Novel Automated Method for the Detection of White Matter Hyperintensities in Brain Multispectral MR Images

BACKGROUND

According to the Standards for Reporting Vascular Changes on Neuroimaging, White Matter Hyperintensities (WMHs) are cerebral white matter lesions that are characterized by abnormal tissues of variable sizes and appear hyperintense in T2-weighted Magnetic Resonance (MR) measurements without cavitation (i.e., their tissue signals differ from those of Cerebrospinal Fluid or CSF). Such abnormal tissue regions are typically observed in the MR images of brains of healthy older adults and are associated with a number of geriatric neurodegenerative diseases. Explanations of the exact causes and mechanisms of these diseases remain inconclusive. Moreover, WMHs are typically identified by visual assessment and manual examination, both of which require considerable time. This brings up a need of developing a method for detecting WMHs more objectively and enabling patients to be treated early. As a consequence, damages on nerve cells can be limited and the severity of patients' conditions can be contained.

AIMS

This paper presents a computer-aided technique for automatically detecting and segmenting anomalies in MR images.

METHODS

The method has two steps: (1) a Band Expansion Process (BEP) to expand the dimensions of brain MR images nonlinearly and (2) anomaly detection algorithms to detect WMHs. Synthesized MR images provided by BrainWeb were used as benchmarks against which the detection performance of the algorithms was determined.

RESULTS

The most notable findings are as follows: Firstly, compared with the other anomaly detection algorithms and the Lesion Segmentation Tool (LST), BEP-anomaly detection is shown to be the most effective in detecting WMHs. Secondly, across all levels of background noise and inhomogeneity, the mean Similarity Index (SI) produced by our proposed algorithm is higher than that produced by LST, indicating that the algorithm is more effective than LST in segmenting WMHs from brain MR images.

CONCLUSION

Experimental results demonstrated a significantly high accuracy of the BEP-K/R-RX method in detection of synthetic brain MS lesion data. In the meantime, it also effectively enhances the detection of brain lesions.

Outcome analysis in 270 radiologically guided implantations of totally implantable venous access ports via basilic vein

BACKGROUND

Totally implantable venous access ports (TIVAPs) are widely applied in patients who require chemotherapy, parenteral nutrition, or frequent intravenous drug infusion. Although various venous access routes are possible for TIVAP insertion, the best method remains a topic of controversy. We present a single-center retrospective study of radiologically guided placement of TIVAPs through the basilic vein, with analysis of technical feasibility, patient safety, and device-related complications.

METHODS

We retrospectively reviewed 270 patients who received TIVAP implantation through the basilic vein from November 2013 to July 2016, under imaging guidance by an interventional radiology team at our institution. Fluoroscopic images, chest radiographs, computed tomography scans, and medical records were reviewed after port implantation. Catheter maintenance days were calculated and catheter-related complications were recorded.

RESULTS

The procedural success rate was 99.3%. In total, 270 TIVAPs were implanted in 270 patients, of which 150 remained functional at the end of the study period. The total catheter maintenance days was 77 543 days, and the mean catheter indwelling duration was 287 ± 207 days. In 20 (7.4%) patients, TIVAP-related complications occurred during the follow-up period, resulting in a postprocedural complication rate of 0.26 incidences per 1000 catheter days. No significant relationship was observed between complications and gender (p = 0.188), age (p = 0.528), body mass index (p = 0.547), the type of primary malignancy (p = 0.914), or between the left and right basilic veins (p = 0.319).

CONCLUSION

Real-time ultrasound and fluoroscopic guidance provides a safe method for TIVAP implantation through the basilic vein, with a high technical success rate and few device-related complications.

Trends in computed tomography scan uses in Taiwan from 2000 to 2013

BACKGROUND

The trends in computed tomography (CT) scan uses in Taiwan were examined in different age and sex groups and compared between catastrophic illness and noncatastrophic illness groups.

METHODS

This retrospective cohort study used data from the National Health Insurance Research Database (NHIRD) in Taiwan to analyze CT scan uses from the beginning of 2000 to the end of 2013. The number, annual growth rate, and cumulative fold change ratio were estimated in different groups classified by sex, age, or disease category (catastrophic illness, noncatastrophic illness).

RESULTS

The number of CT scan uses per million people per year in Taiwan increased 2.5 times from 24 257 in 2000 to 60 351 in 2013, at the average annual growth rate of 7.4% ± 5.9%. The annual number of CT scan uses in different age groups and disease category groups was significantly higher in males than in females. However, the average annual growth rate and the cumulative fold change ratio were slightly higher in females than in males. The majority of CT scan uses were in middle age and young adult groups. The annual number of CT scan uses in the young adult, child/adolescent, and middle age groups increased 3.7-, 3.5-, and 2.7-fold from 2000 to 2013, but decreased 0.8-fold in the old-age group. The annual number of CT scan uses was highest in the noncatastrophic illness group, followed by the catastrophic illness cancer group and catastrophic illness others group.

CONCLUSION

CT scan uses in Taiwan increased continuously from 2000 to 2013, even in the groups with higher radiation-related cancer risk. Therefore, clinicians, radiologists, and medical policy makers should weigh diagnostic benefit against sex-specific and age-specific risks in the future.

Investigation of chemotherapy-induced brain structural alterations in breast cancer patients with generalized q-sampling MRI and graph theoretical analysis

BACKGROUND

Breast neoplasms are the most common cancer among women in Taiwan. Cognitive deficits are common complications of breast cancer survivors treated with chemotherapy. The most frequently observed disorders involve executive function and memory impairment. With improvements in tumor intervention and the consequent increase in the number of cancer survivors, the quality of life of patients has become an important issue. We are interested in the early effects of chemotherapy on the brain structures of patients. In addition, generalized q-sampling imaging (GQI), a wide range of q-space datasets for a more accurate and sophisticated diffusion MR approach, was first used in this topic.

METHODS

As diffusion tensor imaging (DTI) is associated with restrictions in the resolution of crossing fibers, we attempted to use GQI, which can overcome these difficulties and is advantageous over DTI for tractography of the crossing fibers. This cross-sectional study included two groups: breast cancer survivors who had completed their chemotherapy (n = 19) and healthy controls (n = 20). All participants underwent diffusion MRI exams and neuropsychological assessments. We included four parts in our image analysis, i.e., voxel-based statistical analysis, multiple regression analysis, graph theoretical analysis and network-based statistical analysis.

RESULTS

The results from the voxel-based statistical analysis showed significantly lower GFA and NQA values in the breast cancer group than those in the control group. We found significant positive correlations between the FACT-Cog and GQI indices. In the graph theoretical analysis, the breast cancer group demonstrated significantly longer characteristic path length. Adjuvant chemotherapy affected the integrity of white matter and resulted in poor cognitive performance, as indicated by the correlations between the neuropsychological assessment scales and the GQI indices. In addition, it was found that the characteristic path lengths in the breast cancer group increased, indicating that the brain network integration became worse.

CONCLUSIONS

Our study demonstrated alterations in structural brain networks and associated neuropsychological deficits among breast cancer survivors.

Noninvasive assessment of intracranial elastance and pressure in spontaneous intracranial hypotension by MRI

BACKGROUND

Spontaneous intracranial hypotension (SIH) is often misdiagnosed, and can lead to severe complications. Conventional MR sequences show a limited ability to aid in this diagnosis. MR-based intracranial pressure (MR-ICP) may be able to detect changes of intracranial elastance and pressure.

PURPOSE

To determine whether MR-ICP is able to differentiate SIH patients from normal subjects, improve diagnostic sensitivity, and provide an insight into the pathophysiology.

STUDY TYPE

Prospective.

SUBJECTS

Twenty-eight SIH cases with orthostatic headache and 20 healthy volunteers.

FIELD STRENGTH/SEQUENCE

Cine phase-contrast MRI on a 1.5T scanner.

ASSESSMENT

Intracranial elastance (IE) was derived from the ratio of the peak-to-peak cerebrospinal fluid (CSF) pressure gradient (PG_csf-pp ) and intracranial volume change, obtained by summing all flows before each sequential cardiac frame.

STATISTICAL TESTS

Student's t-test was used to compare the MR-ICP indexes and flow parameters between SIH patients and healthy volunteers (P < 0.01).

RESULTS

The SIH patients with cervical epidural venous dilatation (EVD) had an IE of 0.121 ± 0.027 mmHg/cm/ml, significantly higher than that of the normal volunteers (0.085 ± 0.027 mmHg/cm/ml; P = 0.002). In contradistinction, the EVD-negative SIH patients, including four with no sign of CSF leaks, had significantly lower IE (0.055 ± 0.012 mmHg/cm/ml) compared with the normal volunteers and the EVD-positive group (P = 0.001, P < 0.001). The EVD-negative patients had significantly lower PG_csf-pp (0.024 ± 0.007 mmHg/cm) compared with the normal volunteers and the EVD-positive group (0.035 ± 0.011 mmHg/cm, 0.040 ± 0.010 mmHg/cm; P = 0.003, P < 0.001). Additionally, the MRI flow study showed a significant decrease in transcranial inflow and outflow of SIH patients (P < 0.01).

DATA CONCLUSION

We found that the MR-ICP method is potentially more sensitive than morphological MRI in the early diagnosis of SIH. Also, contrary to common belief, our results suggest that an abnormal craniospinal elastance might be the cause of SIH, instead of CSF leak.

LEVEL OF EVIDENCE

2 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2018;47:1255-1263.

Adult-to-adult living donor liver transplantation preoperative survey using MDCT, a single medical center experience in Taiwan

This study evaluated multi-detector computed tomography (MDCT) scans performed on potential living donors for adult-to-adult liver transplantation (LDLT), with the aim of identifying significant findings that could be used to exclude potential transplantation donors. We retrospectively reviewed the medical records of 151 consecutive potential adult donors for LDLT from May 2007 to January 2015. Liver parenchyma steatosis, focal hepatic mass or intraabdominal malignancy, vascular variations, and donor liver volume were evaluated via MDCT. Grounds for excluding potential donors were also recorded and analyzed. Of the 151 potential donors, nine (6.0%) had moderate to severe fatty liver, 37 (24.5%) had hepatic arterial variants, 22 (14.6%) had significant portal venous variants, and more than half were found to have right accessory inferior hepatic vein. No intraabdominal malignancies were found. Eighty-eight potential donors were rejected, with the most common cause being insufficient recipient volume or remnant donor volume (47.7%), moderate to severe parenchymal steatosis (10.2%), and recipient expiration prior to transplantation (8.0%). An additional 16 potential donors were excluded by the surgical team due to the complexity of their portal venous variations. The rate of exclusion by pre-transplant imaging evaluation with MDCT was 33.8%. MDCT can provide accurate quantification of donor liver volume and steatosis severity along with precise demonstration of vascular variants, which are crucial for the preoperative evaluation of LDLT. However, MDCT may be ineffective for evaluating the biliary system without hepatobiliary-excreted contrast agent and has the disadvantage of ionizing radiation.

Patient safety during radiological examinations: a nationwide survey of residency training hospitals in Taiwan

OBJECTIVES

Variations in radiological examination procedures and patient load lead to variations in standards of care related to patient safety and healthcare quality. To understand the status of safety measures to protect patients undergoing radiological examinations at residency training hospitals in Taiwan, a follow-up survey evaluating the full spectrum of diagnostic radiology procedures was conducted.

DESIGN

Questionnaires covering 12 patient safety-related themes throughout the examination procedures were mailed to the departments of diagnostic radiology with residency training programmes in 19 medical centres (with >500 beds) and 17 smaller local institutions in Taiwan. After receiving the responses, all themes in 2014 were compared between medical centres and local institutions by using χ(2) or 2-sample t-tests.

PARTICIPANTS

Radiology Directors or Technology Chiefs of medical centres and local institutions in Taiwan participated in this survey by completing and returning the questionnaires.

RESULTS

The response rates of medical centres and local institutions were 95% and 100%, respectively. As indicated, large medical centres carried out more frequent clinically ordered, radiologist-guided patient education to prepare patients for specific examinations (CT, 28% vs 6%; special procedures, 78% vs 44%) and incident review and analysis (89% vs 47%); however, they required significantly longer access time for MRI examinations (7.00±29.50 vs 3.50±3.50 days), had more yearly incidents of large-volume contrast-medium extravasation (2.75±1.00 vs 1.00±0.75 cases) and blank radiographs (41% vs 8%), lower monthly rates of suboptimal (but interpretable) radiographs (0.00±0.01% vs 0.64±1.84%) and high-risk reminder reporting (0.01±0.16% vs 1.00±1.75%) than local institutions.

CONCLUSIONS

Our study elucidates the status of patient safety in diagnostic radiology in Taiwan, thereby providing helpful information to improve patient safety guidelines needed for medical imaging in the future.

Magnetic Resonance Angiography in the Diagnosis of Cerebral Arteriovenous Malformation and Dural Arteriovenous Fistulas: Comparison of Time-Resolved Magnetic Resonance Angiography and Three Dimensional Time-of-Flight Magnetic Resonance Angiography

Background

Traditional digital subtraction angiography (DSA) is currently the gold standard diagnostic method for the diagnosis and evaluation of cerebral arteriovenous malformation (AVM) and dural arteriovenous fistulas (dAVF).

Objectives

The aim of this study was to analyze different less invasive magnetic resonance angiography (MRA) images, time-resolved MRA (TR-MRA) and three-dimensional time-of-flight MRA (3D TOF MRA) to identify their diagnostic accuracy and to determine which approach is most similar to DSA.

Patients and Methods

A total of 41 patients with AVM and dAVF at their initial evaluation or follow-up after treatment were recruited in this study. We applied time-resolved angiography using keyhole (4D-TRAK) MRA to perform TR-MRA and 3D TOF MRA examinations simultaneously followed by DSA, which was considered as a standard reference. Two experienced neuroradiologists reviewed the images to compare the diagnostic accuracy, arterial feeder and venous drainage between these two MRA images. Inter-observer agreement for different MRA images was assessed by Kappa coefficient and the differences of diagnostic accuracy between MRA images were evaluated by the Wilcoxon rank sum test.

Results

Almost all vascular lesions (92.68%) were correctly diagnosed using 4D-TRAK MRA. However, 3D TOF MRA only diagnosed 26 patients (63.41%) accurately. There were statistically significant differences regarding lesion diagnostic accuracy (P = 0.008) and venous drainage identification (P < 0.0001) between 4D-TRAK MRA and 3D TOF MRA. The results indicate that 4D-TRAK MRA is superior to 3D TOF MRA in the assessment of lesions.

Conclusion

Compared with 3D TOF MRA, 4D-TRAK MRA proved to be a more reliable screening modality and follow-up method for the diagnosis of cerebral AVM and dAVF.

The merit of proton magnetic resonance spectroscopy in the longitudinal assessment of spinocerebellar ataxias and multiple system atrophy-cerebellar type

BACKGROUND

Spinocerebellar ataxia (SCA) and multiple system atrophy-cerebellar type (MSA-C) often present with similar clinical manifestations in the beginning. Magnetic resonance spectroscopy (MRS) has been proved to be a useful tool to help differentiate different types of SCA and MSA-C on cross-sectional studies. However, longitudinal changes of the MRS metabolites in these subjects have never been reported. The purpose of this study was to track the longitudinal evolution of the MRS metabolites in these patients and to ascertain the correlation between clinical severity measured by Scale of the Assessment and Rating of Ataxia (SARA) and MRS metabolites.

RESULTS

Significant reductions of NAA/Cr and NAA/Cho in the cerebellar hemispheres in all patients and lower Cho/Cr in the cerebellar hemispheres in patients with SCA2 or MSA-C were found at all times. At initial assessments, patients with MSA-C or SCA2 tended to have lower NAA/Cr and Cho/Cr in the cerebellar hemispheres than those with SCA3 or SCA6. At follow-ups, patients with SCA2 or MSA-C had a lower NAA/Cr in cerebellar hemispheres than those with SCA3 or SCA6. Patients with MSA-C had a lower NAA/Cr in the vermis and Cho/Cr in the cerebellar hemispheres than those with SCA2 at the start, and had a lower NAA/Cr in cerebellar hemispheres than those with SCA2 at follow-ups.

CONCLUSION

Characteristic patterns of neurodegenerative evolution were observed in patients with disparate SCAs and MSA-C using MRS and SARA. A continual impairment of neuronal integrity was observed in all groups of patients. The longitudinal changes of MRS metabolites and SARA scores were most striking in patients with SCA2 and MSA-C. Although the changes in the metabolites on MRS may still be used to help understand the pathophysiology of ataxia disorders, they are short of being a good biomarker.

Usefulness of phase-contrast magnetic resonance imaging for diagnosis and treatment evaluation in patients with SIH

BACKGROUND

Most diagnostic tools for spontaneous intracranial hypotension (SIH) are either invasive or occasionally inconsistent with the clinical condition. In this study, we examined the cerebrospinal fluid (CSF) dynamics in SIH using phase-contrast magnetic resonance (PC-MR) imaging.

MATERIALS AND METHOD

Seventeen SIH patients and 32 healthy individuals, matched by sex and age, were recruited. Each person underwent brain and PC-MR imaging using 3-Tesla MRI. We evaluated the differences in image parameters among patients during the initial and recovery stages against the status of the control group.

RESULTS

SIH patients had lower CSF flow-volume, flux, peak velocity, and higher systolic-to-diastolic time ratio, as well as systolic-to-diastolic volume ratio compared to the control group and the conditions when they recovered. The flow time and volume of the diastolic phase markedly increased after treatment. The discriminating power of PC-MR for SIH was good. Diffuse pachymeningeal enhancement and venous engorgement were present when their PC-MR values were lower than the cut-off values for SIH diagnosis. The headache scores correlated with the peak velocity and pituitary volume.

CONCLUSION

Noninvasive PC-MR could provide valid parameters for diagnosis and treatment follow-up in SIH patients. It may be more sensitive than conventional brain MRI.

Multi-detector row computed tomographic evaluation of a rare type of complete vascular ring: double aortic arch with atretic left arch distal to the origin of left subclavian artery

Double aortic arch with an atretic left arch distal to the origin of left subclavian artery was diagnosed with multi-detector row computed tomography (MDCT) in two children with dysphagia. This rare type of complete vascular ring is clinically important because it may be confused with right aortic arch in mirror imaging. Anatomic details of this rare type of complete vascular ring demonstrated on MDCT facilitated appropriate surgical treatment.

Cranial magnetic resonance imaging findings in children with nonsyndromic mitochondrial diseases

Cranial magnetic resonance imaging findings suggestive of specific mitochondrial syndromes are reported. However, cranial magnetic resonance imaging features in children with nonsyndromic mitochondrial diseases are rarely described. From January 1992-September 2009, data from 33 patients with nonsyndromic mitochondrial diseases were collected. We investigated cranial magnetic resonance imaging features in children with nonsyndromic mitochondrial diseases, and identified potential diagnostic characteristics. Eleven of 33 patients (33.3%) demonstrated normal findings, and 22 (66.7%) demonstrated abnormal findings. The most common abnormal finding was cerebral atrophy, with or without other lesion sites (15/33; 45.5%). The second most common was bilateral basal ganglia involvement (6/33; 18.2%). Follow-up imaging was performed in 20 patients. Ten of these 20 (50.0%) demonstrated evolutionary changes, in which progressive global brain atrophy was evident. Three patients with normal results and one patient with cerebral atrophy on initial imaging demonstrated prominent signal changes over the basal ganglia, brainstem, gray matter, white matter, and bilateral cerebellar hemispheres on follow-up imaging. Imaging in children with nonsyndromic mitochondrial diseases may produce variable findings. Normal results and cerebral atrophy on the initial cranial magnetic resonance imaging are commonly evident in this patient group.

MDCT evaluation of cardiac involvement in hypereosinophilic syndrome: differentiating mural thrombus, infarcted, and noninfarcted myocardium by delayed-phase scanning

Hypereosinophilic syndrome is a rare disease that can cause multiple-organ damage. Cardiac involvement, which presents as myocardial necrosis, infarction, or thrombus formation, is the leading cause of morbidity and death. Here, we present the case of a 17-year-old girl who had hypereosinophilic syndrome with cardiac involvement, which was evaluated by multidetector-row computed tomography. By means of arterial-phase and low-dose delayed-phase scanning, multidetector-row computed tomography clearly identified the mural thrombus and the infarcted and noninfarcted myocardium-which surpassed the performance of echocardiography in tissue characterization. Therefore, we propose that multidetector-row computed tomography could be a useful noninvasive tool for evaluating patients with cardiac involvement of hypereosinophilic syndrome.

Adenocarcinoma arising from colonic duplication cyst with metastasis to omentum: A case report

Gastrointestinal tract duplications are uncommon congenital abnormalities. Carcinoma arising from duplication cyst is extremely rare, not to mention metastasis to other organs. We present a case of adenocarcinoma arising from a colonic duplication cyst with invasion of the serosa and metastasis to the omentum in a 40-year-old man. Duplication cysts should be included in the differential diagnosis of cystic masses of the gastrointestinal tract. Because these lesions occur so infrequently, they are often not suspected until encountered intraoperatively. The specific findings and advantages of sonography are reviewed.

Radiosurgery for dural carotid-cavernous sinus fistulas: Gamma Knife compared with XKnife radiosurgery

OBJECT

In the modern era, stereotactic radiosurgery is an important part of the multidisciplinary and multimodality approach used to treat dural carotid-cavernous fistulas (DCCFs). Based on the ease of performance of techniques to fuse cerebral angiography studies with MR images or CT scans during the radiosurgical procedure, the Gamma Knife and XKnife are 2 of the most popular radiosurgical instruments for patients with DCCF. In this study, the authors compared the efficacy, neurological results, and complications associated with these 2 radiosurgical devices when used for DCCF.

METHODS

Records for 41 patients with DCCF (15 treated using the XKnife and 26 with Gamma Knife surgery [GKS]) were retrieved from a radiosurgical database encompassing the period of September 2000 to August 2008. Among these patients, at least 2 consecutive MR imaging or MR angiography studies obtained after radiosurgery were available for determining radiological outcome of the fistula. All patients received regular follow-up to evaluate the neurological and ophthalmological function at an interval of 1-3 months. The symptomatology, obliteration rate, radiation dose, instrument accuracy, and adverse effects were determined for each group and compared between 2 groups. The data were analyzed using the Student t-test.

RESULTS

The mean age of the patients was 63 ± 2.6 years, and the mean follow-up period was 63.1 ± 4.4 months (mean ± SD). Thirty-seven patients (90%) achieved an obliteration of the DCCF (93% in the XKnife cohort and 88% for the GKS cohort). In 34 of 40 patients (85%) with chemosis and proptosis of the eyes, these symptoms were resolved after treatment (4 had residual fistula and 2 had arterializations of sclera). All 5 patients with high intraocular pressure demonstrated clinical improvement. Ten (71%) of 14 patients with cranial nerve palsy demonstrated improvement following radiosurgery. Significant discrepancies of treatment modalities existed between the XKnife and GKS groups, such as radiation volume, conformity index, number of isocenters, instrument accuracy, peripheral isodose line, and maximum dosage. The XKnife delivered significantly higher radiation dosage to the lens, optic nerve, optic chiasm, bilateral temporal lobe, and brainstem. Few adverse events occurred, but included 1 patient with optic neuritis (GKS group), 1 intracranial hemorrhage (XKnife group), 1 brainstem edema (XKnife), and 3 temporal lobe radiation edemas (XKnife).

CONCLUSIONS

Radiosurgery affords a substantial chance of radiological and clinical improvement in patients with DCCFs. The Gamma Knife and XKnife demonstrated similar efficacy in the obliteration of DCCFs. However, a slightly higher incidence of complications occurred in the XKnife group.

Quantitative analysis in clinical applications of brain MRI using independent component analysis coupled with support vector machine

PURPOSE

To effectively perform quantification of brain normal tissues and pathologies simultaneously, independent component analysis (ICA) coupled with support vector machine (SVM) is investigated and evaluated for effective volumetric measurements of normal and lesion tissues using multispectral MR images.

MATERIALS AND METHODS

Synthetic and real MR data of normal brain and white matter lesion (WML) data were used to evaluate the accuracy and reproducibility of gray matter (GM), white matter (WM), and WML volume measurements by using the proposed ICA+SVM method to analyze three sets of MR images, T1-weighted, T2-weighted, and proton density/fluid-attenuated inversion recovery images.

RESULTS

The Tanimoto indexes of GM/WM classification in the normal synthetic data calculated by the ICA+SVM method were 0.82/0.89 for data with 0% noise level. As for clinical MR data experiments, the ICA+SVM method clearly extracted the normal tissues and white matter hyperintensity lesions from the MR images, with low intra- and inter-operator coefficient of variations.

CONCLUSION

The experiments conducted provide evidence that the ICA+SVM method has shown promise and potential in applications to classification of normal and pathological tissues in brain MRI.

Olfactory bulb volume in Taiwanese patients with posttraumatic anosmia

BACKGROUND

Olfactory bulb (OB) volume has been shown to be an indicator of olfactory function. However, few studies have been done in Asia to investigate the influence of different disorders on OB volume.

METHODS

Data from patients with posttraumatic anosmia were collected in our department. Their olfactory thresholds were assessed by the phenyl ethyl alcohol threshold test. They were treated with a course of high-dose steroid, and followed up for at least 3 months without any olfactory improvement. Magnetic resonance imaging was subsequently used to measure patients' OB volumes. Subjects who self-reported their olfactory function was normal were also included in the control group for comparison.

RESULTS

Fifty-four patients with posttraumatic anosmia and 30 subjects who self-reported their olfactory function was normal were enrolled in this study. The mean right OB volume was 45.2 mm3, and the mean left OB volume was 46.3 mm3 in patients with posttraumatic anosmia. The mean right OB volume was 59.7 mm3, and the mean left OB volume was 66.0 mm3 in control subjects. The OB volumes were significantly lower in patients with posttraumatic anosmia.

CONCLUSION

OB volumes were significantly lower in Taiwanese patients with posttraumatic anosmia.

An automatic computer-aided detection system for meniscal tears on magnetic resonance images

Knee-related injuries including meniscal tears are common in both young athletes and the aging population, and require accurate diagnosis and surgical intervention when appropriate. With proper techniques and radiologists' experienced skills, confidence in detection of meniscal tears can be quite high. This paper develops a novel computer-aided detection (CAD) diagnostic system for automatic detection of meniscal tears in the knee. Evaluation of this CAD system using an archived database of images from 40 individuals with suspected knee injuries indicates that the sensitivity and specificity of the proposed CAD system are 83.87% and 75.19%, respectively, compared to the mean sensitivity and specificity of 77.41% and 81.39%, respectively, obtained by experienced radiologists in routine diagnosis without using the CAD. The experimental results suggest that the developed CAD system has great potential and promise in automatic detection of both simple and complex meniscal tears of the knee.

Leigh syndrome: clinical and neuroimaging follow-up

Leigh syndrome, caused by dysfunction in mitochondrial energy metabolism, is an inherited, heterogeneous, and progressive neurodegenerative disorder of infancy and childhood. From 1983 to August 2006, 14 cases diagnosed with Leigh syndrome were studied in terms of characteristic neuroimaging findings and abnormal mitochondrial configurations under electron microscopy, as well as molecular analysis. Of the 14 cases, 11 presented clinical features before age 1 (79%). All 14 presented with variable symptoms of central nervous system involvement. The three most common symptoms were developmental delay (12/14; 86%), seizures (11/14; 79%), and altered consciousness (8/14; 57%). Extra-central nervous system manifestations were observed in 10 of the 14 cases, the most common symptoms being failure to thrive (5/14; 36%), pericardial effusion and dilated cardiomyopathy (3/14; 21%), and liver function impairment (3/14; 21%). In all 14 cases, neuroimaging revealed abnormal findings over the basal ganglion, brainstem, or both. The putamen was the most common lesion site in the basal ganglia (11/12; 92%). Cranial magnetic resonance imaging was used for follow-up in 6 cases because of changes in clinical features; in all 6 cases the imaging revealed evolution in the brain. Cranial magnetic resonance spectroscopy was performed in 3 cases and in 2 of them revealed lactate peaks during deterioration of the disease course. The prognosis for Leigh syndrome was poor during long-term follow-up. Seven cases were early fatalities, before 1 year and 6 months of age. Follow-up cranial magnetic resonance imaging together with magnetic resonance spectroscopy in cases with clinical evolution is helpful for monitoring this disease.

Neuroimaging and quality-of-life outcomes in patients with brain metastasis and peritumoral edema who undergo Gamma Knife surgery

OBJECT

Gamma Knife surgery (GKS) has been shown to be effective for treating many patients with brain metastasis. Some brain metastases demonstrate significant peritumoral edema; radiation may induce cerebral edema or worsening preexisting edema. This study was conducted to evaluate the imaging and neurobehavioral outcomes in patients with preexisting peritumoral edema who then undergo GKS.

METHODS

Between August 2003 and January 2008, 63 cases of brain metastasis with significant peritumoral edema (> 20 cm(3)) were prospectively studied. The study inclusion criteria were as follows: 1) a single metastatic lesion with significant edema (perilesional edema signal volume on FLAIR > 20 cm(3)); and 2) inclusion of only 1 lesion > 20 cm(3) in the study (in cases of multiple lesions noted on FLAIR images). All patients received MR imaging with pulse sequences including T1-weighted imaging and FLAIR with or without contrast and T2-weighted imaging at an interval of 3 months. A neurological assessment and Brain Cancer Module (BCM-20) questionnaire were obtained every 2-3 months. Kaplan-Meier, Cox regression, and logistic regression were used for analysis of survival and associated factors.

RESULTS

At the time of GKS, the median Karnofsky Performance Scale (KPS) score was 70 (range 50-90), and the mean BCM-20 score was 45.5 +/- 6.1. The mean tumor volume (+/- standard deviation) was 5.2 +/- 4.6 cm(3) with corresponding T2-weighted imaging and FLAIR volumes of 59.25 +/- 37.3 and 62.1 +/- 38.8 cm(3), respectively (R(2) = 0.977, p < 0.001). The mean edema index (volume of peritumoral edema/tumor volume) was 17.5 +/- 14.5. The mean peripheral and maximum GKS doses were 17.4 +/- 2.3 and 35 +/- 4.7 Gy, respectively. The median survival was 11 months. The longer survival was related to KPS scores >or= 70 (p = 0.008), age < 65 years (p = 0.022), and a reduction of > 6 in BCM-20 score (p = 0.007), but survival was not related to preexisting edema or tumor volume. A reduction in BCM-20 score of > 6 was related to decreased volume in T1-weighted and FLAIR imaging (p < 0.001). Thirty-eight (79.2%) of 48 patients demonstrated decreased tumor volume and accompanied by decreased T2-weighted imaging and FLAIR volume. Eight (16.7%) of the 48 patients exhibited increased or stable tumor volume. A margin dose > 18 Gy was more likely to afford tumor reduction and resolution of peritumoral edema (p = 0.005 and p = 0.006, respectively). However, prior external-beam radiation therapy correlated with worsened preexisting peritumoral edema (p = 0.013) and longer maintenance of corticosteroids (p < 0.001).

CONCLUSIONS

Patients demonstrating a reduction in the BCM-20 score > 6, age < 65 years, and KPS score >or= 70 exhibited longer survival. Significant preexisting edema did not influence the tumor response or clinical outcome. The resolution of edema was related to better quality of life but not to longer survival.

Pseudoaneurysm in the left ventricular outflow tract after prosthetic aortic valve implantation: evaluation upon multidetector-row computed tomography

The high accuracy of multidetector-row computed tomography (MDCT) in evaluating prosthetic valve disorders has been confirmed. This, we believe, is the 1st report of the use of MDCT to detect and evaluate left ventricular outflow tract (LVOT) pseudoaneurysms in patients who have undergone aortic valve replacement with prosthetic valves. We used MDCT to scan 21 such patients, 3 of whom had a small pseudoaneurysm in the LVOT. Each pseudoaneurysm projected away from the LVOT and had a narrow neck that was located just below the sewing ring of the prosthetic aortic valve. One pseudoaneurysm was not thrombotic, 1 was partially thrombotic, and 1 was completely thrombotic. One of these had gone undetected earlier on transthoracic echocardiography.We consider MDCT to be superior to echocardiography in the detection of LVOT pseudoaneurysms in patients who have undergone aortic valve replacement with prosthetic valves. We publicize our results in the hope that larger studies will be undertaken in order to investigate the prevalence and clinical implications of our findings.

Angioplasty as the First-Line Therapeutic Option for Venous Hypertension with Outlet Obstruction of Dural Sinus

We describe a nonconventional endovascular approach to the treatment of pseudotumor cerebri with venous outlet stricture or obstruction. In three patients presenting with acute visual loss, angiograms showed sinus occlusion and stasis of contrast material, with an increased pressure gradient in the venous system. We used venous sinus angioplasty as the first therapeutic option. This treatment was effective, and symptoms and signs of all three patients subsided quickly. In our initial and limited experience, sinus balloon angioplasty appeared to be a good first-line treatment for patients with pseudotumor cerebri, sinus outlet obstruction and acute vision loss. We prefer to use sinus stent placement as a second-line option when initial attempts are unsuccessful, especially in pediatric and young-adult patients, as illustrated in our cases.

Vertebral and carotid artery anomalies in patients with aberrant right subclavian arteries

BACKGROUND

There is little published evidence regarding the patterns and prevalence of vertebral artery (VA) and common carotid artery (CCA) anomalies in patients with an aberrant right subclavian artery (ARSCA).

OBJECTIVE

To study the patterns and prevalence of VA and CCA anomalies in patients with ARSCA.

MATERIALS AND METHODS

In a 2-year period we reviewed the children referred with suspected vascular ring who had undergone multidetector-row CT. Patients with ARSCA were reviewed for VA and CCA patterns and their prevalence and relevance were calculated.

RESULTS

In total, 102 patients with ARSCA were identified. VA anomalies were present in 16 patients (15.7%), and CCA anomalies (common carotid trunk) in 21 patients (20.6%). In some patients with VA anomalies, the right VA arose from the right CCA and in some the left VA arose from the aortic arch. When the left VA arose from the aortic arch it was situated between the left CCA and the left SCA or between the left SCA and the ARSCA.

CONCLUSION

If neurointerventionalists understand these potential anomalies and their prevalence, time and contrast medium could be saved when catheterizing the VA and CCA in patients with ARSCA.

Nasal NK/T-cell lymphoma: computed tomography and magnetic resonance imaging findings

BACKGROUND

Primary nasal natural killer (NK)/T-cell lymphoma is the most common cellular subtype seen in nasal lymphomas. It is rare in the Western population but occurs more frequently in Asia, South America, and Mexico. The purpose of this study was to describe the computed tomography (CT) and magnetic resonance (MR) imaging findings of primary nasal NK/T-cell lymphoma.

METHODS

During the period between January 1990 and June 2006, the CT (n=24) and MR (n=6) images of 24 patients with biopsy-proved nasal NK/T-cell lymphoma were reviewed retrospectively. Both CT and MR images were evaluated for site and extent of disease and for pattern of involvement of adjacent areas.

RESULTS

The most common symptoms at presentation were nasal obstruction, nasal discharge, and epistaxis. There was involvement of the unilateral nasal cavity in 16, bilateral nasal cavity including nasal septum in 5 and nasal choana in 3. Sites of extension outside the nasal cavity included tumor extension into paranasal sinuses (n=15), nasopharynx (n=5), nasal labial fold (n=3), oropharynx (n=2), infratemporal fossa (n=2), other subcutaneous soft tissue of the face (n=2) and anterior cranial fossa base (n=1). Bony destruction was demonstrated in 18 cases, involving the sinus bony wall (n=15), nasal turbinate (n=10), lamina papyracea (n=6), orbital floor (n=3), and hard palate (n=2). Regional lymphadenopathy was also detected in 3 patients with nasal NK/T-cell lymphoma.

CONCLUSION

The CT and MR appearances of nasal NK/T-cell lymphoma are nonspecific, and the diagnosis requires histologic confirmation. However, the differential diagnosis of nasal NK/T-cell lymphoma should be included if the images present soft tissue of the nasal cavity with bony erosion or destruction; involvement of the orbital cavity, nasopharynx and infratemporal fossa; and subcutaneous or nasolabial fold soft tissue infiltration, especially in Asian populations.

Characterization of Focal Brain Lesions by Gradient-Echo Arterial Spin-Tagging Perfusion Imaging

A simple gradient-echo arterial spin tagging (GREAST) technique allows for quick assessment of regional tissue perfusion without the need for exogenous contrast agent. The purpose of this prospective study was to validate GREAST imaging in characterizing the regional perfusion status of focal brain lesions by comparing with relative cerebral blood volume (rCBV) maps obtained by using echo-planar imaging (EPI)–based dynamic susceptibility contrast MR imaging. Thirty-two patients whose nonenhanced brain MR images showed 34 focal brain lesions during routine examination were selected to immediately undergo GREAST and dynamic susceptibility contrast MR imaging to evaluate regional perfusion of the lesions. The Pearson correlation coefficient was used to test the relative quantification of local perfusion with the two imaging methods. Qualitative perfusion measurements agreed in 23 (79%) of 29 lesions for which GREAST and dynamic susceptibility contrast MR imaging were successful. On rCBV maps, six focal lesions with local hemorrhage were underestimated. In three patients with metal surgical implants, lesions could not be measured because of susceptibility artifacts and distortion on EPIs. After these lesions were excluded, the Pearson correlation coefficient between relative quantitative perfusion measurements on GREAST images versus rCBV maps was about 0.90 (p value = 0.000). The success rate of GREAST imaging was 94% (30 of 32 patients), higher than that of dynamic susceptibility contrast MR imaging (72%, or 23 of 32 patients). GREAST imaging was comparable to rCBV mapping for the relative quantification of regional perfusion of focal brain lesions. This technique may be useful in routine MR examination for characterizing the regional perfusion of brain focal lesions.

Combination of transverse myelitis and arachnoiditis in cauda equina syndrome of long-standing ankylosing spondylitis: MRI features and its role in clinical management

The cauda equina syndrome (CES) is a rare neurological complication of ankylosing spondylitis (AS). Imaging diagnosis of CES in long-standing AS patients (CES-AS) using myelography, computed tomography (CT), and magnetic resonance imaging (MRI) were reported in the literature. They, however, demonstrate only the chronic abnormalities of CES-AS, i.e., dural ectasia, dorsal dural diverticula, and selective bone erosion at the posterior elements of the vertebrae. To our knowledge, imaging features of acute intradural inflammation in CES-AS were not described. We report a patient of CES-AS in whom MRI disclosed acute transverse myelitis and arachnoiditis along the lower spinal cord, and discuss the pathogenesis of CES-AS and the role of MRI in clinical management.

Intradural cement leakage: a devastatingly rare complication of vertebroplasty

STUDY DESIGN

The aim of this case report is to examine the devastating complication that may follow vertebroplasty.

OBJECTIVES

To report 1 case of intradural cement leakage caused by percutaneous vertebroplasty with polymethyl methacrylate.

SUMMARY OF BACKGROUND DATA

Cement leakage is not a rare complication of vertebroplasty. But intradural cement leakage is rare. We herein report a rare but devastating complication of vertebroplasty.

METHODS

A 90-year-old woman with a T12 and L1 osteoporotic compression fracture underwent percutaneous vertebroplasty using polymethyl methacrylate at local hospital. A literature search was performed to assess complications of vertebroplasty.

RESULTS

She was transferred to our hospital due to abdominal pain. Physical examination revealed distended abdomen with local tenderness and weakness of both legs (muscle power: Grade 2). Plain radiograph of abdomen showed ileus and intradural cement leakage. Conservative treatment with nasogastric decompression was done, and her abdominal pain subsided 1 week later.

CONCLUSIONS

Percutaneous vertebroplasty with polymethyl methacrylate is relatively safe, but it still should be proceeded under careful safeguard. The needle tip should not cross the medial border of the pedicle on the anteroposterior view before it has crossed the posterior cortex of the vertebral body on the lateral view. Good quality of image monitoring and clear visualization of cement should be helpful to prevent complications.

CT angiography and MR angiography in the evaluation of carotid cavernous sinus fistula prior to embolization: a comparison of techniques

BACKGROUND AND PURPOSE

This study compared CT angiography (CTA), MR angiography (MRA), and digital subtraction angiography (DSA) in elucidating the size and location of carotid cavernous sinus fistulas (CCFs) before embolization treatment.

METHODS

This was a retrospective study of 53 patients with angiographically confirmed CCF. All patients underwent pre- and postcontrast-enhanced CTA and DSA, and 50 patients also underwent MRA. Two neuroradiologists rated detectability of the fistula tract as "good," "moderate," or "poor" in source images obtained by using each procedure. The chi(2) test was used to compare the imaging modalities with respect to their ability to detect fistulas.

RESULTS

CTA did not differ significantly from DSA (P = .155), and both CTA (P = .001) and DSA (P = .007) performed significantly better than MRA in the population as a whole. Differences in performance among the methods, however, depended upon the segmental location of the fistula along the internal carotid artery (ICA). CTA and MRA were similar in detection of CCFs in patients with a fistula at segment 3. CTA significantly outperformed MRA in patients with a fistula at segment 4, who accounted for approximately half of the population.

CONCLUSIONS

CTA source imaging has proved itself as useful as DSA for detecting CCFs. Of the 2 noninvasive techniques, CTA performed better than MRA in the population as a whole and in most patients whose fistula was located at segment 4 or 5 of the ICA.

Hyperglycemia with occipital seizures: images and visual evoked potentials

PURPOSE

Hyperglycemia may rarely be seen with visual seizures. Observation of both visual evoked potentials (VEPs) and magnetic resonance imaging (MRI) in visual status epilepticus (SE) has not been reported. We describe acute and follow-up VEP and MRI findings of a patient with hyperglycemia-related visual SE of occipital origin.

METHODS

In a 59-year-old diabetic woman, complex visual hallucinations and illusions developed with < or =10 seizures per hour as an initial manifestation of nonketotic hyperglycemia.

RESULTS

Neurologic examination revealed ictal nystagmus to the right and continuous right hemianopsia. Ictal electroencephalography (EEG) and Tc-99m hexamethylpropylene amine oxime (HMPAO) single-photon emission computed tomography (SPECT) revealed an epileptogenic focus in the left occipital lobe. MRI with fluid-attenuated inversion recovery showed focal subcortical hypointensity and gyral hyperintensity. Follow-up MRI showed only minimal gyral hyperintensity at 6 months. The P100 amplitude of VEP was significantly higher at the right occipital area during SE, but slightly higher on the left after the patient had been seizure free for 6 months.

CONCLUSIONS

Occipital seizures and hemianopsia can be caused by hyperglycemia and may be accompanied by special MRI and VEP findings.

Unilateral subcortical calcification: a manifestation of dural arteriovenous fistula

We describe the imaging findings in a dural arteriovenous fistula (AVF) with unilateral subcortical calcification. A 50-year-old woman patient suffered from hypertension and chronic headache. Recently, marked headache and a changed consciousness level were noted. The imaging studies demonstrated left subcortical calcification and cerebral sulcus effacement. MR imaging and angiography revealed multiple abnormal tortuous vessels, mainly from left external carotid artery with left-sided transverse sinus occlusion. The final diagnosis was type II a + b dural AVF (classification of Djindjian and Merland), and the patient underwent endovascular embolization and radiosurgery.

Imaging characteristics of familial Wolfram syndrome

Wolfram syndrome is a rare diffuse neurodegenerative disorder also known as DIDMOAD due to its characteristics of diabetes insipidus, diabetes mellitus, optic nerve atrophy and deafness. It is also associated with a wide variety of abnormalities of the central nervous system, urinary tract and endocrine glands. It may be familial or sporadic. Imaging findings include absence of the short T1 nature of the pituitary posterior lobe, atrophy of the optic nerve, chiasma, and tracts. Atrophy of the brain stem and cerebellum has also been reported. We describe a 15-year-old boy and an 11-year-old girl with Wolfram syndrome who were siblings from a diabetes mellitus family. They received regular insulin control at our hospital and had symptoms of frequent urinary tract infection and diabetes insipidus. Magnetic resonance imaging revealed marked pons and cerebellar atrophy. Optic nerve and chiasma atrophy was also noted.

Clinical findings of intracranial vertebral artery disease using magnetic resonance angiography

The vertebral artery lesion has a variety of clinical characteristics. We sought to clarify the clinical patterns and the location of the intracranial vertebral artery (ICVA) diseases according to analyses of images obtained using magnetic resonance angiography (MRA). We studied vascular lesions, risk factors, symptoms, signs, and outcomes in 35 patients with ICVA disease (3 had bilateral occlusion; 9, unilateral occlusion; 6, bilateral stenosis; and 17, unilateral stenosis). The most common site of unilateral and bilateral lesions was the distal ICVA after the origin of posterior inferior cerebellar artery (PICA). We found accompanying basilar artery disease in 28.6% of patients with unilateral and bilateral ICVA disease. The majority of the ICVA lesions were associated with internal carotid arteries disease (48.8%). The common vascular risk factors were hypertension (71%), diabetes mellitus (34%), hyperlipidemia (31%), smoking (29%), and coronary artery disease (23%). Eighteen patients (51.4%) had transient ischemic attacks (TIAs) only, 10 patients (28.6%) had TIAs before stroke, and 5 patients (14.3%) had strokes without TIAs. Most patients (80%) with TIAs, with or without stroke, had multiple episodes. Vertigo or dizziness, ataxia, limbs weakness and abnormal gait were the common symptoms and signs. At 6 months follow-up, 66.7% patients had no symptoms or only slight symptoms that caused no disability. Our data showed (1) the usual location of ICVA disease (occlusion or severe stenosis) was distal to PICA, especially near the vertebrobasilar junction; (2) the risk factors were hypertension, diabetes mellitus, hyperlipidemia, smoking, and coronary artery disease; (3) patients with ICVA disease had a high frequency of accompanying internal carotid, middle cerebral, or basilar artery disease; (4) vertigo or dizziness, and ataxia were the common symptoms and signs; (5) TIA was the most common clinical pattern; (6) the outcome was favorable, except in cases with bilateral ICVA occlusion.

Nasopharyngeal carcinoma spreading along the eustachian tube: the imaging appearance

Nasopharyngeal cancer (NPC) is one of the most common cancers in Taiwan. It can spread anteriorly, laterally, posteriorly, superiorly and inferiorly. Skull base invasion is the common presentation, in up to one-third of cases. We report a rare spreading pathway of NPC, via the eustachian tube. A 44-year-old male suffered from NPC and got radiotherapy about 2 years ago. He suffered from middle ear effusion and facial nerve palsy on the right side recently. The computed tomography and magnetic resonance image could clearly depict the infiltrating tumor over the mastoid region and tympanic cavity on the right side, spreading along the eustachian tube. It could result in eustachian tube dysfunction and middle ear effusion. The nature of the right facial palsy was most likely due to tumor infiltration.

Intraspinal extradural ganglion cyst of the cervical spine

Intraspinal ganglion cyst is an uncommon lesion, which occurs most frequently in the lower lumbar region; occurrence in the cervical region is extremely rare. We report a case of ganglion cyst in the cervical region and describe its clinical pathological and radiological findings. A 59-year-old man presented with sudden lower limbs weakness and numbness below the nipple level. Magnetic resonance imaging revealed an intraspinal extradural lobulated cystic lesion at the level of C6-7 in contact with the left facet joint and posterior erosion of the spinal process at C7. The spinal cord was severely compressed by this lesion which was hypointense on T1-weighted imaging and hyperintense on T2-weighted imaging and short T1 inversion recovery. The cyst wall was strongly enhanced after contrast injection. Intraoperatively, the mass was found to arise from the capsule of the C6-7 facet joint. The excised cyst contained jelly-like fluid. The patient's neurologic symptoms had fully recovered 20 days after the operation. The histopathologic analysis was consistent with ganglion cyst. Ganglion cyst of the cervical region is extremely rare, but must be considered in the differential diagnosis of intraspinal extradural compressive syndromes.

Endovascular treatment of the carotid artery rupture with massive hemorrhage

BACKGROUND

To assess the efficacy and safety of endovascular embolization in the treatment of the carotid artery rupture.

METHODS

A series of 21 patients who had carotid artery rupture (CAR) with massive transoronasal or transcervical hemorrhage, all treated with endovascular embolization, were reviewed. There were 17 males and 4 females ranging in age from 21 to 79 years, with a mean of 47 years. The predisposing factors of the CAR were head and neck tumors associated with surgical treatment and/or post-radiation therapy (n = 17), surgical complications (n = 1) and trauma (n = 3). Detachable balloons with liquid adhesives were used in 13 patients for vascular occlusion and obliteration of pseudoaneurysm of the internal or common carotid artery. Liquid adhesives and/or coils were used in 8 patients, in whom only the branches of the external carotid artery were involved (n = 6), or obliteration of a pseudoaneurysm with preservation of the ICA (n = 2).

RESULTS

Endovascular treatment was technically successful in all 21 cases of the CAR with cessation of profuse hemorrhage immediately after embolization. No recurrence of bleeding was observed. Two patients developed permanent hemiparesis several hours later after occlusion of the carotid artery (10%). Three patients had a transient ischemic attack; all returned to normal neurological conditions later (14%). Ten patients having advanced head and neck carcinoma died during follow-up period owing to the disease itself. Clinical follow-up period for these patients lasted 2 to 48 months, with a mean of 16 months.

CONCLUSIONS

Therapeutic endovascular embolization of the CAR is the primary invasive modality for treating CAR with profuse hemorrhage. It was proven both safe and effective over a relatively long follow-up period.

Detection of spectral signatures in multispectral MR images for classification

This paper presents a new spectral signature detection approach to magnetic resonance (MR) image classification. It is called constrained energy minimization (CEM) method, which is derived from the minimum variance distortionless response in passive sensor array processing. It considers a bank of spectral channels as an array of sensors where each spectral channel represents a sensor and object spectral signature in multispectral MR images are viewed as signals impinging upon the array. The strength of the CEM lies on its ability in detection of spectral signatures of interest without knowing image background. The detected spectral signatures are then used for classification. The CEM makes use of a finite impulse response (FIR) filter to linearly constrain a desired object while minimizing interfering effects caused by other unknown signal sources. Unlike most spatial-based classification techniques, the proposed CEM takes advantage of spectral characteristics to achieve object detection and classification. A series of experiments is conducted and compared with the commonly used c-means method for performance evaluation. The results show that the CEM method is a promising and effective spectral technique for MR image classification.

Spoiled gradient-echo as an arterial spin tagging technique for quick evaluation of local perfusion

PURPOSE

To introduce a simple gradient-echo arterial spin tagging (GREAST) technique available for most commercial magnetic resonance (MR) systems, for a quick evaluation of tissue perfusion.

MATERIALS AND METHODS

The GREAST technique uses a combination of a short TR spoiled gradient-echo (SPGR) sequence with a selective presaturation radio frequency (RF) pulse that allows acquiring each tagged and control image within 10-20 seconds. The phantom and human studies were performed for evaluating the feasibility in measurement of local perfusion and the efficacy in alleviation of the asymmetric magnetization transfer (MT) and slice profile effects.

RESULTS

Results show a good linear relationship between the signal attenuation caused by the presaturation pulse and flow rates in the phantom experiment and effective alleviation of the asymmetric MT and slice profile effects for various orientations of imaging slices. Human studies showed good perfusion results in brain imaging. Perfusion imaging on the liver and kidney were also conducted. The results could be significantly improved by effectively lessening motion-related artifacts.

CONCLUSION

The GREAST technique is simple, easy to use, and applicable to examine local perfusion of the brain and other organs in the trunk.