MR imaging of radiation osteitis in the sacroiliac joints

The purpose of this study was to analyze magnetic resonance (MR) images of radiation osteitis of sacroiliac joints, retrospectively. Seven patients with radiation osteitis, which was diagnosed by pelvic plain radiographs and CT images, underwent MRI. T(1)-weighted spin echo images and T(2)-weighted fast spin echo images were obtained in all patients. Four patients were examined after gadolinium injection. Major signal changes of radiation osteitis were distributed on the iliac side. T(1)-weighted images showed diffuse low intensity both in sacral and iliac sides. T(2)-weighted images showed very low intensity adjacent to sacroiliac joints, but mixed intensity was illustrated apart from joints, and high intensity in the peripheral areas. Radiation osteitis showed slight to mild, but irregular enhancement in four patients after gadolinium administration. MRI can illustrate abnormal bone change distribution and is useful for diagnosing this entity by characteristic intensity patterns on T(1)-weighted images with and without gadolinium and T(2)-weighted image. However, the diagnosis of accompanied insufficiency fractures in the area of radiation osteitis is occasionally difficult with conventional MRI.     

An evaluation of reconstructed ACL impingement on PCL using MRI

Using magnetic resonance imaging (MRI), we evaluated 42 reconstructed anterior cruciate ligaments (ACLs) for impingement on corresponding posterior cruciate ligaments (PCLs) in the knee-extended position. Thirty-one single-bundle ACL reconstructions and 11 double-bundle ACL reconstructions were performed. MR examinations were performed at 3 and 12 months after arthroscopic ACL reconstructions. Using oblique axial MRIs of reconstructed ACLs, we evaluated the shape of the PCL and divided them into two groups: an impingement-positive group and an impingement-negative group. Using sagittal images, we measured the PCL index (Liu's method) and examined the correlation between the degree of impingement and the index. At 3 months after surgery, 14 of 31 single-bundle ACL reconstructions and 5 of 11 double-bundle ACL reconstructions were regarded as positive impingement on PCLs. At 12 months after surgery, 17 of 31 single-bundle ACL reconstructions and 5 of 11 double-bundle ACL reconstructions were regarded as positive impingement on PCLs. At 3 months in single-bundle reconstructions and at 3 and 12 months in all reconstructions, the PCL index of the impingement-positive group was significantly lower than that of the negative group. This study indicated that reconstructed ACLs in the impingement-positive group pressed the PCLs more posteriorly than did the impingement-negative group.     

MRI characterization of residual mediastinal masses in Hodgkin's disease: long-term follow-up

Our purpose was to evaluate the role of MRI in distinguishing fibrous from active residual masses in treated Hodgkin's disease. Forty patients with residual mediastinal mass larger than 1.5 cm underwent MRI 1, 3, 6, and 12 months after the end of cycles of prescribed chemotherapy or combined chemoradiotherapy. The MRI examinations were performed on a 0.5 and a 1.5 T systems, using T(1) before and after gadolinium injection and T(2)-weighted sequences. Each time the residual mass was evaluated in size and signal intensity on spin echo (SE) T(2)-weighted images and on SE T(1)-weighted images after contrast medium. Low signal intensity and low contrast enhancement were considered signs of inactive residues; homogeneous high signal intensity and high contrast enhancement were indicative of active residual disease; heterogeneous signal intensity and heterogeneous contrast enhancement were indicative of partial remission or necrotic/inflammatory phenomena. MR showed high diagnostic accuracy in the evaluation of Hodgkin's mediastinal residues after treatment, if performed at least 6 months after the end of therapy, reaching the highest sensitivity and specificity values at 12 month follow-up (considering the three parameters-T(2) signal intensity, contrast-enhancement, and size-all together). If we consider the single parameters individually, we can observe that size variation remains the more valuable parameter to predict or to exclude a relapse. MR diagnostic accuracy at the 6-month follow-up was lower due to the higher incidence of inhomogeneous pattern. The accuracy of MR performed at 1 and at 3 months after the end of therapy was not satisfying. This represents a clinical problem because the most important clinical decisions have to be taken just in this early post-treatment phase.     

Chorioangioma: antenatal diagnosis with fast MR imaging

We report a case of chorioangioma of the placenta, in which fast magnetic resonance imaging (MRI) was useful adjunct to ultrasonography for the antenatal diagnosis. MRI allowed clear demonstration of 6.8 x 6.0 cm solid placental mass along with hydramnios and anatomically normal fetus. On T(1)-weighted breath-hold spoiled gradient-echo (fast low-angle shot [FLASH]) images, chorioangioma was mostly isointense to the placenta, but had an area of high signal intensity near the base and at the periphery, suggestive of hemorrhage. On T(2)-weighted half-Fourier single-shot fast spin echo (HASTE) images, the mass showed heterogeneous high signal intensity, but had an area of low signal intensity near the surface.     

Medial tibial pain: a dynamic contrast-enhanced MRI study.

The purpose of this study was to compare the sensitivity of different magnetic resonance imaging (MRI) sequences to depict periosteal edema in patients with medial tibial pain. Additionally, we evaluated the ability of dynamic contrast-enhanced imaging (DCES) to depict possible temporal alterations in muscular perfusion within compartments of the leg. Fifteen patients with medial tibial pain were examined with MRI. T1-, T2-weighted, proton density axial images and dynamic and static phase post-contrast images were compared in ability to depict periosteal edema. STIR was used in seven cases to depict bone marrow edema. Images were analyzed to detect signs of compartment edema. Region-of-interest measurements in compartments were performed during DCES and compared with controls. In detecting periosteal edema, post-contrast T1-weighted images were better than spin echo T2-weighted and proton density images or STIR images, but STIR depicted the bone marrow edema best. DCES best demonstrated the gradually enhancing periostitis. Four subjects with severe periosteal edema had visually detectable pathologic enhancement during DCES in the deep posterior compartment of the leg. Percentage enhancement in the deep posterior compartment of the leg was greater in patients than in controls. The fast enhancement phase in the deep posterior compartment began slightly slower in patients than in controls, but it continued longer. We believe that periosteal edema in bone stress reaction can cause impairment of venous flow in the deep posterior compartment. MRI can depict both these conditions. In patients with medial tibial pain, MR imaging protocol should include axial STIR images (to depict bone pathology) with T1-weighted axial pre and post-contrast images, and dynamic contrast enhanced imaging to show periosteal edema and abnormal contrast enhancement within a compartment.     

Magnetic resonance imaging in the evaluation of inflammatory lesions in muscular and soft tissues: an experimental infection model induced by Candida albicans

We have developed an experimental model to monitor inflammatory lesions in muscle and soft-tissues during the different stages of the disease by means of Magnetic Resonance Imaging (MRI). MRI of mice legs infected with Candida albicans was performed by standard two-dimensional spin echo and fast spin echo (RARE) using customized coils. The MRI findings were compared with pathologic examinations at the initial acute and established acute inflammatory stages, which provided accurate and detailed information on the evolution of the processes involved. The yeast caused inflammation within the first hours post-inoculation, appearing on T2-weighted images as an inhomogeneous mass with increased signal intensity. The presence of fungal hyphae was observed as hypointense signal areas in both T2 and T1 weighted images, with histologic confirmation. Areas of decreased signal intensity on T2 weighted images were apparent on the last experimental day and were attributed to the granulation tissue located within the capsule surrounding the abscess. The close correlation found between MRI and histopathology suggests that MRI is an ideal radiologic technique for monitoring the clinical and therapeutic follow-up of fungal infections in muscle and soft tissues.     

Early MRI findings of rapidly destructive coxopathy

To diagnose rapidly destructive coxopathy (RDC) in its early stages and understand the pathomechanism of associated joint destruction, ten cases of RDC were followed by periodic MRI from onset of the disease. In the initial stage (stage 1) of RDC, when radiographs revealed slight narrowing of the joint space, a small subchondral area of low signal intensity was observed on T(1)-weighted images (T1WI) and inhomogeneous high intensity was observed on T(2)-weighted images (T2WI) in the antero-lateral portion of the femoral head. When radiographs showed obliteration of the joint space (stage 2), MRI revealed a diffuse area of low intensity on TIWI and high intensity on T2WI in the proximal femur, including the femoral neck and head, suggesting extensive bone marrow edema. The femoral head and acetabulum were aggressively destroyed (stage 3) in all cases 3 to 6 months after the diffuse abnormal pattern was observed on MRI. MRI in stage 3 cases showed low intensity areas on both T1WI and T2WI. RDC did not show the band-like pattern of low intensity on T1WI and high intensity on T2WI that typify MRI findings in cases of osteonecrosis. When joint space narrowing is observed radiographically, the diffuse abnormal pattern of low intensity on T1WI and high intensity on T2WI induced by a subchondral small lesion might be an early sign of RDC.     

Demonstration of aortic lesions via cine magnetic resonance imaging

Cine-MRI was used to evaluate eight patients with known thoracic aorta disease. Included in this study were three aortic coarctations, two aortic dissections, an aneurysm, a posttraumatic pseudoaneurysm, and a patent ductus arteriosus. Cine-MRI was found to be valuable in the assessment of the pathologic anatomy and associated flow disturbances in these disorders. In seven cases, the images demonstrated the aortic lesion and aberrant blood flow. Our technique was unable to image the structural lesion in the patient with patent ductus arteriosus, but the abnormal blood flow was shown. Angiographic data were available on three of the cases to confirm the MR findings. The MRI images were obtained in axial, coronal, sagittal, and oblique planes using fast field echo acquisition technique of cine-MRI. We found the additional data or benefits provided by cine-MRI, when compared to cardiac gated spin echo images, to be most advantageous in the cases of aortic coarctation and dissection only.     

Giant hemangioma of the liver: MR imaging characteristics in 24 patients

We retrospectively reviewed the magnetic resonance imaging (MRI) of giant hemangiomas in 24 patients. MRI studies comprised T1-weighted, T2-weighted and serial gadolinium-enhanced spoiled gradient echo (SGE) images. Morphologic features, signal characteristics and enhancement patterns were assessed. Histopathologic evaluation was obtained in nine patients. On T2-weighted images all lesions (size 5.7-24 cm) were hyperintense relative to the spleen and two dominant patterns of heterogeneity were demonstrated: a central heterogeneous area of either bright, dark, or mixed signal intensity, and a network of multiple fibrous septa of low signal intensity. Histopathologic evaluation of two lesions with a central bright area demonstrated the presence of hypocellular myxoid tissue. Central enhancement (9 lesions) and an irregular flame-shaped peripheral pattern of enhancement (12 lesions) were present in lesions with a mean diameter greater than 10 cm. Although giant hemangiomas show greater variability in their MR imaging appearance, an accurate diagnosis can be made through still characteristic features of high signal intensity on T2-weighted images and discontinuous peripheral enhancement.     

多孔岩芯渗透率与孔隙度的MRI研究

运用自旋回波序列,得到一系列用盐水饱和的多孔岩芯的磁共振自旋密度象,可以直观、准确地观察岩芯的结构,并对象的信号强度与渗透率和孔隙度之间的相关关系进行了分析,发现它们之间存在良好的定性关系,得到了较好的结果.     

MRI of blood volume with MS 325 in experimental choroidal melanoma

Functional magnetic resonance imaging (MRI) allows quantitative blood volume imaging in vivo at high tissue resolution. The purpose is to apply this technique for untreated and hyperthermia-treated experimental choroidal melanoma. MS 325 was used as new intravascular albumin-bound gadolinium-based contrast agent. Pigmented choroidal melanomas were established in albino rabbits. MRI was performed in 7 untreated eyes and 7 eyes treated with a Neodymium:Yttrium-Lanthanum-Fluoride-laser at 1047 nm. 3D-spoiled gradient echo pulse sequences were used to acquire T' weighted axial images. First, a set of images was collected without contrast agent. MS 325 was then injected i.v. and images were obtained within 12 min after injection. Signal intensities were measured within tumor, ciliary body, choroid, and iris and relative signal intensities were determined for these tissues in relation to vitreous. In untreated tumors, the relative signal intensity was higher after injection of MS 325 (5.61+0.70) than without MS 325 (2.90+0.33; p = 0.0002). In contrast, the relative signal intensity of treated tumors did not differ significantly before and after MS 325 (6.19+1.59 and 6.13+1.64). Histopathological sections indicated vascular occlusion in treated tumors. All other studied tissues of untreated and treated eyes showed a significant increase of relative signal intensities in the presence of MS 325. An animal model for the research on contrast agents in MRI is presented. Blood volume measurement with MS 325 was adapted for experimental choroidal melanomas. Reduced change of relative signal intensity indicates compromised blood volume after vascular occlusion in hyperthermia-treated melanoma. Further studies are needed to investigate whether this technique allows the evaluation of tumor viability following treatments.     

Liver imaging at 1.5 tesla: pulse sequence optimization based on improved measurement of tissue relaxation times

In order to predict the most sensitive MR imaging sequence for detecting liver metastases at 1.5 T, in vivo measurements of T1 and T2 relaxation times and proton density were obtained using multipoint techniques. Based on these measurements, two-dimensional contrast contour plots were constructed demonstrating signal intensity contrast between hepatic lesions and surrounding liver parenchyma for different pulse sequences and pulse timing parameters. The data predict that inversion recovery spin echo (IRSE) imaging should yield the greatest contrast between liver metastases and liver parenchyma at 1.5 T, followed by short tau inversion recovery (STIR) and spin-echo (SE) pulse sequences. T2-weighted SE images provided greater liver/lesion contrast than T1-weighted SE pulse sequences. Calculated T1, T2, and proton density values of the spleen were similar to those of hepatic metastatic lesions, indicating that the signal intensity of the spleen may be used as an internal standard to predict the signal intensity of hepatic metastases on T1- and T2-weighted images at 1.5 T.     

Magnetic resonance imaging and pulsed Doppler sonography of poststenotic jets: Correlation between signal void and flow velocity distribution

To correlate the appearance of poststenotic jets on gradient echo images with features of localized Doppler spectra of the jets, we studied an in vitro model of steady flow-through stenoses of 86, 96, and 99% area reduction. As fluids, water and a 40% glycerol solution in water were used. MRI was performed with a 1.5 T whole body imager and gradient echo images were obtained in planes parallel to the direction of flow. Doppler spectra were acquired separately from the MR measurements at 1 cm intervals for a distance of 10 cm downstream from the stenosis. Poststenotic signal void was observed for water and for the 40% glycerol solution only if the mean velocity within the stenosis exceeded a limit of 50–60 cm/sec. On the MR images, the jets could be divided into two segments: A proximal jet segment of uniform width equal to the diameter of the stenosis, followed by a distal jet segment which was characterized by broadening and then dissipating signal void. Except for the 99% stenosis, a high signal intensity core was present within the proximal jet segment. In the proximal jet segment, the Doppler measurements showed a low temporal fluctuation of the maximal flow velocity and only little flow opposite to the main flow direction. In the distal jet segment, the velocity fluctuation and the intensity of reverse flow increased sharply. The high signal intensity core of the jet was associated with a poststenotic zone of constant maximal flow velocity. The results demonstrate a close relationship between characteristic features of poststenotic jets in MRI and pulsed Doppler sonography.     

Magnetic resonance findings in sarcoidosis of the thorax.

Fifteen patients with sarcoidosis underwent thoracic MRI examinations. The T2 signal intensity of lymphadenopathy varied, with no characteristic pattern noted. Three of four patients with bright lymph nodes on T2 images had stage I sarcoidosis, but low intensity nodes were also seen in stage I patients. Coronal images were complementary to axial images and better depicted subcarinal adenopathy. MRI does not distinguish the lymphadenopathy of sarcoidosis from other entities, but is useful for defining the anatomic extent of disease and differentiating pulmonary artery enlargement from adenopathy.     

Venous cavernoma at 8 Tesla MRI

Cavernous angiomas or cavernomas are vascular malformations, which may be associated with risk of bleeding episodes. We present a case report comparing high resolution 8 Tesla gradient echo (GE) imaging with routine fast spin echo (FSE) at 1.5 Tesla in a patient with venous cavernoma. A 55-year-old male with a history of hemorrhagic stroke was studied using high-resolution 8 Tesla magnetic resonance imaging (MRI) system, which revealed venous cavernoma (9 x 8.6 mm) in the left parietal region and visualized adjacent microvascular supply. Signal loss was prominent in the cavernoma region compared to surrounding brain tissue, and signal intensity declined by factor 7.3 +/- 2.4 (679 +/- 62%) on GE images at 8 Tesla. Cavernoma was not apparent on routine T(2)-weighted FSE images at 1.5 Tesla MRI. This case report indicates that GE images at 8 Tesla can be useful for evaluation of vascular pathologies and microvasculature.     

MR signal change in venous thrombus relates organizing process and thrombolytic response in rabbit

Venous thrombus is subsequently organized and replaced by fibrous connective tissue. However, the sequential changes in venous thrombi are not reliably detected by current noninvasive diagnostic techniques. The purpose of this study is to reveal whether magnetic resonance (MR) can detect venous thrombus, define thrombus age and predict thrombolytic responses. Thrombus in the rabbit jugular vein was imaged with a 1.5-T MR system at 4 h and at 1, 2 and 4 weeks using three-dimensional (3D) fast asymmetric spin echo T2-weighted (T2W) and 3D-gradient echo T1-weighted (T1W) sequences. The jugular veins were histologically assessed at each time point. Magnetic resonance imaging (MRI) was also performed in vivo before and 30 min after tissue plasminogen activator (t-PA) administration. The thrombi in MRI were comparable in size to histological sections. The signal intensity (SI) of thrombi at 4 h was heterogeneously high or low on T2W or T1W images, respectively. The SI of thrombi on T2W images decreased time-dependently, but increased on T1W images at 1 and 2 weeks. Morphological analysis showed time-dependent decreases in erythrocyte, platelet and fibrin areas and time-dependent increases in smooth muscle cell, macrophage, collagen and iron areas. The t-PA administration significantly decreased thrombus volume at 4 h but not at 1, 2 and 4 weeks. Venous thrombosis can be reliably and noninvasively detected by MRI. Measurement of SI might support assessments of thrombus age and thrombolytic response.     

Hepatic alveolar echinococcosis: MRI findings

The purpose of this study was to describe the magnetic resonance imaging (MRI) appearance of hepatic alveolar echinococcosis (HAE) on T(1)-weighted, T(2)-weighted and postgadolinium images. A total of 13 lesions were demonstrated in 13 patients. All patients underwent MR examination at 1 T imager. MR examinations included precontrast T(1)-weighted breathing averaged spin echo (SE), breath-hold spoiled gradient echo, T(2)-weighted TSE sequences with and without fat suppression, and T(1)-weighted breath-hold spoiled gradient echo (SGE) sequence following i.v. after gadolinium administration. All lesions were confirmed with histopathology. HAE hepatic lesions revealed geographic patterns of variable signal intensities on noncontrast T(1)- and T(2)-weighted images. Slightly hyperintense, iso- and hypointense signal on T(1)-weighted images corresponded to calcified regions, which appeared hypo-isointense signal on T(2)-weighted images. Necrotic areas were hypointense signal on T(1)-weighted and hyperintense signal on T(2)-weighted images. On postgadolinium images, lesions did not reveal enhancement. Dilatation of intrahepatic bile ducts distal to HAE abscesses were observed in five patients and portal vein invasion or compression was observed in four patients, lobar atrophy of the liver was coexistent finding in cases with portal vein compression. The MRI appearance of HAE abscesses included large irregularly marginated masses with heterogenous signal on T(1)- and T(2)-weighted images and lack of enhancement with gadolinium.     

Initial clinical evaluation of gadolinium DTPA for contrast-enhanced magnetic resonance imaging

Gadolinium DTPA was evaluated as an intravenous contrast agent for magnetic resonance imaging in 15 patients with primary or secondary intracranial neoplastic disease. T1 and T2 weighted images were obtained prior to contrast administration. T1 weighted spin echo 35/800 (TE/TR) images were utilized to detect enhancement. The increase in signal intensity observed, identifying areas of breakdown of the blood-brain barrier (BBB), was similar in magnitude to the contrast enhancement observed on CT. This permitted differentiation of neoplastic tissue from surrounding cerebral edema on MRI. Direct visualization of otherwise "isomagnetic" lesions was also demonstrated. The use of intravenous contrast media should significantly extend the diagnostic potential and specificity of magnetic resonance imaging.     

Pretibial cyst formation after anterior cruciate ligament reconstruction using auto hamstring grafts: two case reports in a prospective study of 89 cases

Eighty-nine cases after anterior cruciate ligaments (ACL) reconstruction were followed prospectively with magnetic resonance imaging (MRI). The patients were examined using axial and sagittal MRI at least twice during the postoperative evaluation of reconstructed ACL. Two cases of pretibial cyst formation were observed. At the time of cyst formation, neither patient had any subjective or objective evidence of knee instability. The cyst of one case communicated with the intra-articular. The minimum follow-up period after the surgical excision was 9 months, with no evidence of recurrence. We might speculate that the critical period for cyst formation in both patients occurred at less than 12 months after their ACL reconstruction. We concluded that the cyst formation was most likely due to incomplete graft tendon incorporation within the osseous tunnel.     

Skeletal muscle lymphoma: MRI evaluation.

The magnetic resonance imaging (MRI) features of two cases of malignant lymphoproliferative disease involving skeletal muscle are presented. In both cases involved muscles were quantitatively and subjectively hypointense to fat on T1-weighted spin echo images, hypointense or isointense on T2-weighted spin echo images, and hyperintense on short tau inversion recovery (STIR) images. The findings suggest that lymphoproliferative disease should be considered as an etiology of a skeletal muscle lesion that is hypointense or isointense to fat on T2-weighted spin echo magnetic resonance images.