Capability Of Magnetic Resonance Imaging Research Articles

Integrating Anatomic and Functional Dual-Mode Magnetic Resonance Imaging: Design and Applicability of a Bifunctional Contrast Agent.

In recent decades, extensive attention has been paid to developing anatomic and functional imaging contrast agents that could provide a wealth of complementary bioimaging information. Among them, dual-mode nanoprobes that combine anatomic magnetic resonance imaging (MRI) with functional fluorescent imaging have been mostly used for separated imaging. However, the lack of a machine for simultaneous dual-mode imaging greatly limits further clinical application. One effective strategy is to rationally design MRI contrast agents that own both anatomic and functional MR imaging capability on a single MRI machine, which is highly attractive but remains a great challenge. Herein, ultrasmall NaGdF4@PLL nanodots (NDs) were developed as a novel class of MR contrast agent, which offers a high longitude relaxivity (6.42 mM(-1) s(-1)) for T1-weighted MRI and an excellent sensitive chemical exchange saturation transfer (CEST) effect for pH mapping (at +3.7 ppm). Further in vivo animal experiments show the feasibility of NaGdF4@PLL NDs as contrast agents for efficient kidney and brain tumor diagnosis and pH mapping, which will undoubtedly enhance the diagnosis accuracy and is beneficial for disease precaution and prognosis. Different from other complex dual-mode nanoprobes, the as-constructed NaGdF4@PLL NDs enable both anatomic and functional imaging on a single MR machine, which is a simple and cost-effective new approach to realize dual-mode MR imaging and holds great potential for future clinical application.

Utility of Combining PET and MR Imaging of Carotid Plaque.

By harnessing the versatility and soft tissue imaging capabilities of MR imaging alongside the unmatched sensitivity and biomolecular flexibility of PET, the potential to provide detailed multiparametric plaque characterization in the carotid arteries is clear. The ability to acquire simultaneous, and dynamic multimodal data is perhaps PET/MR's greatest strength that will be of major interest to researchers investigating carotid and coronary atherosclerosis alike. This review summarizes the current status of dedicated hybrid PET/MR imaging; to crystallize the rationale for and advantages of this technique with respect to carotid atherosclerosis; and to discuss current limitations, challenges, and future directions.

Quantitative 3D Analysis of Plant Roots Growing in Soil Using Magnetic Resonance Imaging.

Precise measurements of root system architecture traits are an important requirement for plant phenotyping. Most of the current methods for analyzing root growth require either artificial growing conditions (e.g. hydroponics), are severely restricted in the fraction of roots detectable (e.g. rhizotrons), or are destructive (e.g. soil coring). On the other hand, modalities such as magnetic resonance imaging (MRI) are noninvasive and allow high-quality three-dimensional imaging of roots in soil. Here, we present a plant root imaging and analysis pipeline using MRI together with an advanced image visualization and analysis software toolbox named NMRooting. Pots up to 117 mm in diameter and 800 mm in height can be measured with the 4.7 T MRI instrument used here. For 1.5 l pots (81 mm diameter, 300 mm high), a fully automated system was developed enabling measurement of up to 18 pots per day. The most important root traits that can be nondestructively monitored over time are root mass, length, diameter, tip number, and growth angles (in two-dimensional polar coordinates) and spatial distribution. Various validation measurements for these traits were performed, showing that roots down to a diameter range between 200 μm and 300 μm can be quantitatively measured. Root fresh weight correlates linearly with root mass determined by MRI. We demonstrate the capabilities of MRI and the dedicated imaging pipeline in experimental series performed on soil-grown maize (Zea mays) and barley (Hordeum vulgare) plants.

CURRENT CAPABILITIES OF COMPUTED TOMOGRAPHY AND MAGNETIC RESONANCE IMAGING FOR THE DETECTION OF COMPLICATIONS AFTER COMBINED PANCREAS AND KIDNEY TRANSPLANTATION

Objective: to give computed tomography (CT)- and magnetic resonance imaging (MRI)-based new anatomic-topographic relationships in patients after combined pancreas and kidney transplantation and to describe main visualization tasks and the types and frequency of various complications occurring in different periods after transplantation. Material and methods. Spiral CT and MRI images were analyzed in 45 patients after pancreas and kidney transplantation. A total of 51 studies (35 CTs and 16 MRIs) using intravenous contrast enhancement (n=34 (66%)) were performed. Results. A total of 55 complications, among which pancreatitis after pancreas transplantation was most common (55%), were found. Necrotizing pancreatitis following pancreas transplantation, which required open operative or percutaneous intervention, was diagnosed in 6.6%. Vascular complications were detected in 22%. Conclusion. The current capabilities of CT and MRI enable us to quickly obtain objective information on the status of transplanted organs, their vascular architectonics, as well as on the presence and type of occurred complications. Timely correction of identified complications positively affects the survival of transplanted organs and quality of life in a recipient.

Comparison of radiography, computed tomography and magnetic resonance imaging in the detection of sacroiliitis in ankylosing spondylitis

Objective: The objectives of our study were to evaluate the role of conventional radiography, computed tomography (CT), and magnetic resonance imaging (MRI) in the detection of sacroiliitis in ankylosing spondylitis (AS), along with the radiological spectrum of disease. Materials and Methods: Thirty-six patients with symptoms of inflammatory back pain (IBP) were evaluated with conventional radiography, CT, and MRI. The sacroiliac (SI) joints were evaluated for joint margins, joint space, sclerosis, and bone marrow changes. Imaging findings were analyzed for correlation with multiple clinical characteristics and comparison among different imaging modalities. Results: CT and MRI are extremely useful in the absence of alterations or minimal changes on plain radiographs. CT is comparable to MRI for joint space alteration, however, itis superior for evaluating bone sclerosis and erosion, and is indicated especially for detecting chronic alterations. The capability of MRI to distinguish between acute and chronic changes and estimate the degree of disease activity and damage present at diagnosis can be beneficial in monitoring the effect of pharmacological treatment. The administration of Gadolinium did not provide any additional information for the diagnosis of sacroiliitis and the evaluation of the features of active inflammation. Conclusions: Between radiography, CT and MRI, MRI outscores the others in being able to delineate the inflammatory changes of early sacroiliitis in AS. Therefore, if early sacroiliitis is suspected clinically, MRI should be the preferred imaging modality for evaluating the SI joint. However, CT is more sensitive than radiography and MRI in detailing the structural changes of sacroiliitis in AS.

Quantitative Biomedical Imaging: Techniques and Clinical Applications.

Quantitative Biomedical Imaging: Techniques and Clinical Applications.

Theranostic metal-organic framework core-shell composites for magnetic resonance imaging and drug delivery.

Metal-organic frameworks (MOFs) have shown great potential in designing theranostic probes for cancer diagnosis and therapy due to their unique properties, including versatile structures and composition, tunable particle and pore size, enormous porosity, high surface area, and intrinsic biodegradability. In this study, we demonstrate novel MOF-based theranostic Fe3O4@UiO-66 core-shell composites constructed by in situ growth of a UiO-66 MOF shell on a Fe3O4 core for simultaneous drug delivery and magnetic resonance (MR) imaging. In the composites, the UiO-66 shell is devoted for encapsulating the drug, whereas the Fe3O4 core serves as a MR contrast agent. The Fe3O4@UiO-66 core-shell composites show good biocompatibility, high drug loading capacity, sustained drug release, and outstanding MR imaging capability, as well as effective chemotherapeutic efficacy, demonstrating the feasibility of designing theranostic Fe3O4@UiO-66 core-shell composites for cancer diagnosis and therapy.

A New Tailored Sinc Pulse and Its Use for Multiband Pulse Design

In comparison with other imaging modalities such as X-ray, computed tomography (CT), ultrasound etc., magnetic resonance imaging (MRI) has unique appealing features of not only offering various image contrasts with anatomical, physiological, and chemical meanings, but also allowing slice-selective 2D imaging as well as 3D tomographic imaging. Especially, MRI capability of slice selection originates from This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/ by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Received: February 29, 2016 Revised: March 23, 2016 Accepted: March 25, 2016

Modulation of the structural properties of mesoporous silica nanoparticles to enhance the T1-weighted MR imaging capability.

In this study, we have investigated the contrast enhancement of Gd(iii) incorporated nanoparticle-based contrast agents (CA) by the modulation of the synthesis and structural parameters of the mesoporous silica nanoparticle (MSN) matrix. In the optimisation process, the structure of the MSN matrix, post-synthesis treatment protocols, as well as the source and incorporation routes of paramagnetic gadolinium centers were considered, with the aim to shorten the T1 weighted relaxation time. After preliminary evaluation of the prepared MSNs as nanoparticulate T1/positive contrast agents based on relaxivity, the structure of the MSN matrix was affirmed as the most decisive property to enhance the r1 relaxivity value, alongside the incorporation route of paramagnetic Gd(iii) centers. Based on these findings, the most promising Gd(iii) incorporated MSN-based CA candidate was further evaluated for its cytocompatibility and intensity enhancement by in vitro phantom MR-imaging of labeled cells. Furthermore, pre-labeled tumors grown on a chick embryo chorioallantoic membrane (CAM) were imaged as an in vivo model on a 3T clinical MRI scanner. Our findings show that the optimized MSN-based CA design enables proper access of water to Gd-centers in the selected MSN matrices, and simultaneously decreases the required amount of Gd(iii) content per mass when evaluated against the other MSNs. Consequently, the required Gd amount on a per-dose basis is significantly decreased with regard to clinically used Gd-based CAs for T1-weighted MR imaging.

On-line MR imaging for dose validation of abdominal radiotherapy

For quality assurance and adaptive radiotherapy, validation of the actual delivered dose is crucial.Intrafractional anatomy changes cannot be captured satisfactorily during treatment with hitherto available imaging modalitites. Consequently, dose calculations are based on the assumption of static anatomy throughout the treatment. However, intra- and interfraction anatomy is dynamic and changes can be significant.In this paper, we investigate the use of an MR-linac as a dose tracking modality for the validation of treatments in abdominal targets where both respiratory and long-term peristaltic and drift motion occur.The on-line MR imaging capability of the modality provides the means to perform respiratory gating of both delivery and acquisition yielding a model-free respiratory motion management under free breathing conditions.In parallel to the treatment, the volumetric patient anatomy was captured and used to calculate the applied dose. Subsequently, the individual doses were warped back to the planning grid to obtain the actual dose accumulated over the entire treatment duration. Ultimately, the planned dose was validated by comparison with the accumulated dose.Representative for a site subject to breathing modulation, two kidney cases (25 Gy target dose) demonstrated the working principle on volunteer data and simulated delivery. The proposed workflow successfully showed its ability to track local dosimetric changes. Integration of the on-line anatomy information could reveal local dose variations −2.3–1.5 Gy in the target volume of a volunteer dataset. In the adjacent organs at risk, high local dose errors ranging from −2.5 to 1.9 Gy could be traced back.

Role of MRI in medical diagnostics

Magnetic resonance imaging (MRI) is a well-established imaging modality capable of providing high resolution structural and functional images of tissues of in the human body. MRI is also relatively safer than some of the other imaging modalities such as X-ray CT and PET with respect to ionization. In this article, we discuss the basic working principles and role of MRI in the diagnosis of diseases of head and neck, breast, cardiac, abdomen and musculoskeletal system to provide an overview of the diagnostic and/or prognostic potential and capability of MRI in the clinic.

Fast and Noninvasive Characterization of Suspicious Lesions Detected at Breast Cancer X-Ray Screening: Capability of Diffusion-weighted MR Imaging with MIPs.

To evaluate the ability of a diagnostic abbreviated magnetic resonance (MR) imaging protocol consisting of maximum intensity projections (MIPs) from diffusion-weighted imaging with background suppression (DWIBS) and unenhanced morphologic sequences to help predict the likelihood of malignancy on suspicious screening x-ray mammograms, as compared with an abbreviated contrast material-enhanced MR imaging protocol and a full diagnostic breast MR imaging protocol. This prospective institutional review board-approved study included 50 women (mean age, 57.1 years; range, 50-69 years), who gave informed consent and who had suspicious screening mammograms and an indication for biopsy, from September 2014 to January 2015. Before biopsy, full diagnostic contrast-enhanced MR imaging was performed that included DWIBS (b = 1500 sec/mm(2)). Two abbreviated protocols (APs) based on MIPs were evaluated regarding the potential to exclude malignancy: DWIBS (AP1) and subtraction images from the first postcontrast and the unenhanced series (AP2). Diagnostic indexes of both methods were examined by using the McNemar test and were compared with those of the full diagnostic protocol and histopathologic findings. Twenty-four of 50 participants had a breast carcinoma. With AP1 (DWIBS), the sensitivity was 0.92 (95% confidence interval [CI]: 0.73, 0.98), the specificity was 0.94 (95% CI: 0.77, 0.99), the negative predictive value (NPV) was 0.92 (95% CI: 0.75, 0.99), and the positive predictive value (PPV) was 0.93 (95% CI: 0.75, 0.99). The mean reading time was 29.7 seconds (range, 4.9-110.0 seconds) and was less than 3 seconds (range, 1.2-7.6 seconds) in the absence of suspicious findings on the DWIBS MIPs. With the AP2 protocol, the sensitivity was 0.85 (95% CI: 0.78, 0.95), the specificity was 0.90 (95% CI: 0.72, 0.97), the NPV was 0.87 (95% CI: 0.69, 0.95), the PPV was 0.89 (95% CI: 0.69, 0.97), and the mean reading time was 29.6 seconds (range, 6.0-100.0 seconds). Unenhanced diagnostic MR imaging (DWIBS mammography), with an NPV of 0.92 and an acquisition time of less than 7 minutes, could help exclude malignancy in women with suspicious x-ray screening mammograms. The method has the potential to reduce unnecessary invasive procedures and emotional distress for breast cancer screening participants if it is used as a complement after the regular screening clarification procedure.

Feasibility of diffusion weighted magnetic resonance imaging in evaluation of different small bowel pathology

BackgroundIncreasing capability of MR imaging via applying DWI gives additional information about the functional state of tissues with high potentials due to lacking radiation exposure and contrast hazards. Application included evaluation of gastrointestinal tumors and follow-up to assess response to treatment. In IBD, DWI is useful in highlighting bowel segments of active disease and the purpose of this study is to evaluate role of DWI-MRI in neoplastic and inflammatory small bowel diseases. Materials and methodsProspective study included 50 patients subjected to MRI enterography using 1.5T closed magnet followed with DWI and then ADC values were estimated. Ileo-colonoscopy and biopsy were done and pathological data were reviewed. ResultsTwenty-four males and 26 females with small bowel lesions were divided into two groups, 26 neoplastic (5 benign, 21 malignant) and 24 inflammatory lesions (48%). Mean ADC value of inflamed bowel was 1.59±0.45×10–3mm2/s, compared to 2.74±0.68×10–3mm2/s in normal bowel. ADC value of neoplastic lesions ranged from 0.6 to 1.5 and non-neoplastic lesions from 1.1 to 2. ADC value of lymphoma ranged from 0.6 to 0.7×10–3mm2/s and adenocarcinomas from 0.8 to 1.0×10–3mm2/s. ConclusionDWI is an important complementary sequence with the routine MRI of the small bowel helping in lesion characterization and differentiation of pathology.

Site-Specific Amphiphilic Magnetic Copolymer Nanoaggregates for Dual Imaging

Molecular imaging along with combinations of imaging modalities can provide a thorough understanding of disease, in particular, tumors. Magnetic resonance imaging (MRI) offers exceptional tissue contrast and resolution; whereas optical imaging provides high sensitivity. Hence a norbornene based copolymer (Nor-Cob-Py-Fol) is reported in this paper as a dual-imaging agent. Nor-Cob-Py-Fol having Co2+ complex, pyrene and poly(ethylene glycol) derived folate, have been synthesized using ring-opening metathesis polymerization (ROMP). All the monomers and polymers are characterized by 1H NMR, IR, GPC, and TGA techniques. The morphology of the copolymer nanoaggregates has been evaluated with DLS, TEM, and SEM techniques. The functionalization of Co2+ to the polymer is monitored by FTIR, 1H NMR, and 13C NMR spectroscopy. Furthermore, the presence of Co2+ in the nanoaggregates is confirmed by the EDX (SEM) technique. To prove the MRI capabilities nature of copolymer nanoaggregates, NMR experiment is performed at room temperature. Cell viability studies suggest the biocompatibility nature of the copolymer. Flow cytometry as well as epifluoroscence microscope experiments clearly demonstrate the dual-imaging ability of the newly designed copolymer. The much higher relaxivity ratio (r2/r1) of the present method clearly establishes the superiority of our system as one of the best contrast agents known to the practitioners of magnetic resonance imaging.

Implementing MRI-based target delineation for cervical cancer treatment within a rapid workflow environment for image-guided brachytherapy: A practical approach for centers without in-room MRI.

Magnetic resonance imaging (MRI)-based intracavitary brachytherapy offers several advantages over computed tomography (CT)-based brachytherapy, but many centers are unable to offer it at the time of brachytherapy because of logistic and/or financial considerations. We have implemented a method of integrating MRI into a CT-guided, high-dose-rate intracavitary brachytherapy workflow in clinics that do not have immediately available MRI capability. At our institution, patients receiving high-dose-rate intracavitary brachytherapy as a component of the definitive treatment of cervical cancer have a Smit sleeve placed during the first brachytherapy fraction in a dedicated suite with in-room CT-on-rails. After the first fraction of brachytherapy, an MRI is obtained with the Smit sleeve, but no applicator, in place. For each subsequent fraction, CT scans are coregistered to the MRI scan by the Smit sleeve. The gross target volume is defined by MRI and overlaid on the CT images for each brachytherapy treatment for dose optimization. This MRI-integrated workflow adds <5 minutes to the brachytherapy session for image fusion. Our initial clinical experience suggests that this approach is feasible and results in target volume reductions compared with CT-alone brachytherapy. Our proposed combination MRI and/or CT workflow is a feasible compromise to preserve an efficient workflow while integrating MRI target delineation, and it provides many of the advantages of both MRI- and CT-based brachytherapy. The future collection and analysis of clinical data will serve to compare the proposed approach to non-MRI containing techniques.

Diffusion-weighted MR imaging using FASE sequence for 3T MR system: Preliminary comparison of capability for N-stage assessment by means of diffusion-weighted MR imaging using EPI sequence, STIR FASE imaging and FDG PET/CT for non-small cell lung cancer patients

PurposeTo prospectively compare the diagnostic capability of diffusion-weighted MR imaging obtained with fast advantage spin-echo sequence (FASE-DWI) and echo planar imaging sequence (EPI-DWI), short inversion time inversion recovery fast advanced spin-echo (STIR FASE) imaging and FDG PET/CT for N-stage assessment of non-small cell carcinoma (NSCLC) patients. Materials and methods95 consecutive operable NSCLC patients underwent STIR FASE imaging, FASE-DWI and EPI-DWI with a 3T system, integrated PET/CT, surgical treatment and pathological and follow-up examinations. Probability of lymph node metastasis was visually assessed using a 5-point visual scoring system. ROC analyses were used to compare diagnostic capability of all methods, while their diagnostic performance was also compared by means of McNemar's test on a per node basis. Finally, McNemar's test was also used for statistical comparison of accuracy of N-stage assessment. ResultsAreas under the curve (Azs) for STIR FASE imaging (Az=0.95) and FASE-DWI (Az=0.92) were significantly larger than those for EPI-DWI (Az=0.78; p<0.0001 for STIR FSE imaging and FASE-DWI) and PET/CT (Az=0.85; p=0.0001 for STIR FSE imaging, p=0.03 for FASE-DWI) on a per node basis analysis. Accuracy of N-stage assessment using STIR FASE imaging (84.2% [80/95]) and FASE-DWI (83.2% [79/95]) was significantly higher than that using EPI-DWI (76.8% [73/95]; p=0.02 for STIR FASE imaging, p=0.03 for FASE-DWI) and PET/CT (73.7% [70/95]; p=0.002 for STIR FSE imaging, p=0.004 for FASE-DWI). ConclusionQualitative N-stage assessments of NSCLC patients obtained with FASE-DWI as well as STIR FASE imaging are more sensitive and/or accurate than those obtained with EPI-DWI and FDG PET/CT.

Facile Fabrication of Near-Infrared-Resonant and Magnetic Resonance Imaging-Capable Nanomediators for Photothermal Therapy.

Although many techniques exist for fabricating near-infrared (NIR)-resonant and magnetic resonance imaging (MRI)-capable nanomediators for photothermal cancer therapy, preparing them in an efficient and scalable process remains a significant challenge. In this report, we exploit one-step siloxane chemistry to facilely conjugate NIR-absorbing satellites onto a well-developed polysiloxane-containing polymer-coated iron oxide nanoparticle (IONP) core to generate dual functional core-satellite nanomediators for photothermal therapy. An advantage of this nanocomposite design is the variety of potential satellites that can be simply attached to impart NIR resonance, which we demonstrate using NIR-resonant gold sulfide nanoparticles (Au2SNPs) and the NIR dye IR820 as two example satellites. The core-satellite nanomediators are fully characterized by using absorption spectra, dynamic light scattering, ζ potential measurements, and transmission electron microscopy. The enhanced photothermal effect under the irradiation of NIR laser light is identified through in vitro solutions and in vivo mice studies. The MRI capabilities as contrast agents are demonstrated in mice. Our data suggest that polysiloxane-containing polymer-coated IONPs can be used as a versatile platform to build such dual functional nanomediators for translatable, MRI-guided photothermal cancer therapy.

Hybrid PET/MRI Insert: &lt;formula formulatype="inline"&gt;&lt;tex Notation="TeX"&gt;${B_0}$&lt;/tex&gt;&lt;/formula&gt; Field Optimization by Applying Active and Passive Shimming on PET Detector Level

The design of an MRI (Magnetic Resonance Imaging) compatible PET (Positron Emission Tomography) detector is regarded to be a challenging task since both imaging devices are likely interacting with each other potentially leading to performance degradation. A typically expected consequence of this interaction is the distortion of the MRI system’s ${B_0}$ field homogeneity. The ${B_0}$ field gets distorted by any material with non-zero susceptibility brought into the MRI system. Typically, MRI machines have a so-called active shimming system available which allows the field optimization by using additional dedicated shim coils. However, this active shimming mechanism is limited and might not be capable to compensate localized higher order field patterns caused by e.g. a PET system. Since the high ${B_0}$ field quality is needed for an undisturbed MRI acquisition in general and especially for more advanced MR sequences (spectroscopic studies, sequences which utilizes spectral selective pre-pulses), the PET system’s hardware needs to be designed carefully. Consequently, the typical design paradigm regarding this ${B_0}$ field distortion is the careful selection of all components according to their susceptibility (as low as possible). This design paradigm certainly limits the flexibility of the system design since worse performing components might be chosen over better alternatives because of their higher susceptibility. To overcome this limitation and to retain the MRI capabilities, we propose the application of localized shimming on PET detector level, meaning that the distortion profile caused by PET modules is compensated using either additional components such as magnetic materials (passive shimming) or DC coils (active shimming) on the PET modules or by intelligently arranging the hardware components of the PET detector. We have implemented a software framework which covers three parts: firstly, it calculates the ${B_0}$ distortion of various objects (susceptibility objects, conductor configuration). Secondly, it allows the characterization of magnetic objects by fitting the implemented models to data and thirdly, it performs a ${B_0}$ field homogenization of measured distortion maps by superimposing field disturbances of additional simulated objects. We tested this software framework in a first attempt with a single PET module of the Hyperion-II $^ {\rm D}$ scanner. The measured distortion map of the single PET module shows a strong localized ${B_0}$ distortion with a volume RMS value of about $0.6~\hbox{ppm}$ . After optimization, the homogeneity of the simulated field distribution is strongly improved by a factor of 8 (volume RMS $ \approx 0.075~\hbox{ppm}$ ).

Diagnostic Capability of Low- Versus High-Field Magnetic Resonance Imaging for Lumbar Degenerative Disease

Cohort study. To investigate the diagnostic capability of low-field magnetic resonance imaging (MRI) compared with high-field MRI for degenerative disease of the lumbar spine. Low-field MRI has several advantages over high-field magnetic resonance systems (easier installation, lower purchase, and maintenance cost). The diagnostic capability of low-field MRI for degenerative disease of the lumbar spine has not been compared with that of high-field MRI. Hundred patients (mean age: 56.3 yr, range: 32-80; F:M = 59:41) with neurogenic claudication or sciatica were studied. All patients underwent MRI of the lumbar spine on both low-field (0.25T) and high-field (1.5T or 3.0T) magnetic resonance systems. Intervertebral disc herniation, central canal, lateral recess, and exit foraminal stenosis as well as nerve root compression at L3-L4, L4-L5, and L5-S1 were evaluated by 2 radiologists for both low- and high-field systems using established reliable grading systems. There was excellent agreement between low- and high- field MRI with regard to grading the presence and severity of disc herniation (r = 0.92-0.94; P < 0.05), central canal stenosis (r = 0.89-0.91; P < 0.05), lateral recess stenosis (r = 0.81-0.87; P < 0.05), and exit foramen stenosis (r = 0.81-0.89; P < 0.05). Descending or exiting nerve root compression occurred in 52% of patients at L3-L4, L4-L5, or L5-S1 levels, with good agreement between low-field and high-field MRI (r = 0.71-0.76; P < 0.05) for nerve root compression. Excellent reliability between low- and high- field MRI was found for most features of lumbar disc degeneration, with good agreement for nerve root compression. 0.25T MRI was more susceptible to motion artifact, probably due to longer scanning time. 3.

A logistic model including risk factors for lymph node metastasis can improve the accuracy of magnetic resonance imaging diagnosis of rectal cancer.

To evaluate use of magnetic resonance imaging (MRI) and a logistic model including risk factors for lymph node metastasis for improved diagnosis. The subjects were 176 patients with rectal cancer who underwent preoperative MRI. The longest lymph node diameter was measured and a cut-off value for positive lymph node metastasis was established based on a receiver operating characteristic (ROC) curve. A logistic model was constructed based on MRI findings and risk factors for lymph node metastasis extracted from logistic-regression analysis. The diagnostic capabilities of MRI alone and those of the logistic model were compared using the area under the curve (AUC) of the ROC curve. The cut-off value was a diameter of 5.47 mm. Diagnosis using MRI had an accuracy of 65.9%, sensitivity 73.5%, specificity 61.3%, positive predictive value (PPV) 62.9%, and negative predictive value (NPV) 72.2% [AUC: 0.6739 (95%CI: 0.6016-0.7388)]. Age (<59) (p=0.0163), pT (T3+T4) (p=0.0001), and BMI (<23.5) (p=0.0003) were extracted as independent risk factors for lymph node metastasis. Diagnosis using MRI with the logistic model had an accuracy of 75.0%, sensitivity 72.3%, specificity 77.4%, PPV 74.1%, and NPV 75.8% [AUC: 0.7853 (95%CI: 0.7098-0.8454)], showing a significantly improved diagnostic capacity using the logistic model (p=0.0002). A logistic model including risk factors for lymph node metastasis can improve the accuracy of MRI diagnosis of rectal cancer.