Clinical and in vitro magnetic resonance imaging of prostatic carcinoma

Magnetic resonance imaging (MRI) of the prostate was accomplished in 10 patients who subsequently had surgical exploration for histologic confirmation and tumor staging. Eight patients were found to have carcinoma of the prostate. Two patients had malignancies of the urinary bladder and were treated with radical resection of the bladder and prostate. The prostatic glands in the latter two patients were free of tumor. One gland was entirely normal; the other had extensive acute and chronic prostatitis. Two resected prostates with carcinoma and one normal prostate were available for in vitro MRI in a clinical magnetic resonance unit. The MRI finding of prostatic carcinoma was heterogeneous signal patterns, seen best on T2-weighted studies. A similar pattern was identified in the gland with acute and chronic prostatitis. There was a homogeneous MRI signal pattern of the normal prostate gland examined in vitro. In two instances, the MRI studies were accurate for the identification of tumor spread to the seminal vesicles, not diagnosed at the time of surgical resection. Microscopic metastatic disease of the lymph nodes in four patients was not identified by MRI.     

Future of prostate imaging: Artificial intelligence in assessing prostatic magnetic resonance imaging

Prostate cancer (Pca; adenocarcinoma) is one of the most common cancers in adult males and one of the leading causes of death in both men and women. The diagnosis of Pca requires substantial experience, and even then the lesions can be difficult to detect. Moreover, although the diagnostic approach for this disease has improved significantly with the advent of multiparametric magnetic resonance, that technology has certain unresolved limitations. In recent years artificial intelligence (AI) has been introduced to the field of radiology, providing new software solutions for prostate diagnostics. Precise mapping of the prostate has become possible through AI and this has greatly improved the accuracy of biopsy. AI has also allowed for certain suspicious lesions to be attributed to a given group according to the Prostate Imaging-Reporting & Data System classification. Finally, AI has facilitated the combination of data obtained from clinical, laboratory (prostate-specific antigen), imaging (magnetic resonance), and biopsy examinations, and in this way new regularities can be found which at the moment remain hidden. Further evolution of AI in this field is inevitable and it is almost certain to significantly expand the efficacy, accuracy and efficiency of diagnosis and treatment of Pca.     

Stiffness-weighted magnetic resonance imaging.

An imaging method is introduced in which the signal in MR images is affected by the stiffness distribution in the object being imaged. Intravoxel phase dispersion (IVPD) that occurs during MR elastography (MRE) acquisitions decreases the signal in soft regions more than in stiff regions due to changes in shear wave amplitude and wavelength. The IVPD effect is enhanced by lowpass filtering the MR k-space data with a circular Gaussian lowpass filter. A processing method is introduced to take the time series of MRE magnitude images with IVPD and produce a final stiffness-weighted image (SWI) by calculating the minimum signal at each pixel from a small number of temporal samples. The SWI technique is demonstrated in phantom studies as well as in the case of a preserved postmortem breast tissue specimen with a stiff lesion created by focused ultrasound ablation to mimic a breast cancer. When free of significant sources of depth-dependent wave attenuation, interference, and boundary effects, SWI is a simple, fast, qualitative technique that does not require the use of phase unwrapping or inversion algorithms for localizing stiff regions in an object.     

Transesophageal magnetic resonance imaging.

The purpose of this study was to develop a non-invasive method of imaging the thoracic aorta that would provide both morphological detail within the aortic wall and information about regional aortic wall motion. An esophageal probe is described that allows transesophageal MR imaging (TEMRI) of the thoracic aorta and has several potential advantages over the competing non-vasculoinvasive techniques of transesophageal echocardiography (TEE) or standard MRI. The probe consists of a loopless antenna housed inside a modified Levin gastric tube, with external matching and tuning circuitry. Using this probe, the thoracic aorta has been imaged in longitudinal and cross-sectional views. Details of the aortic wall were readily seen. Tissue tagging for measurement of focal stress/strain relationships was demonstrated to be feasible. TEMRI avoids the risks inherent in intravascular MRI yet provides comparable image quality. Potential applications of the device are discussed.     

Error optimization of a three-dimensional magnetic resonance imaging tagging-based cartilage deformation technique.

Three-dimensional strain fields in articular cartilage subjected to compressive loading can be determined using a recently developed MRI-based cartilage deformation by tag registration technique. The objective of this study was to determine the experimental variables that minimize the technique error, which has not been previously reported. Error (strain bias and precision) was determined using direct experiments and Monte Carlo simulations for four variables: spatial resolution, tag line spacing, applied nominal strain, and number of control points used to describe tag lines in a B-spline model. The important results include the following: (1) bias was not significantly different from zero, (2) precision increased with image resolution and with tag line spacing, (3) precision was independent of applied nominal strain, and (4) error was a minimum (absolute precision = 0.41% strain) for the following values: spatial resolution = 0.05 x 0.05 mm2; tag line spacing = 2.0 mm; control points = 6. With these results the technique can now be used in various applications while minimizing error.     

Staging of prostatic carcinoma. Accuracy of magnetic resonance

Twenty-nine prostatic cancer patients were evaluated for staging purpose by Magnetic Resonance (MR). MR findings were correlated with the pathologic examination in 18/29 patients who underwent radical prostatectomy. Four MR staging parameters were evaluated individually: periprostatic fat; periprostatic venous plexus; seminal vesicles and pelvic adenopathy. MR correctly staged 16/18 patients, with one case of overstaging and one case of understaging. The diagnostic accuracy of MR in differentiating intracapsular stage B from extracapsular stage C was 87%, with a sensitivity of 90% and a specificity of 87%. MR and CT results agreed in 4 of the 7 operated patients who were examined with both techniques; in 3 cases there was disagreement, and MR was correct.     

PACS-based functional magnetic resonance imaging.

The picture archiving and communication system (PACS) technology reaches its 10th anniversary. Retrospectively no one could foresee the impact the PACS would have to the health care enterprise, but it is common consent today, that PACS is the key technology crucial to daily clinical image operations and especially to image related basic and clinical research. During the past 10 years the PACS has been matured from a research and developmental stage into commercial products which are provided by all major modality and health care equipment vendors. The PACS, originally implemented in the Radiology Department, needs to grow and has already carried well beyond departmental limits conquering all image relevant areas inside the hospital. During the past 10 years a dramatic development in imaging techniques especially within MRI emerged. Advanced 3D- and 4D-MR imaging techniques result in much more images and more complex data objects than ever before which need to be implemented into the existing PACS. These new imaging techniques require intensive post-processing apart from the imaging modality which need to be integrated into the image workflow and the PACS implementation. Along with these new imaging techniques new clinical applications, e.g. stroke detection, and research applications, e.g. study of heart and brain function, in Neurology and Cardiology require changes to the traditional PACS concept. Therefore inter-disciplinary image distribution will become the high-water mark for the next 10 years in the PACS endeavor. This paper focuses on one new advanced imaging technique, functional magnetic resonance imaging (fMRI), and discusses how fMRI data is defined, what fMRI requires in terms of clinical and research applications and how to implement fMRI in the existing PACS.     

Fast magnetic resonance imaging of liver.

Recent magnetic resonance (MR) units with a stronger gradient system have allowed various fast MR imaging techniques to develop. These fast scan techniques have easily realized breath-holding acquisition in the liver and the image quality has been greatly improved without sacrificing spatial resolution. The majority of the fast imaging techniques have been devoted to T2-weighted imaging to obtain useful T2-weighted images in the shortest possible time. Among the fast sequences, fast spin-echo (FSE) sequence is the most promising technique and allows high-quality T2-weighted images with reduced motion artifacts. However, FSE sequences using multiple refocused pulses may essentially realize only poor soft-tissue contrast due to magnetization transfer and T2-filtering effects, and therefore, echo-planar (EP) imaging is expected to provide high image contrast. In addition, single-shot EP imaging allows even diffusion-weighted (DW) and perfusion-weighted (PW) imaging in the liver due to its short scanning time. Recent development of fast gadolinium-enhanced 3D MR angiography has also impacted liver imaging. Combined with such gadolinium-enhanced 3D-MRA sequences and zerofilling image interpolation technique, biphasic gadolinium-enhanced 3D-MRA (whole-liver dynamic MR imaging in the arterial phase and MR portography in the portal phase) can be obtained.     

Time course of prostatic edema post permanent seed implant determined by magnetic resonance imaging

PurposeTo quantify the time course of postimplant prostatic edema magnitude and spatial isotropy using serial magnetic resonance imaging (MRI).Methods and MaterialsForty patients with histologic diagnosis of prostate cancer received an iodine-125 seed implant (Day 0) and consented to 1.5-T MRI on Days ?1, 0, 14, and 28. Seeds of strength 0.39 mCi were placed in a modified peripheral loading pattern to deliver 145 Gy to the target volume. MR images consisted of 3–4 mm thick axial slices with no gap. The image sets were anonymized and randomized to minimize contouring bias, then contoured by a single radiation oncologist. Contours were reoriented about their center of mass to align the prostate long axis with the superior–inferior (S?I) direction; prostate volumes and dimensions in the left–right (L?R), anterior–posterior (A?P), and S?I directions through the center of mass were calculated.ResultsThe average relative edema volume was 1.18 ± 0.14 (1 standard deviation) on Day 0 and 1.01 ± 0.15 on Day 30. Between Days 0 and 30, the edema resolved linearly with time on average. Average relative edema dimensions on Day 0 in the L?R, A?P, and S?I directions were 1.01 ± 0.07, 1.11 ± 0.09, and 1.08 ± 0.13, respectively.ConclusionsAs measured using MRI, the average edema magnitude for our study population was ～20% on Day 0 and resolved linearly with time to ～0% on Day 30. The edema exhibited spatial anisotropy, the prostate expanding on Day 0 by ～10% in each of the A?P and S?I directions and by ～0% in the L?R direction.     

High-speed interlaced spin-echo magnetic resonance imaging.

A new method is introduced for increasing the efficiency in multislice single spin-echo MRI. The method interlaces the excitation and measurement of different slices, resulting in an effective use of the echo delay time between RF excitation and reception. Under certain conditions, the method allows for scan time reduction compared to standard single spin-echo MRI, in particular for long echo times. The technique is demonstrated in examples of brain scans, indicating that a substantial increase is scan speed can be achieved without loss in image signal-to-noise ratio or contrast. Potential applications include perfusion imaging using T(2)-contrast agents, as well as BOLD-based functional imaging. Magn Reson Med 43:905-908, 2000. Published 2000 Wiley-Liss, Inc.     

Vascular magnetic resonance imaging

Natural contrast from flow void potentiates the diagnosis of the intimal flap of aortic dissection, the dilated contour of aortic aneurysm, the protruding plaque of atherosclerotic disease, the recognition of deep vein thrombosis, and the identification of a number of acquired and congenital vascular abnormalities. Although MRI is costly at the present, the advantages of vascular MRI include noninvasive multiplanar imaging, no ionizing radiation, no contrast material requirements, and its use as an alternative to technically limited ultrasonography or computed tomography. MRI can define anatomy, measure blood flow, and be used for serial examinations in following disease processes and response to treatment. Future research with tissue characterization of atherosclerotic plaque may allow for early diagnosis and treatment of this ubiquitous disease. Not only chemical but also metabolic studies, including tissue perfusion in the heart and other solid viscera, would be of great value. Undoubtedly, MRI will have a permanent role in cardiovascular diagnosis.     

Dynamic magnetic resonance imaging

Among the devices helping with an accurate diagnosis, neither MRI nor arthroscopy is perfect; both delineate pathology in the knee joint with reasonable sensitivity and specificity. MRI, as a noninvasive and nonionizing modality, has made a significant contribution to the understanding of musculoskeletal disturbances. Static images through the patellofemoral joint in different degrees of flexion reveal only the degree of patellar tilt or subluxation, parameters that can be measured also on the axial view of conventional radiography. The accuracy of patellar position on static axial MRI is limited by the absence of muscle contraction, movement, and loading. Dynamic axial images of patellofemoral articulation can demonstrate the degree of flexion where patellar malalignment is maximal and assess whether or not it reduces. Arthroscopy, aside from its diagnostic values, provides the opportunity for treatment of intra-articular changes contributing to knee joint disturbances, but it is an invasive technique with potential risks of complications. The performed cost-effectiveness analysis of MRI is based mainly on estimation of intra-articular pathology of the acutely-injured knee [49,52,56]. There are scarce data on the cost-effectiveness of MRI of patellofemoral alignment in patellofemoral pain knees. Total examination time for active movement dynamic MRI procedure is approximately 8 to 10 minutes, thus it can be performed during routine MRI examination of the knee. In cases of suspected patellofemoral malalignment with symptoms that mimic other types of internal derangement of the knee joint, dynamic MRI can be a procedure of choice for detection of transient patellar dislocation, whereas a single clinical examination cannot differentiate from other internal knee pathologies. Dynamic MRI, although in an experimental phase, gives us a new perspective for dynamic study of the patellofemoral joint.     

Breast magnetic resonance imaging

Mammography has long been considered the gold standard for screening breast cancer. Although it reduces the risk of breast cancer mortality by enabling early diagnosis, it does not detect all breast cancers. Numerous breast imaging technologies are emerging as effective adjunctive diagnostic tools when mammography results are negative or inconclusive. Contrast-enhanced magnetic resonance (CE-MR) imaging, in particular, has demonstrated a high sensitivity and has proven to be most effective, especially with patients at high risk for developing breast cancer. This article discusses the clinical applications for breast MR imaging, use of CE-MR for breast cancer detection, and other emerging breast imaging technologies.     

腰骶部脊神经MRI成像技术的应用进展

MRI具有良好的组织对比分辨力,能清晰的显示腰骶部脊神经根及其周围的软组织,成为评估脊神经根病变的理想手段。随着MRI技术的发展,越来越多的新的成像技术应用于临床,包括磁共振神经成像术、选择性水激励脂肪抑制技术、平衡式稳态自由进动序列、扩散张量成像等对神经根病变的诊断、术前评估等方面起着越来越重要的作用。本文综述了MRI成像技术在腰骶部脊神经根中的应用进展。     

Shoulder magnetic resonance imaging

MRI provides excellent soft tissue contrast and allows for multiplanar imaging in anatomic planes. Because of these advantages MRI has become the study of choice for imaging of shoulder pathology. Some structures, such as the rotator cuff, humeral head contour, and glenoid shape, are evaluated well with conventional MRI. When more sensitive evaluation of the labrum, capsule, articular cartilage, and glenohumeral ligaments is required or when a partial-thickness rotator cuff tear is suspected,magnetic resonance arthrography with intra-articular contrast can be performed. For MR arthrography contrast is injected directly into the glenohumeral joint. This article reviews the appearances of normal anatomic structures in MRI of the shoulder and disorders involving the rotator cuff and glenoid labrum.