The role of time-resolved 3D contrast-enhanced MR angiography in the assessment and grading of cerebral arteriovenous malformations

Purpose

To assess the role of three-dimensional (3D) contrast-enhanced, time-resolved MR angiography (CE TR MRA) in patients with intracranial arteriovenous malformations (AVMs).

Methods

We studied 12 patient with intracranial AVMs on a 3.0 T MR imaging system (Magentom TIM Trio, Siemens Medical Solutions, Erlangen, Germany) using 3D CE TR MRA with autocalibrating partially parallel acquisitions and echo sharing schemes, which provided temporal resolution of 0.58 or 1.7 s and near isotropic voxels. We qualitatively assessed image quality of the 3D CE TR MRA and compared the grading of the AVMs based on modified Spetzler-Martin system for 3D CE TR MRA and catheter digital subtraction angiography (DSA).

Results

CE TR MRA provided good quality images in the 3 standard orthogonal planes, and good arterial-venous separation in all cases. All AVMs were correctly graded by CE TR MRA when compared with DSA.3D CE TR MRA provides a non-invasive alternative to DSA for the evaluation of cerebral AVMs.     

Gadofosveset trisodium-enhanced magnetic resonance angiography of the left atrium—A feasibility study

Aim

Imaging of the left atrium is regularly performed prior to pulmonary vein isolation. The aim of the study was to evaluate the feasibility of contrast-enhanced high-resolution magnetic resonance angiography (MRA) of the left atrium using the blood-pool contrast agent gadofosveset trisodium in comparison to noncontrast MRA.

Materials and methods

Twenty consecutive patients were examined by free-breathing electrocardiogram-gated whole-heart MRA (reconstructed spatial resolution, 0.7 mm × 0.6 mm × 0.8 mm) with a noncontrast T2-prepared steady state free precession sequence (T2-prep SSFP) and a gadofosveset trisodium-enhanced inversion-recovery SSFP sequence (CE IR-SSFP). Contrast-to-noise ratio (CNR) of blood in the left atrium was determined. Depiction of the left atrium was rated by two radiologists in consensus. A cardiologist segmented the MR data sets and rated depiction of the left atrium.

Results

Five of 20 patients had irregular breathing patterns with navigator efficiency less than 35% and were excluded from evaluation. CNR was significantly higher for CE IR-SSFP compared with T2-prep SSFP (18.4 ± 5.3 vs. 11.7 ± 3.5, p < 0.01). Depiction of the left atrium by T2-prep SSFP was rated as good in four patients, moderate in ten patients, and poor in one patient, whereas depiction of the left atrium by CE IR-SSFP was rated as excellent in nine patients, good in four patients, and moderate in two patients. CE IR-SSFP allowed for semiautomated segmentation of the left atrium in 15 patients, whereas T2-prep SSFP allowed for segmentation only in ten patients.

Conclusion

Gadofosveset trisodium-enhanced MRA of the left atrium is feasible with significantly improved image quality compared to noncontrast MRA.     

Cranial involvement in sickle cell disease

Purpose

To evaluate cranial findings in patients with neurologically symptomatic sickle cell disease (SCD).

Materials and methods

We studied 50 consecutive patients with SCD and neurologic symptoms. All patients underwent brain MR examinations: all 50 underwent classic MR imaging; 42, diffusion-weighted MR imaging; 10, MR angiography; four, MR venography; and three patients, digital subtraction angiography.

Results

Of the 50 SCD patients, 19 (38%) had normal MR findings, and 31 (62%) showed abnormalities on brain MR images. Of the 50 patients, 16 (32%) had ischemic lesions; two (4%), subarachnoid hemorrhage; one (2%), moya-moya pattern; one (2%), posterior reversible encephalopathy; one (2%), dural venous sinus thrombosis; 12 (24%), low marrow signal intensity and thickness of the diploic space; 12 (24%), cerebral atrophy; and two (4%), osteomyelitis. Twenty-seven patients (54%) presented with headache, which was the most common clinical finding.

Conclusions

The cranial involvement is one of the most devastating complications of SCD. Early and accurate diagnosis is important in the management of cranial complications of SCD.     

Embolization of intracranial dural arteriovenous fistulas with Onyx-18

Background and purpose

The use of Onyx in the treatment of AVMs has been reported in the literature, but experience in the treatment of DAVF is lacking. We report the clinical outcome obtained in the treatment of dural arteriovenous fistulas (DAVFs) using a new liquid embolic agent, Onyx-18.

Methods

The present series included 21 patients; 9 had DAVFs draining directly into the cortical veins, 6 had DAVFs draining directly into the dural sinus, 4 had DAVFs draining through the ophthalmic veins and 2 had DAVFs involving the dural sinus with leptomeningeal retrograde venous drainage Clinical data were extracted from hospital files and all patients were followed.

Results

In 14 patients (70%) there was complete angiographic elimination of the shunts and resolution of the symptoms. The remaining 7(30%) patients was not cured with residual shunts. Adverse events occurred in 6(30%) of 21 patients with 1 DAVF located at the transverse sigmoid sinus, 2 at tentorium, and 3 at the cavernous sinus. Cranial deficits occurred in 3(15%) patients, brain infarction in 1(5%) patient and microcatheter gluing in 1(3.2%) patient. At final follow up, 20 patients were asymptomatic with 1 showed clinical improvement.

Conclusion

Definitive cure may be attained effectively with Onyx in dural arteriovenous fistulas and adjunctive to surgery and radiotherapy. Location of the DAVFs affected the outcome of transarterial embolization.     

Percutaneous transvenous packing of cavernous sinus with Onyx for cavernous dural arteriovenous fistula

Objective

The aim of this study is to describe the technique and results of the transvenous approach for occlusion of cavernous dural arteriovenous fistulas (DAVFs) with Onyx.

Methods

Eleven patients presenting with clinically symptomatic DAVFs, were treated between August 2005 and February 2007 at Beijing Tiantan Hospital. We were able to navigate small hydrophilic catheters and microguidwires through the facial vein or inferior petrosal sinus (IPS) into the ipsilateral cavernous sinus. After reaching the fistula site the cavernous sinus was packed with Onyx or combining with detachable platinum coils.

Results

We were able to reach the fistula site and to achieve a good packing of Onyx or combining with coils within the arteriovenous shunting zone in 10 patients. The final angiogram showed complete occlusion of the arteriovenous fistula. Two (18.2%) patients developed a bradycardia during DMSO injection. No complications related to the approach were observed.

Conclusions

Transvenous occlusion of cavernous DAVFs is a feasible approach, even via facial vein or via IPS. Onyx may be another option for cavernous packing other than detachable platinum coils.     

New experimental model of sinus and cortical vein thrombosis in pigs for MR imaging studies

Introduction Diagnosis of cerebral sinus vein thrombosis is still a challenge for imaging. MRI and MRA play a major role in sinus imaging. For further development of MR techniques, MR-compatible animal models are required. The aim of this study was to develop an animal model for sinus thrombosis and additional cortical vein thrombosis with a clot of human blood for MR imaging studies.Methods A combined surgical and interventional approach was carried out in 13 pigs. After minimal invasive surgical access to the anterior superior sagittal sinus and cortical vein, thrombosis with human blood was induced using an interventional catheter approach. MR imaging was performed prior to and after thrombus induction.Results Sinus thrombosis was induced in 12 of 13 animals. Three animals suffered acute subdural haemorrhage; one of these animals died during the intervention, and one died after thrombus induction. MR imaging of the thrombosed sinus could easily be performed without significant artefacts in 11 of 13 animals.Conclusion This new model of sinus and cortical vein thrombosis with a clot of human blood allows artefact-free imaging studies on MR.     

View-sharing in keyhole imaging: Partially compressed central k-space acquisition in time-resolved MRA at 3.0 T

Introduction

Time-resolved contrast-enhanced magnetic resonance (MR) angiography (CEMRA) of the intracranial vasculature has proved its clinical value for the evaluation of cerebral vascular disease in cases where both flow hemodynamics and morphology are important. The purpose of this study was to evaluate a combination of view-sharing with keyhole imaging to increase spatial and temporal resolution of time-resolved CEMRA at 3.0 T.

Methods

Alternating view-sharing was combined with randomly segmented k-space ordering, keyhole imaging, partial Fourier and parallel imaging (4DkvsMRA). 4DkvsMRA was evaluated using varying compression factors (80-100) resulting in spatial resolutions ranging from (1.1 × 1.1 × 1.4) to (0.96 × 0.96 × 0.95) mm³ and temporal resolutions ranging from 586 ms/dynamic scan - 288 ms/dynamic scan in three protocols in 10 healthy volunteers and seven patients (17 subjects). DSA correlation was available in four patients with cerebral arteriovenous malformations (cAVMs) and one patient with cerebral teleangiectasia.

Results

4DkvsMRA was successfully performed in all subjects and showed clear depiction of arterial and venous phases with diagnostic image quality. At the maximum view-sharing compression factor (=100), a “flickering” artefact was observed.

Conclusion

View-sharing in keyhole imaging allows for increased spatial and temporal resolution in time-resolved MRA.     

Isolated oculomotor nerve palsy in interventional neuroradiology

Background

Isolated oculomotor nerve palsy (IOP) can be annoying for a patient and can also be the only clue to a potentially devastating and life-threatening disease. In order to understand its clinical spectrum and management better we analyzed the files of 13 patients seen at our institution over a 3-year period.

Methods

Thirteen consecutive patients with IOP between January 2005 and August 2008 presented to our hospital. Magnetic resonance imaging and angiography were employed as investigations tailored to the individual patient. A vascular disorder [i.e. arteriovenous fistula, aneurysm of the posterior communicating artery (Pcoma)] was found in 7 patients (63%), most commonly a dural carotid-cavernous sinus fistula (DCCF) or a Pcoma aneurysm.

Results

In 7 patients with a vascular abnormality (4 DCCFs; 3 Pcoma aneurysms), IOP was the presenting symptom. Pcoma aneurysms were coiled endovascularly and DCCFs were managed transvenously. Of the patients with more than 1 year (6 months to 2 years) of follow-up, all 7 endovascular patients recovered completely. Time to complete resolution of ONP was 6 months.

Conclusion

Patients with IOP should be investigated with noninvasive techniques (MRI and MRA). If these are negative or to clarify abnormal findings of noninvasive techniques, selective angiography is needed for diagnosis and to guide treatment.     

Recovery of opthalmoplegia associated with cavernous sinus dural arteriovenous fistulas after transvenous cavernous sinus packing

Background

We report the recovery of ophthalmoplegia in 11 patients with cavernous sinus dural arteriovenous fistula (CSDAVF) after sinus packing at follow-up.

Methods

Of 18 patients with CSDAVF treated with transvenous cavernous sinus packing between August 2002 and December 2007 at Beijing Tiantan Hospital, there were 9 patients with initial CNIII or CNVI dysfunction and 2 patients with CNVI dysfunction immediately after cavernous sinus packing selected and reevaluated.

Results

Of 11 patients with CNIII or CNVI palsy, recovery was complete in 10. In 1 patient, complete CNVI palsy was unchanged because the CSDAVF was not cured. There were 6 men and 5 women with a mean age of 52.9 years. In 5 patients, CNVI palsy was associated with chemosis, proptosis and pulsatile tinnitus. Timing of treatment after onset of symptoms was from 4 to 35 days in 9 patients. All CSDAVFs were Barrow type D. Mean follow-up after treatment was 17.7 months (range, 2-54 months).

Conclusion

CSDAVF-induced CNIII or CNVI palsies can be cured after cavernous sinus packing transvenously in most patients.     

Diagnosis of portal vein thrombosis discontinued with liver tumors in patients with liver cirrhosis and tumors by contrast-enhanced US: A pilot study

Aims

We assessed the role of contrast-enhanced ultrasound (CEUS) in the differential diagnosis between benign and malignant portal vein thrombosis (PVT) in patients who had liver tumors.

Methods

Seventeen consecutive patients who had cirrhosis, liver tumors, and PVT were prospectively studied with CEUS. CEUS was performed at low mechanical index after intravenous administration of a second-generation contrast agent (SonoVue, Bracco, Milan, Italy). Presence or absence of thrombus enhancement on CEUS were considered diagnostic for malignant or benign PVT. Five patients also underwent percutaneous portal vein fine-needle biopsy under US guidance. All patients were followed-up. Shrinkage of the thrombus and/or recanalization of the vessels on CDUS during follow-up were considered definitive evidence of the benign nature of the thrombosis, whereas the enlargement of the thrombus, disruption of the vessel wall, and parenchymal infiltration over follow-up were considered consistent with malignancy.

Results

Follow-up showed signs of malignant thrombosis in 14 of 17 patients. CEUS showed early arterial enhancement of the PVT in 14 patients of 14 malignant PVT, 1 patient of 3 benign PVT and the absence of thrombus enhancement in 2 patients of 3 benign PVT. FNB confirmed the results for malignant PVT in four of five patients, for benign granulomatous inflammation PVT in one of five patients in which CEUS showed early arterial enhancement of the PVT. The sensitivity, specificity and accuracy is 100%, 66.7% and 93.3% at diagnosis of malignant PVT using CEUS. In one patient with intrahepatic bile duct stone, CEUS were positive for malignant PVT, whereas FNB was negative (benign granulomatous inflammation PVT); follow-up examination confirmed benign PVT.

Conclusion

CEUS seems to be the pretty sensitive and specific test for diagnosing malignant portal vein thrombosis in patients with cirrhosis and tumors.     

Magnetresonanz-Angiographie bei entzündlichen Hirnerkrankungen

In this review, we discuss the diagnostic potential of time of flight (TOF) MRA and contrast enhanced (CE) MRA in inflammatory disorders of the meninges and the brain. Cerebrovascular complications are frequently observed during infectious meningoencepalitis. 3D TOF-MRA and CE-MRA are complementary for the detection of basal intracranial artery stenosis and septic cerebral vein and sinus thrombosis due to secondary vasculitis. MRA reveals stenosis and occlusion as indirect signs of vasculitis, whereas MRI shows the inflammation of the brain and meninges and occasionally the vessel wall, together with the ischemic or hemorrhagic complication. In case of septic emboli MRA can detect peripheral occlusions and "mycotic" aneurysms. For the diagnosis of noninfectious vasculitides of the intracranial vessels, high resolution 3D TOF-MRA is superior to CE-MRA for the detection of multiloculated segmental stenoses. However, there are presently no prospective studies on the sensitivity and specificity of MRA for these indications. Therefore, only positive MRA results can directly influence clinical management. In case of normal MRA, confirmation by catheder angiography may still be required.     

Endovascular treatment of dural fistulas with the venous outflow of laterocavernous sinus

Objective

To report our findings concerning the laterocavernous sinus (LCS) drainage of dural fistulas, focusing our attention on the important implications in treatment of the LCS, which is one of the principal drainage pathways of the superficial middle cerebral vein (SMCV).

Methods

Consecutive 32 patients with dural fistulas treated endovascularly between 2005 and 2008 were reviewed. Seven patients had angiographic features such as dural fistulas draining with SMCV via LCS. Clinical records for these 7 patients were focused to determine their presenting symptoms, angiographic features, endovascular treatments, and clinical outcomes.

Results

Over 3 years, 7 patients had 7 dural fistulas drained with SMCV via LCS were treated. Six-vessel angiography confirmed the presence of the dural fistulas. All fistulas were Cognard Type III featured by leptomeningeal veins drainage. One fistula involving the lesser sphenoid wing and 6 fistulas involving CS were supplied by external carotid artery branches with or without dural branches of the internal carotid artery. LCS was identified as a contiguous to SMCV drainage in these cases. One patient was treated with transvenous coil embolization alone, two with transvenous a combination of Onyx and coil embolization, and 4 with transarterial embolization. An angiographic obliteration and clinical cure was achieved in all patients. Complication was local hair loss due to X-ray radiation in one patient.

Conclusion

It is very important to diagnose the presence of LCS in dural fistulas during the diagnostic angiography. It is believed that the knowledge of LCS might be relevant for the understanding and treatment of dural fistulas involving the LCS.     

Potential advantages and limitations of the Leo stent in endovascular treatment of complex cerebral aneurysms

Objective

The Leo self-expandable stent is a new retractable stent that is delivered via a conventional catheter. The aim of this study was to evaluate the use of this stent for endovascular treatment of complex aneurysms.

Methods

Twenty-eight complex cerebral aneurysms (27 saccular and 1 fusiform) in 28 patients were treated electively. They were located at the internal carotid artery (17), basilar trunk (3), anterior cerebral artery (1), anterior communicating artery (3), vertebral artery (2) and middle cerebral artery (2). One aneurysm exhibited recanalization after primary endovascular treatment without stent. Clinical outcome was assessed with the modified Glasgow Outcome Scale.

Results

Deployment of Leo stent was successful in 26 lesions, and difficulties in stent positioning due to tortuous cerebral circulation in 2 cases, which were treated with Neuroform stent. Additional coil embolization was performed in 26 lesions. No permanent neurological deficits were encountered consequent to endovascular procedure. Complete or partial occlusion immediately after stent deployment was achieved in all aneurysms. There was no immediate coil embolization was chosen in 3 cases because of subsequent reduced filling of the aneurysms with contrast agent on angiograms. There were 3 asymptomatic parent artery occlusion related to the deployment of the Leo stent, one stent migration. Follow-up revealed patent stents in the remaining cases. No angiographic recurrences arose.

Conclusion

The Leo stent is very useful for endovascular treatment of complex cerebral aneurysms because it is easy to navigate and place precisely. A drawback is that in-stent thrombosis caused by stent placement and stiffer delivery catheters to place larger stents.     

A comparative evaluation of Cone Beam Computed Tomography (CBCT) and Multi-Slice CT (MSCT). Part II: On 3D model accuracy

Aim

The study aim was to compare the geometric accuracy of three-dimensional (3D) surface model reconstructions between five Cone Beam Computed Tomography (CBCT) scanners and one Multi-Slice CT (MSCT) system.

Materials and methods

A dry human mandible was scanned with five CBCT systems (NewTom 3G, Accuitomo 3D, i-CAT, Galileos, Scanora 3D) and one MSCT scanner (Somatom Sensation 16). A 3D surface bone model was created from the six systems. The reference (gold standard) 3D model was obtained with a high resolution laser surface scanner. The 3D models from the five systems were compared with the gold standard using a point-based rigid registration algorithm.

Results

The mean deviation from the gold standard for MSCT was 0.137 mm and for CBCT were 0.282, 0.225, 0.165, 0.386 and 0.206 mm for the i-CAT, Accuitomo, NewTom, Scanora and Galileos, respectively.

Conclusion

The results show that the accuracy of CBCT 3D surface model reconstructions is somewhat lower but acceptable comparing to MSCT from the gold standard.     

Quantitative assessment of the superior sagittal sinus on unenhanced computed tomography

Purpose

To determine the relationship between hemoglobin levels and attenuation measurements of the superior sagittal sinus (SSS) on unenhanced computed tomography (UECT). Secondly, to determine if SSS attenuation values are normally distributed such that measurements below and above certain thresholds are suggestive of pathology, such as anemia or acute venous thrombosis respectively.

Methods

Institutional review board approval was obtained for retrospective review of adult patients having both an UECT head examination and a complete blood count within 24 h of the scan. A cohort of 151 consecutive patients formed the study sample (76 males and 75 females, 17-91 years of age with a mean of 61). The dorsal aspect of the SSS was divided into upper, middle and lower segments. Using freehand and circle region of interest (ROI) techniques, a total of six attenuation measurements were obtained from each patient. Next, statistical analyses were preformed to assess the correlation between Hgb levels and attenuation values, and distribution curves were plotted to assess the normal range of SSS attenuation measurements.

Results

There is a moderate, yet statistically significant (p < 0.001), correlation between Hgb levels and attenuation values in upper, middle and lower segments of the SSS (r = 0.487, 0.497 and 0.533 respectively). Based on the calculated mean, median and mode, the attenuation values are normally distributed. When using the freehand ROI technique, the mean value is 50 Hounsfield Units (HU) with a standard deviation (SD) of 7.5. Attenuation values less than 2 SDs (35 HU) are highly suggestive of anemia (specificity and PPV = 100%).

Conclusion

There is a moderate, yet statistically significant, correlation between Hgb levels and attenuation of the SSS on UECT. Furthermore, attenuation measurements of the SSS are normally distributed with a mean of 50 HU and a SD of 7.5. Therefore, quantitative assessment of the SSS may prove useful in the clinical practice of a radiologist; namely, in the diagnosis of anemia and acute venous thrombosis.     

A comparative study for spatial resolution and subjective image characteristics of a multi-slice CT and a cone-beam CT for dental use

Purpose

Multi-slice CT (MSCT) and cone-beam CT (CBCT) are widely used in dental practice. This study compared the spatial resolution of these CT systems to elucidate which CT modalities should be selected for various clinical cases.

Materials and methods

As MSCT and CBCT apparatuses, Somatom Sensation 64 and 3D Accuitomo instruments, respectively, were used. As an objective evaluation of spatial resolution of these CT systems, modulation transfer function (MTF) analysis was performed employing an over-sampling method. The results of MTF analysis were confirmed with a line-pair test using CATPHAN. As a subjective evaluation, a microstructure visualization ability study was performed using a Jcl:SD rat and a head CT phantom.

Results

MTF analysis showed that for the in-plane direction, the z-axis ultrahigh resolution mode (zUHR) of the Sensation 64 and 3D Accuitomo instruments had higher spatial resolutions than the conventional mode (64×) of the Sensation 64, but for the longitudinal direction, the 3D Accuitomo had clearly higher spatial resolution than either mode of the Sensation 64. A line-pair test study and microstructure visualization ability studies confirmed the results for MTF analysis. However, images of the rat and the CT phantom revealed that the 3D Accuitomo demonstrated the failure to visualize the soft tissues along with aliasing and beam-hardening artifacts, which were not observed in the Sensation 64.

Conclusions

This study successfully applied spatial resolution analysis using MSCT and CBCT systems in a comparative manner. These findings could help in deciding which CT modality should be selected for various clinical cases.     

Evaluation of suspicious nipple discharge with MRI: review of 50 cases

Purpose

To determine the role of MRI in the evaluation and management of patients with suspicious nipple discharge and normal mammographic and US evaluation.

Patients and methods

A total of 50 patients with suspicious nipple discharge and normal mammographic and US evaluation prospectively underwent MRI. The first 16 patients underwent routine breast MRI, while MR-ductography with image fusion at the console was added for the last 34 patients.

Results

In 22 of 25 high-risk and malignant lesions, MRI showed enhancement whereas it was normal in three cases. In 25 benign cases (resolution of discharge/benign non-proliferative breast disease), MRI was negative in 22 cases and falsely positive in three cases.

Conclusion

In this clinical setting, MRI shows excellent sensitivity, PPV and NPV. A negative result on MRI would support clinical follow-up as opposed to surgery.     

Neuroimaging findings in children with retinopathy-confirmed cerebral malaria

Purpose

To describe brain CT findings in retinopathy-confirmed, paediatric cerebral malaria.

Materials and methods

In this outcomes study of paediatric cerebral malaria, a subset of children with protracted coma during initial presentation was scanned acutely. Survivors experiencing adverse neurological outcomes also underwent a head CT. All children had ophthalmological examination to confirm the presence of the retinopathy specific for cerebral malaria. Independent interpretation of CT images was provided by two neuroradiologists.

Results

Acute brain CT findings in three children included diffuse oedema with obstructive hydrocephalus (2), acute cerebral infarctions in multiple large vessel distributions with secondary oedema and herniation (1), and oedema of thalamic grey matter (1). One child who was reportedly normal prior to admission had parenchymal atrophy suggestive of pre-existing CNS injury.Among 56 survivors (9-84 months old), 15 had adverse neurologic outcomes—11/15 had a follow-up head CT, 3/15 died and 1/15 refused CT. Follow-up head CTs obtained 7-18 months after the acute infection revealed focal and multifocal lobar atrophy correlating to regions affected by focal seizures during the acute infection (5/11). Other findings were communicating hydrocephalus (2/11), vermian atrophy (1/11) and normal studies (3/11).

Conclusions

The identification of pre-existing imaging abnormalities in acute cerebral malaria suggests that population-based studies are required to establish the rate and nature of incidental imaging abnormalities in Malawi. Children with focal seizures during acute cerebral malaria developed focal cortical atrophy in these regions at follow-up. Longitudinal studies are needed to further elucidate mechanisms of CNS injury and death in this common fatal disease.     

Improving the image quality of contrast-enhanced MR angiography by automated image registration: A prospective study in peripheral arterial disease of the lower extremities

Objective

If a patient has moved during digital subtraction angiography (DSA), manual pixel shift can improve the image quality. This study investigated whether such image registration can also improve the quality of contrast-enhanced magnetic resonance angiography (MRA) in patients with peripheral arterial disease of the lower extremities.

Materials and methods

404 leg MRAs of patients likely to have peripheral artery disease were included in this prospective study. The standard non-registered MRAs were compared to automatically linear, affine and warp registered MRAs by four image quality parameters, including the vessel detection probability (VDP) in maximum intensity projection (MIP) images and contrast-to-noise ratios (CNR). The different registration types were compared by analysis of variance.

Results

All studied image quality parameters showed similar trends. Generally, registration improved the leg MRA quality significantly (P < 0.05). The 12% of lower legs with a body shift of 1 mm or more showed the highest gain in image quality when using linear registration instead of no registration, with an average VDP gain of 20-49%. Warp registration improved the image quality slightly further.

Conclusion

Automated image registration can improve the MRA image quality especially in the lower legs, which is comparable to the effect of pixel shift in DSA.     

Fire victim identification by post-mortem dental CT: Radiologic evaluation of restorative materials after exposure to high temperatures

Objectives

The aim of this study was to evaluate the use of high resolution CT to radiologically define teeth filling material properties in terms of Hounsfield units after high temperature exposure.

Methods

122 human molars with 10 different filling materials at defined filling diameters were examined. The teeth were CT scanned both before and after the exposure to different temperatures. After image reconstruction, the teeth and filling materials were analyzed regarding their morphology and Hounsfield units (HU) using an extended HU scale.

Results

The majority of filling materials diminished in size at temperatures ≥400 °C. HU values were stable for all materials up till 200 °C, and only slightly changed up to 600 °C. Cerec, Dyract and dentin showed only minor changes in HU at all temperatures. The other materials, inclusive enamel, showed specific patterns, either increasing or decreasing in HU with increasing temperatures over 600 °C.

Conclusions

Over 600 °C the filling materials show specific patterns that can be used to discriminate filling materials. Ultra high resolution CT may improve the identification processes in fire victims. Existing 3D visualization presets for the dentition can be used until 600 °C and have to be optimized for bodies exposed to higher temperatures.