Fat-saturated T1 Research Articles

Del edema de médula ósea a la osteonecrosis. Nuevos conceptos

The widespread use of MRI in the diagnosis of articular pathology has allowed for an improved knowledge of a series of disturbances that occur with epiphyseal bone edema as a main radiological sign, featured as low signal intensity of the bone marrow on T1 and high signal on STIR and fat saturated T2 sequences. The new etiopathogenic theories postulate a clear differentiation between primary and secondary osteonecrosis. While secondary osteonecrosis is related to risk factors, primary osteonecrosis is a result of a subcondral insufficiency fracture. Both have different characteristic and MRI criteria. The pathogenesis of transient bone edema syndrome (BMES) is currently under discussion, divided between the biomechanic theory and the more classic one that relates to the complex and poorly understood mechanisms associated with complex regional pain syndrome type I (reflex sympathetic dystrophy). The BMES, classically considered a reversible form of osteonecrosis, has enough differentiated features to be considered as a distinct disease. Bone marrow edema can be as extensive in either insufficiency or fatigue stress fractures than in BMES. The diagnostic key is the display of a subcondral bone fracture. These can be resolved or occasionally evolve into a primary osteonecrosis.

025: Diffusion weighted imaging in the analysis of pediatric orbital tumors

Purpose: To identify common radiographic features of pediatric orbital tumors using magnetic resonance imaging (MRI) techniques, particularly diffusion weighted imaging (DWI), fat saturated FSE T2 and pre- and post-gadolinium T1. DWI is hypothesized to help identify and predict the malignancy of specific brain tumors. To our knowledge similar analysis has not been performed with pediatric orbital tumors.

From bone marrow edema to osteonecrosis. New concepts

The widespread use of MRI in the diagnosis of articular pathology has allowed for an improved knowledge of a series of disturbances that occur with epiphyseal bone edema as a main radiological sign, featured as low signal intensity of the bone marrow on T1 and high signal on STIR and fat saturated T2 sequences. The new etiopathogenic theories postulate a clear differentiation between primary and secondary osteonecrosis. While secondary osteonecrosis is related to risk factors, primary osteonecrosis is a result of a subcondral insufficiency fracture. Both have different characteristic and MRI criteria. The pathogenesis of transient bone edema syndrome (BMES) is currently under discussion, divided between the biomechanic theory and the more classic one that relates to the complex and poorly understood mechanisms associated with complex regional pain syndrome type I (reflex sympathetic dystrophy). The BMES, classically considered a reversible form of osteonecrosis, has enough differentiated features to be considered as a distinct disease. Bone marrow edema can be as extensive in either insufficiency or fatigue stress fractures than in BMES. The diagnostic key is the display of a subcondral bone fracture. These can be resolved or occasionally evolve into a primary osteonecrosis.

Imaging Diagnosis: Current Approach and New Acquisitions

Imaging Diagnosis: Current Approach and New Acquisitions

Évaluation de la diffusion dans la pathologie tumorale rachidienne

Purpose To evaluate the contribution of diffusion weighted MR imaging in malignant spine pathology. Materials and methods Between February 2004 and January 2005, 49 patients (43 to 86 years old) were included. Three groups were made: osteoporotic collapses (n=13), malignant collapses (n=15) and malignant spine lesions (n=21). The MRI (Symphony 1.5T) allowed SENSE imaging. After conventional MRI examination (T1, T2 fat sat, T1 with Gadolinium), all patients underwent diffusion weighted imaging (Spin Echo) with variable b values: 0, 250, 500, 750 and 1000. The diffusion sequence lasted 2 min 29 s. The Apparent Diffusion Coefficient (ADC) was calculated automatically. The analysis was qualitative (signal study b=1,000 mm 2/s) and quantitative (ADC measurement). Results The image quality was good except for some cervical examinations. Qualitative analysis did not show a difference between benign and malignant lesions. Quantitative results are: malignant spine lesion (mean ADC=0.826 10 -3 s/mm 2), malignant spinal collapses (mean ADC=0.912 10 -3 s/mm 2) and benign spinal collapses (mean ADC=1.497 10 -3 s/mm 2). There was overlapping results between benign and malignant lesion. The statistical study showed a significant difference (t test with p< 1/10 000). For an ADC threshold value of 1.089 (malignant lesion ADC<1.089), ROC curve showed a specificity=80% and a sensitivity=83.3%. Conclusion Performig diffusion weighted imaging of the spine is easy with new MR technology. The ADC measurement of spine lesion provides important additional information, but does not serve as a substitute for the routine MRI sequences. In the future, it could become an important point in this difficult diagnosis.

Rationale for the Use of Magnetic Resonance with Gadolinium Administration and FAT/SAT Sequences before Spinal Interventional Neuroradiology Procedures

The role of CT scanning in presurgical planning for stabilisation surgery using metal implants is well-established. However, the advent of new interventional neuroradiology techniques like vertebroplasty, kyphoplasty, ozone discolysis, periganglionic and intraforaminal infiltration of ozone and/or steroids demands more accurate diagnostic assessment of the spine both for surgical planning and during follow-up. In this study we selected 140 candidates for spinal interventional procedures studying them by magnetic resonance scanning (MR) before and after treatment using T2 and T1 fat-saturation (FAT-SAT) sequences after gadolinium administration. T2 and T1-weighted fat-saturation (FAT-SAT) sequences yielded additional information with respect to standard MR investigation of the spine, improving clinical classification and accurate recruitment of surgical candidates. Additional information obtained during follow-up after surgery proved essential in planning the most appropriate maintenance therapy for these patients.

Osteonecrosis of the femoral head after femoral neck fracture

简要叙述股骨颈骨折后股骨头坏死的早期诊断和坏死预测等的最新进展.为使骨折后骨坏死尽量减少,早期手术和关节穿刺减压,避免髋关节放置在伸直及内旋位是必要的,建议屈曲位牵引.应用Gd-DTPA增强MRI T1脂肪浸润扫描,可预测股骨头坏死的可能性.建议将股骨头坏死分为静息型骨坏死和临床型骨坏死。

Magnetic resonance imaging of the equine foot: 15 horses.

Foot pain is a common cause of equine lameness and there have been significant limitations of the methods available for the diagnosis of the causes of foot pain (radiography, nuclear scintigraphy and ultrasonography). Until recently, magnetic resonance imaging (MRI) in the horse has been limited to examination of cadaver limbs. Our purpose was to 1) describe MRI of the foot in live horses, 2) describe MRI findings in horses with foot pain in which a definitive diagnosis could not be established by alternative means and 3) correlate MRI findings with other methods of clinical investigation. The feet of 15 horses with unilateral (12) or bilateral (3), forelimb (14) or hindlimb (1) lameness associated with foot pain of previously ill-defined origin were examined using MRI. The horses were examined in right lateral recumbency under general anaesthesia, with the feet positioned in the isocentre of a flared end 1.5 Tesla GE Signa Echospeed magnet. Images were obtained in sagittal, transverse and dorsal planes using 3-dimensional (3D) T2* gradient echo (GRE), spoiled gradient echo, fat-saturated 3D T2* GRE and short inversion recovery sequences. Image acquisition took approximately 1 h. Abnormalities of the distal interphalangeal joint (DIP) cartilage and/or subchondral bone, periarticular osteophyte formation, distension of the DIP joint capsule with or without synovial proliferation, distension of the navicular bursa with or without evidence of chronic inflammation, surface and core lesions in the deep digital flexor tendon, abnormal signal within the navicular bone, evidence of mineralised fragments in the distal sesamoidean impar ligament, irregular outline of and signal in the medial cortex of the distal phalanx, and an abnormal signal on the dorsal aspect of the distal phalanx consistent with laminitis were identified. MRI permits the diagnosis of a variety of lesions involving different structures within the foot that cannot be diagnosed using other means, thus enhancing our knowledge of the causes of foot pain. With further experience it is likely that lesions involving other structures will also be identified. Long-term follow-up data is required to determine the prognosis for the injuries described.

Prostate swelling following permanent implants is an artifact of the imaging technique

Purpose: American Brachytherapy Society guidelines recommend that post-implant dosimetry of permanent prostate implants be based on CT images. The prostate as imaged by CT has poor visualization of the apex, prostate-seminal vesicle interface, and distortion of margin due to seeds and trauma. MRI has been employed to better visualize the prostate volume. We have attempted to define the optimal technique to image the prostate after implantation using CT, and several MRI techniques (T1 -weighted, T2- weighted, and T1 fat saturation imaging sequences).

Methods: MRT

MRI has become the imaging method of choice in special regions of the head and neck (e.g. nasopharynx, oropharynx, oral cavity, floor of the mouth). Superconducting MR-equipment with field strengths of 1.0–1.5 T are appropriate for the evaluation of the head and neck region.. Signal acquisition is optimal with circular polarized head coils or with specially designed surface coils; the body coil is insufficient. When imaging tumors we need T1 contrast, T2 contrast and contrast medium information (enhancement information). For the T1 contrast T1-spin-echo is and remains the best sequence. For T2-contast T2 turbo-spin-echo with fat suppression has replaced the T2 spin-echo sequences because it is faster and shows good contrast between tumor and saturated fat tissue. Fat saturated T1 turbo-spin-echo enables best tissue contrast after Gd-DTPA application.

Acute swelling of the limbs: magnetic resonance pictorial review of fascial and muscle signal changes

Objective: This pictorial review analyzes the magnetic resonance (MR) fascial/muscular changes in 69 patients referred as emergencies with acute swelling of the limbs (ASL) from various causes. Methods and material: A prospective MR imaging (MRI) study of 69 patients referred as emergencies for ASL was performed. Our population consisted of 45 patients with skin and soft-tissue infections (cellulitis and necrotizing fasciitis, and pyomyositis), six patients with soft-tissue inflammatory diseases (dermatomyositis, graft-versus-host disease), 11 patients with acute deep venous thrombosis, three patients with rhabdomyolysis, one patient with acute denervation and three other patients with rare diseases. Hematomas, tumorous or infectious bone involvement and soft-tissue tumors were excluded. All studies included spin echo T1-weighted images and spin echo T2-weighted images. Gadolinium-enhanced spin echo T1-weighted images were obtained when an abscess was suspected on T2-weighted images. Selective fat-saturated T1- and T2-weighted sequences were also used. MRI analysis was performed to obtain a compartmentalized anatomical approach according to the location of signal abnormalities in subcutaneous fat, superficial and deep fascia and muscle. Results: In all patients with ASL, MRI demonstrated soft-tissue abnormalities involving subcutaneous fat, superficial fascia, deep fascia, or muscle. Although MR findings were non-specific, MRI appears sensitive for detecting subtle fascial and muscle signal changes. Conclusions: In skin and soft-tissue infections, MRI can be helpful for therapeutic management by determining the depth of soft-tissue involvement, particularly within fasciae and muscles, which is partly related to the severity of cellulitis with severe systemic manifestations. MRI can also aid the surgeon in diagnosing abscesses. In inflammatory diseases, MRI can determine the best site for biopsy and also monitor therapeutic response.

MR imaging of biodegradable polylevolactide osteosynthesis devices in the ankle.

To assess the feasibility of magnetic resonance (MR) imaging in the postoperative follow-up after internal fracture fixation using biodegradable polylevolactide (PLLA) plugs and to investigate the MR characteristics of these devices. MR findings in ten patients with displaced malleolar fractures treated by internal fixation using absorbable PLLA plugs were evaluated after three different postoperative periods. The average postoperative follow-up time was thirty months for four patients, forty-two months for another four patients, and fifty-one months for the remaining two patients. On T1-weighted coronal images, the geometry of the PLLA plug was clearly visible in all cases, without signs of fatigue failure or absorption. The host-to-tissue area between the deployed two fins of the plug showed higher signal intensity than the surrounding cancellous bone on fat-saturated proton density (PD) and turbo inversion recovery (tIR) images. This area had signal intensity similar to articular cartilage on T1-weighted coronal images. In none of the cases could any fluid accumulation be seen around the plug. In all ten cases, a thin rim with signal intensity similar to the area between the deployed fins was detected around the PLLA plug on fat-saturated axial PD images. On fat-saturated T2 and tIR sequences, this rim was less clearly detectable in all cases. No differences in the signal intensity or geometry of the PLLA plug on the MR images emerged between the three patient groups with mean follow-ups of thirty, forty-two, and fifty-one months. No artifacts produced by the implants were seen on any of the MR images. A biopsy specimen obtained at a reoperation necessary seventeen months postoperatively showed no signs of degradation of the PLLA plug. MR imaging can visualize PLLA implants within bone. It also shows, without artifacts, the tissue interaction between the artificial biodegradable material and bone tissue in humans.

Adrenal adenomas: characteristic hyperintense rim sign on fat-saturated spin-echo MR images.

To determine whether adrenal adenomas can be differentiated from metastases on fat-saturated magnetic resonance (MR) images. Twenty-eight adrenal adenomas and 20 metastatic lesions were imaged at 1.5 T by means of fat-saturated T1- and T2-weighted and gadolinium-enhanced T1-weighted sequences. The authors evaluated visually whether structures of high signal intensity (hyperintense rim sign) could be observed in the outer margin of the adrenal masses. Twenty-six of 28 adrenal adenomas revealed the hyperintense rim sign on at least one kind of fat-saturated image, compared with only one of 20 metastases. The sensitivity of the hyperintense rim sign as suggestive of adrenal adenoma was 92%, specificity was 95%, and overall accuracy was 94%. The hyperintense rim sign is characteristic of adrenal adenomas. Thus, adrenal adenomas can be differentiated from metastases by means of this new imaging sign on fat-saturated MR images.