility of reconstructing a virtual endoscopy from MR imaging data sets of the upper urinary tract. METHOD: The data obtained from 28 contrast-enhanced MR urographic examinations (5 normal; 23 pathologic) were post-processed to reconstruct a virtual ureterorenoscopy (VURS) using a threshold image segmentation. The visualization of the upper urinary tract was based on the acquisition of T1-weighted 3D gradient-echo sequences after intravenous administration of gadolinium-DTPA and a prior injection of low-dose furosemide. RESULTS: The employed MR urography technique created in all 28 cases a complete and strong contrast enhancement of the urinary tract. These 3D sequence data allowed the reconstruction of a VURS, even when the collecting system was not dilated. The best accuracy was provided by the MR urography sequences with the smallest voxel size. Moreover, the data acquisition based on a breath-hold technique has proved superior to that using a respiratory gating. Inside the renal pelvis, all calices could be assessed by turning the virtual endoscope in the appropriate direction. The visualization of the ureteral orifices in the bladder was also possible. All filling defects that were diagnosed by MR urography could be evaluated from the endoluminal view using the VURS. The exact characterization of the lesions based only on the assessment of the surface structure was difficult. CONCLUSION: A virtual endoscopy of the upper urinary tract can be successfully reconstructed using the data sets of high-resolution 3D MR urography sequences.

Embolotherapy of aneurysms under temporary balloon occlusion of the neck. In vitro study of a newly designed eccentric balloon catheter.

RATIONALE AND OBJECTIVES: To test embolotherapy of aneurysms in an in vitro model using standard and specially designed eccentric occlusion balloon catheters for simultaneous delivery of the embolization agent and occlusion of the neck of the aneurysm. METHODS: Two different in vitro set-ups were used: a bifurcational aneurysm and an aneurysm with a straight parent vessel segment, both made from elastic silicone and glass. Each model was exposed to a pulsating perfusion. The effluent was collected and filtered. For the bifurcational aneurysms, commercially available occlusion balloon catheters with a working channel exiting at the tip were used. For the aneurysms with straight parent vessel, the catheters were modified so that the balloon opened eccentrically. The working channel of the catheter led to a side hole, which was located where the balloon membrane was fixed to the catheter shaft. The aneurysms were filled with coils, ethibloc, or hydrogel, and with coils combined with ethibloc or hydrogel, while the expanded balloon occluded the neck. RESULTS: Embolization of aneurysms under balloon occlusion of the neck was technically feasible with the catheter devices. Dense packing with coils was possible in all cases without coil dislocation, but unfilled interspaces remained between the coil wires. Best filling was achieved with ethibloc or hydrogel alone or in combination with coils. During the filling procedure, there was no distal embolization of the liquid agents. However, after balloon deflation, considerable amounts of hydrogel or ethibloc were washed out from the aneurysm. CONCLUSIONS: The results suggest that balloon occlusion of the neck allows compact filling and minimizes the risk of dislocation in coil embolotherapy of aneurysms. In nonbifurcational aneurysms, the eccentric balloon catheter seems to be suitable for this treatment concept. Although liquid agents may be safely delivered into the aneurysm under balloon protection, their considerable washout rate after balloon removal requires further refinements of the technique before clinical application is advisable.

[Repositioning of a central venous catheter with a guide wire with movable core]. / Korrektur zentralvenöser Katheter über einen Führungsdraht mit beweglichem Kern.

PURPOSE: A simple method to redirect malpositioned central venous catheters using a guide wire with movable core is described. METHODS: A 0.89 mm guide wire with movable core is inserted into the catheter. The core is withdrawn for a few centimeters producing a floppy wire tip segment, which follows the malpositioned course of the catheter. The core is then advanced in small steps, until the catheter tip flips into the correct vein. RESULTS: In 8 cases rapid repositioning of malpositioned catheters was accomplished with this technique, without moving the catheters at the entry site. CONCLUSIONS: The repositioning technique described is simple, fast, and inexpensive. Movement of the catheter at the entrance site is not necessary, thus not jeopardizing sterility, and without the need to solve the suture fixation.

Simulated flow pattern in massive pulmonary embolism: significance for selective intrapulmonary thrombolysis.

PURPOSE: The flow pattern in the central pulmonary arteries proximal to large pulmonary emboli was studied experimentally. The currents to which thrombolytic agents are exposed when administered via an intrapulmonary catheter were visualized in order to explain the lack of benefit of local versus systemic administration. METHODS: By illumination of suspended microspheres, the flow pattern proximal to an obstructing embolus was visualized in an in vitro pulmonary arterial flow model. In six dogs massive pulmonary embolism was created. A pigtail catheter was positioned in the pulmonary artery immediately proximal to the central edge of the occluding embolus. To allow visualization of the local flow pattern, a small amount of contrast material (4 ml) was injected through the catheter at a high flow rate (25 ml/sec). The course of the radiopaque spot that emerged from the catheter tip within 160 msec was monitored with digital subtraction angiography at a frame rate of 12.5 frames/sec. In two dogs, the study was repeated after embolus fragmentation with the same catheter position. RESULTS: The flow model study revealed formation of a vortex proximal to the occluding embolus. In vivo experiments showed that the radiopaque spot was whirled by the vortex proximal to the embolus and made only evanescent contact with the edge of the embolus. Regardless of the embolus location, the contrast spot was washed into the non-occluded ipsilateral and contralateral pulmonary arteries within 0.40-0.64 sec. After embolus fragmentation, the contrast spot was carried completely into the formerly occluded artery. CONCLUSION: Flow studies explain why thrombolytic agents administered via a catheter positioned adjacent to the embolus may have no more effect than systemically administered agents. An enhanced local effect is precluded by the rapid washout into the non-occluded pulmonary arteries and subsequent systemic dilution. These results support the practice of direct intrathrombic injection of thrombolytics or local thrombolysis as an adjunct to embolus fragmentation.

Bedside testing (SimpliRED) in the diagnosis of deep vein thrombosis. Evaluation of 250 patients.

RATIONALE AND OBJECTIVES: The authors evaluate the sensitivity and specificity of a bedside test (SimpliRED) in the diagnosis of deep vein thrombosis compared with contrast phlebography. METHODS: Two hundred fifty patients, referred for phlebography, underwent bedside testing for detection of deep vein thrombosis. Contrast phlebography was performed immediately afterward. SimpliRED provides a clearly visible agglutination of the patient's red blood cells in the presence of elevated levels of cross-linked fibrin derivative (D-dimer), which is specific for fibrin breakdown. RESULTS: In 82 (32.8%) patients, deep vein thrombosis was confirmed venographically. An abnormal D-Dimer test was found in 79 of the 82 patients with thrombosis (sensitivity: 96.3%). The three patients who were diagnosed falsely as normal on agglutinin testing, had venograms which showed only an isolated calf thrombosis in small muscle veins (< 2 cm in diameter) not requiring treatment. One hundred of 168 patients without venographic thrombosis were diagnosed correctly by SimpliRED (specificity: 59.5%). The positive predictive value was 53.7%; the negative predictive value was 96.8%. CONCLUSIONS: All thrombotic disorders in the leg that required further treatment were identified correctly. SimpliRED is a very sensitive test with moderate specificity in the diagnosis of deep vein thrombosis. Therefore, further invasive testing is needed only in those patients in whom the D-dimer test is abnormal. A false-positive result of the bedside test may be nonspecific or due to elevated levels of fibrin split products, which can occur whenever the coagulation system has been activated by any of several conditions.

[The diagnosis of deep venous thromboses of the leg using a new rapid test (SimpliRED)]. / Diagnostik tiefer Beinvenenthrombosen mittels eines neuen Schnelltests (SimpliRED).

PURPOSE: Evaluation of sensitivity and specificity of a bed-side test in the diagnosis of deep-vein thrombosis compared to contrast phlebography. METHODS: 122 patients, referred for phlebography, underwent bedside testing (SimpliRED) for detection of deep vein thrombosis. Contrast phlebography was confirmed immediately afterwards. SimpliRED provides a clearly visible agglutination of the patient's red blood cells in the presence of elevated levels of crosslinked fibrin derivatives (D-dimer) in the sample, being specific for fibrin breakdown. RESULTS: In 37 (30.3%) patients deep vein thrombosis could be confirmed. An abnormal D-dimer test was found in 35 of the 37 patients with thrombosis (sensitivity: 94.6%). Two patients who had not been identified by agglutinin testing, showed an isolated calf thrombosis in small muscle veins (< 2 cm in diameter) not requiring treatment. 55 of 85 patients without thrombosis in phlebography were stated correctly by SimpliRED (specificity: 64.7%). CONCLUSION: All thrombotic disorders in the leg with the need for further treatment were identified correctly. SimpliRED is a very sensitive test with moderate specificity in the diagnosis of deep vein thrombosis. Therefore, further invasive testing is needed only in such patients where the D-dimer test is abnormal. A false positive result of the bed-side test may be non-specific or due to elevated levels of fibrin split products, if the coagulation system is activated in several other conditions.

[Osteoporotic stress fractures of the sacrum: MR-tomography findings]. / Osteoporotische stressfrakturen des Os sacrum: MR-tomographische Befunde.

PURPOSE: Evaluation of the morphologic appearance of sacral osteoporotic insufficiency fractures in MRI. PATIENTS AND METHOD: 6 patients (5 female and one male, 54-80 years) with osteoporotic insufficiency fractures of the sacrum were examined with CT and MRI. Plain and contrast-enhanced T1- and T2-weighted spin-echo images were acquired, three patients were studied with T1-weighted gradient-echo-sequences with fat suppression. RESULTS: Fracture-lines and sclerotic areas of the massae laterales were visible in 5 of 6 CT examinations, one patient showed no abnormalities of the sacrum on the initially performed CT scans. All patients had a diffuse bone marrow oedema of the fractured massae laterales with a decreased signal on the T1-weighted spin-echo images and an increased signal on the T1-weighted gradient-echo images with fat suppression and in the T2-weighted SE-sequences. Gadopentate dimeglumine enhanced MRI images showed a remarkable diffuse configurated high signal of the whole sacrum in bilateral fractures (H-pattern). An additional soft tissue mass could be excluded in each case. CONCLUSION: Gadopentate dimeglumine enhanced MRI of sacral insufficiency fractures allows early diagnosis and helps to exclude intraosseous tumour formation.

[Goals, requirements and prerequisites of teleradiology. An assessment of current status]. / Ziele, Anforderungen und Rahmenbedingungen der Teleradiologie. Eine Bestandsaufnahme.

Specific radiological requirements have to be considered for the realization of telemedicine. In this article the goals and requirements for an extensive introduction of teleradiology will be defined from the radiological user's point of view. Necessary medical, legal and professional prerequisites for teleradiology are presented. Essential requirements, such as data security, maintenance of personal rights and standardization, must be realized. Application-specific requirements, e.g. quality and extent of teleradiological functions, as well as technological alternatives, are discussed. Each project must be carefully planned in relation to one's own needs, extent of functions and system selection. Topics, such as acknowledgement of electronic documentation, reimbursement of teleradiology and liability, must be clarified. Legal advice and the observance of quality guidelines are recommended.

[Cerebral sinus thrombosis: rapid test diagnosis by demonstration of increased plasma D-dimer levels (SimpliRED)]. / Zerebrale Sinusthrombose--Schnelltest-Diagnostik mittels Nachweis erhöhter D-dimer Konzentrationen im Plasma (SimpliRED).

PURPOSE: To perform an initial evaluation of the accuracy in detection of dural sinus and cerebral venous thrombosis using a bed-side test (SimpliRED). MATERIAL AND METHODS: Early diagnosis and treatment of cerebral sinus thrombosis are important. A screening test to decide which patients should undergo further diagnostics would be valuable due to the low incidence. Six patients with MR proven cerebral sinus thrombosis underwent bed-side testing. The SimpliRED kit provides a clearly visible agglutination of the patient's red blood cells in the presence of elevated levels of the crosslinked fibrin derivative (D-dimer) in the sample. RESULTS: The assay yielded a positive result in all six patients, even 56 days following the onset of clinical symptoms. CONCLUSION: The sensitivity of SimpliRED in the detection of sinus venous thrombosis is not known. This assay, therefore, should be evaluated in a large prospective study. In addition, the capability of the test to assess the effect of and predict the duration of anticoagulation therapy should be considered.

Guidelines for cost-effective implementation of Picture Archiving and Communication Systems. An approach building on practical experiences in three European hospitals.

This paper describes a comprehensive approach for the assessment of the impact of (partial) Picture Archiving and Communication Systems (PACS). The approach is developed, based on actual clinical experience in three European hospitals and tested in these environments. The approach departs from a thorough analysis of the working procedures and information flows before implementation, both descriptive and quantitative. On the basis of this analysis, quantitative (and hence testable) objectives of the implementation are defined. The implementation strategy is defined after comparison of various scenarios, taking costs and effects for both the final and the transition phases into account. The approach is supported by a comprehensive evaluation protocol and a software package (PACER). The approach is demonstrated in this paper by applying it on a hypothetical PACS implementation for CT, ultrasound and for the part of the radiology department serving ICU. The objectives of this PACS are: (1)--to shorten the turn around time between the radiology department and ICU from 4 h to 30 min, (2)--to save 2000 m2 of film per year and (3)--to save personnel time. In this case the PACS is introduced in three phases and completed after three years. The cost analysis shows that, if started in 1995, a financial break even point is reached after 6 years, when comparing costs for the film-based system with those of the PACS. Experiences in the three sites show that the approach helps to harvest potential benefits, allowing a cost-effective implementation of PACS.

Differentiation of spontaneous canine breast tumors using dynamic magnetic resonance imaging with 24-Gadolinium-DTPA-cascade-polymer, a new blood-pool agent. Preliminary experience.

RATIONALE AND OBJECTIVES: The author assess the enhancement characteristics over time of spontaneous breast tumors in dogs comparing gadopentetate dimeglumine with a new blood-pool agent (24-gadolinium [Gd]-DTPA-cascade polymer). METHODS: Eighteen dogs with spontaneous breast tumors (5 carcinomas, 4 adenomas, and 9 benign mixed-tissue tumors) underwent dynamic magnetic resonance imaging after intravenous injection of gadopentetate dimeglumine and the blood-pool agent. Signal intensity time curves were followed up to 30 minutes after injection of both agents in the same animal. A nonlinear fitting routine enabled calculation of the delivery and clearance half lives of the contrast agent kinetics in each tumor. RESULTS: For gadopentetate dimeglumine, a fast signal increase was found immediately after intravenous injection, with a subsequent signal decay in all tumors. No difference was observed between the enhancement kinetics of different tumor types after gadopentetate dimeglumine application. Similar kinetics were found in benign lesions after injection of the blood-pool agent. However, in carcinomas the blood-pool agent displayed a slower delivery, delayed peak enhancement, and slower tumor tissue clearance or even a signal plateau of more than 30 minutes. CONCLUSIONS: Dynamic magnetic resonance imaging of breast neoplasms using a blood-pool agent may help to better differentiate between benign and malignant lesions because it demonstrates the enlarged interstitial space and increased capillary permeability in carcinomas.

Fragmentation of pulmonary emboli: in vivo experimental evaluation of two high-speed rotating catheters.

PURPOSE: To test two over-the-wire systems for fragmentation of pulmonary emboli. METHODS: In 11 dogs, 22 embolic occlusions of lobar or central pulmonary arteries were performed by injection of preformed emboli through a jugular vein sheath. A commercially available device (thrombolizer) and a modified version of the impeller catheter were introduced via the femoral vein and positioned at the embolus site. RESULTS: Catheter placement at the site of the emboli was possible. In more than half of the cases a hydrophilic or an extra-stiff guidewire was necessary. The thrombolizer did not rotate properly with its original pneumatic drive and required a major modification. When sufficient rotation was provided, both fragmentation catheters were able to clear the occluded main arteries. Side branches were partly obstructed by the resulting fragments. Recanalization led to a reduction of the emboli-induced elevation of the pulmonary arterial pressure by two-thirds. Histology of the recanalized pulmonary artery segments revealed localized (impeller catheter) and widespread (thrombolizer) periarterial hemorrhage. CONCLUSION: Embolus fragmentation led to a hemodynamic improvement. The impeller catheter was less traumatic compared with the thrombolizer, which was technically insufficient.

[Detectability of focal liver lesions: comparison of MRI at 1.5 T and dynamic spiral CT]. / Erkennbarkeit fokaler Leberläsionen: Vergleich von MRT bei 1,5 T und dynamischer Spiral-CT.

PURPOSE: To compare dynamic spiral CT with MR imaging in the detectability of focal liver lesions. MATERIAL AND METHODS: Thirty-one patients with 62 focal liver lesions (27 benign) were evaluated retrospectively. Dynamic spiral CT scans were compared with T1- and T2- weighted spin-echo (SE) sequences and in part with multi slice 2-D-FLASH and single-shot slice-selective inversion recovery Turbo-FLASH sequences at 1.5 T. RESULTS: Dynamic spiral CT detected 89% of all lesions and was superior to each sequence alone (56-70%), and also to MRI overall (79%) regardless of lesion size, localization, and histology. However, statistical significance (p < 0.05) was only found for the differences between CT and the T1-weighted SE sequence. CONCLUSION: Compared to conventional SE and GE MR imaging sequences, dynamic spiral CT scanning seems to be more effective in the detection of focal liver lesions.

Dynamic Gd-enhanced MR imaging of hepatic hemangioma: is high temporal resolution requisite for characterization?

We assessed the value of high temporal resolution in the dynamic characterization of hepatic hemangioma with use of magnetization-prepared gradient-echo (MP-GRE) imaging. Single-level inversion recovery incremental flip angle MP-GRE images were obtained in 26 patients with 34 hemangiomas before and at a repetition rate of 30 images/min after injection of Gd-DTPA without breath-holding. Enhancement patterns and temporal changes thereof were analyzed. Hemangiomas were categorized as small ( < 2.0 cm), medium (2.0-5.0 cm), and large ( > 5 cm) lesions. Classic early peripheral nodular enhancement (PNE) with progressive hyperintense fill-in was observed in 31 lesions (91%). Two of 10 small and 1 of 20 medium lesions showed complete fill-in within 10 s, and three small and one medium lesions within 45 s after the onset of PNE. In no cases of hemangioma was immediate homogenous hyperintensity observed without preceding PNE. In conclusion, temporal resolution of less than 10 s is a prerequisite for confident dynamic characterization of some hemangiomas, predominantly small hemangiomas.

[The MR tomography of avascular necrosis of bone: the primary findings and the follow-up observations after core decompression]. / MR-Tomographie avaskulärer Knochennekrosen: Primärbefunde und Verlaufsbeobachtungen nach Markraumdekompression.

PURPOSE: To assess the signal changes of avascular bone necrosis after core decompression. PATIENTS AND METHODS: 17 patients with avascular epiphyseal necrosis were examined by MRI using T1-weighted spin echo sequences before and after gadopentetate dimeglumine application, T2-weighted spin echo sequences and in some patients with fat-saturated 2D gradient echo sequences up to 22 months after core decompression. RESULTS: All patients but one recovered from symptoms after core decompression. Although the signal morphology of the necrotic area remained unchanged in the majority of the cases, a decrease of the joint effusion was observed as well as an ongoing signal increase after gadopentetate dimeglumine application. The last examinations displayed similar signal characteristics as on the preoperative scans; however, a reduction of the necrotic zone became evident. CONCLUSIONS: The decrease of joint effusion indicates successful core decompression, while a persistent signal increase after gadopentetate dimeglumine application reflects the viability of the necrotic area as well as an ongoing healing process.

[The diagnosis of acute pulmonary embolism: a comparison between spiral CT and DSA in an animal experiment]. / Diagnostik der akuten Lungenembolie: Vergleich zwischen Spiral-CT und DSA im Tierexperiment.

PURPOSE: The value of helical computed tomography (CT) for diagnosis of acute pulmonary embolism was assessed and compared with digital subtraction angiography (DSA) as a reference method. MATERIAL AND METHODS: In 11 dogs, lobar, segmental, and subsegmental occlusions of the pulmonary arteries were produced. Subsequent to selective pulmonary angiography, the animals were examined with contrast-enhanced helical CT. RESULTS: In the main and lobar pulmonary arteries there was a complete correlation between CT and DSA in documentation of total and partial embolic occlusions. Identification of segmental and subsegmental pulmonary emboli by CT required a second run with optimized parameters in 7 of 11 cases. Nevertheless, 18% of the peripheral arteries could not be classified. CONCLUSION: Helical CT as less invasive modality is competitive with DSA in demonstration of central pulmonary emboli. However, CT imaging of peripheral pulmonary emboli requires optimal bolus timing.

[Intrarenal duplex sonography in detecting flow changes after renal PTA]. / Intrarenale Duplexsonographie zur Erfassung von Flussänderungen nach renaler PTA.

PURPOSE: Changes of the intrarenal Doppler signal were analysed before and after renal balloon dilatation to assess the technical success of PTRA. MATERIALS AND METHOD: In 33 patients, intrarenal Doppler signal was depicted before and after renal PTA. Doppler flow curve was analysed by using the acceleration index (AI), acceleration time index (AT) and resistance index (RI); for all indices side ratios (AI-R, AT-R and RI-R) were calculated. Balloon dilatation was angiographically successful in all cases. Average stenosis graded 71% before and 21% after PTA. RESULTS: By definition of limits for all indices used, a single patient was graded as non-stenotic before balloon dilatation by application of AI/AI-R and no patient was graded nonstenotic by AI/RI-R. After renal PTA, all indices significantly changed towards normal findings and by application of both AI/AI-R and AI/RI-R, only a single patient was graded stenotic after PTA. CONCLUSION: Intrarenal Doppler signal analysis reliably allows to detect flow changes following renal PTA in patients with renal artery stenosis. It may therefore be used as a noninvasive method to monitor flow improvement after renal PTA and during follow-up.

[Color-coded duplex ultrasonography in the diagnosis of renal artery stenosis]. / Farbkodierte Duplexsonographie in der Erkennung von Nierenarterienstenosen.

PURPOSE: Colour-coded duplex sonography was performed for diagnosis of renal artery stenosis to define standards and criteria for stenosis. MATERIAL AND METHODS: In 20 normotensive volunteers and 123 patients with arterial hypertension, bilateral intrarenal Doppler spectra were examined and the following parameters including side ratios were calculated: pulsatility index (PI), resistance index (RI), acceleration time index (AT) and acceleration index (AI). RESULTS: In 29 of the 123 patients, angiography showed unilateral renal artery stenosis. Acceleration index (AI) was found as the most reliable parameter with a sensitivity of 100% and a specificity of about 94% for stenoses grading at least 70%. CONCLUSIONS: Colour-coded duplex sonography can depict relevant stenoses reliably, but anatomical variations may limit its value as a single screening method. Colour-coded duplex sonography can be, therefore, recommended as an adjunct to angiography for assessment of haemodynamic relevance.