Audit of a policy of magnetic resonance imaging with diffusion-weighted imaging as first-line neuroimaging for in-patients with clinically suspected acute stroke

AIM: To audit the feasibility and use of diffusion-weighted (DW) magnetic resonance imaging (MRI) as initial neuroimaging for in-patients with clinically suspected acute stroke. MATERIALS AND METHODS: In April 2000, MRI with DW and T2-weighted sequence was locally instituted as initial neuroimaging for patients with clinically suspected acute stroke. This retrospective study reviewed imaging performed for in-patients with suspected acute stroke over a 9-month period. Data were collected on image type, result and need for repeat imaging. RESULTS: During the study period, 124 patients had neuroimaging for suspected cerebrovascular accident, and 119 were MRI safe. Eighty-eight (73.9%) patients underwent DW MRI as first-line investigation. Five patients were not MRI safe and 31 had computed tomography (CT) as first-line imaging due to lack of available MRI capacity. Repeat neuroimaging was performed in 16 (12.9%) patients. Study times were comparable for both types of neuroimaging: a mean of 13 min for MRI and 11 min for CT. CONCLUSION: The audit standard was achieved in 88 (73.9%) patients. The use of DW MRI as a first-line investigation for patients with a clinical diagnosis of acute stroke is achievable in a district general hospital setting.     

CT and MR findings in HIV-negative neurosyphilis

BACKGROUND AND PURPOSE: The purpose of this study was to describe and evaluate neuroimaging findings of patients with neurosyphilis. METHODS: The neuroimaging studies of 14 patients with documented neurosyphilis were reviewed. Diagnosis was established in 14 patients with cerebrospinal fluid for a Treponema Pallidum Particle Agglutination (TPPA) test. All patients had reactive TPPA and Unheated Serum Regain test (USR) in their sera. Imaging studies included plain, contrast-enhanced CT of the brain, plain and gadolinium-enhanced MR, and MR angiography. RESULTS: In the 14 HIV-negative patients with neurosyphilis, CT and MR showed the presence of cerebral infarction in six cases, arteritis in four cases, nonspecific white matter lesion in three cases, acute syphilitic meningitis in one case and normal neuroimaging finding in one case. In addition, 4 in 14 patients had general paresis, and MRI showed high signal intensity on T2 -weighted images involving frontotemporal lobes, hippocampus and periventricular area. Treatment with penicillin significantly diminished the size of these high signal intensity on T2-weighted images with general paresis. CONCLUSION: These results suggest that MR and CT images have some characteristic manifestations in patients of neurosyphilis. Because early diagnosis and treatment of neurosyphilis are crucial to avoid persistent brain damage, the neuroimaging findings are valuable adjunct to clinical diagnosis and to provide useful information to follow-up after therapy.     

Diffusion tensor imaging of brain tumours at 3T: a potential tool for assessing white matter tract invasion?

AIM: To determine whether diffusion tensor imaging (DTI) of brain tumours can demonstrate abnormalities distal to hyperintensities on T2-weighted images, and possibly relate these to tumour grade. MATERIALS AND METHODS: Twenty patients with histologically confirmed supratentorial tumours, both gliomas (high and low grade) and metastases, were imaged at 3T using T2-weighted and DTI sequences. Regions of interest (ROI) were drawn within the tumour, in white matter at various distances from the tumour and in areas of abnormality on DTI that appeared normal on T2-weighted images. The relative anisotropy index (RAI)-a measure of white matter organization, was calculated for these ROI. RESULTS: The abnormality on DTI was larger than that seen on T2-weighted images in 10/13 patients (77%) with high-grade gliomas. New abnormalities were seen in the contralateral white matter in 4/13 (30%) of these cases. In these high-grade tumours the RAI in areas of white matter disruption with normal appearance on T2-weighted images was reduced (0.19+/-0.04). Even excluding patients with previous radiotherapy this difference remains significant. In all non high-grade tumours (WHO grade II gliomas and metastases) the tumour extent on DTI was identical to the abnormalities shown on T2-weighted imaging and RAI measurements were not reduced (0.3+/-0.04). CONCLUSIONS: Subtle white matter disruption can be identified using DTI in patients with high-grade gliomas. Such disruption is not identified in association with metastases or low-grade gliomas despite these tumours producing significant mass effect and oedema. We suggest the changes in DTI may be due to tumour infiltration and that the DTI may provide a useful method of detecting occult white matter invasion by gliomas.     

Supratentorial glioblastoma: Neuroradiological findings and survival after surgery and radiotherapy

Few studies have attempted to correlate neuroimaging with outcome in patients with glioblastoma. Our aim was to evaluate the relationship between neuroradiological findings and survival in these patients. We studied 18 consecutive patients with glioblastoma who had undergone surgery and radiotherapy. We assessed the following features, using preoperative CT and/or MRI: tumour size, extent of necrotic area within the mass, extent of perifocal oedema and contrast enhancement. The mean survival was 14.2 ± 5 months (range 6–22). The extent of radiological evidence of necrosis within the mass correlated significantly with survival time, whereas tumour size, perifocal oedema and contrast enhancement did not.     

Imaging features of aggressive angiomyxoma

AIM: To describe the imaging features of aggressive angiomyxoma in a rare benign mesenchymal tumour most frequently arising from the perineum in young female patients. MATERIALS AND METHODS: We reviewed the computed tomography (CT) and magnetic resonance (MR) imaging features of patients with aggressive angiomyxoma who were referred to our hospital. The imaging features were correlated with clinical information and pathology in all patients. RESULTS: Four CT and five MR studies were available for five patients (all women, mean age 39, range 24-55). Three patients had recurrent tumour at follow-up. CT and MR imaging demonstrated a well-defined mass-displacing adjacent structures. The tumour was of low attenuation relative to muscle on CT. On MR, the tumour was isointense relative to muscle on T1-weighted image, hyperintense on T2-weighted image and enhanced avidly after gadolinium contrast with a characteristic "swirled" internal pattern. MR imaging demonstrates the extent of the tumour and its relation to the pelvic floor. Recurrent tumour has a similar appearance to the primary lesion. CONCLUSION: The MR appearances of aggressive angiomyxomas are characteristic, and the diagnosis should be considered in any young woman presenting with a well-defined mass arising from the perineum.     

Diffusion-weighted MRI postoperative assessment of an epidermoid tumour in the cerebellopontine angle

Cerebellopontine angle epidermoid tumour generally has a typical appearance with conventional MRI sequences. The lesion is irregular in shape and gives slightly higher signal than cerebrospinal fluid on T1- and T2-weighted images, with a characteristic marbled inner pattern on T1-weighted images. Diffusion-weighted imaging (DWI) can be useful for the diagnosis of an atypical epidermoid tumour. Our case report illustrates the usefulness of DWI for postoperative assessment of residual foci of tumour. The specific appearance of an epidermoid tumour is illustrated, with emphasis on apparent diffusion coefficient (ADC) measurements. Received: 20 April 1999 Accepted: 7 May 1999     

FLAIR imaging in the follow-up of low-grade gliomas: time to dispense with the dual-echo?

Fluid-attenuated inversion-recovery (FLAIR) imaging has established its utility in neuroimaging. We propose this imaging sequence as a replacement for proton density (PD) and T2-weighted spin-echo sequences in the follow-up of low-grade glioma. 26 MRI examinations of 18 patients with such tumours were reviewed by three neuroradiologists and a neurosurgeon. FLAIR was found to be superior for appreciation of the lesion (91% of studies) and for demonstration of its margin (92%). FLAIR was also better at showing different tumour components, particularly in regions difficult to demonstrate in some planes, such as the vertex in axial imaging. The sequence also defines the postoperative cavity, shows the least amount of susceptibility effect associated with surgical clips, and demonstrates local spread (to white matter tracts, subependymal and capsular) more distinctly. We conclude that FLAIR can replace PD and T2-weighted spin-echo imaging in radiological follow-up of low-grade glioma.     

低场磁共振T_1FLAIR序列在颅脑肿瘤诊断中的应用

目的 :通过T1FLAIR(液体反转恢复 )序列与传统SE(自旋回波 )序列T1加权图像对比分析 ,评价T1FLAIR作为T1成像序列对颅脑肿瘤的诊断价值。方法 :对 2 3例颅脑疾病患者均用两种序列检查。结果 :在 2 3例颅脑肿瘤中 ,T1FLAIR序列对病灶显示的图像清晰度比SE序列高。结论 :在相同病变检出率的情况下 ,T1FLAIR像在显示颅脑中灰白质对比度、病变和背景对比情况及病变的边界、大小、范围方面优于传统SE序列T1加权像 ,具有重要的临床诊断价值。     

Tumour extent and T stage of nasopharyngeal carcinoma: a comparison of magnetic resonance imaging and computed tomographic findings.

PURPOSE: To compare magnetic resonance imaging (MRI) and computed tomography (CT) in defining the T stage and full tumour extent of nasopharyngeal carcinoma. PATIENTS AND METHODS: Forty-eight patients with pathologically proven nasopharyngeal carcinoma underwent MRI and CT examinations within 2 weeks of each other. Contrast medium was used in both examinations. The T stage and full tumour extent according to MRI and CT were compared. RESULTS: In 32 patients MRI and CT findings agreed completely. MRI findings resulted in assignment of a higher stage than CT findings in another 8 patients. In the remaining 8 patients MRI showed wider tumour spread than CT, although there was no discordance in the T stage assigned. CONCLUSION: When compared with CT in defining the full tumour extent and assigning the T stage in 48 patients with nasopharyngeal carcinoma, MRI showed more extensive disease in 16 patients, including 8 in whom the T stage was revised upward. Therapy was altered as a result of the MRI findings.     

High-relaxivity contrast-enhanced magnetic resonance neuroimaging: a review

Evaluation of brain lesions using magnetic resonance imaging (MRI) provides information that is critical for accurate diagnosis, prognosis, therapeutic intervention and monitoring response. Conventional contrast-enhanced MR neuroimaging using gadolinium (Gd) contrast agents primarily depicts disruption of the blood-brain barrier, demonstrating location and extent of disease, and also the morphological details at the lesion site. However, conventional imaging results do not always accurately predict tumour aggressiveness. Advanced functional MRI techniques such as dynamic contrast-enhanced perfusion-weighted imaging utilise contrast agents to convey physiological information regarding the haemodynamics and neoangiogenic status of the lesion that is often complementary to anatomical information obtained through conventional imaging. Most of the Gd contrast agents available have similar T1 and T2 relaxivities, and thus their contrast-enhancing capabilities are comparable. Exceptions are gadobenate-dimeglumine, Gd-EOB-DTPA, Gadobutrol and gadofosveset, which, owing to their transient-protein-binding capability, possess almost twice (and more) the T1 and T2 relaxivities as other agents at all magnetic field strengths. Numerous comparative studies have demonstrated the advantages of the increased relaxivity in terms of enhanced image contrast, image quality and diagnostic confidence. Here we summarise the benefits of higher relaxivity for the most common neuroimaging applications including MRI, perfusion-weighted imaging and MRA for evaluation of brain tumours, cerebrovascular disease and other CNS lesions.     

Interpretation of scintigraphic findings of oral malignant tumours with a new scanning agent of technetium-99m-hexakis-2-methoxy-isobutyl-isonitrile (Tc-99m-MIBI)

OBJECTIVES: The purpose of this study was to investigate the usefulness of a new scanning agent of technetium-99m-hexakis-2-methoxy-isobutyl-isonitrile (Tc-99m-MIBI) for the diagnosis of malignant tumours of the head and neck. METHODS: Scintigraphy with Tc-99m-MIBI was performed in 19 patients with malignant tumours of the head and neck. Factors of the early and delayed static scans (hot, warm or cold uptake), the early and delayed retention indexes, the blood flow index and the tumour retention index were obtained from Tc-99m-MIBI scintigraphy. Tumour retention indexes were classified into three grades; slightly (>0.9), moderately (0.9-0.8) and severely (0.8>) decreased. Grade of tissue differentiation of tumour (well, moderately or poorly differentiated) and tumour size (T1 approximately T4) were examined using the excised tumour. Scintigraphic indexes and tumour characteristics were compared. RESULTS: The early static scan and tumour size showed a correlation with the blood flow index. However, the delayed static scan did not show any relationship with blood flow index and tumour size. The tumour retention index had a tendency to decrease in malignant tumours, and showed a significant correlation with the grade of tissue differentiation of the tumour. CONCLUSIONS: The tendency of the tumour retention index to decrease in Tc-99m-MIBI scintigraphy showed the malignancy of tumour and would be useful for the diagnosis of malignant tumours of the head and neck.     

72例脊柱转移瘤的MRI诊断

目的：探讨ＭＲＩ对脊柱转移瘤的诊断价值。方法：包括７２例脊柱转移瘤，其中男４５例，女２７例，均有明确原发癌灶。使用安科ＡＳＰ－０１５型永磁型ＭＲＩ扫描机。结果：１８例为单椎体病变，５４例为多椎体病变。６８例在Ｔ１加权图呈低信号，Ｔ２加权图呈高信号。４例在Ｔ１及Ｔ２加权图均呈低信号。２１例附件受累，１９例有椎旁肿块，３５例有椎管受侵或脊髓受侵。７２例椎间盘形态及信号均大致正常。结论：ＭＲＩ在评价脊柱转移瘤方面优于Ｘ线平片及ＣＴ并可与核素骨扫描相互印证补充。     

Inflammatory demyelinating disease mimicking malignant glioma.

The differential diagnosis between inflammatory demyelinating disease and malignant glioma is difficult based only on neuroimaging methods. METHODS: Four patients with inflammatory demyelinating disease who presented with clinical and neuroimaging findings strongly suggestive of malignant glioma were examined. RESULTS: MRI showed a mass lesion with prolonged T1 and T2 values and gadolinium enhancement in all cases. Proton MR spectroscopy and (201)Tl SPECT showed findings supportive of the diagnosis of malignant glioma in all cases. However, surgical biopsy revealed inflammatory demyelinating disease. After the diagnosis, 2 patients were treated by steroid administration and 2 were just observed. The gadolinium enhancement of all lesions decreased and finally disappeared. CONCLUSION: Such cases illustrate the importance of considering a demyelinating lesion in the differential diagnosis of a mass lesion. The difficulties encountered in establishing the correct diagnosis of inflammatory disease are related to the variations in the radiologic appearance, which require exclusion of gliomas or other brain tumors by surgical biopsy before the therapeutic strategy can be selected.     

Pituicytoma: case report and literature review

Pituicytoma is a rare primary tumour of the neurohypophysis or infundibulum, which masquerades as a pituitary adenoma. We present a pituicytoma case in a 45-year-old female presenting as a focal lesion of the neurohypophysis. This case report reviews the clinical, neuroimaging and histopathological features of this rare tumour in order to understand it better.     

T1 Gd-enhanced compared with CISS sequences in retinoblastoma: superiority of T1 sequences in evaluation of tumour extension

BackgroundAs adequate therapy for retinoblastoma in young children depends on infiltration of extra-retinal structures, diagnostic modalities play an essential role.Methods: In this widely extended study, 80 children with retinoblastoma were studied with MRI (standard fat-suppressed Gd-enhanced T1, T2 thin-slice sequences (additionally with small loop surface coil), constructive interference in steady state (CISS) sequence covering the orbita). The images were analysed by two blinded neuroradiologists. Histology was used as the gold standard.Results: MRI assumed infiltration of extra-retinal structures in 13 of 80 patients of which ten were confirmed by histology. Affected extra-retinal structures were: optic nerve (five, of which two were on CISS and three on T1 with higher image resolution using the surface coil), scleral infiltration (five, of which four on CISS and T1) and ciliary body infiltration (one on CISS and T1). Another 61 enucleated patients did not have any extra-retinal infiltration in histology. The CISS sequence with multiplanar reconstruction was mainly helpful in revealing exact three-dimensional tumour extension with excellent clinical acceptance and pre-surgical planning but T1 fat-suppressed Gd-enhanced images were superior in revealing exact tumour extension.Conclusion: CISS sequences allow to produce excellent anatomical images and to perform multiplanar reconstruction to better demonstrate tumour extension. However, T1-weighted sequences after contrast application are more sensitive (60 versus 40%) in detecting infiltration of the optic nerve but equal in detecting scleral infiltration.     

Malignant renal neoplasms: correlation between ADC values and cellularity in diffusion weighted magnetic resonance imaging at 3 T

PURPOSE: This study aimed at exploring the feasibility of high-field diffusion-weighted magnetic resonance imaging (DW-MRI) (3 T) and to correlate apparent diffusion coefficient (ADC) values with tumour cellularity in renal malignancies. MATERIALS AND METHODS: Thirty-seven patients (ten healthy volunteers and 27 patients with suspected renal malignancy) underwent T1-, T2-weighted and T1-weighted contrast-enhanced magnetic resonance imaging (MRI). Diffusion-weighted images were obtained with a single-shot spin-echo echo-planar imaging (SE-EPI) sequence with a b value of 500 s/mm(2). All lesions were surgically resected, and mean tumour cellularity was calculated. Comparison between tumour cellularity and mean ADC value was performed using simple linear regression analysis. RESULTS: The mean ADC value in normal renal parenchyma was 2.35+/-0.31 x 10(-3) mm(2)/s, whereas mean ADC value in renal malignancies was 1.72+/-0.21 x 10(-3) mm(2)/s. In our population, there were no statistically significant differences between ADC values of different histological types. The analysis of mean ADC values showed an inverse linear correlation with cellularity in renal malignancies (r=-0.73, p<0.01). CONCLUSIONS: DW-MRI is able to differentiate between normal and neoplastic renal parenchyma on the basis of tissue cellularity.     

MRI of local disease in nasopharyngeal carcinoma: tumour extent vs tumour stage

The purpose was to use MRI to study in detail local tumour extension in patients presenting with nasopharyngeal carcinoma (NPC) and to compare the extent of local disease with the current T-stage classification. MR images of 150 patients with newly diagnosed nasopharyngeal carcinoma were obtained on a 1.5 T unit. 10 extranasopharyngeal sites were analysed for tumour involvement. The number of concurrently involved sites was determined. The extent of tumour invasion was compared with staging as defined by the fifth edition of the AJCC classification. The T-stage distribution was T1 21%, T2 16%, T3 41% and T4 22%. The frequencies of tumour invasion into an individual site, and the mean number of other concurrently involved sites were as follows: skull base 63%, 3.9 sites; parapharyngeal 56%, 3.9 sites; nasal cavity 53%, 4.0 sites; oropharyngeal 17%, 5.2 sites; sphenoid sinus 27%, 5.6 sites; cranium 21%, 5.7 sites; infratemporal fossa 2%, 6.3 sites; ethmoid sinus 14%, 6.5 sites; orbit 5%, 7.0 sites; maxillary sinus 5%, 7.1 sites; and hypopharynx 0%, 0 sites. Extranasopharyngeal extension commonly occurred superiorly into the skull base rather than inferiorly to the oropharynx (p < 0.0001). Anatomical sites defined within the same T-stage category had different frequencies of involvement and different frequencies of concurrently involved sites. Oropharyngeal involvement (T2 stage) was associated with a number of concurrently involved sites comparable to structures in the T3 category. Maxillary and ethmoid sinus involvement (T3 stage) were associated with a number of involved sites comparable to the T4 stage. Invasion of the maxillary antrum and orbit are markers of the most bulky form of NPC.     

Imaging features of retroperitoneal and pelvic schwannomas

AIM: To describe the imaging features of retroperitoneal and pelvic schwannomas. MATERIALS AND METHODS: The presenting cross-sectional imaging for 18 sequential patients with retroperitoneal or pelvic schwannomas was reviewed retrospectively. Note was made of tumour diameter, position, homogeneity, margin, shape, calcification and invasion into adjacent structures. Where MRI had been performed, T1 and T2 signal intensity relative to skeletal muscle, and the degree and pattern of enhancement with gadolinium, were also assessed. RESULTS: Imaging from 13 patients was available for review. The mean tumour diameter was 8.7 cm (range 4 to 15 cm); 9 schwannomas were located in the pelvis and 4 in the retroperitoneum; 12 cases showed smooth, regular margins and 1 case irregular, invasive margins. The tumours were homogeneous in 5 cases and heterogeneous with cystic change in 8; in 2 cases there was smooth expansion of a sacral nerve root exit foramen, and in 1 there was bony destruction of the sacrum and extension of tumour into the spinal canal. In 5 cases MRI was performed; on T1-weighted images all tumours were isointense; on T2-weighted images 4 tumours were hyperintense and 1 was isointense to skeletal muscle. In all cases the diagnosis was confirmed by core biopsy. CONCLUSION: Retroperitoneal and pelvic schwannomas typically form large, well-circumscribed masses in the retroperitoneum or presacral area, and frequently undergo cystic degeneration. They can occasionally cause bony changes in the spine, but otherwise do not invade or obstruct adjacent structures. Although they are rare, it is important for the radiologist to recognize the typical appearance of schwannomas because they can be mistaken for malignant tumours.     

A ring-enhancing metastasis with central high signal on diffusion-weighted imaging and low apparent diffusion coefficients

Diffusion-weighted imaging (DWI) has been reported to be useful in the differential diagnosis between abscesses and cystic or necrotic tumours. However, experience is still limited and the true sensitivity and specificity remain to be determined. Our purpose is to describe a ring-enhancing metastasis of adenocarcinoma with a DWI pattern similar to that reported for abscesses. The tumour had a diameter of 1.5 cm and give signal from its centre similar to that of normal brain on T1-weighted images, whereas it was increased on T2-weighted images, and surrounded by a low signal ring, suggesting a capsule. The signal was high on DWI and the apparent diffusion coefficient (ADC) was low (0.55 × 10^–3 mm²/s). The findings were misinterpreted as representing an abscess in the early capsule-formation stage, but the signal pattern probably represented early tumour necrosis with intracellular oedema, but without liquefaction. Findings on DWI during the early capsule formation stage in abscesses and early tumour necrosis are probably similar and must be interpreted with caution. Received: 24 January 2000 Accepted: 4 April 2000     

Magnetic susceptibility-weighted MR phase imaging of the human brain

BACKGROUND AND PURPOSE: MR gradient echo imaging is sensitive to the magnetic susceptibility of different tissue types. The purpose of this study was to investigate the diagnostic potential of MR phase imaging of the human brain. METHODS: High-spatial-resolution, T2*-weighted, single-echo images were acquired in five volunteers and one patient with a brain tumor on a 1.5T system by applying a 3D, first-order, velocity-compensated gradient echo sequence by using a quadrature transmit-receive head coil. Phase images were reconstructed from the raw data and unwrapped by using a region-growing phase-unwrapping algorithm. Low-spatial-frequency components originating from static background susceptibility effects were removed by high-pass filtering. RESULTS: Phase images showed excellent image contrast and revealed anatomic structures that were not visible on the corresponding magnitude images. CONCLUSION: Improved processing of susceptibility-weighted MR phase images offers a new means of contrast for neuroimaging applications.