Sonographic detection and follow up of an atypical pineal cyst: a comparison with magnetic resonance imaging. Case report

The incidental ultrasonographic detection of an asymptomatic cystic pineal lesion in a young woman is described and compared with findings on magnetic resonance (MR) images. Follow-up studies obtained using both imaging modalities are presented. The results indicate that transcranial ultrasonography may represent an easy and cost-effective imaging technique for follow up of cystic lesions of the pineal gland, especially in patients unable to undergo MR imaging.     

High-resolution three-dimensional T2-weighted sequence for neuronavigation: a new setup and clinical trial

OBJECT: Conventional imaging for neuronavigation is performed using high-resolution computerized tomography (CT) scanning or a T1-weighted isovoxel magnetic resonance (MR) sequence. The extension of some lesions, however, is depicted much better on T2-weighted MR images. A possible fusion process used to match low-resolution T2-weighted MR image set with a referenced CT or T1-weighted data set leads to poor resolution in the three-dimensional (3D) reconstruction and decreases accuracy, which is unacceptable for neuronavigation. The object of this work was to develop a 3D T2-weighted isovoxel sequence (3D turbo-spin echo [TSE]) for image-guided neuronavigation of the whole brain and to evaluate its clinical application. METHODS: The authors performed a phantom study and a clinical trial on a newly developed T2-weighted isovoxel sequence, 3D TSE, for image-guided neuronavigation using a common 1.5-tesla MR imager (Siemens Sonata whole-body imager). The accuracy study and intraoperative image guidance were performed with the aid of the pointer-based Medtronic Stealth Station Treon. The 3D TSE data set was easily applied to the navigational setup and demonstrated a high registration accuracy during the experimental trial and during an initial prospective clinical trial in 25 patients. The sequence displayed common disposable skin fiducial markers and provided convincing delineation of lesions that appear hyperintense on T2-weighted images such as low-grade gliomas and cavernomas in its clinical application. CONCLUSIONS: Three-dimensional TSE imaging broadens the spectrum of navigational and intraoperative data sets, especially for lesions that appear hyperintense on T2-weighted images. The accuracy of its registration is very reliable and it enables high-resolution reconstruction in any orientation, maintaining the advantages of image-guided surgery.     

Comparative evaluation of intracranial epidermoid tumors with computed tomography and magnetic resonance imaging

The diagnosis of intracranial epidermoid tumors with computed tomography (CT) is often difficult because of indistinct margins, close proximity to the skull base, and a density similar to that of cerebrospinal fluid (CSF). Recent experience with six histologically confirmed epidermoid tumors served to emphasize the value of magnetic resonance (MR) imaging in studying these lesions. MR images were obtained using varying spin echo and inversion recovery techniques with a 0.5-tesla superconducting magnet. CT with and without enhancement had been performed in each case. In Case 1, CT showed an ill-defined left cerebellopontine angle hypodensity. MR imaging clearly showed the presence of abnormal tissue at that location. Case 2 showed a CSF density mass in the right upper posterior fossa. MR imaging of that area showed a variegated signal of a mass extending supratentorially. CT of Case 3 showed a left medial middle fossa hypodensity with an enhancing rim. MR imaging showed a clearly extraaxial mass in that location. In Case 4, a diffuse cerebellar hemispheric hypodensity was observed on CT and was clearly demarcated by MR studies. A huge lesion, thought initially to be an arachnoid cyst on CT of Case 5, was seen on MR imaging to be a large, extraventricular mass displacing the temporal lobe. Finally, CT in Case 6 was suggestive of a poorly demarcated right cerebellopontine angle lesion, which was seen on MR images to be extraaxial, displacing the brain stem. Various MR images more clearly demonstrate the extent of abnormal tissue than CT of epidermoid tumors.(ABSTRACT TRUNCATED AT 250 WORDS)     

Interactive magnetic resonance imaging-guided management of intracranial cystic lesions by using an open magnetic resonance imaging system.

OBJECT: The authors present their experience with neurosurgical procedures requiring real-time imaging feedback such as aspiration of a cystic structure or abscess cavity, decompression of hydrocephalic ventricles, management of arachnoid cysts, and installation of permanent or temporary drainage conduits, in which interactive magnetic resonance (MR) imaging guidance was used to monitor structural alterations associated with the procedure. METHODS: Drainage of eight intraparenchymal brain abscesses in seven patients, decompression of space-occupying cystic or necrotic brain tumors in four patients, and endoscopic management of hydrocephalus associated with arachnoid cysts in three patients were performed using MR imaging-guided frameless stereotaxy in an open-configuration 0.5-tesla superconducting MR imaging system. Intraoperative MR imaging guidance provided accurate information on the course of the surgical procedure and associated intraoperative changes in tissue position, such as the degree of cyst aspiration, the presence or absence of hemorrhage or induced swelling, and changes associated with decompression of adjacent brain parenchyma and the ventricular system. No clinically significant complications were encountered in any patient. There were no targeting errors, and procedural objectives were accomplished in all cases. CONCLUSIONS: Drainage of brain abscesses, punctures of cystic or necrotic intracranial lesions with subsequent aspiration, and management of hydrocephalus can be performed safely and accurately by monitoring the procedure using real-time MR imaging to obtain immediate feedback on associated dynamic tissue changes.     

Noninvasive imaging of the renal arteries.

Currently, four screening/diagnostic studies are available that provide imaging of the renal arteries: duplex ultrasonography, CT angiography, MR angiography, and intravenous DSA. Intravenous DSA is no longer used because of better imaging with MR and CT angiography. MR angiography, CT angiography, and duplex ultrasonography provide excellent sensitivity and specificity when performed by experienced personnel. The screening test of choice depends on the availability, expertise, and cost at individual centers.     

Three-dimensional navigated laparoscopic ultrasonography

BACKGROUND: A three-dimensional (3D) display of diagnostic imaging methods is technically feasible and increasingly important. However, the technical integration of laparoscopic ultrasound and 3D image reconstruction has not yet been realized. For this purpose, an electromagnetic navigation system was integrated into the tip of a conventional laparoscopic ultrasound probe. This first experience with a certified prototype of a navigated 3D laparoscopic ultrasound probe is reported. METHODS: Navigated 3D laparoscopic ultrasound was compared with the imaging data of 3D-navigated transcutaneous ultrasound and 3D computed tomography (CT) scan. The 3D CT scan served as the "gold standard." Clinical applicability, imaging quality, diagnostic potential, and accuracy in volumetric assessment of various well-defined hepatic lesions were analyzed. RESULTS: Navigated 3D laparoscopic ultrasound facilitates exact definition of tumor location and margins. As compared with the "gold standard" of the 3D CT scan, 3D laparoscopic ultrasound has a mild tendency to underestimate the volume of the region of interest (ROI) (D 3.1%). A comparison of 3D laparoscopy and transcutaneous 3D ultrasonography clearly demonstrated that the former is more accurate for volumetric assessment of the ROI. CONCLUSIONS: Three-dimensional laparoscopic ultrasound imaging with a navigated probe is technically feasible. The technique facilitates detailed ultrasound evaluation of laparoscopic procedures involving visual, in-depth, and volumetric perception of complex liver pathologies. Navigated 3D laparoscopic ultrasound may have the potential to improve the significance of laparoscopic ultrasonography, and additionally to become a valuable technology for planning and improving interventions guided by laparoscopic ultrasound.     

Evaluation on major cerebral arterial stenotic lesions with three-dimensional magnetic resonance cisternograms and coordinated MR.CT angiograms

To evaluate major cerebral arterial stenotic lesions within a cisternal space, the outer wall contours of the arteries were depicted on three-dimensional (3D) MR cisternograms. The 3D MR cisternograms were reconstructed by perspective volume-rendering algorithm from the source volume data obtained from the T2-weighted 3D fast spin-echo sequence. Those images were compared with coordinated 3D MR angiograms, and then with 3D CT angiograms through the similar visual projections. The presence of stenotic lesions was indicated by the morphological discrepancy between the outer wall configuration of the itracisternal stenotic artery depicted on the 3D MR cisternograms and the intraluminal boundary shown on the 3D CT angiograms. With application of these techniques, spatial expansion of the stenotic lesions was able to be visualized. In this way, clinical 3D evaluation of the therapeutic effect on and follow-up of intracisternal major cerebral arterial stenotic lesions would be possible in patients with acute ischemic stroke.     

Three-dimensional magnetic resonance imaging based on time-of-flight magnetic resonance angiography for superficial cerebral arteriovenous malformation--technical note

Direct surgery remains important for the treatment of superficial cerebral arteriovenous malformation (AVM). Surgical planning on the basis of careful analysis from various neuroimaging modalities can aid in resection of superficial AVM with favorable outcome. Three-dimensional (3D) magnetic resonance (MR) imaging reconstructed from time-of-flight (TOF) MR angiography was developed as an adjunctive tool for surgical planning of superficial AVM. 3-T TOF MR imaging without contrast medium was performed preoperatively in patients with superficial AVM. The images were imported into OsiriX imaging software and the 3D reconstructed MR image was produced using the volume rendering method. This 3D MR image could clearly visualize the surface angioarchitecture of the AVM with the surrounding brain on a single image, and clarified feeding arteries including draining veins and the relationship with sulci or fissures surrounding the nidus. 3D MR image of the whole AVM angioarchitecture was also displayed by skeletonization of the surrounding brain. Preoperative 3D MR image corresponded to the intraoperative view. Feeders on the brain surface were easily confirmed and obliterated during surgery, with the aid of the 3D MR images. 3D MR imaging for surgical planning of superficial AVM is simple and noninvasive to perform, enhances intraoperative orientation, and is helpful for successful resection.     

Transcranial color-coded duplex sonography allows to assess cerebral perfusion pressure noninvasively following severe traumatic brain injury

Objective  

Assess optimal equation to noninvasively estimate intracranial pressure (eICP) and cerebral perfusion pressure (eCPP) following severe traumatic brain injury (TBI) using transcranial color-coded duplex sonography (TCCDS).     

Reversible cortical auditory dysfunction caused by cerebral vasospasm after ruptured aneurysmal subarachnoid hemorrhage and evaluated by perfusion magnetic resonance imaging. Case report

A 52-year-old woman developed subarachnoid hemorrhage (SAH) caused by a ruptured right internal carotid artery (ICA) aneurysm. Because of the aneurysm configuration, the authors decided to delay surgery and instead undertook serial imaging studies of the aneurysm. The patient remained alert but developed acute bilateral deafness on Day 7. Audiological examination and auditory brainstem responses suggested that the hearing disturbance was cortical in origin. Three-dimensional computed tomography (CT) angiography showed severe vasospasm in the right middle cerebral artery (MCA) and moderate vasospasm in the left ICA and MCA. Three-tesla magnetic resonance (MR) imaging was performed 2 days after the onset of symptoms. Diffusion-weighted and T2-weighted MR images showed an acute infarction in the right insular cortex caused by vasospasm. Perfusion-weighted MR imaging, particularly mean transit time mapping, revealed hypoperfusion in both temporal lobes including the auditory cortex and right auditory radiation. The vasospasm was treated with induction of mild hypertension and hypervolemia. Follow-up MR images, 3D CT angiograms, and audiometry performed 2 weeks after the first examination showed recovery of vasospasm and resolution of perfusion abnormality and hearing disturbance. On Day 26, the aneurysm was successfully occluded with clips and the patient was discharged with no deficits. To the authors' knowledge, this is the first reported case of reversible cortical auditory dysfunction purely due to bilateral cerebral vasospasm detected using perfusion MR imaging after SAH.     

Measurement of lesion area and volume by three-dimensional spoiled gradient-echo MR imaging in osteonecrosis of the femoral head.

The purpose of this investigation is to evaluate the diagnostic ability of three-dimensional spoiled gradient-echo (3D SPGR) magnetic resonance (MR) imaging in cases of osteonecrosis of the femoral head (ONFH), and to determine the accuracy of 3D SPGR imaging in area and volume measurement of ONFH. T1-weighted spin-echo (SE) and 3D SPGR imaging were performed on 20 femoral heads obtained from patients with ONFH. After MR imaging, the femoral heads were cut parallel to the imaging plane and were evaluated histologically. Areas and volumes of necrotic lesions were measured with a computer program and the deviation between MR images and anatomical measurements was evaluated. A low signal intensity band on 3D SPGR MR images was observed in all femoral heads and corresponded histologically to repaired marrow with viable fibrous mesenchymal tissue. The area proximate to the low band area coincided with the necrotic region. Both area and volume measurements by T1-weighted SE and 3D SPGR images showed a strong correlation to histological measurements. The discrepancies between histological and imaging results were minimal in 3D SPGR imaging, especially at the anterior and posterior portions of the femoral head. Three-dimensional SPGR imaging provides more accurate measurements of the area and volume of a necrotic lesion than T1-weighted SE imaging.     

Surgical treatment of poorly visualised and complex cerebrovascular lesions using pre-operative angiographic data as angiographic DynaCT datasets for frameless stereotactic navigation

Background  

Digital subtraction angiography (DSA) is the “gold standard” for the imaging of cerebrovascular lesions, particularly cerebral aneurysms and arteriovenous malformations (AVMs). Current stereotactic navigation is based on computed tomography (CT) and magnetic resonance (MR) images, which—even despite the use of CT angiographic (CTA) or MR angiographic (MRA) sequences—may not reveal small lesions, and may not demonstrate all the different facets of complex lesions.     

New diagnostic imaging for navigation surgery

Progress in diagnostic computed tomography (CT) and magnetic resonance (MR) imaging has been remarkable. Multidetector-row CT provides thin-slice images through the upper abdomen, multiphase abdominal imaging, and 3D images of high quality including CT angiography and multiplanar reformation. The development of MR units provides diffusion-weighted images for detecting abdominal tumors, and the steady-state coherent echo method can be used for imaging of vessels without using contrast media. The 3D images provided in CT and MR imaging facilitate anatomic understanding of tumors and vessels and are useful for preoperative navigation. However, we must be careful when using 3D images for diagnosis, because the subjectivity of the 3D image creator may affect the results. Therefore the original axial images should also be referred to.     

Efficacy of navigation in skull base surgery using composite computer graphics of magnetic resonance and computed tomography images

The efficacy of a neurosurgical navigation system using three-dimensional composite computer graphics (CGs) of magnetic resonance (MR) and computed tomography (CT) images was evaluated in skull base surgery. Three-point transformation was used for integration of MR and CT images. MR and CT image data were obtained with three skin markers placed on the patient's scalp. Volume-rendering manipulations of the data produced three-dimensional CGs of the scalp, brain, and lesions from the MR images, and the scalp and skull from the CT. Composite CGs of the scalp, skull, brain, and lesion were created by registering the three markers on the three-dimensional rendered scalp images obtained from MR imaging and CT in the system. This system was used for 14 patients with skull base lesions. Three-point transformation using three-dimensional CGs was easily performed for multimodal registration. Simulation of surgical procedures on composite CGs aided in comprehension of the skull base anatomy and selection of the optimal approaches. Intraoperative navigation aided in determination of actual spatial position in the skull base and the optimal trajectory to the tumor during surgical procedures.     

A rapid noninvasive method to visualize ruptured aneurysms in the emergency room: three-dimensional power Doppler imaging

OBJECT: Three-dimensional (3D) power Doppler ultrasonography imaging provides a rapid, noninvasive visualization of ruptured intracranial aneurysms, including their relationship to other vascular structures. METHODS: The authors used transcranial 3D power Doppler imaging in the emergency room to examine patients with acute subarachnoid hemorrhage. In all patients, the ruptured aneurysm was rapidly located with 3D power Doppler imaging. Conventional x-ray angiography confirmed both the ultrasonography-based diagnosis and the location of aneurysmal bleeding. CONCLUSIONS: These preliminary results indicate that 3D power Doppler imaging is a rapid, noninvasive screening method for the visualization of ruptured aneurysms.     

Fusion of magnetic resonance angiography and magnetic resonance imaging for surgical planning for meningioma--technical note

A fusion technique for magnetic resonance (MR) angiography and MR imaging was developed to help assess the peritumoral angioarchitecture during surgical planning for meningioma. Three-dimensional time-of-flight (3D-TOF) and 3D-spoiled gradient recalled (SPGR) datasets were obtained from 10 patients with intracranial meningioma, and fused using newly developed volume registration and visualization software. Maximum intensity projection (MIP) images from 3D-TOF MR angiography and axial SPGR MR imaging were displayed at the same time on the monitor. Selecting a vessel on the real-time MIP image indicated the corresponding points on the axial image automatically. Fusion images showed displacement of the anterior cerebral or middle cerebral artery in 7 patients and encasement of the anterior cerebral arteries in 1 patient, with no relationship between the main arterial trunk and tumor in 2 patients. Fusion of MR angiography and MR imaging can clarify relationships between the intracranial vasculature and meningioma, and may be helpful for surgical planning for meningioma.     

Dual-Source CT-Angiographie von Karotisstenosen im Vergleich zu MR-Angiographie und Duplexsonographie

Aim

The aim of this study was to evaluate the accuracy of dual source CT angiography of the carotid artery in comparison with MR angiography and color-coded duplex ultrasound (US).

Material and methods

From 15 symptomatic patients 30 carotid arteries were evaluated for the degree of stenosis following the NASCET criteria for angiography and the DEGUM criteria for sonography. Each patient was examined using duplex ultrasound, 3T MR angiography and contrast-enhanced dual source CT angiography (DSCT) (tube A 140 kV, 55 mA, tube B 80 kV, 230 mA; 64×0.6 mm coll, pitch 0.65 rot. 0.33 s) of the extracranial carotid artery. Images were reconstructed in 1 mm section thickness and direct bone removal was performed for optimal visualization after the scan. All dual source CT and MR angiography images were evaluated and measured by the same experienced radiologist and all duplex ultrasound results by the same neurologist. Measurement results were compared and correlated.

Results

The mean degree of stenosis was 48% by CT (SD 35%), 49% by MR (SD 38%) and 47% by US (SD 41%). There was no statistically significant difference in stenosis evaluation between CT and MR (p=0.83) or between CT and US (p=0.75). The correlation coefficient between CT and MR was r=0.8327, between CT and US r=0.8424 and between US and MR r=0.8260.

Conclusion

Dual source CT evaluation of the carotid arteries allows a reliable measurement of carotid artery stenosis. Results are comparable to MR angiography and US.     

New strategy for the diagnosis of parotid gland lesions utilizing three-dimensional sialography.

Three-dimensional (3D) imaging for parotid gland lesions was performed using 3D sialography. This method provided a detailed surface structure of the parotid gland, and made it possible to overcome the disadvantages of X-ray sialography, planar CT, and MRI. Immediately after the conventional sialography via an oral route, CT scanning was performed with a slice-thickness of 3 mm using a helical CT scanner. CT data were analyzed on a workstation to reconstruct 3D images. 3D sialography was found to have the following advantages: (1) The structure of the acinar surface is visualized in detail; (2) The 3D structure of the entire parotid system from Stensen's duct to the gland is shown in one image; (3) The parotid gland can be assessed in the context of the bony architecture of facial bones; (4) The surface structure of the parotid gland can be understood very easily, like a scanning electron micrograph. We conclude that 3D sialography is a useful imaging technique for parotid gland lesions.     

Fusion imaging of the 3D MR cisternography/angiography for the assessment of the intracranial major cerebral arterial stenosis

The fusion imaging of the 3D MR cisternography (MRC) and 3D MR angiography (MRA) was applied for the assessment of the major cerebral arterial stenosis. The outer wall configurations of the stenotic lesions of the intracranial major cerebral arteries within a cisternal space were depicted by 3D MRC. Flow-related vascular structures were shown by 3D MRA. Fusion imaging was created by compositing volumetric data of MRC and co-registered MRA by using a workstation with transparent perspective volume-rendering technique. Stenotic lesions of the intracranial cerebral arteries were assessed as a discrepancy of 3D MRC and 3D MRA findings on a fusion image. Fusion imaging of 3D MRC/MRA could visualize stenotic lesions of the intracranial major cerebral arteries caused by atherosclerotic plaques; and this may provide useful information in the management of acute and chronic ischemic stroke caused by atherosclerosis of the intracranial major cerebral arteries.     

Noninvasive procedures for diagnosis of renovascular hypertension in renal transplant recipients--a prospective analysis.

The purpose of this study was to clarify the selectivity and specificity of noninvasive procedures for diagnosis of clinically suspected posttransplant renovascular hypertension. We prospectively investigated 25 renal transplant recipients with arterial hypertension and clinically suspected stenosis of the graft artery (8 female and 17 male patients; ages 45 +/- 15 years). We performed a captopril test with 25 mg captopril (n = 25), renography with technetium-99m diethylene triamine penta-acetic acid (99mTc-DTPA) before and after angiotensin-converting enzyme (ACE) inhibition with determination of glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) (n = 23) and color-coded duplex ultrasonography of the transplant kidney vessels (n = 24). Renal transplant artery stenosis (RTAS) was excluded by renal arteriography in 20 patients and by operative evaluation or clinical follow-up in 5 patients. We identified 4 patients with RTAS and renovascular hypertension. The noninvasive methods showed the following results (sensitivity/specificity): (1) captopril test: 75%/67%; (2) renography combined with ACE-inhibition: 75%/84%; and (3) color-coded duplex ultrasonography: 100%/75%. We conclude that in patients with clinical evidence of RTAS most noninvasive diagnostic procedures are not sufficiently accurate to exclude the diagnosis. Only color-coded duplex ultrasonography did not fail to detect all patients with RTAS and may act as a screening test. Intraarterial renal angiography remains the most reliable and as-yet indispensable diagnostic test for transplant recipients to rule out RTAS.