Role of diffusion weighted imaging and proton magnetic resonance spectroscopy in ring enhancing brain lesions

Aim of the work

To assess and compare the usefulness and efficacy of both diffusion weighted imaging (DWI) and proton magnetic resonance spectroscopy (¹HMRS) in brain lesions with ring enhancement in post contrast T1WI and to determine which method is more effective.

Subjects and methods

Thirty patients with ring-enhanced brain lesions were classified into 2 groups, abscess group (11 patients) and tumor group (19 patients), were examined using diffusion-weighted imaging (DWI) and H-proton magnetic resonance spectroscopy (¹HMRS).

Results

Restricted diffusion and low ADC value were seen in 9 (81%) patients of brain abscesses, however, free diffusion and high ADC value were found in 18 (94%) patients with necrotic brain tumor. The abscess group showed aminoacids, acetate and lactate in 9 patients and extra peak of succinate was found in 1 patient; however in the tumor group lactate alone was found in 12 patients, lactate and choline were seen in 5 patients, none of the patients showed amino acids, succinate or acetate.

Conclusion

Both DWI and ¹HMRS are useful and efficient imaging techniques in ring enhancing brain lesions and differentiate between pyogenic brain abscesses and necrotic tumors, but DWI is accurate, has less imaging time than ¹HMRS, also is available in many imaging centers.     

Proton MR spectroscopy in patients with pyogenic brain abscess: MR spectroscopic imaging versus single-voxel spectroscopy

Purpose

Single-voxel spectroscopy (SVS) has been the gold standard technique to diagnose the pyogenic abssess. Two-dimensional magnetic resonance spectroscopic imaging (MRSI) is able to provide spatial distribution of metabolic concentration, and is potentially more suitable for differential diagnosis between abscess and necrotic tumors. Therefore, the purpose of this study was to evaluate the equivalence of MRSI and SVS in the detection of the metabolites in pyogenic brain abscesses.

Materials and methods

Forty-two patients with pyogenic abscesses were studied by using both SVS and MRSI methods. Two neuroradiologists reviewed the MRS data independently. A κ value was calculated to express inter-reader agreement of the abscesses metabolites, and a correlation coefficient was calculated to show the similarity of two spectra. After consensus judgment of two readers, the binary value of metabolites of pyogenic abscesses (presence or absence) was compared between SVS and MRSI.

Results

The consistency of spectral interpretation of the two readers was very good (κ ranged from 0.95 to 1), and the similarity of two spectra was also very high (cc = 0.9 ± 0.05). After consensus judgment of two readers, the sensitivities of MRSI ranged from 91% (acetate) to 100% (amino acids, succinate, lactate, lipid), and the specificities of MRSI were 100% for detecting all metabolites with SVS as reference.

Conclusion

SVS and MRSI provide similar metabolites in the cavity of pyogenic brain abscess. With additional metabolic information of cavity wall and contralateral normal-appearing brain tissue, MRSI would be a more suitable technique to differentiate abscesses from necrotic tumors.     

MRI findings in 6 cases of children by inadvertent ingestion of diphenoxylate-atropine

Purpose

Compound diphenoxylate (diphenoxylate-atropine) poisoning can cause toxic encephalopathy in children, and magnetic resonance imaging (MRI) of the brain in this condition has not been reported. This study is to analyze brain MRI findings and to investigate the relations between MRI features and possible pathophysiological changes in children.

Methods

Six children accidentally swallowed compound diphenoxylate, 4 males, 2 females, aged 20-46 months, average 33 months. Quantity of ingested diphenoxylate-atropine was from 6 to 30 tablets, each tablet contains diphenoxylate 2.5 mg and atropine 0.025 mg. These patients were referred to our hospital within 24 h after diphenoxylate-atropine ingestion, and underwent brain MRI scan within 24-72 h after emergency treatment. The characteristics of conventional MRI were analyzed.

Results

These pediatric patients had various symptoms of opioid intoxication and atropine toxicity. Brain MRI showed abnormal low signal intensity on T1-weighted images (T1WI) and abnormal high signal intensity on T2-weighted images (T2WI) and fluid-attenuated inversion recovery (FLAIR) imaging in bilateral in all cases; abnormal high signal intensity on T1WI, T2WI and FLAIR in 4 cases. Encephalomalacia was observed in 3 cases during follow-up.

Conclusion

In the early stage of compound diphenoxylate poisoning in children, multiple extensive edema-necrosis and hemorrhagic-necrosis focus were observed in basic nucleus, pallium and cerebellum, these resulted in the corresponding brain dysfunction with encephalomalacia. MRI scan in the early stage in this condition may provide evidences of brain impairment, and is beneficial for the early diagnosis, treatment and prognosis assessment.     

Role of diffusion-weighted MR imaging in discrimination between the intracranial cystic masses

Objective

Discriminating pyogenic brain abscesses from cystic or necrotic tumors is sometimes difficult with CT or conventional MR imaging. Diffusion MR imaging is a valuable diagnostic test in cases of intracranial cystic masses.

Methods

This work was conducted from July 2008 to June 2013 on 90 patients; 43 males and 47 females. Their ages range from 5 to 70 years. All patients were subjected to routine MRI examination and diffusion weighted imaging using 1.5 T MRI scanner. Gadolinium was given to some cases on routine MRI. Diffusion weighted imaging was performed with a single-shot spin-echo echo-planar pulse sequence (b = 0–1000 s/mm²). The apparent diffusion coefficient values and ratio were measured.

Results and conclusions

Patients in this study were categorized into three main groups; first group is brain abscesses (36 cases), 91.6% of them showed restricted diffusion, second group is malignant cystic or necrotic brain tumors, 28 cases of high grade necrotic glioma, 60.7% of them are free diffusion, and third group is benign cystic masses, arachnoid and epidermiod cysts (11 cases); all arachnoid cysts are free diffusion. From these results diffusion-weighted imaging is playing an important role in discrimination of cystic intracranial masses.     

MR findings of Rosai-Dorfman disease in sellar and suprasellar region

Background

Rosai–Dorfman disease (RDD) in sellar/suprasellar region is a rare intracranial disorder. The diagnostic evaluation of this condition using magnetic resonance imaging (MRI) has seldom been described previously. The purpose of our study was to describe MRI characteristics of sellar/suprasellar region RDD.

Methods

Five patients with proved sellar/suprasellar region RDD from May 2005 to March 2010 were retrospectively reviewed. All the patients had undergone magnetic resonance scanning. The number, location, signal intensity (SI), and enhancement pattern of the lesions on MRI were retrospectively evaluated.

Results

Pathological diagnosis of RDD was achieved in all 5 cases including 4 by surgery and 1 by biopsy. The most common presenting symptoms were headache (n = 4) and blurred vision (n = 3). On MRI, isolated suprasellar lesion was found in 2 cases. Suprasellar lesion combined with intrasellar, dural, intra-axial and orbital lesions was found in 3 cases. All lesions showed homogeneous isointense SI on T1-weighted images and hypointense to isointense SI on T2-weighted images except one lesion in the midbrain with slight hyperintense SI on T2-weighted images. All lesions showed homogeneous enhancement.

Conclusion

Homogenously enhancing sellar/suprasellar masses of hypointense to isointense SI on T2-weighted images are suggestive of RDD, and central hypointensity on T2-weighted images may be a specific finding. Intra-axial and extra-axial involvements may coexist with sellar/suprasellar region RDD. Although radiological findings can provide some evidence for this rare entity, differential diagnosis is still needed.     

Role of brain magnetic resonance spectroscopy in the evaluation of suspected mitochondrial diseases in children: Experience in 30 pediatric cases

Introduction

Mitochondrial diseases are a group of inherited disorders caused by derangement of mitochondrial respiration. MR spectroscopy (MRS) has been shown to detect abnormal accumulation of lactate in brain parenchyma and CSF in patients with mitochondrial disorders, but the frequency of detection is largely unknown.

Aim of the work

To evaluate the role of brain MR spectroscopy in the assessment of suspected mitochondrial diseases in the pediatric age group.

Patients and methods

Thirty children with suspected mitochondrial diseases were examined by MRS. Examination was done using multisection technique and multiple echo times mainly short (35 ms) and intermediate (144 ms). Mitochondrial disease criteria scoring system was used to confirm the suspected diagnosis.

Results

All patients showed elevated lactate peak with the CSF being the most sensitive (100%). Among the 30 patients, 26 (86.7%) had elevated levels of blood lactate/pyruvate ratio. Conventional MRI showed highly suggestive features in 15 patients while non specific findings were detected in 11 patients and 4 showed normal appearing brain.

Conclusions

MRS provides a noninvasive tool for the diagnosis of mitochondrial diseases, especially in children with non specific findings on MRI, normal appearing MRI or a normal blood lactate/pyruvate ratio.     

Neurochemical-structural changes evaluation of brain in patients with obstructive sleep apnea syndrome

Purpose

To evaluate neurochemical and structural changes in the patients with newly diagnosed obstructive sleep apnea syndrome (OSAS) by MR spectroscopy (MRS), T2 relaxometry, and diffusion weighted imaging (DWI).

Material and methods

Following the acquisition of routine cranial MR, MRS, T2 relaxometry, and DWI images; spectroscopic metabolite ratios and DWI–T2 relaxometry findings of the thalami, hippocampi, frontal white matter (FWM) and frontal cortex of 24 OSAS patients and 9 controls were statistically compared. The relationship between two groups was evaluated with Mann–Whitney test.

Results

Spectroscopic measurements in the frontal cortex and frontal white matter of the OSAS patients revealed significantly lower NAA/Cr ratios than those of the control group (P = 0.004 and P = 0.006, respectively). The measurements in the frontal white matter of the OSAS patients exhibited significantly lower NAA/Cho ratios compared with those of the control group (P = 0.005). Thalamic Cho/Cr ratios of the patient group were significantly higher than those of the control group (P = 0.002). In terms of the ADC–T2 relaxometry values, there was no significant relationship between the patient and the control groups (P > 0.05).

Conclusion

MRS is a useful and non-invasive modality in showing neurochemical changes in various regions of the brain but our data does not show any change on diffusion weighting or T2 quantification in the OSAS group. DWI and T2 relaxometry appear to be not effective techniques to evaluate the brain structural changes of the patients with newly diagnosed OSAS.     

An experimental study on acute brain radiation injury: Dynamic changes in proton magnetic resonance spectroscopy and the correlation with histopathology

Purpose

To investigate the correlation between the alterations of single-voxel ¹H MRS and the histopathological characteristics of radiation brain injury following radiation.

Materials and methods

Twenty-seven rabbits were randomized into nine groups to receive radiation with a single dose of 25 Gy. The observation time points included a pre-radiation and 1, 2, 3, 4, 5, 6, 7, and 8 wk following radiation. Each treatment group underwent conventional MRI and single-voxel ¹H MRS, N-acetyl aspartate (NAA), choline (Cho), and creatine (Cr) were observed over the region of interest, and the presence or absence of lactate (Lac) and lipid (Lip) was detected. Histological specimens of each group were obtained after image acquisition.

Results

The values of Cho were significantly increased in the first 3 wk, and decreased over the following 5 wk after radiation. Levels of NAA showed a trend toward a decrease 5 wk after radiation. The levels of Cr were not changed between before and after radiation. The Cho/NAA metabolic ratio was significantly increased in weeks 6, 7, and 8 following irradiation, compared to pre-radiation values. Vascular and glial injury appeared on 2 wk after RT in the histology samples, until 4 wk after RT, necrosis of the oligodendrocytes, neuronal degeneration and demyelination could be observed.

Conclusions

MRS is sensitive to detect metabolic changes following radiation, and can be used in the early diagnosis of radiation brain injury.     

Brain abscess and necrotic brain tumor: discrimination with proton MR spectroscopy and diffusion-weighted imaging

BACKGROUND AND PURPOSE: Discriminating pyogenic brain abscesses from cystic or necrotic tumors is sometimes difficult with CT or MR imaging. We compared findings of proton MR spectroscopy ((1)H-MRS) with those of diffusion-weighted imaging to determine which technique was more effective for this differential diagnosis. METHODS: Fourteen patients (necrotic or cystic tumor [n = 7]; pyogenic abscess [n = 7]) who underwent 1.5-T (1)H-MRS and diffusion-weighted imaging and had findings of ring-shaped enhancement after contrast agent administration were enrolled in this study. Diffusion-weighted imaging was performed with a single-shot spin-echo echo-planar pulse sequence (b = 1000 s/mm(2)). The apparent diffusion coefficient and ratio were also measured. RESULTS: Spectra for two patients were unacceptable because of either poor shimming conditions or contamination from neighboring fat. Spectra in three of five patients with abscess had lactate, amino acids (including valine, alanine, and leucine), and acetate peaks; one of the three spectra had an additional peak of succinate. In one patient with abscess treated by antibiotics, only lactate and lipid peaks were detected. Spectra for four of seven patients with cystic or necrotic tumors showed only lactate peaks. Lactate and lipids were found in three patients with tumors. Hyperintensity was seen in all the pyogenic abscess cavities and hypointensity in all the cystic and necrotic tumors on diffusion-weighted images. CONCLUSION: (1)H-MRS and diffusion-weighted imaging are useful for differentiating brain abscess from brain tumor, but the latter requires less time and is more accurate than is (1)H-MRS. (1)H-MRS is probably more limited in cases of smaller peripheral lesions, skull base lesions, and treated abscesses.     

Apparent diffusion coefficient measurements in the differentiation between benign and malignant neck masses

Aim

Evaluate the role of ADC value measurements in the differentiation between benign and malignant neck masses.

Methods

From April 2011 to February 2013, prospective study was conducted on 30 patients (17 male and 13 female), with the mean age 43.3 ± 6 years. Collected from wards and clinics of General Surgery and Otolaryngology Departments complaining from neck masses. MRI, Diffusion-Weighted Imaging (b value 0, 100, 500 and 1000 s/mm) and ADC value calculation were performed and the results were correlated with histopathological results and/or follow up.

Results

The present study include 30 patients (Lymphadenopathy {(n = 15) (11 as single entity), (4 associated with other entities)}, Focal thyroid swelling (n = 5), Salivary gland masses (n = 3) {Parotitis (1 case), Parotid carcinoma (2 cases)}, Nasopharyngeal masses (n = 5), Oropharyngeal masses (n = 2), Ludwig angina (n = 2) and Laryngeal masses (n = 2).The mean ADC of the malignant neck masses was (0.699 + 0.267 × 10^-3 mm²/s) while that of the benign masses was (1.879 + 0.751 × 10^-3 mm²/s).The results confirmed by biopsy in 23 cases and follow up (7 cases).The sensitivity, specificity, PPV, NPV and overall accuracy of quantitative diffusion WI in differentiating benign from malignant neck masses were 95.4%, 83.3%, 95.4%, 83%, and 92%.

Conclusion

ADC value calculation are promising noninvasive imaging approach that can be used in distinguishing between benign and malignant neck masses. Benign lesions have higher mean ADC values than malignant lesions, the cutoff value was 1.25 × 10^-3 mm²/s while 0.8 × 10^-3 mm²/s in thyroid lesions.     

T2-Weighted Liver MRI Using the MultiVane Technique at 3T: Comparison with Conventional T2-Weighted MRI

Objective

To assess the value of applying MultiVane to liver T2-weighted imaging (T2WI) compared with conventional T2WIs with emphasis on detection of focal liver lesions.

Materials and Methods

Seventy-eight patients (43 men and 35 women) with 86 hepatic lesions and 20 pancreatico-biliary diseases underwent MRI including T2WIs acquired using breath-hold (BH), respiratory-triggered (RT), and MultiVane technique at 3T. Two reviewers evaluated each T2WI with respect to artefacts, organ sharpness, and conspicuity of intrahepatic vessels, hilar duct, and main lesion using five-point scales, and made pairwise comparisons between T2WI sequences for these categories. Diagnostic accuracy (Az) and sensitivity for hepatic lesion detection were evaluated using alternative free-response receiver operating characteristic analysis.

Results

MultiVane T2WI was significantly better than BH-T2WI or RT-T2WI for organ sharpness and conspicuity of intrahepatic vessels and main lesion in both separate reviews and pairwise comparisons (p < 0.001). With regard to motion artefacts, MultiVane T2WI or BH-T2WI was better than RT-T2WI (p < 0.001). Conspicuity of hilar duct was better with BH-T2WI than with MultiVane T2WI (p = 0.030) or RT-T2WI (p < 0.001). For detection of 86 hepatic lesions, sensitivity (mean, 97.7%) of MultiVane T2WI was significantly higher than that of BH-T2WI (mean, 89.5%) (p = 0.008) or RT-T2WI (mean, 84.9%) (p = 0.001).

Conclusion

Applying the MultiVane technique to T2WI of the liver is a promising approach to improving image quality that results in increased detection of focal liver lesions compared with conventional T2WI.     

MR spectroscopy,S100B protein and NSE analysis as early predictors of hypoxic ishaemic encephalopathy

Aim of work

The aim of this work is to assess S100B protein, neuron specific enolase and magnetic resonance spectroscopy as biochemical and imaging findings in neonatal hypoxic ischemic encephalopathy.

Methods

This prospective study on 30 full-term neonates suffering from HIE who were attendants of the Neonatology Unit of Pediatric Department and Radiodiagnosis Department of Tanta University Hospital. Duration of the study extended from June 2010 to June 2012.

Results

Thirty patients (16 males and 14 females), HIE group classification according to Lac/Cr ratio in MRS to three groups: Groups – group I: where Lac/Cr < 0.5, group II: where Lac/Cr 0.5–1.5 and group III: where Lac/Cr > 1.5.¹HMRS group I contained 17 patients (15 patients were present in Sarnat stage I and two patients were present in Sarnat stage II). Group II contained nine patients (all patients were present in Sarnat stage II). Group III contained four patients (all patients were present in Sarnat stage III).Serum level of S100B protein and NSE were significantly higher in the HIE group than control group also serum level of S100B protein and NSE in HIE stage III was significantly higher than control, HIE stage I and stage II.

Conclusion

¹HMRS is a useful tool for evaluating the severity and prognosis of HIE noninvasively. Higher lactate/Cr ratio in basal ganglia and thalamus predict the poor prognosis of neonates.Serum level of S100B protein and NSE has an important meaning in adjuvant diagnosing and ruling out diagnosis of early HIE and prognosis of birth asphyxia.     

Measurement of the apparent diffusion coefficient in paediatric mitochondrial encephalopathy cases and a comparison of parenchymal changes associated with the disease using follow-up diffusion coefficient measurements

Objectives

To reveal the contribution of MRI and diffusion-weighted imaging (DWI) to the diagnosis of mitochondrial encephalopathy (ME) and to evaluate the parenchymal changes associated with this disease in the involved parenchymal areas using the apparent diffusion coefficient (ADC) parameter.

Methods

Ten patients who had undergone MRI and DWI analysis with a pre-diagnosis of neurometabolic disease, and who were subsequently diagnosed with ME in laboratory and/or genetic studies, were included in our study. ADC values were compared with a control group composed of 20 patients of similar age with normal brains. Evaluations involved measurements made in 20 different areas determined on the ADC map. The dominance or contribution of ADC coefficient measurements to the conventional sequences was compared with the controls.

Results

In the first examination, an increase in both diffusion and ADC values was detected in six cases and diffusion restriction and a decrease in ADC values in three patients. While an increase in both diffusion and ADC values was demonstrated in four cases, there was diffusion restriction and a decrease in ADC values in three cases in the control examinations.

Conclusions

DWI provides information that complements conventional MRI sequences in the diagnosis of ME.     

An analysis of the magnetic resonance imaging and pathology of intracal lymphoplasmacyte-rich meningioma

Objective

To discuss the MRI features of the intracranial lymphoplasmacyte-rich meningioma and the correlation between the MRI features and pathology.

Methods

Review retrospectively the MRI and pathologic data of seven patients with lymphoplasmacyte-rich meningioma which were confirmed by surgery and pathology.

Results

The seven cases of lymphoplasmacyte-rich meningioma were solitary, six cases demonstrated flat growth along the meninges, five cases had not yet formed specific nodules, and two cases exhibited irregular lobulation. Seven cases had no clear boundary, peritumoral brain edema was obvious and adjacent brain tissues were invaded to varying degrees. After plain MRI scans, the focuses of seven cases exhibited lower-isointense signal in T1WI, five cases revealed higher-isointense signal and two cases showed lower-isointense signal in T2WI. Enhancement scans demonstrated marked enhancement in seven cases, and the meninges in six cases thicken irregularly and extensively. Pathology showed the richness and diversity of cells, an infiltration containing plasma cells and lymphocytes, as well as the unequal areas of neoplastic spindle cells and meninge epithelial cells.

Conclusion

Lymphoplasmacyte-rich meningioma is a subtype meningioma of WHO I-grade, which is seldom seen and whose imaging appearances are varied from ordinary meningioma. Its features include growing flat along the meninges, irregular forms, unclear boundary, obvious edema, notable strengthening effect, usual invasion of adjacent brain tissues, and similar inflammation.     

Role of magnetic resonance imaging in pre-operative assessment of ano-rectal fistula

Aim of the work

To evaluate the role of magnetic resonance imaging (MRI) in preoperative assessment of ano-rectal fistula and tracing its full extent and relationship.

Materials and methods

Twenty-four patients with ano-rectal fistula were enrolled in this study. They were examined with different MRI sequences for evaluation of the fistulas and their extent. Fistulas were classified according to St. James’s University Hospital MRI based classification system (which correlates the Parks surgical classification to anatomic MRI findings) into 5 grades. Then, interrelation between surgical and MRI findings was statistically analyzed with evaluation of the accuracy of each MRI sequence used.

Results

Grade 1 was the most frequent (37.5%) type of ano-rectal fistula. The most common location of the internal opening of the fistula was at 6 o’clock position. Combination of oblique coronal and axial planes of contrast-enhanced fat suppressed T1-weighed fast spin-echo (CE FS T1WFSE) sequence images showed the highest accuracy (99.4%) in diagnosis of ano-rectal fistula.

Conclusion

MRI is a useful imaging tool in the preoperative assessment of ano-rectal fistula. A significant accordance between surgical and MRI findings was achieved by using combination of coronal and axial planes of CE FS T1WFSE sequence images.     

Role of diffusion MRI and proton magnetic resonance spectroscopy in characterization of ovarian neoplasms

Introduction

Adnexal masses are a common clinical problem and considered as the leading indication for gynecological surgery. The ovary and adnexal structures are relatively difficult to image with any technology. Magnetic resonance spectroscopy (MRS) can detect metabolic changes. As molecular changes often precede morphologic alterations, sensitivity is expected to improve by MRS. Diffusion weighted magnetic resonance imaging (DW-MRI) is sensitive to molecular diffusion which is due to random microscopic translational motion of molecules (known as Brownian motion). In the event of morphologic evaluation of cystic ovarian tumors, whether benign or malignant, DW-MR imaging and calculated apparent diffusion coefficient (ADC) values would be useful for evaluation.

Purpose

The aim of this study is to evaluate the role of diffusion MRI & proton magnetic resonance spectroscopy (H-MRS) in diagnosis of ovarian neoplasms.

Subjects and methods

This study included 20 patients, their ages ranged from 20 to 72 years. In all cases, diagnosis was proven by surgical and pathological examination. Trans-abdominal ultrasound (n = 20) and trans-vaginal ultrasound (n = 11) were included in our routine protocol to obtain baseline information preceding MR examination. The routine MR examination protocol included: T1WI, T2WI, and post contrast fat suppressed T1WI. Diffusion weighted imaging (DWI) was done to all patients at b0, b500, b1000 and ADC values were calculated. MRS was performed in all cases using multi-voxel point resolved surface coil spectroscopy (PRESS sequence) for volume localization.

Results

Fourteen cases (70%) had benign ovarian masses while the remaining six cases (30%) had malignant masses. High lipid peak was detected in all three cases of mature cystic teratoma. All cases of simple serous cysts showed choline and creatine signals that were higher than the average noise level but lower than the two fold higher noise level. Sharp choline peak was detected in all malignant ovarian masses (except a case of metastases under chemotherapy) as well as the case of fibroma. Creatine signal was detected in all benign and malignant masses except two cases of mature cystic teratoma and cases of endometrioma. Lactate signal was detected only in cases of hemorrhagic cysts, mature cyst teratoma and one case of endometrioma and not obtained in any of malignant lesions except dysgerminoma. High NAA signal was detected in dysgerminoma and all three cases of mature cystic teratomas. The mean Cho/Cr ratio was significantly higher in malignant than benign ovarian masses (<0.05), there was no significant difference in mean and lowest ADC values between malignant and benign lesions.

Conclusion

Proton MRS using Cho/Cr ratio added useful information for the diagnosis of different ovarian neoplasms. Direct visual assessment of DWI of ovarian lesions is not useful in differentiating benign from malignant ovarian lesions; determining the threshold of the ADC for diagnosing cystic ovarian tumors is difficult because of their large variance. Further experience with a larger and more biologically variable range of tumors is recommended.     

Role of diffusion-weighted echo-planar MRI in distinguishing between brain abscess and tumour: a preliminary report

Our purpose was to evaluate diffusion-weighted (DW) echo-planar MRI in differentiating between brain abscess and tumour. We examined two patients with surgically confirmed pyogenic brain abscess and 18 with metastatic brain tumours or high-grade glioma, using a 1.5 T system. The apparent diffusion coefficient (ADC) of each necrotic or solid contrast-enhancing lesion was measured with two different b values (20 and 1200 s/mm²). All capsule-stage brain abscesses (4 lesions) and zones of cerebritis (2 lesions) were identified on high-b-value DWI as markedly high-signal areas of decreased ADC (range, 0.58–0.70 [(10–3 mm²/s; mean, 0.63)]). All cystic or necrotic portions of brain tumours (14 lesions) were identified on high-b-value DWI as low-signal areas of increased ADC (range, 2.20–3.20 [(10–3 mm²/s; mean, 2.70)]). Solid, contrast-enhancing portions of brain tumours (19 lesions) were identified on high-b-value DWI as high-signal areas of sightly decreased or increased ADC (range, 0.77–1.29 [(10–3 mm²/s; mean, 0.94)]). Our preliminary results indicate that DW echo-planar MRI be used for distinguishing between brain abscess and tumour. Received: 23 January 1998 Accepted: 5 June 1998     

Correlation study of 3T-MR-DTI measurements and clinical symptoms of cervical spondylotic myelopathy

Objective

To discuss the correlation between diffusion tensor imaging (DTI) measurements, diffusion tensor tractography and the clinical symptoms of cervical spondylotic myelopathy.

Methods

Based on the Japanese Orthopedics Association (JOA) score, 104 cervical spondylotic myelopathy cases were first divided into four groups: mild, moderate, severe and serious groups. According to lesion signal characteristics, all cases were again divided into three groups: A(N/N): normal signal in both T1WI and T2WI; B (N/H): normal signal in T1WI but high signal in T2WI; and C (L/H): low signal in T1WI and high signal in T2WI. The apparent diffusion coefficient (ADC), fractional anisotropy (FA), λ1, λ2, and λ3 were measured and diffusion tensor tractography was performed in the seriously compressed section of the spinal cord.

Results

The FA values were positively correlated with JOA scores (r = 0.883, P < 0.05), and significantly different among four JOA groups (P < 0.05). The ADC, λ2, and λ3 were significantly different among the moderate, severe and serious groups as well as among the A, B, and C groups (P < 0.05). Declining FA values were found associated with increasing fiber bundle damage.

Conclusions

The FA values and the change patterns of fiber bundle were more sensitive than T2WI for spinal cord lesion, and were positively correlated with clinical symptoms.     

Hepatic iron deposition in patients with sickle cell disease: Role of breath-hold multiecho T2-weighted MRI sequence

Introduction

The purpose of this study is to detect the role of breath-hold multiecho T2^∗-weighted MRI, in quantification of hepatic iron deposition in patients with sickle cell disease.

Methods

Thirty-seven patients underwent 1.5-T MRI of the liver that included a multiecho T2^∗-weighted sequence. Hepatic T2^∗ iron grading was done for each patient by placing regions of interest in the hepatic parenchyma. Hepatic T2^∗ values were correlated with histopathological iron grade. Liver biopsy was done for all patients. Written consent was obtained from all patients prior to MRI studies.

Results

Thirty-two patients (86.5 %) had evidence of hepatic iron deposition on histopathological examination, including eight (25%) with grade 3, eleven (34%) with grade 2 and thirteen patients (41%) with grade 1.Patients with negative iron deposition histologically, had T2^∗ values ranging from 28–32 ms. For the patients with positive hepatic iron deposition, hepatic T2^∗ decreased with increasing iron grade.Statistical analysis showed that for differentiation of hepatic iron deposition grade 3 from grades 1 and 2, hepatic T2^∗ less than 13 ms had a sensitivity and specificity of 100 % and 98%, respectively.

Conclusion

Breath-hold multiecho T2^∗-weighted MRI sequence offers an accurate estimation of hepatic iron deposition.     

Differentiation of intracranial tuberculomas and high grade gliomas using proton MR spectroscopy and diffusion MR imaging

Objective

The purpose of this study was to determine whether proton MR spectroscopy (¹H MRS) and diffusion-weighted (DW) imaging can be used to differentiate intracranial tuberculomas from high grade gliomas (HGGs).

Materials and methods

A total of 41 patients (19 with intracranial tuberculomas and 22 with HGGs) were examined in our study. ¹H MRS and DW imaging were performed at a 1.5T MR scanner before operation or treatment. Concentrations of N-acetylaspartate (NAA), creatine (Cr), choline (Cho), and lipid and lactate (LL) in the contrast-enhancing rim of each lesion were expressed as metabolite ratios and were normalized to the contralateral hemisphere. The apparent diffusion coefficient (ADC) was also calculated. The metabolite ratios and ADC values in the enhancing rim of intracranial tuberculomas and HGGs were compared using the Wilcoxon rank sum test. Diagnostic accuracy was compared using receiver operating characteristic (ROC) analysis.

Results

Significant differences were found in the maximum Cho/Cr (P = 0.015), Cho/NAA (P = 0.001) and Cho/Cho-n ratios (P = 0.002), and minimum ADC value (P < 0.001) between the intracranial tuberculomas and HGGs. Diagnostic accuracy was higher by minimum ADC value than maximum Cho/Cr, Cho/NAA and Cho/Cho-n ratios (93.8% versus 75.7%, 80.8% and 78.1%).

Conclusion

These results suggest a promising role for ¹H MRS and DW imaging in the differentiation between the intracranial tuberculomas and HGGs.