Magnetic resonance imaging signal characteristics in hydatid cysts

The MRI features of hydatid cysts were retrospectively studied in 12 patients to look for specific signal characteristics. Twelve patients in the series included eight with abdominal, two with abdominal-pelvic, one with a sacral and one with a lung hydatid cyst. The T1-, T2- and proton density (PD)-weighted images of spin-echo sequence were used for imaging. The signal characteristics of the hydatid parent cyst capsule and fluid, daughter cyst fluid, detached germinal membrane and surrounding soft tissue reaction were noted. Observations revealed that the capsule is best seen on T2- and PD-weighted images. The daughter cysts are best demonstrated on T1-weighted images, whereas the difference in the signal intensities of parent cyst and daughter cyst fluid is better demonstrated on T2-weighted and T1-weighted images, and the detached germinal membrane is best seen on T2- and PD-weighted images. The signal characteristics of hydatid cyst morphology can help distinguish it from other entities.     

MRI of extradural spinal tumours at 0.3 T

Ninety-one patients with extradural spinal tumours were examined by magnetic resonance imaging. There were 76 metastases (6 from unknown primary tumours). Seven patients had primary spinal tumours and 8 had multiple myeloma. Sixteen had bulging, diseased vertebral bodies compressing the subarachnoid space and 67 had extradural tumour compressing the spinal cord. Sixty patients had paravertebral involvement. Intraspinal involvement did not correlate with the extent of spinal lesions. All patients had vertebral destruction, with hypointense or combined hypo- and isointense signal relative to bone marrow on T1-weighted images. In most of the 22 patients with T2-weighted images the tumours were isointense or slightly hyperintense. It was usually impossible to differentiate the various tumours on the basis of signal intensity and morphology. However, metastases from carcinoma of the prostate were often more hypointense than other tumours on T1- and T2-weighted images. An inhomogeneous pattern in which diffusely low signal is combined with focal lower signal on T1-weighted images may suggest myeloma. In the 22 patients examined with both T1- and T2-weighted images, T1-weighted images gave the best information in 18; in 3 they were equivalent and in 1 inferior to T2-weighted images; they are therefore recommended for routine imaging of epidural spinal tumours.     

Cerebellomedullary ganglioglioma: CT and MR findings.

We present a case of cerebellomedullary ganglioglioma in a young child with indolent clinical symptoms. CT demonstrated a region of hypodensity with central contrast enhancement in the right cerebellar hemisphere and the inferior peduncle. On MR the lesion was iosintense on T1-weighted images with fairly homogeneous enhancement with gadolinium, and of high signal intensity on T2-weighted images.     

MR imaging of dural arteriovenous fistulas draining into cerebellar cortical veins

BACKGROUND AND PURPOSE: Retrograde leptomeningeal venous drainage (RLVD) in a dural arteriovenous fistula (DAVF) is associated with intracerebral hemorrhage, nonhemorrhagic neurologic deficit, or death, and recognizing the presence of this drainage is important. We investigated the MR findings of DAVFs draining into cerebellar cortical veins and compared these findings with those of conventional angiography. METHODS: The MR and angiographic findings of six patients (five men, one woman; mean age, 73.4 years) with DAVF with RLVD into cerebellar cortical veins were reviewed retrospectively. Signal intensity characteristics, contrast material enhancement, topography of the lesion, and presence of signal voids were evaluated on MR images. Site of the shunt, feeding arteries, and draining veins were evaluated on angiograms. RESULTS: In all patients, MR images showed high signal intensity on T2-weighted images and peripheral enhancement on gadolinium-enhanced T1-weighted images at the inferior aspect of the cerebellar hemisphere. A combination of posterior meningeal and occipital arteries was the most frequent blood supply (83%) for these DAVFs. In all six patients, the inferior hemispheric vein was the primary draining vein. CONCLUSION: The characteristic MR findings of DAVF draining into cerebellar cortical veins represent venous congestive encephalopathy in the territory of the involved cortical vein.     

Mottled MR appearance of a hyperacute intracerebral hemorrhage at 0.5 T

A hypertensive patient was examined by CT and magnetic resonance (0.5 T) within 3 h from stroke onset. Computed tomography revealed a thalamocapsular hemorrhage. Hematoma was isointense to the white matter on T1-weighted and hyperintense on T2-weighted spin echo images. The T2-weighted gradient echo images showed a mixture of hypointense and hyperintense signal. This latter aspect has not previously been reported and is probably related to abundant intracellular deoxyhemoglobin in clotted areas rich in red blood cells.     

Adrenal neuroblastoma in an adult with tumor thrombus in the inferior vena cava

We describe the appearance of an adrenal neuroblastoma associated with tumor thrombus occurring in an adult patient. The tumor measured 14 x 12 x 12 cm, showed heterogeneous signal intensity on both T1-weighted and T2-weighted images, and displayed peripheral nodular enhancement on early post-gadolinium images. Tumor thrombus was identified within the inferior vena cava, which extended into the right atrium.     

Cerebral venous angiomas

Summary Sixteen cases of cerebral venous angiomas, seven cerebellar and nine supratentorial were imaged by magnetic resonance, using a T1 sequence and a motion compensated T2 sequence. The transcerebral draining vein of the lesion could be identified in thirteen out of sixteen patients. On T1-weighted images all the lesions were hypointense. On T2-weighted images, five lesions were hypointense, and eleven were hyperintense consistent with slow flow. In three cases the lesion was hemorrhagic. Three lesions with hypointense aspect on T1 and hyperintense aspect on T2-weighted images were only seen in retrospect, due to partial volume averaging in two and concomitant chronic hemorrhage in one. Before contrast, the peripheral dilated medullary veins could only be identified in five cases. On T2-weighted images, in three of these lesions the signal was higher than in the draining veins, pointing to a slower flow. After intravenous administration of Gadolinium, performed in twelve patients, the main transcerebral draining vein as well as the peripheral medullary veins could be well identified in all patients.     

Progressive supranuclear palsy: MRI and pathological findings

Our purpose was to investigate brain atrophy and signal intensity changes on MRI in patients with progressive supranuclear palsy (PSP) and to correlate them with pathological features. We reviewed MRI and brain specimens of six patients with PSP, nine with Parkinson's disease (PD) and six with striatonigral degeneration (SND). Sagittal T1-weighted images showed that four patients with PSP had obvious reduction of anteroposterior midbrain diameter. T2-weighted images demonstrated diffuse high-signal lesions in the tegmentum and tectum of the midbrain of four patients, the upper pontine tegmentum of four, and the lower pontine tegmentum of two, but in no patient with PD or SND. The inferior olivary nuclei gave high signal intensity on T2-weighted images in one patient with PSP These signal intensity changes were consistent with the pathological findings. One patient with PSP showed abnormal signal intensity in the upper pontine tegmentum without atrophy of the midbrain. Midbrain atrophy and diffuse high-signal lesions on T2-weighted images in the tegmentum and tectum of the brain stem are characteristic of PSP     

CT and MR imaging of advanced Zollinger-Ellison syndrome

The CT and magnetic resonance (MR) findings in 13 patients with advanced Zollinger-Ellison syndrome are described. In eight patients (62%) one or more primary tumors were found with both methods. All patients with proven liver metastases (n = 7) were identified by MR. Computed tomography was positive in six of these patients. Three patients with lymph node metastases were identified on CT and MR and one patient had bone metastases. Computed tomography and MR were inferior to selective arteriography in the detection of multiple lesions of the pancreas in a patient with multiple endocrine neoplasia-I syndrome. On the T1-weighted MR images, the primary tumors demonstrated no consistency with regard to their signal intensity relative to the adjacent pancreatic parenchyma. All gastrinomas had an increased relative signal intensity on the T2-weighted images with the exception of a calcified tumor. Liver and lymph node metastases had a low signal intensity on the T1-weighted images and an increased signal intensity on the T2-weighted images. The signal intensity of primary tumors and metastases was independent of size. In conclusion, MR was able to detect abnormalities based on its outstanding lesion/normal tissue contrast, whereas CT diagnosis was based mostly on contour distortion. For the current technique, MR is considered at least equal to CT.     

Imaging of spinal infection

MR imaging is the modality of choice for the detection, staging, and differential diagnosis of inflammatory disorders of the spine. Infectious spondylitis is characterized by the involvement of two adjacent vertebrae and the intervening disk with severe BME and early destruction of the end plates. The disk space is narrowed and typically exhibits water-equivalent signal intensity on T2-weighted or STIR images. Prevertebral and epidural extensions, abscess formation, enhancement of the BME, the disk space, and the surrounding granulation tissue are well demonstrated by gadolinium-enhanced images. Cervical spondylitis frequently involves more than one level. Bone marrow abnormalities may be subtle at this level and increased signal intensity of the disk space on T2-weighted or STIR images is an important finding. The risk for neurologic complications is increased. Granulomatous infections caused by tuberculosis, brucellosis, fungi, and parasites, including hydatid disease (Echinococcus), are frequently associated with imaging findings different from those seen with nonspecific bacterial infection. In patients with chronic infectious spondylitis, diffuse reactive bone marrow changes with decreased signal intensity on T1-weighted images, increased signal intensity on T2-weighted and STIR images, and increased uptake after gadolinium administration may occur. This phenomenon is probably caused by reactive bone marrow stimulation, simulating diffuse hematologic neoplastic disease. Erosive intervertebral osteochondrosis with bandlike disk gadolinium enhancement and BME, which is commonly associated with local pain, is the most important differential diagnosis of bacterial spondylitis.     

Fatigue fractures of the sacrum in children: two case reports and a review of the literature

We present the clinical and radiological features of two children with fatigue fractures of the sacrum. Both patients were active, had no underlying bone disease and presented with insidious onset of low back pain. Plain radiography was non-contributory to the diagnosis. In both patients a focal area of increased activity was present in the lateral aspect of the sacrum on bone scintigraphy, which corresponded to linear medullary sclerosis in the sacral ala demonstrated by computed tomography. Magnetic resonance imaging in one patient revealed a linear signal void in the sacral ala on T1- and T2-weighted images. This was surrounded by diffuse low marrow signal on T1-weighted images, and increased marrow signal on T2-weighted images. Fatigue fractures of the sacrum should be considered in the differential diagnosis of low back pain in children. An awareness of their appearance on magnetic resonance imaging is important as this modality is increasingly utilised, particularly in children.     

Improved detection of enhancing and nonenhancing lesions of multiple sclerosis with magnetization transfer.

PURPOSETo determine whether magnetization transfer imaging can improve visibility of contrast enhancement of multiple sclerosis plaques.METHODSFifty-nine enhancing and 63 nonenhancing lesions in 10 patients with multiple sclerosis were evaluated to calculate contrast-to-noise ratios on conventional T1-weighted and T1-weighted magnetization transfer images. The signal intensity of the lesion and the background (white matter) were measured on precontrast T1-weighted and T1-weighted magnetization transfer images (800/20/1 [repetition time/echo time/excitations]) and on postcontrast T1-weighted and T1-weighted magnetization transfer images. Mean contrast-to-noise ratios was calculated for all lesions.RESULTSThe contrast-to-noise ratio was significantly higher for enhancing and nonenhancing lesions on T1-weighted magnetization transfer images than on conventional T1-weighted images. For enhancing lesions, the contrast-to-noise ratio was significantly higher on postcontrast T1-weighted magnetization transfer images, 32 +/- 2 compared with 21 +/- 2 on conventional T1-weighted images. Fifty of the 59 enhancing lesions were seen on both the T1-weighted and the T1-weighted magnetization transfer images. Nine enhancing lesions were seen only on the postcontrast T1-weighted magnetization transfer images. In addition, of 63 nonenhancing lesions seen on proton-density, T2-weighted, and T1-weighted magnetization transfer images, 16 were not seen on the conventional T1-weighted images. Seven of the 63 nonenhancing lesions and 7 of the 59 enhancing lesions had high signal intensity on the precontrast T1-weighted magnetization transfer images suggestive of lipid signal, a finding not seen on the conventional precontrast T1-weighted images.CONCLUSIONMagnetization transfer improves the visibility of enhancing multiple sclerosis lesions, because they have a higher contrast-to-noise ratio than conventional postcontrast T1-weighted images. High signal intensity on both nonenhancing and enhancing lesions noted only on precontrast T1-weighted magnetization transfer suggests a lipid signal was unmasked. If magnetization transfer is used in multiple sclerosis patients, a precontrast magnetization transfer image is necessary.     

Proton spectroscopic imaging (Dixon method) of the liver: clinical utility

The contribution of proton spectroscopic (PS) imaging to magnetic resonance (MR) imaging of the liver was assessed at 0.5 T in 55 patients with known or suspected hepatic malignancy. PS images were compared subjectively with T1- and T2-weighted spin-echo (SE) images for hepatic lesion detection and conspicuity. For hepatic metastases (n = 27), PS images were equal to T1-weighted images in lesion detection in 17 patients but showed fewer lesions in five patients and false-negative results in two. When compared with T2-weighted images, PS images depicted more lesions in six patients, an equal number of lesions in 18, and fewer lesions in two. Hepatomas (n = 8) were detected with each sequence in all patients. Hepatomas were often more conspicuous on PS images than on T2-weighted images; they were of equal conspicuity on PS and T1-weighted images in most cases. Whereas fatty infiltration (n = 16) appeared on PS images as areas of low signal intensity similar to that of paraspinal muscle, it produced no detectable abnormality on either T1- or T2-weighted images. PS imaging is inferior to T1-weighted SE imaging in the detection of hepatic metastases. The major role of PS imaging at intermediate field strength is to differentiate focal fatty infiltration from hepatic metastases.     

Brodie Abscess: MR imaging appearance in 10 patients

The magnetic resonance (MR) imaging features of Brodie abscess have not yet been fully evaluated. Ten patients with Brodie abscess, eight of long bone and two of vertebra, were studied with MR imaging. Long bone abscess had a characteristic “target” appearance with four layers: (a) a center with low signal intensity on T1-weighted images and high signal intensity on T2-weighted and STIR (short-inversion-time inversion recovery) images, (b) an inner ring isointense to muscle on T1-weighted images and with high signal intensity on T2-weighted and STIR images, (c) an outer ring hypoin-tense on all images, and (d) a peripheral halo hypointense on T1-weighted images. In six of eight cases, a soft-tissue mass was found. The two vertebral abscesses had a less specific appearance, with low signal intensity on T1-weighted images and high signal intensity on T2-weighted and STIR images. Only the peripheral halo was clearly identified in both cases.     

Usefulness of T1-weighted image with fast inversion recovery technique in intracranial lesions: comparison with T1-weighted spin echo image

To evaluate the usefulness of T1-weighted images using the fast inversion recovery (T1FIR) technique as compared with routine T1-weighted spin echo (T1SE) images in various intracranial lesions. Routine spin echo and T1FIR images were performed in 15 consecutive patients with 18 lesions, cerebral infarction in five, astrocytoma in four, vascular lesion in three, encephalomalacia and hemorrhage in each two, arachnoid cyst and meningioma in each one. T1FIR images were performed with 1.5-T Signa [repetition time (TR)/echo time (TE)/inversion time (TI) was 2000/34/800 in 14, 4000/34/1200 in four lesions] and qualitatively compared with the T1SE images in signal intensity, lesion detectability, determination of lesion extent and conspicuity, contrast between lesion and background. Additionally, gray-to-white matter and cerebrospinal fluid (CSF)-to-white matter contrast were evaluated. The signal intensity of the lesions was similar on both T1FIR and T1SE images in all cases. The lesion detectability was similar on both sequences in 15 lesions, and the determination of the lesion extent was definitely higher in 16 lesions on the T1FIR images. Lesion conspicuity was superior in 11, similar in 5, and inferior in 2 patients on the T1FIR images. And also, contrast of lesion-to-background, gray-to-white matter, and CSF-to-white matter was superior on the T1FIR images. The T1FIR technique improved the determination of lesion extent and lesion conspicuity and was qualitatively superior for image contrast as compared with T1SE, but it takes more time than T1SE. The clinical application of T1FIR images depends on whether the superior aspect of the T1FIR images outweighs the disadvantage of the longer time required for this technique.     

前交叉韧带斜冠状面薄层解剖断面与MRI表现对照研究

目的对冰冻膝关节前交叉韧带（ACL）斜冠状面薄层解剖断面与正常人膝关节MRI特点进行对照研究，为ACL损伤分级诊断建立基础。方法1例（1只）膝关节标本行斜冠状面MRI确定角度，冰冻后沿斜冠状面1mm层厚铣切，观察ACL薄层解剖特点。选择50名正常人对其ACL进行MR斜冠状面扫描，观察ACL的MRI特点。结果1只膝关节标本的ACL在斜冠状面薄层断面清晰显示其全程走行，清晰地显示ACL前内束与后外束，前内束从股骨髁附着点后上方区自后向外侧及前内侧走行，止于髁间棘附着区前内侧方，后外侧束从股骨髁附着点前下方区，自后外侧及外下走行，止于髁间棘附着区后外侧方。斜冠状面MRI能够显示50名正常人ACL全程，显示率为100％。MRI能够区分ACL前内束与后外束结构，显示前内束自后外侧向前内走行，止于髁间棘附着区前内侧方，后外束自后外侧向外下走行，止于髁间棘附着区后外侧方。MRI显示ACL走行与薄层断面显示的走行一致。结论斜冠状面是观察ACL的最佳方位，临床对怀疑ACL损伤的患者必要时行MR斜冠状面扫描。     

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.     

Persistent and recurrent hyperparathyroidism: assessment with gadopentetate dimeglumine-enhanced MR imaging

The effect of gadopentetate dimeglumine on signal intensity of abnormal parathyroid glands was assessed in 14 patients with persistent and recurrent hyperparathyroidism. Non-contrast material-enhanced T1- and T2-weighted spin-echo images were compared with T1-weighted images obtained 1 minute and 10 minutes after administration of gadopentetate dimeglumine. Percentage of contrast between the abnormal gland and surrounding tissue was determined with the use of skeletal muscle, subcutaneous fat, and thyroid gland as reference tissues. All 11 abnormal parathyroid glands showed low to intermediate signal intensity on T1-weighted images and high signal intensity on T2-weighted images. Gadopentetate dimeglumine significantly increased the signal intensity enhancement ratio of all abnormal parathyroid glands, causing increased percentage of contrast relative to the thyroid gland and skeletal muscle on T1-weighted images. However, the percentage of contrast relative to these tissues was even greater on nonenhanced T2-weighted images. Thus, gadopentetate dimeglumine can substantially enhance the signal intensity of abnormal parathyroid glands and improve differential contrast with some neighboring tissues on T1-weighted images, but it does not improve contrast with surrounding tissue beyond that achieved on T2-weighted images.     

Determinants of signal intensity in MRI of human astrocytomas

MRI studies at 1.5 T of 38 patients with histologically confirmed astrocytomas were reviewed to search for a relationship of signal intensity with grade of malignancy, rediotherapy used for recurrent tumours and calcium deposits in surgical specimens. Signal intensity of tumours compared with normal brain was rated on a scale of 1 to 5 on T1- and T2-weighted images. Surgical specimens of each tumour were graded histopathologically on a scale of I to III and examined for calcium deposits. CT scans were searched for evidence of calcification. The majority of astrocytomas appeared hypointense on T1-weighted and hyperintense on T2-weighted images. Of 18 tumours with increased signal on T1-weighted images, grade II were prevalent, followed by calcified astrocytomas. Among 14 tumours with decreased signal on T2-weighted images the order was similar, but the ratio of high-grade to low-grade tumours did not differ in relation to signal intensity, while on T1-weighted images the ratio was higher in the group with increased signal intensity. A high grade of malignancy and microcalcifications were associated with an increased signal intensity of astrocytomas on T1-weighted sequences without contrast agent. The above factors did not influence significantly the signal intensity on T2-weighted images. Correspondence to: B. Góraj     

Supratentorial parenchyma in the developing fetal brain: in vitro MR study with histologic comparison.

PURPOSETo assess the in vitro MR signal of the developing brain through histologic comparisons.METHODSFive healthy fetal specimens aged 16, 19, 22, 27, and 34 gestational weeks were studied in vitro using T1- and T2-weighted sequences in frontal and axial planes. Neuropathologic studies included sections in the same frontal plane. Comparison of histologic sections with measurements of the relative widths of the layers of different signal intensities enabled us to assign cellular correspondence to each MR layer.RESULTSIn the cerebral mantle, a layered pattern was observed on both T1- and T2-weighted images. In the basal ganglia, signal from the pallidum and thalamus was isointense with white matter from 16 to 22 weeks'' gestation; then, from 27 and 34 weeks'' gestation, the signal was relatively high on T1-weighted images and low on T2-weighted images. The neostriatum had a relatively low signal on T1-weighted images and a high signal on T2-weighted images from 16 to 27 weeks'' gestation: then, at 34 weeks'' gestation, the signal was relatively high on T1-weighted images and low on T2-weighted images.CONCLUSIONMR imaging can clearly show specific patterns of growing fetal brain in vitro.