Short Time Inversion Recovery Images Research Articles

Pediatric whole-body magnetic resonance imaging: comparison of STIR and T2 Dixon sequences in the detection and grading of high signal bone marrow changes

ObjectivesTo compare short time inversion recovery (STIR) and T2 Dixon in the detection and grading of high signal intensity areas in bone marrow on whole-body MRI in healthy children.MethodsProspective study, including whole-body 1.5-T MRIs from 77 healthy children. Two experienced radiologists in consensus identified and graded areas of high bone marrow signal on STIR and T2-weighted (T2W) turbo spin echo (TSE) Dixon images (presence, extension) in two different sessions at an interval of at least 3 weeks. In a third session, a third observer joined the two readers for an additional consensus reading with all sequences available (substitute gold standard).ResultsFour hundred ninety of 545 (89.9%) high signal areas were visible on both sequences, while 27 (5.0%) were visible on STIR only and 28 (5.1%) on T2W Dixon only. Twenty-four of 27 (89%) lesions seen on STIR only, and 25/28 (89%) seen on T2W Dixon only, were graded as mildly increased signal intensity. The proportion of true positive high signal lesions was higher for the T2W Dixon images as compared to STIR (74.2% vs. 68.2%) (p = 0.029), while the proportion of false negatives was lower (25.9% vs. 31.7% (p = 0.035) for T2W Dixon and STIR, respectively). There was a moderate agreement between the T2W Dixon and STIR-based extension scores on a 0–4 scale, with a kappa of 0.45 (95% CI = 0.34–0.56).ConclusionsMost high signal bone marrow changes identified on a 1.5-T whole-body MRI were seen on both STIR and water-only T2W Dixon, underscoring the importance of using identical protocols when following bone-marrow signal changes over time.Key Points• Whole-body MRI is increasingly being used to diagnose and monitor diseases in children, such as chronic non-bacterial osteomyelitis, malignant/metastatic disease, and histiocytosis.• Standardized and validated imaging protocols, as well as reference standards by age for the growing skeleton are lacking.• Prospective single-center study showed that 90% of high signal bone marrow areas identified on a 1.5-T whole-body MRI in healthy children is seen on both STIR and water-only T2W Dixon, while 5% is seen on STIR only and 5% on T2W Dixon only.

Efficacy of diffusion weighted imaging in sacroiliac joint MRI in children.

Because of the immature bone marrow signal in children, assessment of the sacroiliac joint is more difficult than in adults. Aim of this study is to evaluate the efficacy of diffusion-weighted imaging (DWI) in sacroiliac joint magnetic resonance imaging (MRI). Sacroiliac joint MRI, including DWI sequences, were evaluated by two pediatric radiologists in 54 patients with sacroiliitis and 85 completely normal controls. In MRI evaluation, subchondral bone marrow edema and contrast enhancement in the sacroiliac joints were considered as active sacroiliitis. Apparent diffusion coefficient (ADC) measurements were made in six areas from each sacroiliac joint. A total of 1668 fields were evaluated retrospectively without their diagnosis being known. When the postcontrast T1W series were referenced, the sensitivity, specificity, positive predictive value, and negative predictive value of short time inversion recovery (STIR) images in the diagnosis of sacroiliitis were 88%, 92%, 83% and 94% respectively, compared to contrast-enhanced images. False positive results in STIR images were observed secondary to the flaring signal in the immature bone marrow. ADC measurements obtained from diffusion-weighted images were recorded in all patients and healthy groups. The ADC values were 1.35x10-3 mm2/s (SD: 0.21) in the areas of sacroiliitis, 0.44x10-3 mm2/s (SD: 0.71) in the normal bone marrow and 0.72x10-3 mm2/s (SD: 0.76) in the immature bone marrow areas. Although STIR studies are an effective sequence in the diagnosis of sacroiliitis, they cause false positive results in immature bone marrow in children in inexperienced hands. DWI is an objective method that prevents errors in the assessment of sacroiliitis by means of ADC measurements in the immature skeleton. In addition, it is a short and effective MRI series that makes important contributions to the diagnosis without the need for contrast-enhanced examinations in children.

Hand and Foot Glomus Tumors: Significance of MRI Diagnosis Followed by Histopathological Assessment.

Introduction Glomus tumors are benign lesions with hamartomatous proliferation in the neuromyoarterial glomus bodies. Glomus tumors are small, reddish, painful blue nodules usually underneath the fingernail. Objectives This study is mainly focusing on magnetic resonance imaging (MRI) findings of glomus tumors on T1, T2, short inversion time inversion recovery (STIR), and post-gadolinium images. Further study of clinical and histopathological findings to support the radiological diagnosis. Material & methods The retrospective study included an elaborate study of MRI imaging findings of 24 cases of glomus tumors of the hand and leg at a tertiary care center in Udaipur. Patients with imaging findings confirmed on histopathology were included in the study. MRI study was conducted using a 3-T MR unit and a high-spatial-resolution module. Results A total of 24 cases of glomus tumors were diagnosed during the six years between January 2015 and November 2020. Out of 24 patients, 14 were female and 10 were male. The most common site of involvement was a hand, followed by a foot. All 24 cases showed isointense to hyperintense lesions on T2-weighted images with a conspicuous hyperintense lesion on STIR images. Further histopathological examination confirmed the diagnosis showing nests of monomorphic tumor nuclei arranged in a perivascular pattern. Conclusion Glomus tumors can present with variable pain. A high index of suspicion is needed for diagnosis. Contrast MRI has a significant role in the diagnosis of glomus tumors. The clinical and histopathological picture further confirms the diagnosis. MRI imaging is further supportive to differentiate postoperative fibrosis from residual or recurrent tumors.

Generative models: an upcoming innovation in musculoskeletal radiology? A preliminary test in spine imaging

BackgroundDeep learning is a ground-breaking technology that is revolutionising many research and industrial fields. Generative models are recently gaining interest. Here, we investigate their potential, namely conditional generative adversarial networks, in the field of magnetic resonance imaging (MRI) of the spine, by performing clinically relevant benchmark cases.MethodsFirst, the enhancement of the resolution of T2-weighted (T2W) images (super-resolution) was tested. Then, automated image-to-image translation was tested in the following tasks: (1) from T1-weighted to T2W images of the lumbar spine and (2) vice versa; (3) from T2W to short time inversion-recovery (STIR) images; (4) from T2W to turbo inversion recovery magnitude (TIRM) images; (5) from sagittal standing x-ray projections to T2W images. Clinical and quantitative assessments of the outputs by means of image quality metrics were performed. The training of the models was performed on MRI and x-ray images from 989 patients.ResultsThe performance of the models was generally positive and promising, but with several limitations. The number of disc protrusions or herniations showed good concordance (κ = 0.691) between native and super-resolution images. Moderate-to-excellent concordance was found when translating T2W to STIR and TIRM images (κ ≥ 0.842 regarding disc degeneration), while the agreement was poor when translating x-ray to T2W images.ConclusionsConditional generative adversarial networks are able to generate perceptually convincing synthetic images of the spine in super-resolution and image-to-image translation tasks. Taking into account the limitations of the study, deep learning-based generative methods showed the potential to be an upcoming innovation in musculoskeletal radiology.

Value of imaging in the diagnosing echinococcosis of ribs

Objective To investigate the imaging features of CT and MRI of echinococcosis, and improve the imaging knowledge of the disease. Methods Clinical and radiological findings of echinococcosis of ribs were retrospectively analyzed by reviewing the seventeen cases confirmed by clinical and pathological findings. All patients had CT scan, eight had X-ray plain film and five had MR examination, while 4 patients underwent additional contrast-enhanced CT examination. Results All lesions were unilateral. There were 33 ribs involved, and single involved rib was seen in 7 cases. On CT scans, 10 cases showed cystic, swelling and osteolytic bone destruction, and 7 cases showed moth-eaten osteolytic bone destruction. There were 13 cases of hydatid cyst, 3 cases of a single sac watery density shadow and 10 cases of polycystic separating wheels form. There were 4 cases of fractured ribs, 2 cases of the longitudinal fracture and 2 cases of the transverse fracture. On MRI, there was one case of rib medullary cavity expansion destruction. It was a single cyst with hypointensity on T1WI, hyperintensity on T2WI and hyperintensity on short time inversion recovery (STIR) images. There were one case of rib medullary cavity expansion destruction and 3 cases of hydatid erosion ribs cortex among 4 cases of polycystic type. Polycystic type echinococcosis appeared hypointensity on T1WI, hyperintensity on T2WI and hyperintensity on STIR images. Polycystic type had mother sac and ascus structure, and signal intensity of ascus was higher. STIR sequence showed more clearly polycystic structure. Conclusions CT and MRI can clearly show location of echinococcosis of ribs. There are the imaging features of cystic, swelling and osteolytic bone destruction or complicating cyst of polycystic type which can help the qualitative diagnosis of rib echinococcosis. Key words: Ribs; Echinococcosis; Tomography, X-Ray computed; Magnetic resonance imaging

First experience of simultaneous PET/MRI for the early detection of cardiac involvement in patients with Anderson-Fabry disease.

Anderson-Fabry disease (AFD) is an X-linked lysosomal storage disorder associated with severe multiorgan dysfunction and premature death. Early diagnosis and treatment strategies play a key role in patient outcome. We investigated the potential role of hybrid PET/MR imaging in the assessment of early cardiac involvement in AFD patients. Thirteen AFD patients without cardiac symptoms and with normal left ventricular function underwent simultaneous cardiac PET/MR imaging after administration of (18)F-FDG. Cardiac FDG uptake was quantified by measuring the standardized uptake value in 17 myocardial segments in each subject. The coefficient of variation (COV, i.e. the standard deviation divided by the average) of the uptake of the 17 segments was calculated as an index of heterogeneity in the heart. Six patients exhibited focal late gadolinium enhancement (LGE) indicating intramyocardial fibrosis, and four of these also had positive short inversion time inversion recovery (STIR) sequences. All patients with LGE and positive STIR MR images showed focal FDG uptake in the corresponding myocardial segments indicating inflammation. Of the seven patients with negative LGE and STIR images, five showed homogeneous FDG cardiac uptake and two showed heterogeneous FDG uptake. The COV was significantly greater in patients with focal FDG uptake (0.25 ± 0.02) than in those without (0.14 ± 0.07, p < 0.01). PET/MR imaging is clinically feasible for the early detection of cardiac involvement in patients with AFD. Further studies evaluating the role of hybrid PET/MR imaging in management of the disease in larger patient populations are warranted.

Magnetic resonance imaging for N staging in non-small cell lung cancer: A systematic review and meta-analysis.

BackgroundLymph node staging in non-small cell lung cancer (NSCLC) is essential for deciding appropriate treatment. This study systematically reviews the literature regarding the diagnostic performance of magnetic resonance imaging (MRI) in lymph node staging of patients with NSCLC, and determines its pooled sensitivity and specificity.MethodsPubMed and Embase databases and the Cochrane library were used to search for relevant studies. Two reviewers independently identified the methodological quality of each study. A meta-analysis of the reported sensitivity and specificity of each study was performed.ResultsNine studies were included. These studies had moderate to good methodological quality. Pooled sensitivity, specificity, positive likelihood ratio (LR+), negative likelihood ratio (LR−) and diagnosis odds ratio (DOR) for per-patient based analyses (7 studies) were 74%, 90%, 7.5, 0.26, and 36.7, respectively, and those for per-lymph node based analyses (5 studies) were 77%, 98%, 42.24, 0.21, and 212.35, respectively. For meta-analyses of quantitative short time inversion recovery imaging (STIR) and diffusion-weighted imaging (DWI), pooled sensitivity and specificity were 84% and 91%, and 69% and 93%, respectively. Pooled LR+ and pooled LR− were 8.44 and 0.18, and 8.36 and 0.36, respectively. The DOR was 56.29 and 27.2 respectively.ConclusionMRI showed high specificity in the lymph node staging of NSCLC. Quantitative STIR has greater DOR than quantitative DWI. Large, direct, and prospective studies are needed to compare the diagnostic power of STIR versus DWI; consistent diagnostic criteria should be established.

Transplantation of Mesenchymal Cells Improves Peripheral Limb Ischemia in Diabetic Rats

Adipose tissue-derived mesenchymal stromal cells (ADSCs) are a prominent cellular source for regenerative medicine. We tested whether transplantation of ADSCs into the ischemic muscular tissue of diabetic animals would attenuate impaired cell metabolism and microcirculatory function. We induced unilateral hind limb ischemia in male streptozotocin-treated rats and nondiabetic controls. One day after femoral artery ligation, six rats per group were intramuscularly injected allogeneic ADSCs (10(6)-10(7)-10(8) cells/mL); or conditioned media from ADSC cultures (CM); or saline; or allogeneic fibroblasts (10(7) cells/mL); or nonconditioned medium. Rats underwent magnetic resonance angiography; short time inversion recovery (STIR) edema-weighed imaging; proton MR spectroscopy ((1)H-MRS); immunoblotting and immunofluorescence on both hind limbs for 4 weeks. T1-weighted and STIR images showed tissue swelling and signal hyperintensity, respectively, in the ischemic tissue. The mean total ratio of creatine/water for the occluded limbs was significantly lower than for the nonoccluded limbs in both nondiabetic and diabetic rats. ADSC and CM groups had greater recovery of tCr/water in ischemic limbs in both diabetic and nondiabetic rats, with increased expression of α-sarcomeric actinin, vascular endothelial growth factor and hepatocyte growth factor, as well as increased vessel density. ADSCs improve ischemic muscle metabolism and increase neovasculogenesis in diabetic rats.

Detection of Acute Reperfusion Myocardial Hemorrhage with Cardiac MR Imaging: T2 versus T2*

To evaluate T2 and T2* changes in acute reperfused hemorrhagic and nonhemorrhagic myocardial infarctions and to determine which technique is more suitable in the detection of intramyocardial hemorrhage at 1.5 T. Patient studies were approved by the institutional review board and were HIPAA compliant. Patients (n = 14, three women) with first ST-elevation myocardial infarction underwent cardiac magnetic resonance (MR) imaging 3 days after angioplasty. T2* maps, T2 short inversion time inversion-recovery (STIR) images, and late gadolinium enhancement (LGE) images were acquired. Animal studies were approved by the institutional animal care and use committee. Canines (n = 20) were subjected to ischemia-reperfusion injury, and cardiac MR imaging was performed 5 days after reperfusion. T2* and T2 maps and T2 STIR and LGE images were acquired. Repeated-measures analysis of variance or the Friedman test was used to compare T2 and T2* changes in patients with hemorrhagic infarctions and those with nonhemorrhagic infarctions. Relative to remote myocardium, mean T2* of hemorrhagic infarctions was 54% ± 13 (standard deviation) lower in patients (15.9 msec ± 4.5 vs 35.2 msec ± 2.1, P < .001) and 40% ± 10 lower in canines (23.0 msec ± 4.0 vs 39.3 msec ± 2.5, P < .001). Mean T2* of nonhemorrhagic infarctions was marginally elevated by 6% ± 2.5 (37.8 msec ± 2.5, P = .021) in patients and by 8% ± 5 (44.6 msec ± 4.8, P = .012) in canines. In contrast, mean T2 STIR signal intensity (SI) of both hemorrhagic infarctions and nonhemorrhagic infarctions was higher than that in remote myocardium both in patients (hemorrhagic: 37% ± 19, P < .001; nonhemorrhagic: 78% ± 27, P < .001) and in canines (hemorrhagic: 42% ± 22, P < .001; nonhemorrhagic: 65% ± 22, P < .001). Consistent with STIR SI findings, mean T2 of both hemorrhagic (62.0 msec ± 4.9) and nonhemorrhagic (71.7 msec ± 7.3) infarctions in canines was elevated relative to mean T2 of remote myocardium (52.1 msec ± 4.8) by 18% ± 9 and 38% ± 13, respectively (P < .001 for both). T2* cardiac MR imaging is more suitable than T2 cardiac MR imaging in the detection and characterization of acute reperfusion myocardial hemorrhage. http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.13122397/-/DC1.

Magnetic resonance spectroscopy to detect functional improvement by adipose tissue-derived stromal cell transplantation in the ischemic hind limb in diabetic rats

Adipose tissue-derived stromal cells (ADSCs) are a prominent cellular source in regenerative medicine. We tested whether transplantation of ADSCs into ischemic muscular tissue of diabetic animals would attenuate the impairment in cell metabolism and microcirculatory with a combination of techniques including magnetic resonance imaging and spectroscopy (1H-MRS). Methods: We induced unilateral hind limb ischemia in male streptozotocin-treated rats and non-diabetic controls. One day after femoral artery ligation, 6 rats per group were randomly injected intramuscularly allogeneic ADSCs (C1: 106, C2: 107, C3: 108 cells/mL); or conditioned media from ADSC cultures (CM); or saline (control). Rats underwent magnetic resonance angiography (MRA); short time inversion recovery (STIR) edema-weighed imaging; 1H-MRS; immunoblotting and immunofluorescence on both hind limbs for 4 weeks. Results: T1-weighted and STIR images showed the presence of tissue swelling and signal hyperintensity respectively in tissue affected by occlusion. Mean total ratio of tissue creatine/water (tCr/water) for the occluded limb was significantly lower than for the non-occluded limbs in both non-diabetic and diabetic rats. At 4 weeks, ADSC and CM groups had greater recovery of tCr/water in ischemic limbs compared with controls in both diabetic- and non-diabetic rats (**p<0.01; *p<0.05) (Figure 1, panel A), with less tissue swelling (panel B), increased expression of α-sarcomeric actinin, vascular endothelial growth factor (VEGF) and hepatocyte growth factor (HGF) (Table 1), as well as increased vessel density (panel C) and suppression of the up-regulation of water channel aquaporin (AQP)-1 and pro-inflammatory early response gene such as cycloxygenase (COX)-2 (panel D). Figure 1 Figure 1 Table 1. VEGF and HGF expression in diabetic rat ischemic tissues after femoral artery ligation and treatments with ADSCs conditioned medium and controls Values (pg/mL) are mean ± SD from 3 independent experiments of vascular endothelial growth factor (VEGF) and hepatocyte growth factor (HGF) in frozen tissues from limbs with femoral artery ligation treated with multiple injections of PBS (1 mL), FB (107 cells/mL), ADSCs (at concentration C1 = 106 cells/mL, C2 = 107 cells/mL, C3 = 108 cells/mL) or supernatants obtained from primary ADSCs (conditioned medium. CM, 1 mL) or non-conditioned medium (1 mL). N=6 rats per each treatment group. **P<0.01 vs non-diabetic non-occluded PBS-treated; °°P<0.01 vs diabetic non-occluded PBS-treated; #P<0.05 vs diabetic occluded PBS treated, ##P<0.01 vs diabetic occluded PBS-treated. Legend: PBS, phosphate buffer saline; ADSCs, adipose tissue-derived stromal cells; CM, conditioned medium; NCM, non-conditioned medium; FB, fibroblasts; VEGF, vascular endothelial growth factor; HGF, hepatocyte growth factor. Conclusions: ADSCs improve ischemic muscle metabolism and increase neovasculogenesis in diabetic rats with hind limb ischemia. 1H-MRS is a useful tool to monitor attempts at salvaging the ischemic tissues with cell-derived novel therapies.

Detection of Acute Reperfusion Myocardial Hemorrhage with Cardiac MR Imaging: T2 versus T2*

To evaluate T2 and T2* changes in acute reperfused hemorrhagic and nonhemorrhagic myocardial infarctions and to determine which technique is more suitable in the detection of intramyocardial hemorrhage at 1.5 T. Patient studies were approved by the institutional review board and were HIPAA compliant. Patients (n = 14, three women) with first ST-elevation myocardial infarction underwent cardiac magnetic resonance (MR) imaging 3 days after angioplasty. T2* maps, T2 short inversion time inversion-recovery (STIR) images, and late gadolinium enhancement (LGE) images were acquired. Animal studies were approved by the institutional animal care and use committee. Canines (n = 20) were subjected to ischemia-reperfusion injury, and cardiac MR imaging was performed 5 days after reperfusion. T2* and T2 maps and T2 STIR and LGE images were acquired. Repeated-measures analysis of variance or the Friedman test was used to compare T2 and T2* changes in patients with hemorrhagic infarctions and those with nonhemorrhagic infarctions. Relative to remote myocardium, mean T2* of hemorrhagic infarctions was 54% ± 13 (standard deviation) lower in patients (15.9 msec ± 4.5 vs 35.2 msec ± 2.1, P < .001) and 40% ± 10 lower in canines (23.0 msec ± 4.0 vs 39.3 msec ± 2.5, P < .001). Mean T2* of nonhemorrhagic infarctions was marginally elevated by 6% ± 2.5 (37.8 msec ± 2.5, P = .021) in patients and by 8% ± 5 (44.6 msec ± 4.8, P = .012) in canines. In contrast, mean T2 STIR signal intensity (SI) of both hemorrhagic infarctions and nonhemorrhagic infarctions was higher than that in remote myocardium both in patients (hemorrhagic: 37% ± 19, P < .001; nonhemorrhagic: 78% ± 27, P < .001) and in canines (hemorrhagic: 42% ± 22, P < .001; nonhemorrhagic: 65% ± 22, P < .001). Consistent with STIR SI findings, mean T2 of both hemorrhagic (62.0 msec ± 4.9) and nonhemorrhagic (71.7 msec ± 7.3) infarctions in canines was elevated relative to mean T2 of remote myocardium (52.1 msec ± 4.8) by 18% ± 9 and 38% ± 13, respectively (P < .001 for both). T2* cardiac MR imaging is more suitable than T2 cardiac MR imaging in the detection and characterization of acute reperfusion myocardial hemorrhage. http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.13122397/-/DC1.

Diagnostic value of MR imaging for dentigerous cysts

It is known that the magnetic resonance (MR) imaging features of dentigerous cysts (DCs) are the same as those of other cysts. The cavities of DCs generally show low signal intensity (SI) on T1-weighted imaging (T1WI). However, in our experience, DCs often show high SI on T1WI, rendering them difficult to distinguish from keratocystic odontogenic tumors (KCOTs). In this study, we evaluated seven cases of DC and 23 cases of KCOT to assess whether MR imaging can provide additional information for the differential diagnosis of DC and KCOT. Two trials were evaluated. The first trial was an analysis of the cystic cavity SI on T1WI. To compare the SI between patients, we performed T1WI with contrast (T1c). The second trial analyzed the SI uniformity (U Σ) on T1WI, T2-weighted imaging (T2WI), and short inversion time inversion recovery (STIR) images of the cystic cavity, because it has been reported that an MR imaging feature of KCOT is heterogeneous SI. Statistical analyses were performed using the Mann–Whitney U test and a receiver operating characteristic (ROC) curve. The T1c values of DCs were significantly higher than those for KCOTs. The U Σ values on T1WI and STIR images were significantly higher for DCs than for KCOTs. The T1c cutoff values (0.66 and 0.84) and U Σ cutoff values for T1WI (82.1 %) and STIR images (79.8 %) were determined from the ROC analyses. T1c and U Σ values provide useful additional information for the differential diagnosis of DC and KCOT.

Supplemental value of diffusion‐weighted whole‐body imaging with background body signal suppression (DWIBS) technique to whole‐body magnetic resonance imaging in detection of bone metastases from thyroid cancer

We compared the efficacy of whole-body MRI (WBMRI) with and without diffusion-weighted whole-body imaging with background body signal suppression (DWIBS) using a 3.0-T MR scanner to [18F] fluoro-2-D-glucose positron emission tomography with CT (integrated FDG-PET/CT) for the detection of bone metastases in patients with differentiated thyroid carcinoma (DTC). We examined 23 patients (16 women, 7 men; mean age, 56; range 17-74) with DTC who had undergone total thyroidectomy and were hospitalised to receive [I-131I] therapy. All patients underwent both WBMRI with DWIBS and whole-body FDG-PET/CT. The skeletal system was classified into 13 anatomic segments and assessed for the presence of bone metastases. Bone metastases were verified when positive findings were indicated on at least two imaging modalities: post-treated [131I] whole-body scans, WBMRI without DWIBS (T1-weighted images and short-inversion time inversion recovery images), [18F]-FDG-PET and CT. Bone metastases were confirmed in 78/290 (27%) segments in 20 (87%) of 23 patients. The sensitivities for bone metastases on a segment basis using WBMRI with DWIBS, WBMRI without DWIBS and integrated FDG-PET/CT were 64 of 78 (82%), 50 of 78 (64%) and 62 of 78 (79%), respectively; the difference between values of WBMRI with and without DWIBS was statistically significant (P = 0.0015). The overall accuracies of WBMRI with DWIBS, WBMRI without DWIBS and integrated FDG-PET/CT were 273 of 290 (94%), 261 of 290 (90%) and 272 of 290 (94%), respectively; the difference between values of MRI with and without DWIBS was also statistically significant (P = 0.003). There were only one to three false positive segments and the difference among specificities was not statistically significant in these modalities. Adding DWIBS improved the sensitivity and the overall accuracy of WBMRI using 3.0-T MRI for the detection of bone metastases in patients with DTC. There was no statistically significant difference in diagnostic accuracy between MRI with DWIBS and integrated FDG-PET/CT.

MR Angiography, MR Imaging and Proton MR Spectroscopy In-Vivo Assessment of Skeletal Muscle Ischemia in Diabetic Rats

To prospectively evaluate the feasibility of using magnetic resonance (MR) techniques for in-vivo assessing a rat diabetic model of limb ischemia. Unilateral hind limb ischemia was induced by ligation of the iliac-femoral artery in male streptozotocin-treated and non-diabetic control rats. Four weeks after ligation, rats underwent MR Angiography (MRA), T1-weighted and Short Time Inversion Recovery (STIR) sequences and muscle Proton MR Spectroscopy (1H-MRS) on both hind limbs. After MR examinations, immunoblotting and immunofluorescence analysis were performed. MRA showed a signal void due to flow discontinuation distal to the artery ligation. T1-weighted and STIR images showed, respectively, the presence of tissue swelling (p = 0.018 for non-diabetic; p = 0.027 for diabetic rats) and signal hyperintensity in tissue affected by occlusion. Mean total creatine/water for the occluded limb was significantly lower than for the non-occluded limbs in both non-diabetic (5.46×10−4 vs 1.14×10−3, p = 0.028) and diabetic rats (1.37×10−4 vs 1.10×10−3; p = 0.018). MR Imaging and 1H-MRS changes were more pronounced in diabetic than in non-diabetic occluded limbs (p = 0.032). MR findings were confirmed by using histological findings. Combined MR techniques can be used to demonstrate the presence of structural and metabolic changes produced by iliac-femoral artery occlusion in rat diabetic model of limb ischemia.

Magnetic resonance imaging (MRI) detection of synovitis and bone lesions of the wrists and finger joints in early-stage rheumatoid arthritis: comparison of the accuracy of plain MRI-based findings and gadolinium-diethylenetriamine pentaacetic acid-enhanced MRI-based findings

Objective To explore whether synovitis and bone lesions in the wrists and finger joints visualized by plain magnetic resonance imaging (MRI)-based findings correspond exactly or not to those judged by gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA)-enhanced MRI-based findings.Methods Magnetic resonance imaging of the wrists and finger joints of both hands were examined in 51 early-stage rheumatoid arthritis (RA) patients whose median disease duration from the onset of articular manifestations to entry was 5 months, by both plain (T1 and short-time inversion recovery images) and Gd-DTPA-enhanced MRI (post-contrast fat-suppressed T1-weighted images) simultaneously. We focused on 15 sites per hand, to examine the presence of synovitis and bone lesions (bone edema and bone erosion). Gd-DTPA-enhanced MRI-based findings were considered “true” lesions, and we evaluated the accuracy of plain MRI-based findings in comparison to Gd-DTPA-enhanced MRI-based findings.Results Synovitis, judged by plain MRI-based findings, appeared as false-positive at pretty frequency; thus, the specificity, positive predictive value and accuracy of the findings were low. The rate of enhancement (E-rate) in false-positive synovitis sites was significantly low compared with true-positive synovitis sites where Gd-DTPA enhancement appears. In contrast to synovitis, the false-positivity of bone lesions, judged by plain MRI-based findings, was very low compared with Gd-DTPA-enhanced MRI-based findings.Conclusion Synovitis judged by plain MRI-based findings is sometimes considered false-positive especially in sites where synovitis is mild. However, plain MRI is effective in identifying bone lesions in the wrist and finger joints in early-stage RA.

Whole body diffusion weighted imaging pattern of normal bone marrow

Objective To analyze the pattern of normal bone marrow on whole body diffusionweighted imaging (WB-DWI) and its influence factors.Methods A total of 98 healthy volunteers (male 47 and female 51). All volunteers underwent WB-DWI at 1.5 T MR scan. The ADC value,the signal intensity on DWI obtained with a b value of 800 s/mm2 ( SIDWI ),and the signal intensity on short time inversion recovery images ( SISTIR ) of thoracic vertebrae,lumber vertebrae,bilateral head of femur,bilateral neck of femur,bilateral superior segment of femur,bilateral inferior segment of femur,bilateral ilium,bilateral head of humerus,bilateral scapula were measured and compared with ANOVA test and StudentNewmar-Keuls test.The normal appearance of bone marrow on WB-DW[ was assessed. The relationship between the SIDwI and the ADC,and the SIDWI and the SISTIR of bone marrow were analyzed.The ADC of bone marrow between male and femaIe were compared. Spearman correlation analysis was performed for different age groups.Results ( 1 ) Bone marrow signal intensity was different among 98 healthy volunteers.Bone marrow in 69 healthy volunteers (female 24,male 45 ) showed low to intermediate signal intensity,whereas in the remaining 29 healthy volunteers (female 27,male 2) showed high signal intensity.(2) The SIDWI of thoracic vertebrae ( median 44.54),lumber vertebrae ( median 35.01 ),head of femur ( median 13.61 ),neck of femur ( median 16.00),superior segment of femur ( median 21.45 ),ilium ( median 25.77),head of humerus (median 18.35),scapula (median 36.12) was positively correlated with the ADC [ (0.55 ±0.08) × l0-3,(0.53 ±0.08) × 10-3,(0.30 ± 0.10) × 10-3,(0.42 ± 0.16) × 10-3,(0.74±0.14) ×l0- 3,(0.49±0.10) ×10-3,(0.36±0.13) ×10-3,(0.49±0.11) × 10-3mm2/s]and the SISTIR ( median 61.81,64.99,53.27,69.08,73.10,66.35,73.16,79.81 ),r =0.513 and 0.695,0.741 and 0.764,0.443 and 0.489,0.641 and 0.656,0.510 and 0.648,0.475 and 0.715,0.366 and 0.446,0.437 and 0.739 ;P ＜ 0.01. (3) There was significant difference of the ADC of bone marrow in different bone,F =138.69,P ＜ 0.01. Student-Newman-Keuls test revealed that no significant difference was found in the ADC between thoracic vertebrae and lumbar vertebrae,ilium and scapula,head of humerus and inferior segment of femur ( P ＞ 0.05 ),and significant difference was found in the ADC values between the remaining two groups ( P ＜ 0.05 ). The bones associated with decreasing ADC values were superior segment of femur,thoracic vertebrae and lumber vertebrae,ilium and scapula,neck of femur,head of humerus,head of femur and inferior segment of femur. ( 4 ) The ADC values of bone marrow of female subjects in thoracic vertebrae [ (0.59 ±0.07) × 10-3 mm2/s],lumber vertebrae [ (0.58 ±0.06) × 10 -3 mm2/s],head of femur ( median 0.33 × 10 -3 mm2/s),neck of femur ( median 0.53 × 10 -3 mm2/s),superior segment of femur ( median 0.81 × 10-3 mm2/s),inferior segment of femur ( median 0.32 ×10-3 mm2/s),ilium [ (0.52 ± 0.09 ) × 10-3 mm2/s ],head of humerus (median 0.42 × 10-3 mm2/s),scapula [ (0.53 ± 0.09) × 10-3 mm2/s] were significantly higher than those of male subjects [ (0.51 ±0.07) × 10-3,(0.48 ±0.07) × 10-3,median 0.23 × 10-3,median 0.31 × 10-3,median 0.66 × 10-3,median 0.23 × 10-3,(0.46 ±0.10) × 10-3,median 0.27 × 10-3,(0.45 ±0.11 ) × 10 3mm2/s].(5)There was significant negative correlation between the ADC values of bone marrow and age in thoracic vertebrae,lumber vertebrae,head of femur,neck of femur,superior segment of femur,ilium,head of humerus for female subjects,r =-0.549, -0.629, -0.329, -0.524, -0.338, -0.548 and -0.416,respectively,P ＜ 0.05.There was no significant correlation between ADC values and age in inferior segment of femur and scapula for female subjects and all the regions for male subjects ( P ＞ 0.05 ).Conclusions The ADC and the SIsTIR of bone marrow correlates with the SIDW1.The ADC values of bone marrow is affected by age and sex,and is different for different bones. Key words: Diffusion magnetic resonance imaging; Bone marrow; Reference values

Carcinoma ex pleomorphic adenoma of the parotid gland

Carcinoma ex pleomorphic adenoma (CXPA) is a rare aggressive epithelial malignancy arising from a primary or recurrent benign mixed tumor. Only a few case reports describing the radiologic features of CXPA have been published. To describe and characterize the magnetic resonance (MR) imaging findings of CXPA in the parotid gland and correlate them with pathologic findings. The MR images of surgically proven CXPA in the parotid gland of five men and five women ranging in age from 28 to 75 years (mean 52 years) were retrospectively reviewed. All MR images were evaluated with emphasis on the size, margin characteristics, extraparotid infiltration, the presence of an encapsulated component, and signal intensity on T2-weighted or short-inversion-time inversion recovery (STIR) images. The average maximal diameter was 4.3 cm. All 10 tumors had ill-defined boundaries, and seven tumors showed extraparotid infiltration, reflecting invasive growth of the malignant component identified on histological examination. Eight tumors had a round encapsulated component and seven of those signal intensities were a mixture of hypo- and hyperintensity on T2-weighted or STIR images. Histological correlation of these components revealed fibrously encapsulated tumors containing hyalinization and myxoid tissue, suggesting degenerated pleomorphic adenoma. Invasive malignant components had non-specific and various signal intensities. An invasive parotid mass co-existing with a round encapsulated component is suggestive of carcinoma ex pleomorphic adenoma.

Magnetic resonance imaging (MRI) detection of synovitis and bone lesions of the wrists and finger joints in early-stage rheumatoid arthritis: comparison of the accuracy of plain MRI-based findings and gadolinium-diethylenetriamine pentaacetic acid-enhanced MRI-based findings

To explore whether synovitis and bone lesions in the wrists and finger joints visualized by plain magnetic resonance imaging (MRI)-based findings correspond exactly or not to those judged by gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA)-enhanced MRI-based findings. Magnetic resonance imaging of the wrists and finger joints of both hands were examined in 51 early-stage rheumatoid arthritis (RA) patients whose median disease duration from the onset of articular manifestations to entry was 5 months, by both plain (T1 and short-time inversion recovery images) and Gd-DTPA-enhanced MRI (post-contrast fat-suppressed T1-weighted images) simultaneously. We focused on 15 sites per hand, to examine the presence of synovitis and bone lesions (bone edema and bone erosion). Gd-DTPA-enhanced MRI-based findings were considered "true" lesions, and we evaluated the accuracy of plain MRI-based findings in comparison to Gd-DTPA-enhanced MRI-based findings. Synovitis, judged by plain MRI-based findings, appeared as false-positive at pretty frequency; thus, the specificity, positive predictive value and accuracy of the findings were low. The rate of enhancement (E-rate) in false-positive synovitis sites was significantly low compared with true-positive synovitis sites where Gd-DTPA enhancement appears. In contrast to synovitis, the false-positivity of bone lesions, judged by plain MRI-based findings, was very low compared with Gd-DTPA-enhanced MRI-based findings. Synovitis judged by plain MRI-based findings is sometimes considered false-positive especially in sites where synovitis is mild. However, plain MRI is effective in identifying bone lesions in the wrist and finger joints in early-stage RA.

MR Monitoring of NaCl-enhanced Radiofrequency Ablations: Observations on Low- and High-Field-Strength MR Images with Pathologic Correlation

To test the hypothesis that magnetic resonance (MR) imaging can be used to monitor both intraparenchymal injection of NaCl solution and subsequent radiofrequency ablation (RFA) within tissues pretreated with NaCl, report the low- and high-field-strength MR appearance of NaCl-enhanced RFAs, and compare MR findings with pathologic findings. Ten ex vivo calf liver specimens were injected with saturated NaCl (seven were mixed with methylene blue during MR fluoroscopic monitoring) and reexamined with fast imaging with steady-state progression (FISP), true FISP, reversed FISP (PSIF), and fast spin-echo T2-weighted MR sequences. The NaCl-to-liver contrast-to-noise ratio (CNR) was calculated for various sequences, and CNRs were compared with the Student t test. Distribution on MR images was compared with the results of pathologic analysis. Forty additional in vivo monopolar RFAs were performed in paraspinal muscles of seven minipigs after animal care committee approval (10 standard control ablations, 30 were preceded by direct injection of saturated NaCl at various volumes [3-9 mL] and rates [1 or 6mL/min]). Postablation low-field-strength (n = 20) and high-field-strength (n = 20) MR examinations consisted of T2-weighted imaging, short inversion time inversion-recovery (STIR) imaging, and contrast material-enhanced T1-weighted imaging. Ablation shape, conspicuity, volume, and signal intensity were compared between the two groups and with the results of pathologic analysis. The difference in volumes with and without NaCl injection was evaluated by using two-way analysis of variance. Mean CNR was highest on fast spin-echo T2-weighted images and was significantly higher for PSIF than for FISP (P < .0001) or true FISP (P = .003). NaCl distribution on MR images corresponded with the results of pathologic analysis in ex vivo livers. Interactive in vivo monitoring of NaCl injection and electrode placement was feasible. NaCl-enhanced ablations had irregular shapes, a higher CNR, and significantly larger volumes (F = 22.0; df = 1, 90; P < .00001). All ablations had intermediate or low signal intensity with high-signal-intensity rims on all images. Fluid signals overlaid NaCl-enhanced ablations on fast spin-echo T2-weighted and STIR images, particularly on high-field-strength MR images. MR imaging can be used to reliably monitor the distribution of injected NaCl solution in tissues. Interventional MR imaging techniques can be used to guide and monitor RFAs within NaCl pretreated tissues, with good correlation with pathologic results.

Axial STIR MRI: A faster method for confirming femoral head reduction in DDH

Non-concentric reduction of the femoral head within the acetabulum is detrimental to its delicate cartilaginous structure and may result in a growth disturbance. Successful relocation of the dislocated femoral head depends on subtle clinical findings and radiography. The combination of a dislocated femoral head and a severely dysplastic acetabulum can result in a clinical examination that is unhelpful in confirming reduction under anaesthesia. In cases where uncertainty existed regarding head reduction in a spica cast, we performed axial short inversion time inversion recovery (STIR) and axial proton density magnetic resonance imaging (MRI) scans. We retrospectively reviewed the efficiency and accuracy of MRI in confirming femoral head location after closed reduction and spica application in eight children. One hundred and fifty-three cases of developmental dysplasia were treated with examination under anaesthesia and spica application in our unit over a 3-year period. Eight cases where MRI scanning was performed were identified. Before application of the spica cast, we used radiographic screening to assess the stability of the reduction. Absence of the ossific nucleus within the femoral head made confirmation of the location with the image intensifier unreliable. To confirm concentric femoral head location after closed reduction and spica application, we performed an MRI scan in the immediate post-anaesthesia period. All scans were performed within 30 min of application of the spica, and the average time for each scan was 5 min. All eight children who had MRI post-application of the spica had concentric reduction of the femoral head. MRI allowed three-dimensional appreciation of the acetabulum and femoral head. Use of the axial STIR images allows accurate assessment of the cartilaginous ossific nucleus. All patients were discharged the same afternoon and followed up as outpatients. No patient in our group required contrast arthrography. While not indicated in all cases of femoral head dislocation, MRI is useful to confirm concentric reduction of the femoral head in a dysplastic acetabulum when examination under anaesthesia and radiographic screening have been uncertain. In our series, 1 in 20 cases needed MRI. This is a reliable, non-invasive method confirming definite reduction of the femoral head prior to discharge in all of our patients. In this initial series, all patients had axial and coronal STIR and proton density MRI. We now only use axial STIR images because they provide adequate information regarding the position of the femoral head relative to the acetabulum.