Current Medical Imaging - Volume 8, Issue 2, 2012

When MRI was introduced, it was first used for neurological and musculoskeletal imaging. The body, due to its size, complex movements, and even more complex pathology remained an elusive domain for MRI. As time went on, this changed quickly as pioneers began exploring what we can do with MRI of abdomen and pelvis. Today MRI is the best non-invasive imaging modality for most abdominal and pelvic diseases. Some of the pioneers in this ever evolving research area have contributed with their invaluable contribution. Though, these works do not encompass all possible fields in abdominal and pelvic MRI, focus has been on the latest improvements and what we now understand from this process. In the following series of articles some of the most prominent groups summarize the latest findings and their own experience from the field. De Souza et al. and Zhen Li, et al. look into the new uses of diffusion weighted imaging in oncology. Diffusion which is basically a functional imaging based on movement of water molecules has become one of the most important methods for detection of malignancies. Malignancies in general restrict free diffusion and thus we have become able to detect malignancies with increased sensitivity. Moreover diffusion plays a role in monitoring tumor response or recurrence....

Pelvic imaging is undergoing rapid changes due to increased use of 3-Tesla (3T) magnetic resonance imaging (3T MRI). One of the advantages of 3T could be the possibility for thin section 3-dimensional (3D) imaging which could improve accuracy and at the same time reduce the need for multi-planar imaging needed for conventional T2 imaging (TSE). In the following text we review the advantages of 3D thin section imaging for assessment of pelvic tumors.

Diffusion-weighted magnetic resonance imaging (DWI) can provide functional information on a cellular level by measuring water diffusion values. DWI is sensitive to changes in the micro diffusion of water and the apparent diffusion coefficient (ADC) is an indicator of the movement of water within the tissue. In abdominal oncology, DWI has been successfully used for the features of liver and prostate lesions, particularly for the differentiation of benign and malignant neoplasm. In addition, ADC values have been shown to predict tumor response to treatment. In some instances low tumor ADC before treatment can be predictive of better outcome. However, studies found a considerable overlap between ADC values of malignant and benign lesions and the reproducibility of DWI measurements is limited. Combinations of conventional MRI, MR spectroscopy or dynamic enhancement as well as standardization of DWI acquisition are needed to receive reliable results. In this review we focus on the most common applications of DWI in abdominal oncology and provide an assessment of the value of DWI.

Diffusion-weighted MRI exploits intrinsic tissue contrast generated by movement of water within tissues over distances of around 1-20 microns. These distances are travelled by water within microcapillaries or in the extracellular space as a result of thermally driven random motion, where movement is limited by structural interfaces such as cell membranes. Diffusion-weighted imaging thus reflects microcapillary perfusion and tissue cellularity. In soft tissue pelvic neoplasms, the quantitative ADC maps generated can be used in conjunction with conventional T2-W images to improve tumour detection and staging, and are increasingly being explored as quantitative functional biomarkers of prognosis and response. This review summarizes the current clinical utility and future potential of diffusion-weighted MRI in prostate, rectal, gynaecological and bladder cancers.

The International Federation of Gynecology and Obstetrics (FIGO) staging system is the oldest and most widely used system for treatment planning and prognosis in cervical cancer. On the 1st of June 2009 the FIGO committee introduced the revised staging of cervical carcinoma updating the previous staging of 1988. Although FIGO staging system does not include radiology in the staging of cervical cancer, the committee encourages the use of imaging techniques if available to assess the important prognostic factors such as parametrial and pelvic side wall invasion, tumor size and the evaluation of lymph node metastases. Imaging is therefore complimentary to the clinical assessment with magnetic resonance (MR) imaging accepted as the optimal modality to stage cervical carcinoma. This article will discuss and illustrate the new FIGO staging, the impact of imaging on treatment and optimal image acquisition with respect to MR imaging. Radiologists must familiarise themselves with the new staging and understand its relevance to patient management

Magnetic resonance imaging, MRI has more advantages than ultrasound, computed tomography, CT, positron emission tomography, PET, or any other imaging modality in diagnosing focal hepatic masses. With a combination of basic T1 and T2 weighted sequences, diffusion weighted imaging, DWI, and hepatobiliary gadolinium contrast agents, that is gadobenate dimeglumine (Gd-BOPTA) and gadoxetic acid (Gd-EOB), most liver lesions can be adequately diagnosed. Benign lesions, as cyst, hemangioma, focal nodular hyperplasia, FNH or adenoma, can be distinguished from malignant lesions. In a non-cirrhotic liver, the most common malignant lesions are metastases which may be hypovascular or hypervascular. In the cirrhotic liver hepatocellular carcinoma, HCC, is of considerable importance. Besides, intrahepatic cholangiocarcinoma and other less common malignancies has to be assessed. In this review, the techniques and typical MRI features are presented as well as the new algorithm issued by American Association for the Study of the Liver Diseases (AASLD).

Laparoscopic hepatobiliary surgery is a popular, blossoming procedure. As a consequence, a range of complications are seen, some of these are rare and not well known. As a tertiary center of hepatobiliary disease, we review our experiences with CT and MR imaging of a spectrum of complications after such surgery.

The article provides a broad overview of functional MRI methods for evaluating the kidney. While the major function of the kidney is excretion and maintenance of homeostasis, functional MRI methods include several techniques that provide tissue characterization above and beyond anatomical depiction. We have divided the review under two major sub-sections based endogenous and exogenous contrast mechanisms. Diffusion MRI, Arterial spin labeling based perfusion MRI, blood oxygenation level dependent (BOLD) MRI, and sodium MRI are discussed under endogenous contrast methods. Dynamic contrast enhanced methods to evaluate renal perfusion and excretory function are covered under exogenous contrast mechanisms. A brief discussion on hyperpolarized MRI and pH measurements is also included. While many of the methods are still considered investigational, where available we have included clinical examples.

Combining the advantages of lack of ionizing radiation with excellent soft tissue contrast, magnetic resonance imaging (MRI) of the gastrointestinal tract has become a clinically accepted tool. Tumor and infectious disease as well as bowel inflammation can be easily visualized on MR images. This article describes current techniques of gastrointestinal MRI, points out particularities of bowel MRI at 3T, explains how to accurately analyze gastrointestinal MR scans and gives an overview of its clinical outcome.

In this work the design and preliminary clinical results obtained with an innovative and dedicated breast PET is presented. A geometrical study clearly pointed out the advantages of the prone position and the technique of hanging breast in comparison to the supine, conventionally used for other imaging modalities. Occult, multifocal and also lesions close to the pectoral muscle were depicted by means of the prone method. The measured diameters of the hanging breasts allowed us to define an optimum transaxial FOV of up to 170 mm. This was achieved by means of 12 detector heads mounted on ring geometry, each using a monolithic LYSO crystal a position sensitive photomultiplier, among other components. The detector showed up an extrinsic spatial resolution as high as 1.4 mm in the center of the FOV with a physical sensitivity of 1.2 %. A clinical trial is undergoing at the Netherlands Cancer Institute in terms of a clinical validation of the dedicated breast PET. An adequate image matching between this device and the whole-body PET was observed, even for deep chest lesions. A preliminary quantitative comparison also shows a good agreement between both systems. However, a tiny deviation to higher Standard Uptake Values is observed for the prototype.

The aim of this study was to investigate the predictive value of vessel-based calcium (Ca) score in the detection of ≥%50 coronary stenosis. The results of 65 patients with typical chest pain or multiple cardiovascular risk factors who underwent coronary Ca scoring and catheter angiography were retrospectively evaluated. 260 coronary arteries were analysed and mean vessel-based Ca score was 179±17.0 (range 0-1729). In 114 coronary arteries with vessel-based Ca scores of ≥100, ≥%50 stenosis was found in 90 of them (79%). On the other hand, in 146 coronary arteries with vessel-based Ca scores of ≤99, ≥%50 stenosis was found in 17 of them (12%). Sensitivity, specificity, positive predictive value, negative predictive value and accuracy results for different vessel-based Ca scores in the detection of ≥%50 coronary stenosis were as follows: 84%, 84%, 79%, 88%, 84% respectively for the cut-off value of 100; 39%, 99%, 95%, 70%, 74% respectively for the cut-off value of 400; 7%, 100%, 100%, 60%, 62% respectively for the cut-off value of 1000. The cut-off value of the vessel-based Ca score was 100 in the ROC curve analysis. During Ca scoring, calculation of both total Ca score and vessel-based Ca score will increase the diagnostic accuracy of coronary artery stenosis. A cut-off value of 100 for the vessel- based Ca score seems to be good in the prediction of ≥50% coronary stenosis.