Vertebral metastases and an equivocal bone scan: value of magnetic resonance imaging.

To assess the value of magnetic resonance imaging (MRI) in the investigation of patients with suspected but nonproven vertebral metastases 45 consecutive patients referred in a 6 month period with known primary malignancy and back pain in whom an isotope bone scan was reported as equivocal were studied. All patients had abnormal isotope uptake localized to the spine. Twelve patients were shown to have bony metastases on plain X-ray. In the remainder, where X-rays showed normal or benign appearance, MRI of the spine was offered. Twenty-four patients underwent MRI examination which showed vertebral metastases in 11 cases. Magnetic resonance imaging is shown to be a useful, noninvasive, complementary investigation for evaluation of patients known to have malignant disease and suspected of having vertebral metastases on bone scintigraphy.     

Early detection and quantification of murine melanoma bone metastases with magnetic resonance imaging

Objective Bone metastases occur in ∼80% of patients with advanced cancer and cause significant morbidity. There are currently no established means by which to identify the early growth of micrometastatic cells or their effects on bone at a time when curative therapy might be initiated. We postulated that high-resolution magnetic resonance imaging (MRI) could detect and quantify the growth and destructive effects of bone micrometastases. Design Using a mouse model for metastasis of malignant melanoma, we have examined the ability of MRI to quantify cortical bone destruction and the percentage of the medullary cavity occupied by tumour, trabecular bone, and marrow. The results from MRI were compared to histomorphometry (the reference standard) and to radiographs. Results In vivo gradient-echo and spin-echo MRI demonstrated that metastatic melanoma replaced the marrow space but that the cortical bone integrity was preserved (P ≤ 0.001). The smallest detectable micrometastasis had an area of 0.323 mm². In contrast, we observed no trends after quantifying the radiograph data. Conclusion These approaches delineated the limits of MRI in its ability to quantify tumour burden and the effect on bone in this model. Given the increasing use of MRI as a non-invasive clinical diagnostic method, the present findings may be applicable in detecting bone metastases in the clinical setting at an early and potentially treatable stage.     

扩散加权成像联合钆塞酸二钠增强MRI在肝转移瘤诊断中的研究进展

早期检出肝脏转移瘤对选择合适的治疗方案和提高病人术后生存率有较大价值。扩散加权成像主要反映活体组织中水分子的布朗运动,在肝脏局灶性病变的检出和定性方面显示出较大优势,尤其是在肝脏微小转移瘤的检出方面;而钆塞酸二钠(Gd-EOB-DTPA)增强MRI是一种既能进行肝脏动态增强扫描又能提供肝脏特异性信息的影像检查方法,在肝脏转移瘤检出方面的价值和准确性均较高。就DWI联合Gd-EOB-DTPA增强MRI在肝脏转移瘤检出中的研究进展予以综述。     

Perfusion magnetic resonance imaging and magnetic resonance spectroscopy of cerebral gliomas showing imperceptible contrast enhancement on conventional magnetic resonance imaging

The purpose of the present paper was to evaluate the utility of perfusion MRI in cerebral gliomas showing imperceptible contrast enhancement on conventional MRI, and to evaluate the relationships of perfusion MRI and magnetic resonance (MR) spectroscopic results in these tumours. Twenty-two patients with histopathologically proven cerebral gliomas and showing insignificant contrast enhancement on conventional MR were included in the present study. All patients underwent perfusion MRI and MR spectroscopy on a 1.5-T MR system. Significant differences of the relative cerebral blood volume (rCBV) values and the choline : creatine ratios were noted between low-grade and anaplastic gliomas (P < 0.01). Good correlation was found between the rCBV values and the choline : creatine values (y = 0. 532x + 1.5643; r = 0.67). Perfusion MRI can be a useful tool in assessing the histopathological grade of non-contrast-enhancing cerebral gliomas. Along with MR spectroscopic imaging it can serve as an important technique for preoperative characterization of such gliomas, so that accurate targeting by stereotactic biopsies is possible.     

Comparison of spin echo T1-weighted and FLASH 90 degrees gadolinium-enhanced magnetic resonance imaging in the detection of cerebral metastases

A direct comparison of post-gadolinium FLASH 90 degrees magnetic resonance (MR) images against conventional post-gadolinium T1-weighted spin echo MR images obtained in patients with suspected cerebral metastatic disease shows the FLASH sequence to be inferior. False negative FLASH 90 degrees gadolinium-enhanced MR scans are thought to be a result of either magnetic susceptibility artefact or inferior contrast resolution. False positive FLASH 90 degrees gadolinium-enhanced MR images are a result of either difficulty in interpreting the high signal seen in small vessels or, again, magnetic susceptibility effects. In addition, our study shows small abnormalities suggestive of cerebral metastases on the FLASH 90 degrees gadolinium-enhanced sequences which were not seen on the spin echo T1-weighted gadolinium-enhanced sequences. We believe that spin echo T1-weighted gadolinium-enhanced MR sequences demonstrated 131 out of 139 (94.2%) and FLASH 90 degrees gadolinium-enhanced MR sequences detected 122 out of 139 (87.8%) possible metastases. From this, we conclude that spin echo T1-weighted gadolinium-enhanced MR sequences is a better test than FLASH 90 degrees gadolinium-enhanced MR in the diagnosis of brain metastases and that either sequence alone is limited as a screening test.     

Mn2+增强磁共振大鼠皮质脊髓束追踪

目的:探讨Mn2 增强在中场磁共振扫描中对活体大鼠皮质脊髓束的显示,为活体状态下广泛开展含Mn2 对比剂增强神经纤维解剖束路的追踪提供依据。方法:10只Wister大鼠,皮质内注射0.8M Mncl21μl,用1.5T超导磁共振扫描,观察皮质脊髓束的走行。结果:Mncl2皮质内注射24h后行磁共振扫描,完整地显示了活体大鼠的皮质脊髓束从皮层、丘脑、大脑脚、桥脑、延髓至上颈段脊髓的走行。结论:在中场磁共振成像系统下能够清晰的显示Mn2 增强神经传导束路。Mn2 增强后的皮质脊髓束的冠状位解剖定位与三维坐标图谱的解剖定位一致。     

Big cat scan: magnetic resonance imaging of the tiger

In August 2002, we performed MRI scans on a female juvenile Bengal tiger. We present the clinical course, imaging and autopsy findings, and some comparative anatomy of the tiger brain and skull. Magnetic resonance images of a tiger have not previously been published.     

Influence of the reference scan and scan time on the arterial phase of liver magnetic resonance imaging

The controlled aliasing in parallel imaging results in higher acceleration (CAIPIRINHA) technique can decrease scan time. The purpose of this study was to determine whether an arterial phase scan can be performed in 5 s using the CAIPIRINHA short-scan and a reference scanning technique. The generalized autocalibrating partially parallel acquisition (GRAPPA), the CAIPIRINHA routine (CAIPI-routine), and the CAIPIRINHA short-scanning (CAIPI-short) methods were compared. The scan time for each method was preset to 20 s, 15 s, and 10 s, respectively. The reference scan had a scan time of 5 s. A phantom study was used to compare the influence of artifacts during the reference scan. For comparison, the phantom was moved during the last 5 s. In the clinical studies of suspected chronic liver diseases, magnetic resonance imaging of the liver is usually performed while the patient is breath-hold. The motion artifacts of each method were compared. Artifacts were reduced in reference scans using the CAIPIRINHA method. At 5 s after initiation, the rate of change in the standard deviation value was within 30% compared to that of the original image. Motion artifacts due to the influence of the reference scan when a patient failed to hold their breath did not complicate image evaluation. The proportion of motion artifacts for each sequence was as follows: GRAPPA, 5.8%; CAIPI-routine, 1.9%; and CAIPI-short, 0.7%. The arterial phase can be scanned in 5 s using the CAIPI-short and reference scan techniques.     

Gadobenate dimeglumine-enhanced magnetic resonance imaging of intracranial metastases: effect of dose on lesion detection and delineation.

Seventy-four patients with one to eight proven intraaxial metastatic lesions to the brain received a total gadobenate dimeglumine dose of 0.3 mmol/kg of body weight, administered as three sequential bolus injections of 0.1 mmol/kg, at 10-minute intervals over a 20-minute period. Quantitative and qualitative assessments of efficacy were performed after each injection and a full evaluation of safety was conducted. Cumulative dosing produced significant (P < 0.01) dose-related increases in lesion-to-brain (L/B) ratio and lesion signal intensity (SI) enhancement. Two independent, blinded assessors noted additional lesions, compared to unenhanced images in 31% and 33%, 49% and 42%, and 50% and 48% of patients after each cumulative dose, respectively. Significantly more lesions were noted after the first injection, compared to unenhanced images (P = 0.002 and P < 0.001; assessors 1 and 2, respectively), and after a second injection, compared to the first (P < 0.001 and P = 0.039; assessors 1 and 2, respectively). Neither assessor noted significantly more lesions after the third injection. For patients with just one lesion observed on unenhanced T1- and T2-weighted images, additional lesions were noted by assessors 1 and 2 for 27% and 26%, 48% and 35%, and 42% and 41% of patients, respectively, following each injection. Contemporaneously, diagnostic confidence was increased and lesion conspicuity improved over unenhanced magnetic resonance imaging (MRI). For patients with one lesion observed after 0.1 mmol/kg of gadobenate dimeglumine, additional lesions were noted for 24% and 17% of patients (assessors 1 and 2, respectively) following a second 0.1 mmol/kg injection. Only assessor 2 noted additional lesions following the third 0.1 mmol/kg injection. The findings of on-site investigators concurred with those of the two off-site assessors. No safety concerns were apparent.     

Negative scintigraphy with positive magnetic resonance imaging in bone metastases

We report three patients with known primary tumor in whom radionuclide skeletal imaging for metastatic disease was normal with or without clinical symptomatology referable to this area. Magnetic resonance imaging (MRI) of the spine demonstrated focal areas of abnormal signal intensity in the vertebral bodies of these patients. In all three patients, biopsy confirmed metastatic disease. All the patients received radiation or chemotherapy depending upon the etiology. These preliminary data suggest that MR imaging may be useful in evaluating patients with known primary tumor in whom clinical suspicion persists despite a negative radionuclide bone scan.     

Diffusion-weighted magnetic resonance imaging of cerebral white matter development

Diffusion-weighted magnetic resonance imaging (DWI) has become a sensitive tool to monitor white matter development. Different applications of diffusion-weighted techniques provide information about premyelinating, myelinating, and postmyelinating states of white matter maturation. Mirroring maturational processes on the cellular level, DWI has to be regarded as a morphological method as well as a functional instrument, giving insight into molecular processes during the formation of axons and myelin sheets and into the steric arrangement of white matter tracts the formation of which is strongly influenced by their function.     

Diffusion-weighted magnetic resonance imaging for demonstration of cerebral infarcts

Summary Forty-one patients demonstrating clinical symptoms for cerebral infarction were investigated by magnetic resonance imaging with diffusion-weighted echo-planar imaging (DWI) and T2-weighted imaging (T2WI). In 8 patients only DWI showed the cerebral lesions clearly. One patient with positive DWI and T2WI suffered from HSV encephalitis. DWI is superior to T2WI in assessment of small cortical infarcts and cerebral infarction in patients with preexisting vascular lesions. DWI is not specific, so other causes like cerebral hematoma and encephalitis have to be considered.      

Rapid scan magnetic resonance angiography

The change in phase of transverse spin magnetization induced by macroscopic spin motion in the direction of an applied magnetic field gradient is used to generate projection angiograms. The method can provide a quantitative measure of laminar and pulsatile flow. Cardiac synchronization is not required provided that data are acquired at many points in the cardiac cycle. The use of short TR and a large number of excitations provides better suppression of stationary tissue and patient motion artifacts than is possible with cardiac gated studies. In addition to improvements in image quality, a substantial shortening of scan time is obtained.     

Assessment of irradiated brain metastases using dynamic contrast-enhanced magnetic resonance imaging

Introduction

The purpose of this study was to evaluate the effect of stereotactic radiosurgery (SRS) on cerebral metastases using the transfer constant (K _trans) assessed by dynamic contrast-enhanced (DCE) MRI. Furthermore, we aimed to evaluate the ability of K _trans measurements to predict midterm tumor outcomes after SRS.

Methods

The study received institutional review board approval, and informed consent was obtained from all subjects. Twenty-six adult patients with a total of 34 cerebral metastases underwent T1-weighted DCE MRI in a 1.5-T magnet at baseline (prior to SRS) and 4–8 weeks after treatment. Quantitative analysis of DCE MRI was performed by generating K _trans parametric maps, and region-of-interest-based measurements were acquired for each metastasis. Conventional MRI was performed at least 16 weeks after SRS to assess midterm tumor outcome using volume variation.

Results

The mean (±SD) K _trans value was 0.13?±?0.11 min^?1 at baseline and 0.08?±?0.07 min^?1 after 4–8 weeks post-treatment (p?<?0.001). The mean (±SD) total follow-up time was 7.9?±?4.7 months. Seventeen patients (22 lesions) underwent midterm MRI. Of those, nine (41 %) lesions had progressed at the midterm follow-up. An increase in K _trans after SRS was predictive of tumor progression (hazard ratio?=?1.50; 95 % CI?=?1.16–1.70, p?<?0.001). An increase of 15 % in K _trans showed a sensitivity of 78 % and a specificity of 85 % for the prediction of progression at midterm follow-up.

Conclusion

SRS was associated with a reduction of K _trans values of the cerebral metastases in the early post-treatment period. Furthermore, K _trans variation as assessed using DCE MRI may be helpful to predict midterm outcomes after SRS.     

Diffusion-weighted and conventional magnetic resonance imaging in cerebral cryptococcoma

A case of cryptococcoma involving the right cerebral hemisphere is reported. The diffusion-weighted image shows hypointensity in the central cavity of the cryptococcoma, while apparent diffusion coefficient maps show hyperintensity. The imaging features of an intracerebral cryptococcoma mimic that of a central necrotic brain tumor, rather than a pyogenic brain abscess.     

Computed tomographic and magnetic resonance imaging of vanishing cerebral infarct

A thalamic infarct in a 65-year-old woman was initially imaged as a discrete low-density mass in the left side of her thalamus by CT. Abnormal MR signal was also noted in the thalamus and midbrain. Follow-up imaging showed nearly complete resolution of the low-density lesion on CT and the abnormal signal on MR.     

White matter changes on magnetic resonance imaging following whole-brain radiotherapy for brain metastases

Purpose The purpose of this study was to evaluate white matter (WM) abnormalities induced by WBRT. Materials and methods Twenty-four patients (11 men and 13 women; age range 38–74 years, median 60 years) who survived for more than 1 year after completion of WBRT (radiation dose range 30–40 Gy, median 35 Gy) at our institution between January 2000 and June 2003 were followed up with magnetic resonance (MR) scans for 11–51 months (median 19 months). We evaluated WM changes attributable to WBRT as grade 0–6 and assessed possible contributing factors by statistical analysis. Results WM changes were found in 20 patients: Eight were assessed as grade 2, three as grade 3, and nine as grade 5. In total, 12 patients developed grade 3 or higher WM changes. Age (<60 vs ≥60 years), sex, radiation dose (≤35 vs >35 Gy), chemotherapy (with CDDP vs without CDDP), biologically effective dose (≤120 vs >120 Gy1), and head width (<16.3 vs ≥16.3 cm) were found not to be relevant to the incidence or severity of the WM changes. Conclusion Long-term survivors who have under-gone WBRT may have a higher incidence of WM abnormalities.     

Comparison of magnetic resonance angiography,magnetic resonance imaging and conventional angiography in cerebral arteriovenous malformation

Summary 10 patients with an AVM of the brain were examined by magnetic resonance angiography (MRA), magnetic resonance imaging (MRI) and conventional cerebral angiography (CCA). From MRA in 7/10 patients important information about vascular supply could be provided; in 3 patients, all with small AVM's it could be only suspected. CCA revealed the vascularisation of the AVM's in all patients and showed additional hemodynamic aspects better than MRA. With MRI in all cases the AVM could be diagnosed, but only the involvement of the main cerebral vessels could be demonstrated; however, MRI is superior to MRA and CCA in showing the nidus and the involved brain structures.     

Diffusion-weighted magnetic resonance imaging and magnetic resonance spectroscopy in the evaluation of focal cerebral tubercular lesions

Purpose: To review magnetic resonance (MR) diffusion-weighted imaging (DWI) and spectroscopy findings in patients with focal cerebral tuberculosis and to assess whether these techniques can adequately characterize focal cerebral tubercular lesions.

Material and Methods: Sixteen patients with single or multiple lesions were evaluated on a 1.5T MR system. DWI was performed with three 'b' values of 50, 500, and 1000 s/mm² and the apparent diffusion coefficient maps were calculated. MR spectroscopy was performed using the point-resolved single-voxel technique with 2 echo time values of 135 ms and 270 ms. The signal intensities of the tubercular lesions on diffusion images and the apparent diffusion coefficients (ADCs) of their centers, along with MR spectroscopy findings, were analyzed in relation to their T2-weighted MR appearances.

Results: DWI identified 17 of the 20 lesions evaluated. Increased signal intensity was seen in 9 of the 17 lesions. The ADCs of the lesions ranged from 0.406 to 2.64×10^-3 mm²/s (mean±SD: 1.038±0.609 mm²/s). Most of the lesions with hyperintense centers on T2-weighted images were of increased intensity on diffusion images, while those with hypointense centers on T2-weighted images were of decreased signal intensity on diffusion images. However, no statistical difference in the ADCs was found between lesions with increased and those with decreased signal intensity centers on T2-weighted images. MR spectroscopy revealed a lipid peak at 0.9-1.3 ppm in all of the 14 lesions evaluated. An increase in normalized choline:creatine ratio was found in all the lesions in which the spectra were obtained with the voxel, including a variable portion of the lesion wall.

Conclusion: DWI and MR spectroscopy help in determining the nature of cerebral tubercular lesions; however, since the findings are varied, they do not help in specific characterization.