Sensitivity Of Magnetic Resonance Research Articles

SPIRAL MRI for in vivo lithium-7 imaging: a feasibility study in mice after oral lithium treatment

Lithium has been the frontline treatment for bipolar disorder for over 60 years. However, its mode of action and distribution in the brain is still incompletely understood. The primary isotope of lithium, lithium-7 (7Li), is a magnetic resonance (MR) active, spin-3/2 nucleus. However, its low MR sensitivity and the small brain size of mice make 7Li MR imaging (MRI) difficult in preclinical research. We tested four MRI sequences (FLASH, RARE, bSSFP, and SPIRAL) on lithium-containing phantoms, and bSSFP and SPIRAL on orally lithium-treated adult C57BL/6 mice. 7Li MR spectroscopy was acquired weekly at 9.4T to monitor the lithium uptake. The in vivo T1 relaxation time of 7Li was estimated in four mice. 4-h SPIRAL 7Li MRI was acquired in ten mice at a resolution of 2 × 2 × 3 mm3. SPIRAL MRI provided the highest signal-to-noise ratio (SNR) per unit acquisition time and the best image quality. We observed a non-homogeneous distribution of lithium in the mouse brain, with the highest concentrations in the cortex, ventricles, and basal brain regions. Almost no lithium signal was detected in the olfactory bulb and the cerebellum. We showed that in vivo 7Li MRI in mice is feasible, although with limited spatial resolution and SNR.

Myeloperoxidase-Sensitive T1 and T2 Switchable MR Imaging for Diagnosis of Nonalcoholic Steatohepatitis.

Nonalcoholic steatohepatitis (NASH) is the critical stage in the development of nonalcoholic fatty liver disease (NAFLD) from simple and reversible steatosis to irreversible cirrhosis and even hepatocellular carcinoma (HCC). Thus, the diagnosis of NASH is important for preventing the progress of NAFLD into a fatal condition. The oxidative enzyme myeloperoxidase (MPO), which is mostly produced by polymorphonuclear neutrophil granulocytes (NEU), has been identified as a key player in lipid peroxidation in inflamed tissues. Considering that the expression of MPO was much higher in NASH than in the nonalcoholic fatty liver (NAFL) with steatosis, we designed a nanoparticle platform based on ultrasmall iron oxide (USIO) nanoparticles to realize MPO-sensitive NASH diagnosis. After modification of USIO nanoparticles with amphiphilic poly(ethylene glycol) (PEG) and conjugation with 5-hydroxytryptamine (5HT), a physiological substrate for MPO, the final nanocomposite (USIO-DA-PEG-5HT) revealed MPO-mediated aggregation at the inflammatory site of NASH. Meanwhile, the intrinsic T1-weighted magnetic resonance (MR) signal of dispersed USIO-DA-PEG-5HT nanoparticles diminishes, while the T2-weighted MR signal is amplified owing to the aggregation effect. These USIO-DA-PEG-5HT nanoprobes offer great potential for improving NASH MR imaging diagnostic accuracy and sensitivity compared to existing molecular MR contrast agents with a single imaging modality.

Diffusion-weighted MR is useful to assess peripheral nerve invasion of soft tissue tumor.

To investigate the feasibility of readout-segmented diffusion-weighted (rsDW) magnetic resonance (MR) in assessing nerve invasion of soft tissue tumor. Forty-four patients with soft tissue mass in upper leg suspected of nerve invasion underwent rsDW MR. Nerve invasion by tumor was rated by 2 radiologists, respectively. Sensitivity and specificity of rsDW MR in identifying nerve invasion were calculated, with operation findings as reference of standard. Apparent diffusion coefficient and fraction of anisotropy of nerve were obtained using DW MR, and then were compared between invaded nerves and noninvasion cases. Inter-reader agreement in using rsDW MR to rate nerve invasion was excellent (kappa = 0.891 ± 0.043, P < 0.001). Sensitivity and specificity of rsDW MR in identifying nerve invasion were 89% and 88%, respectively. Apparent diffusion coefficient was significantly higher in invaded nerves versus normal nerves (1.45 ± 0.67 × 10−3 mm2/s vs 1.39 ± 0.46 × 10−3 mm2/s, P < 0.05). Fraction of anisotropy was significantly lower in invaded nerves versus normal nerves (0.22 ± 0.11 vs 0.37 ± 0.13, P < .05).Readout-segmented DW MR was feasible in assessing sciatic nerve invasion by soft tissue tumor in selected patients.

Magnetic Resonance Imaging of PSMA-Positive Prostate Cancer by a Targeted and Activatable Gd(III) MR Contrast Agent.

Prostate-specific membrane antigen (PSMA) is a transmembrane protein that is highly expressed in aggressive prostate cancer (PCa) and has been extensively studied as a PCa diagnostic imaging biomarker. Multiple imaging modalities have exploited PSMA as a biomarker including magnetic resonance (MR), Optical, and PET imaging. Of all the imaging MR imaging provides the most detailed information, concurrently providing anatomical, functional, and potentially molecular information. However, the lower sensitivity of MR requires development of molecular MR contrast agents that provides high signal-to-noise ratios. Herein, we report the first targeted and activatable Gd(III)-based MR contrast agents prostate cancer probe 1 and 2 (PCP-1 and -2). We successfully used PCP-2 to differentiate between PSMA+ and PSMA- prostate cancer cells with both in vitro fluorescence imaging and in vivo MR imaging. The in vivo MR imaging results were further supported by ex vivo fluorescence imaging studies, showcasing the unique bimodal feature of PCP-2. Furthermore, PCP-2 highlights a unique molecular MR probe design strategy that improved the sensitivity of traditional biomarker-targeted MR imaging, addressing a critical unmet need in molecular MR imaging field. This work represents the first example of a targeted and activatable MR contrast agent that can be systemically administered in vivo to highlight PSMA+ prostate tumors, paving the way for the clinical translation of MR PSMA imaging.

Hyperpolarized Magnetic Resonance and Artificial Intelligence: Frontiers of Imaging in Pancreatic Cancer.

BackgroundThere is an unmet need for noninvasive imaging markers that can help identify the aggressive subtype(s) of pancreatic ductal adenocarcinoma (PDAC) at diagnosis and at an earlier time point, and evaluate the efficacy of therapy prior to tumor reduction. In the past few years, there have been two major developments with potential for a significant impact in establishing imaging biomarkers for PDAC and pancreatic cancer premalignancy: (1) hyperpolarized metabolic (HP)-magnetic resonance (MR), which increases the sensitivity of conventional MR by over 10,000-fold, enabling real-time metabolic measurements; and (2) applications of artificial intelligence (AI).ObjectiveOur objective of this review was to discuss these two exciting but independent developments (HP-MR and AI) in the realm of PDAC imaging and detection from the available literature to date.MethodsA systematic review following the PRISMA extension for Scoping Reviews (PRISMA-ScR) guidelines was performed. Studies addressing the utilization of HP-MR and/or AI for early detection, assessment of aggressiveness, and interrogating the early efficacy of therapy in patients with PDAC cited in recent clinical guidelines were extracted from the PubMed and Google Scholar databases. The studies were reviewed following predefined exclusion and inclusion criteria, and grouped based on the utilization of HP-MR and/or AI in PDAC diagnosis.ResultsPart of the goal of this review was to highlight the knowledge gap of early detection in pancreatic cancer by any imaging modality, and to emphasize how AI and HP-MR can address this critical gap. We reviewed every paper published on HP-MR applications in PDAC, including six preclinical studies and one clinical trial. We also reviewed several HP-MR–related articles describing new probes with many functional applications in PDAC. On the AI side, we reviewed all existing papers that met our inclusion criteria on AI applications for evaluating computed tomography (CT) and MR images in PDAC. With the emergence of AI and its unique capability to learn across multimodal data, along with sensitive metabolic imaging using HP-MR, this knowledge gap in PDAC can be adequately addressed. CT is an accessible and widespread imaging modality worldwide as it is affordable; because of this reason alone, most of the data discussed are based on CT imaging datasets. Although there were relatively few MR-related papers included in this review, we believe that with rapid adoption of MR imaging and HP-MR, more clinical data on pancreatic cancer imaging will be available in the near future.ConclusionsIntegration of AI, HP-MR, and multimodal imaging information in pancreatic cancer may lead to the development of real-time biomarkers of early detection, assessing aggressiveness, and interrogating early efficacy of therapy in PDAC.

Magnetic Resonance Detection of Gas Microbubbles via HyperCEST: A Path Toward Dual Modality Contrast Agent.

Gas microbubbles are an established clinical ultrasound contrast agent. They could also become a powerful magnetic resonance (MR) intravascular contrast agent, but their low susceptibility-induced contrast requires high circulating concentrations or the addition of exogenous paramagnetic nanoparticles for MR detection. In order to detect clinical in vivo concentrations of raw microbubbles via MR, an alternative detection scheme must be used. HyperCEST is an NMR technique capable of indirectly detecting signals from very dilute molecules (concentrations well below the NMR detection threshold) that exchange hyperpolarized 129 Xe. Here, we use quantitative hyperCEST to show that microbubbles are very efficient hyperCEST agents. They can accommodate and saturate millions of 129 Xe atoms at a time, allowing for their indirect detection at concentrations as low as 10 femtomolar. The increased MR sensitivity to microbubbles achieved via hyperCEST can bridge the gap for microbubbles to become a dual modality contrast agent.

Magnetic resonance imaging versus computed tomography and ultrasound for the diagnosis of female pelvic pathology.

We sought to determine the diagnostic accuracy of magnetic resonance (MR) imaging compared with computed tomography (CT) and ultrasound (US) when evaluating for five common pelvic pathologies among women presenting to the emergency department (ED) with right lower quadrant abdominal pain. This prospective, single-center study was conducted at an academic ED as a sub-analysis of a direct comparison of the diagnostic accuracy of CT and MR in the evaluation of appendicitis. Patients were eligible for participation in the parent study if they were at least 12 years old and had a CT performed for evaluation of possible appendicitis. In the current study, only female patients who also underwent pelvic US were included. Three radiologists independently interpreted each MR examination specifically for the presence of pelvic pathology, knowing that patients had initially undergone imaging evaluation for possible appendicitis. The determination of an independent expert panel of two radiologists and one emergency physician based on surgical pathology, comprehensive chart review, clinical information, and follow-up phone calls served as the reference standard. Test characteristics of MR, CT, and US were calculated based on this; the main outcome measure was the summary sensitivity and specificity of MR versus CT and US. Forty-one participants were included with a mean age of 27.6 ± 10.8 years. The MR consensus interpretation had an overall sensitivity and specificity of 57.1% (CI 38.8-75.5%) and 97.2% (CI 94.7-99.6%) respectively, for detecting any of the five pelvic pathologies. By comparison, CT exhibited sensitivity and specificity of 66.7% (CI 50.0-83.5%) and 98.3% (CI 96.4-100.0%) while it was 64.3% (CI 46.5-82.0%) and 97.7% (CI 95.6-99.9%) for US, respectively. No significant differences were identified when comparing these modalities. Overall, Fleiss' kappa interrater reliability value for MR interpretation was 0.75, corresponding to substantial agreement between the three readers. In women who might otherwise undergo multiple imaging tests to evaluate gastrointestinal versus pelvic pathologies, our data suggest that MR may be an acceptable first-line imaging test.

Assessment of Myocarditis: Cardiac MR, PET/CT, or PET/MR?

Diagnosis of myocarditis is challenging given its variable clinical manifestations and non-specific laboratory findings. Cardiac magnetic resonance (MR) is currently the preferred imaging modality for the diagnosis of myocarditis. 18F-fluoro-deoxy-glucose (FDG) positron emission tomography/computed tomography (PET/CT), as a functional imaging tool, has a potential role in the assessment of myocarditis by detecting the underlying myocardial inflammatory activity. Data are accumulating that simultaneous cardiac PET/MR may have complementary and incremental values for the evaluation of myocarditis compared to PET/CT or cardiac MR alone. The article aims to summarize the findings in the literature and discuss future directions of cardiac PET/MR for myocarditis. The Lake Louis Criteria (CLL) of cardiac MR is widely used for the diagnosis of myocarditis. It has an overall acceptable sensitivity of 67% and specificity of 91% for acute myocarditis but does not have the same accuracy for chronic myocarditis. FDG PET/CT is capable of assessing myocarditis by providing metabolic information of inflammation as increased myocardial FDG uptake. In addition to reduced radiation exposure, FDG PET performed on a hybrid PET/MR may detect more myocarditis than FDG PET/CT, because of the delayed PET acquisition time on PET/MR. Case-based observations and small clinical studies of FDG PET/MR have shown that FDG PET findings as abnormally increased myocardial uptake correlate well with the cardiac MR biomarkers. FDG PET findings may add complementary and incremental values to cardiac MR by improving the sensitivity of cardiac MR for mild or borderline myocarditis, and increasing specificity for chronic myocarditis. Preliminary data from retrospective and case-based observational studies have suggested the complementary and incremental values of simultaneous cardiac FDG PET/MR for evaluation of myocarditis, compared to PET/CT or MR alone. Well-designed studies are needed to confirm the findings and to assess the value of cardiac PET/MR for clinical management and more importantly patient's outcome in both acute and chronic myocarditis.

Imaging Hyperpolarized Pyruvate and Lactate after Blood-Brain Barrier Disruption with Focused Ultrasound.

Imaging of hyperpolarized 13C-labeled substrates has emerged as an important magnetic resonance (MR) technique to study metabolic pathways in real time in vivo. Even though this technique has found its way to clinical trials, in vivo dynamic nuclear polarization is still mostly applied in preclinical models. Its tremendous increase in signal-to-noise ratio (SNR) overcomes the intrinsically low MR sensitivity of the 13C nucleus and allows real-time metabolic imaging in small structures like the mouse brain. However, applications in brain research are limited as delivery of hyperpolarized compounds is restrained by the blood–brain barrier (BBB). A local noninvasive disruption of the BBB could facilitate delivery of hyperpolarized substrates and create opportunities to study metabolic pathways in the brain that are generally not within reach. In this work, we designed a setup to apply BBB disruption in the mouse brain by MR-guided focused ultrasound (FUS) prior to MR imaging of 13C-enriched hyperpolarized [1-13C]-pyruvate and its conversion to [1-13C]-lactate. To overcome partial volume issues, we optimized a fast multigradient-echo imaging method (temporal resolution of 2.4 s) with an in-plane spatial resolution of 1.6 × 1.6 mm2, without the need of processing large amounts of spectroscopic data. We demonstrated the feasibility to apply 13C imaging in less than 1 h after FUS treatment and showed a locally disrupted BBB during the time window of the whole experiment. From detected hyperpolarized pyruvate and lactate signals in both FUS-treated and untreated mice, we conclude that even at high spatial resolution, signals from the blood compartment dominate in the 13C images, leaving the interpretation of hyperpolarized signals in the mouse brain challenging.

A Novel Expandable Catheter Wireless Amplified NMR Detector for MR Sensitivity Accessing the Kidney in Rodent Model.

This paper demonstrates the enlarged effective range for MRI sensitivity enhancement with a deformable catheter MRI coils integrated with a wirelessly powered amplifier. The expandable balloon wireless amplified nuclear magnetic resonance detector (WAND) is constructed on a copper-clad polyimide film to resonate at the first and second harmonics of the proton Larmor frequency at 7 Tesla. The WAND is then mounted on a balloon catheter system for easy delivery inside confined orifice. Upon reaching the region of interest, it is unfolded out of the sheath tube to increase its effective size. Magnetic resonance (MR) imaging experiments with and without the WAND are performed both in a water phantom and in a live rat to evaluate the WAND's sensitivity advantage. Expanded from a 3 mm diameter in its folded state, this deformable WAND can change its width by >100% in its inflated state to at least 6mm, leading to a sensitive detection region extending to up to 20 mm in the transverse direction. When the deformable WAND is placed in an artery in the region of the kidney of a live rat, it could achieve at least a 10-fold SNR gain over images acquired by a standard external detector of 22 mm diameter, even though the region of interest is separated from the WAND's surface by a distance larger than the WAND's own width. The proposed expandable catheter WAND could significantly enlarge the effective range for MR sensitivity enhancement in-vivo, enabling versatile applications in interventional MRI.

Role of MRI in the Diagnosis of Injury to the Lisfranc Ligament Complex

Category: Sports Introduction/Purpose: Subtle Lisfranc ligamentous injuries are difficult to diagnose and magnetic resonance is becoming a useful tool. The purpose of this study is to evaluate the efficacy of magnetic resonance (MR) imaging for the diagnosis of injuries of the Lisfranc ligament complex. Methods: The radiology database was searched between Jan 1, 2010 and Mar 10, 2015 to identify patients over the age of 18 years who had MR imaging of the foot for suspected injury of the Lisfranc ligament complex. MR images were reviewed by 2 fellowship trained musculoskeletal radiologists, whom were blinded to the original radiology reports. Findings were categorized as: no injury or injury present. Injury was deemed to be present if 2 of the 3 components of C1-M2 ligament showed disruption or signal alterations on T1 and T2 weighted images. Disagreements were resolved by consensus. Correlation was made with surgical findings whenever performed. In patients not undergoing surgery, the presence or absence of injury was determined by clinical examination performed by an orthopedic surgeon and follow-up. Sensitivity, specificity, positive predictive value(PPV), and negative predictive value (NPV) of MR for diagnosis of Lisfranc ligament complex injury was determined. Results: Of 60 patients, 9 were excluded due to a lack of follow-up. Lisfranc injury was determined to be present on MR in 26 patients and 18 underwent surgery. Injury was confirmed in 16, and 2 were intact. 2 patients underwent closed reduction and were clinically determined to be injured. 6 of the injured 26 patients were sprained and not injured/torn on clinical evaluation. Of the 25 patients determined to have no injury on MR, 24 were intact clinically. 1 patient had a Lisfranc injury on follow-up. Sensitivity, specificity, PPV and NPV of MR for detection of significant Lisfranc injury were 94.7% (CI: 73.9% to 99.9%), 75% (CI: 56.6% to 88.5%), 69.2% (CI: 55% to 80.5%) and 96% (CI: 77.9% to 99.4%) respectively. Conclusion: MR has a high sensitivity and negative predictive value for diagnosis of injury to the Lisfranc ligament complex. MR of the foot should be considered in patients with clinical suspicion of injury to the Lisfranc ligament complex, and it is highly accurate in excluding such injuries.

Sensitivity enhancement of traveling wave MRI using free local resonators: an experimental demonstration.

Traveling wave MR uses the far fields in signal excitation and reception, therefore its acquisition efficiency is low in contrast to the conventional near field magnetic resonance (MR). Here we show a simple and efficient method based on the local resonator to improving sensitivity of traveling wave MR technique. The proposed method utilizes a standalone or free local resonator to amplify the radio frequency magnetic fields in the interested target. The resonators have no wire connections to the MR system and thus can be conveniently placed to any place around imaging simples. A rectangular loop L/C resonator to be used as the free local resonator was tuned to the proton Larmor frequency at 7T. Traveling wave MR experiments with and without the wireless free local resonator were performed on a living rat using a 7T whole body MR scanner. The signal-to-noise ratio (SNR) or sensitivity of the images acquired was compared and evaluated. In vivo 7T imaging results show that traveling wave MR with a wireless free local resonator placed near the head of a living rat achieves at least 10-fold SNR gain over the images acquired on the same rat using conventional traveling wave MR method, i.e. imaging with no free local resonators. The proposed free local resonator technique is able to enhance the MR sensitivity and acquisition efficiency of traveling wave MR at ultrahigh fields in vivo. This method can be a simple solution to alleviating low sensitivity problem of traveling wave MRI.

MAGNETIC RESONANCE IMAGING OF INTRACRANIAL INFLAMMATORY CONDITIONS IN DOGS: SENSITIVITY OF SUBTRACTION IMAGES VERSUS PRE- AND POST-GADOLINIUM T1-WEIGHTED IMAGE PAIRS.

Ante mortem diagnosis of canine meningoencephalitis is usually based on the results of neurologic examination, cerebrospinal fluid analysis and magnetic resonance (MR) imaging. It has been hypothesized that subtraction MR imaging may increase the sensitivity of MR for intracranial inflammatory lesions compared to conventional post-gadolinium T1-weighted imaging. Sensitivity of pre- and post-gadolinium (C-/C+) image pairs and dynamic subtraction (DS) images was compared in a retrospective diagnostic accuracy study of 52 dogs with inflammatory cerebrospinal fluid and 67 dogs with idiopathic epilepsy. Series of transverse C-/C+ and DS images were reviewed independently for signs of abnormal enhancement affecting the pachymeninges, leptomeninges or intra-axial structures. Sensitivity of C-/C+ image pairs and DS images was 48% (95% CI: 35-61%) and 65% (95% CI: 52-77%), respectively (P = 0.01). Intra-axial lesions were observed more frequently than meningeal lesions in both C-/C+ (43% vs. 31%) and DS images (61% vs. 22%). The difference in sensitivities of C-/C+ and DS series was entirely due to increased sensitivity of DS images for intra-axial lesions. Eight (12%) dogs with epilepsy had evidence of intra-axial gadolinium accumulation affecting the cerebral cortex in DS images. This finding may represent a false-positive result or a true sign of pathology, possibly associated with a leaky blood-brain barrier in areas of the brain affected by neovascularization secondary to repeated seizures. Results suggest that DS imaging has higher sensitivity than comparison of pre- and post-gadolinium image pairs for inflammatory intra-axial lesions.

Consensus paper: radiological biomarkers of cerebellar diseases.

Hereditary and sporadic cerebellar ataxias represent a vast and still growing group of diseases whose diagnosis and differentiation cannot only rely on clinical evaluation. Brain imaging including magnetic resonance (MR) and nuclear medicine techniques allows for characterization of structural and functional abnormalities underlying symptomatic ataxias. These methods thus constitute a potential source of radiological biomarkers, which could be used to identify these diseases and differentiate subgroups of them, and to assess their severity and their evolution. Such biomarkers mainly comprise qualitative and quantitative data obtained from MR including proton spectroscopy, diffusion imaging, tractography, voxel-based morphometry, functional imaging during task execution or in a resting state, and from SPETC and PET with several radiotracers. In the current article, we aim to illustrate briefly some applications of these neuroimaging tools to evaluation of cerebellar disorders such as inherited cerebellar ataxia, fetal developmental malformations, and immune-mediated cerebellar diseases and of neurodegenerative or early-developing diseases, such as dementia and autism in which cerebellar involvement is an emerging feature. Although these radiological biomarkers appear promising and helpful to better understand ataxia-related anatomical and physiological impairments, to date, very few of them have turned out to be specific for a given ataxia with atrophy of the cerebellar system being the main and the most usual alteration being observed. Consequently, much remains to be done to establish sensitivity, specificity, and reproducibility of available MR and nuclear medicine features as diagnostic, progression and surrogate biomarkers in clinical routine.

Diagnostic accuracy of MR imaging to identify and characterize focal liver lesions: comparison between gadolinium and superparamagnetic iron oxide contrast media.

To compare the diagnostic value of gadolinium (Gd) and ultrasmall superparamagnetic iron oxide (SPIO) contrast media for characterization of focal liver lesions (FLL), we retrospectively evaluated the results of magnetic resonance (MR) imaging in 68 patients (40 M, 28 F, age from 22 to 81 yrs) of which 36 with diagnosis of colo-rectal cancer, 26 with hepatic cirrhosis and 6 with incidental imaging detection of FLL. MR (Gyroscan Intera 1.5 T, Philips Medical Systems) study was performed using T1 and T2 fast-field-echo (FFE) and T2 turbo-spin-echo (TSE) sequences in axial and coronal views. Dynamic multi-phases gadolinium Gd-enhanced T1-FFE-Bh images were obtained in arterial, portal and equilibrium phases, followed by SPIO-enhanced T2-FFE scans. A qualitative analysis of pre- and post-contrast MR images to classify FLL as benign or malignant was performed using a 3-point scoring system: 0= benign; 1= suspicious for malignancy; 2= malignant. A total of 118 lesions were evaluated. In particular, histology (n=18), cytology (n=14) or clinical-imaging follow-up data (n=86) demonstrated 4 adenomas, 29 cysts, 3 focal steatosis, 25 hemangiomas, 1 focal vascular abnormality, 5 fibrotic lesions as well as 13 regenerative nodules, 6 dysplastic, 14 hepatocellular carcinomas (HCC), 17 metastasis and 1 cholangiocarcinoma. For MR imaging, diagnostic accuracy, sensitivity, specificity, positive (PPV) and negative (NPV) predictive values of Gd vs. SPIO images were respectively 83% vs. 92%, 79% vs. 74%, 85% vs. 99% (P=0.002), 68% vs. 96% (P=0.005) and 91% vs. 90%, respectively. The results suggest that SPIO-MR provides a diagnostic incremental value, as specificity and PPV, particularly to characterize FLL compared to Gd-MR; thus, we strongly recommend the use of SPIO when liver lesion characterization is requested and Gd images are uncertain.

Meta-analysis of diagnostic accuracy of magnetic resonance in restaging of rectal cancer after preoperative chemoradiotherapy

To estimate the diagnostic accuracy of magnetic resonance(MR) in restaging of rectal cancer after preoperative chemoradiotherapy(CRT). Comprehensive search of literature concerning the diagnosis of MR for rectal cancer after preoperative CRT was performed from databases of PubMed, EMbase, OVID and WOK. Sensitivity and specificity of MR on restaging of rectal cancer after preoperative CRT were investigated by SAS and MetaDiSc software. Thirteen articles including 749 patients were enrolled in this meta-analysis. For T3-T4 stage, sensitivity of MR was 82.1%(95%CI:67.9%-90.9%), specificity was 53.5%(95%CI:39.3%-67.3%), and diagnostic odds ratio(DOR) was 5.34(2.73, 6.59). For lymph node involvement, sensitivity of MR was 61.8%(95%CI:50.7%-71.8%), specificity was 72.0%(95%CI:61.3%-80.7%), and DOR was 4.33(95%CI:2.84-6.59). For circumferential resection margin(CRM) by MR, pooled sensitivity was 85.4%(95%CI:60.5%-95.7%), specificity was 80.0%(95%CI:57.4%-92.3%), and DOR was 27.62(95%CI:13.03-58.55). Restaging accuracy of T3-T4 and lymph nodes involvement of rectal cancer after preoperative CRT by MR is not high. MR may be a good method to make reassessment of CRM. To avoid overtreatment for T0-T2, negative lymph node and circumferential resection of rectal cancer, restaging by MR after preoperative CRT is important.

Role of magnetic resonance imaging in probably benign (BI-RADS category 3) microcalcifications of the breast

This study was undertaken to evaluate whether magnetic resonance (MR) imaging is able to rule out malignancy in the case of BI-RADS 3 microcalcifications, providing a sufficient negative predictive value (NPV) for early work-up, and to reduce unnecessary stereotactically guided vacuum-assisted biopsy (SVAB) procedures. We prospectively enrolled consecutive women with BI-RADS 3 microcalcifications, who subsequently underwent MR imaging and SVAB. The MR studies were reviewed according to the MR-BI-RADS classification system; lesions assessed as MR-BI-RADS 1 and 2 were considered negative for malignancy, categories MR-BI-RADS 3, 4 and 5 indicated malignant lesions. The presence of additional findings was recorded. Histologic analysis and follow-up were the reference standard. MR sensitivity, specificity, positive predictive value (PPV) and NPV were calculated. The final population consisted of 71 lesions. Histologic analysis showed malignancy in six cases (malignancy rate 8%). At MR analysis, 60 (85%) lesions were considered negative for malignancy and 11 (15%) malignant. Additional MR imaging findings were identified in 19 (27%) patients, all corresponding to nonmalignant lesions. MR sensitivity was 33%, specificity 86%, PPV 18% and NPV 93%. Because of its relatively low NPV, MR imaging is not able to safely exclude malignancy in the case of BI-RADS 3 microcalcifications. The relatively high malignancy rate found in this study might support SVAB in the case of BI-RADS 3 microcalcifications.

Determining the temperature-dependence of tissue relaxation times (T1 and T2) for prospective optimization of post-mortem magnetic resonance (PMMR) image contrast

Abstract Due to the excellent sensitivity of Magnetic Resonance (MR) imaging to subtle differences in soft tissues, MR enables non-invasive anatomical imaging with superior soft tissue contrast relative to X-ray computed tomography (CT). Soft tissue contrast in MR is not determined primarily by density (as in X-ray imaging) but instead by T1 and T2, tissue-specific parameters that characterize the temporal behavior of the MR signal. However, in the post-mortem setting, the sensitivity of MR to subtle changes in tissue properties presents both opportunities and challenges. Recent reports in the literature demonstrate changes in MR image contrast as a function of subject temperature for a given MRI protocol (e.g., T1-w, T2-2, FLAIR). These normal temperature-dependent changes in MR image contrast, not encountered in clinical MR of live subjects, have the potential to confound the identification of pathology or injury. Tofts et al. have demonstrated that FLAIR image contrast can be corrected by adjusting the protocol, specifically the inversion time (TI), based on knowledge of the temperature-dependence of the apparent diffusion coefficient (ADC) and T1 in brain tissues. Here we present a generalized method for (A) non-invasively determining subject temperature and (B) computing the values of the image acquisition parameters, TR and TE, required to obtain the desired image contrast for a given subject temperature, based on the temperature-dependence of tissue T1 and T2 values. Measurements of the temperature-dependence of T1 and T2 values from various unfixed, ex vivo mammalian tissues and organs will be presented. Author disclosures National Institute of Justice Award 2012-DN-BX-K019 is gratefully acknowledged.

Deep pelvic endometriosis: accuracy of pelvic MRI completed by MR colonography

This study assessed the diagnostic accuracy of pelvic magnetic resonance (MR) imaging completed by MR colonography for the preoperative evaluation of deep pelvic endometriosis in patients undergoing laparoscopic surgery. A total of 143 patients (mean age 34.3 ± 5.1 years) with a clinical suspicion of deep pelvic endometriosis were assessed by pelvic MR and MR colonography. All patients underwent laparoscopic surgery 3-10 weeks after the MR examination. The presence, location, number and extent of endometriotic lesions were evaluated. Data obtained with MR were compared with surgical findings. MR sensitivity, specificity, positive (PPV) and negative (NPV) predictive values and diagnostic accuracy values were calculated for each site by considering the laparoscopic and histological findings as the reference standard. Laparoscopy confirmed the presence of endometriosis in 119/143 patients (83%); in 76/119 (64%) deep pelvic endometriosis was diagnosed, whereas in the remaining 43/119 (36%), superficial peritoneal implants and endometriomas were found. In 32/119 (27%) patients, intestinal lesions were detected. MR had sensitivity, specificity, PPV, NPV and diagnostic accuracy values of 67-100%, 85-100%, 83-100%, 84-100% and 84-100%, respectively, in recognising lesions located in different pelvic sites. MR imaging combined with colonography is a highly accurate tool for characterising deep endometriotic lesions in patients scheduled for laparoscopic surgery. In particular, MR colonography has very high accuracy in detecting colorectal involvement.

The Accuracy of Magnetic Resonance Imaging and Magnetic Resonance Arthrogram Versus Arthroscopy in the Diagnosis of Subscapularis Tendon Injury

The main purpose of this study was to evaluate the accuracy of preoperative magnetic resonance imaging (MRI) in detecting subscapularis tears identified during the gold standard of arthroscopy and determine whether MRI can reliably predict which patients have subscapularis tears. A second purpose was to determine whether magnetic resonance (MR) arthrograms could better identify a subscapularis tear than conventional MRI. This was a retrospective study evaluating 39 consecutive patients (40 shoulders) who had a preoperative 1.5-T MRI study and underwent an arthroscopic subscapularis tendon repair. All cases were performed between December 2007 and November 2010. Subscapularis tears were missed on preoperative MR scanning in 25 of 40 shoulders (62.5%). The sensitivity of noncontrast MRI was 40%, the sensitivity of MR arthrography was 36%, and the overall MR sensitivity was 37.5%. Preoperative 1.5-T MRI of the shoulder does not reliably predict subscapularis tendon tears, regardless of whether conventional MRI or MR arthrography is used. Level II, development of diagnostic criteria on basis of consecutive patients with universally applied gold standard.