Ischemia Increases the Twitch Latent Period in the Soleus and Extensor Carpi Radialis Longus Muscles from Adult Rats

Complete ischemia and reperfusion effects on twitch force (∫(F·t)), twitch latent period (TLP), maximal rate of rise of twitch tension (δF/δt)_max, and twitch maximum relaxation rate (TMRR) were assessed. We divided 36 adult rats into four groups; two control groups (n = 9), a group undergoing 1 hour of ischemia followed by 1 hour of reperfusion (n = 9), and one group exposed to 2 hours of ischemia followed by 1 hour of reperfusion (n = 9). We have induced twitch contractions every 10 minutes in the soleus and the extensor carpi radialis longus (ECRL). Twitch contractions were recorded and then analyzed for ∫(F·t), TLP, (δF/δt)_max, and TMRR. During 1 hour and 40 minutes of ischemia, TLP increased to 179 ± 24% (p < 0.05) in the soleus and to 184 ± 16% (p < 0.05) in the ECRL, an effect that was partially recovered during 1 hour of reperfusion. This increase started after 20 minutes of ischemia in the soleus and after 40 minutes of ischemia in the ECRL. The increase was faster in the ECRL and peaked at the same time for both muscular groups. ∫(F·t) and (δF/δt)_max decreased during 1 hour of ischemia to 46 ± 7% (p < 0.05) in the soleus and to 40 ± 7% (p < 0.05) in the ECRL. TMRR decreased during 1 hour of ischemia to 39 ± 5% (p < 0.05) in the soleus and to 54 ± 8% (p < 0.05) in the ECRL. During 1 hour of reperfusion all of them recovered close to control values.     

Magnetic Resonance Imaging of the Postoperative Meniscus

Imaging of the postoperative meniscus is a challenge. Nevertheless, magnetic resonance imaging (MRI) of the symptomatic knee after meniscal surgery is a valuable diagnostic study of both the menisci and the entire joint. At present, symptomatic patients who have had partial meniscectomy of less than 25% may be evaluated by MRI. For those with partial meniscectomy of greater than 25% or after meniscal repair, direct or indirect magnetic resonance arthrography (MRA) should be considered. Currently, the decision of whether to perform direct (intra-articular) versus indirect (intravenous) MRA must be reviewed on a case-by-case basis considering both the patient's ability to tolerate intra-articular injection and whether a significant effusion already exists, which will imbue the tear with synovial fluid (making intra-articular injection of less importance). In such cases of significant effusion, indirect MRA would be preferred. If MRI or MRA is contraindicated, computed tomography arthrography seems a promising alternative. For a patient who has undergone meniscal allograft transplantation, MRI seems adequate for detecting meniscocapsular healing, allograft extrusion, and allograft tear. Future improvements in MRI sequencing may obviate the need for invasive modalities.     

Magnetic Resonance Imaging of Adhesive Capsulitis: Correlation with Clinical Staging

The purpose of this study was to evaluate non-contrast magnetic resonance imaging (MRI) findings of adhesive capsulitis and correlate them with clinical stages of adhesive capsulitis. This will hopefully define a role for shoulder MR imaging in the diagnosis of adhesive capsulitis as well as in potentially directing appropriate treatment. Forty-seven consecutive non-contrast magnetic resonance imaging examinations of 46 patients with a clinical diagnosis of adhesive capsulitis were retrospectively reviewed and correlated with clinical staging. Specific MRI criteria correlated with the clinical stage of adhesive capsulitis, including the thickness and signal intensity of the joint capsule and synovium as well as the presence and severity of scarring in the rotator interval. Routine MRI of the shoulder without intraarticular administration of gadolinium can be used to diagnose all stages of adhesive capsulitis, including stage 1, where findings may be subtle on clinical examination. We believe that future studies assessing the role of MRI in guiding the initiation of appropriate treatment should be undertaken.     

Significance of Intramedullary High Signal Intensity on Magnetic Resonance Imaging in Patients with Cervical Ossification of the Posterior Longitudinal Ligament

Background

The purpose of this study was to analyze the relation between intramedullary high signal intensity (IMHS) on magnetic resonance imaging (MRI), radiographic parameters, and clinical symptoms in cervical ossification of the posterior longitudinal ligament (OPLL) patients.

Methods

Two hundred forty-one patients, who underwent simple radiography, computed tomography (CT), and MRI were included in the present study. As radiographic parameters, the OPLL occupying ratio and occupying area were measured on CT images. Dynamic factors were assessed by measuring cervical range of motion (ROM) on simple radiographs. Visual analog scale (VAS) for neck and arm pain, and Japanese Orthopaedic Association (JOA) scores were evaluated for clinical analysis. The differences in radiographic and clinical findings were assessed between patients with IMHS on T2-weighted MRI findings (group A) and patients without IMHS (group B).

Results

Eighty-one patients were assigned to group A and 160 patients to group B. The occupying ratios were found to be higher in group A than in group B on both sagittal and axial views (p < 0.01). Group A also showed a higher area occupying ratio (p < 0.01). The length and area of underlying spinal canal on the sagittal and cross-sectional planes were lower in group A than in group B (p < 0.01). No significant difference in ROM was observed (p = 0.63). On the clinical findings, group A had a lower JOA score (p < 0.001), and no intergroup differences in VAS scores were observed.

Conclusions

In cervical OPLL cases, IMHS on MRI was associated with manifestation of myelopathic symptom. Occupying ratio was associated with high signal intensity on MRI, whereas no association was found with ROM. Occurrence of high signal intensity increased inversely with the length and area of underlying spinal canal.     

磁共振功能成像鉴别胰腺癌与肿块型慢性胰腺炎的价值

目的总结各种磁共振(MR)功能成像的原理及在胰腺癌及肿块型慢性胰腺炎诊断中的应用价值。方法回顾分析国内、外近年来关于MR波谱成像、MR弥散成像及MR灌注成像在胰腺癌及慢性胰腺炎诊断和鉴别诊断中应用的文献。结果胰腺癌与慢性胰腺炎在分子扩散、生化代谢、组织灌注等方面存在差异,MR功能成像方法能反映这些差异而用于鉴别诊断。结论MR功能成像作为一种非侵入性的影像检查方法,能够提供鉴别胰腺癌与肿块型慢性胰腺炎有价值的信息。     

Magnetic Resonance Imaging Criteria to Predict Complete Excision of Parasellar Pituitary Macroadenoma on Postoperative Imaging

Purpose To evaluate preoperative magnetic resonance imaging (MRI) criteria for their ability to predict the complete removal of parasellar pituitary macroadenoma on the 3-month postoperative MRI. Methods Dedicated pre- and postoperative pituitary MRI studies were reviewed in 49 patients who had undergone transsphenoidal surgery for macroadenomas with potential unilateral parasellar involvement. Twelve preoperative MRI findings and postoperative MRI outcomes were statistically compared. Results Depiction of the inferolateral (positive predictive value [PPV]: 0.6; negative predictive value [NPV], 0.92) and lateral (PPV: 0.65; NPV: 0.85) compartments of the cavernous sinus and the percentage of intracavernous carotid artery encasement (PPV: 0.63; NPV, 1.0 for <50% encasement) were the only criteria significantly predictive of parasellar tumor complete resection. The odds ratios indicated that depiction of the lateral venous or inferolateral venous compartments increased the likelihood of a complete resection by 6 times, whereas for every 25% reduction in intracavernous carotid artery encasement, the chance of a complete resection increased 3.4 times. Conclusion The preoperative MR imaging features that are useful in predicting the complete removal of the parasellar component of a pituitary adenoma as assessed by postoperative MRI are (1) depiction of the lateral and inferolateral compartment of the cavernous sinus and (2) decreasing encasement of the intracavernous carotid artery.     

Contrast-Enhanced Magnetic Resonance Imaging to Assess Tumor Histopathology and Angiogenesis in Breast Carcinoma

Contrast-enhanced magnetic resonance imaging (cMRI) is a potentially powerful new tool in the early diagnosis and staging of patients with breast carcinoma. Rapid contrast enhancement is suggestive of carcinoma and likely related to high tumor vascularity. We have developed a new cMRI technique that combines anatomic and kinetic information to help characterize breast carcinomas. Signal enhancement ratio (SER) patterns (which quantitate the kinetics of contrast enhancement using a three time point high-resolution method) were correlated in tumors from 32 patients with histopathology and tumor angiogenesis as measured by intratumoral microvessel density (iMVD). Early signal enhancement with rapid washout of intravenous contrast (i.e., corresponding to high SER values) correlated with high tumor vascularity. We found that TARGET MRI with SER analysis has potential as a tool for characterizing breast carcinoma in vivo. It enables anatomic visualization of tumor and appears to add biologic information as well, such as level of tumor angiogenesis. ▪     

Magnetic Resonance Imaging after Translabyrinthine Complete Excision of Vestibular Schwannomas

The objective of this study is to determine whether magnetic resonance imaging (MRI) at 2 years following complete vestibular schwannoma (VS) excision using a translabyrinthine approach is sufficient to detect recurrent tumor. The study is set in a tertiary referral skull base unit. A service evaluation of a prospective database identified patients who underwent complete translabyrinthine VS excision with prospectively recorded MRI results at 2 and 5 years following surgery. The main outcome measures were evidence of tumor recurrence on MRI at 2 and 5 years after surgery. Of 314 patients in the study, all patients where MRI was reported to show no recurrence at 2 years (97%) also had no signs of recurrence on MRI at 5 years. All eight patients with MRI suspicious of recurrence (linear enhancement of internal auditory canal [IAC]) at 2 years had no progression on MRI at 5 to 15 years. One patient had evidence of definite recurrence (nodular enhancement of IAC) at 2 years, who went on to have radiosurgery at 8 years. Where patients have MRI with no linear enhancement of the IAC at 2 years, no further imaging is required. Where linear enhancement is seen, no change in enhancement at 5 years is reassuring and no further imaging is required.     

Intra-articular Lesions in Chronic Lateral Ankle Instability: Comparison of Arthroscopy with Magnetic Resonance Imaging Findings

Background

Chronic lateral ankle instability often accompanies intra-articular lesions, and arthroscopy is often useful in diagnosis and treatment of intra-articular lesions.

Methods

Preoperative magnetic resonance imaging (MRI) examinations and arthroscopic findings were reviewed retrospectively and compared in 65 patients who underwent surgery for chronic lateral ankle instability from January 2006 to January 2010. MR images obtained were assessed by two radiologists, and the inter- and intra-observer reliability was calculated. American Orthopedic Foot and Ankle Society (AOFAS) and visual analogue scale (VAS) scores were evaluated.

Results

Abnormalities of the anterior talofibular ligament (ATFL) were found in all 65 (100%) cases. In arthroscopy examinations, 33 (51%) cases had talar cartilage lesions, and 3 (5%) cases had ''tram-track'' cartilage lesion. Additionally, 39 (60%) cases of synovitis, 9 (14%) cases of anterior impingement syndrome caused by osteophyte, 14 (22%) cases of impingement syndrome caused by fibrotic band and tissue were found. Sensitivity of MRI examination for each abnormality was: ATFL, 60%; osteochondral lesion of talus (OLT), 46%; syndesmosis injury, 21%; synovitis, 21%; anterior impingement syndrome caused by osteophyte, 22%. Paired intra-observer reliability was measured by a kappa statistic of 0.787 (95% confidence interval [CI], 0.641 to 0.864) for ATFL injury, 0.818 (95% CI, 0.743 to 0.908) for OLT, 0.713 (95% CI, 0.605 to 0.821) for synovitis, and 0.739 (95% CI, 0.642 to 0.817) for impingement. Paired inter-observer reliability was measured by a kappa statistic of 0.381 (95% CI, 0.241 to 0.463) for ATFL injury, 0.613 (95% CI, 0.541 to 0.721) for OLT, 0.324 (95% CI, 0.217 to 0.441) for synovitis, and 0.394 (95% CI, 0.249 to 0.471) for impingement. Mean AOFAS score increased from 64.5 to 87.92 (p < 0.001) when there was no intra-articular lesion, from 61.07 to 89.04 (p < 0.001) in patients who had one intra-articular lesion, and from 61.12 to 87.6 (p < 0.001) in patients who had more than two intra-articular lesions.

Conclusions

Although intra-articular lesion in patients with chronic lateral ankle instability is usually diagnosed with MRI, its sensitivity and inter-observer reliability are low. Therefore, arthroscopic examination is strongly recommended because it improved patients'' residual symptoms and significantly increased patient satisfaction.     

The Evaluation of Esophageal Adenocarcinoma Using Dynamic Contrast-Enhanced Magnetic Resonance Imaging

Although neoadjuvant chemoradiation eradicates esophageal adenocarcinoma in a substantial proportion of patients, conventional imaging techniques cannot accurately detect this response. Dynamic contrast-enhanced magnetic resonance imaging is an emerging approach that may be well suited to fill this role. This pilot study evaluates the ability of this method to discriminate adenocarcinoma from normal esophageal tissue. Patients with esophageal adenocarcinoma and control subjects underwent scanning. Patients treated with neoadjuvant therapy underwent pre- and postchemoradiation scans. Parameters were extracted for each pixel were K ^trans (equilibrium rate for transfer of contrast reagent across the vascular wall), v _e (volume fraction of interstitial space), and τ _i (mean intracellular water lifetime). Five esophageal adenocarcinoma patients and two tumor-free control subjects underwent scanning. The mean K ^trans value was 5.7 times greater in esophageal adenocarcinoma, and τ _i is 2.0 times smaller, than in the control subjects. K ^trans decreased by 11.4-fold after chemoradiation. Parametric maps qualitatively demonstrate a difference in K ^trans. DCE MRI of the esophagus is feasible. K ^trans, a parameter that has demonstrated discriminative ability in other malignancies, also shows promise in differentiating esophageal adenocarcinoma from benign tissue. The determination of K ^trans represents an in vivo assay for endothelial permeability and thus may serve as a quantitative measure of response to induction chemoradiation. Presented at the 20th World Congress of the International Society for Digestive Surgery November, 2006, Rome, Italy.     

Magnetic Resonance Imaging Findings Predict the Recurrence of Chronic Subdural Hematoma

The exact predictive factors for postoperative recurrence of chronic subdural hematoma (CSDH) are still unknown. Based on the preoperative magnetic resonance imaging (MRI), low recurrence rate of T₁-hyperintensity hematoma was previously reported. We investigated the other types of radiological findings which are related to the recurrence rate of CSDH in large number of patients analyzed by multivariate logistic regression model. Preoperative MRI and postoperative computed tomography (CT) were performed and the influence of the preoperative use of antiplatelet or anticoagulant drugs was also studied. The overall recurrence rate was 9.3% (47 of 505 hematomas). The MRI T₁-iso/hypointensity group showed a significantly higher recurrence rate (18.2%, 29 of 159) compared to the other groups (5.2%, 18 of 346; p < 0.001). Multivariate logistic regression analysis showed T₁ classification was the solo significant prognostic predictor among various factors such as bilateral hematoma, antiplatelet or anticoagulant drug usage, residual hematoma on postoperative CT, and MRI classification (p < 0.001): adjusted odds ratio for the recurrence in T₁-iso/hypointensity group relative to the T₁-hyperintensity group was 5.58 [95% confidence interval (CI), 2.09–14.86] (p = 0.001). Postoperative residual hematoma and antiplatelet or anticoagulant drug usage did not increase the recurrence risk. The preoperative MRI findings, especially T₁WI findings, have predictive value for postoperative recurrence of CSDH and the T₁-iso/hypointensity group can be assumed to be a high recurrence risk group.     

术前功能磁共振在脑功能区肿瘤切除中的应用

目的探讨术前功能磁共振（fMRI）在功能区肿瘤切除中的临床应用价值。方法10例肿瘤邻近脑运动功能区患者，平均51．3岁，7例肢体无力，2例抽搐，1例口角偏斜，术前Karnofsky评分平均82分。常规行头颅核磁增强扫描，证实肿瘤位于功能区，再行fMRI检查。依据fMRI中活化区与肿瘤的位置关系决定全切或者次全切除肿瘤，术中避免活化区的损伤。术后观察肢体肌力恢复情况、进行术后Karnofsky评分并复查核磁了解术后肿瘤切除情况，与术前进行对比。结果10例fMRI活化区显示清晰，8例活化区被肿瘤挤压移位，拉伸变形。肿瘤边缘与活化区的最近距离0～26mm，平均13．6mm。本组肿瘤全切7例，次全切除3例。术后肌力好转7例，2例抽搐患者术后未再出现抽搐；1例口角歪斜患者术后面神经功能分级减轻。术后1个月Karnofsky评分平均93分。术后1周复查MRI显示：肿瘤消失7例，余3例肿瘤缩小95％～99％。结论fMRI对邻近脑运动功能区肿瘤患者的术前评价有重要临床意义，对手术切除脑功能区周围肿瘤并保留运动功能有重要的指导作用。