[en] Nuclear magnetic resonance (NMR) has been a common tool for physicists and chemists to probe molecular structures since the phenomenon of NMR was discovered in 1946. The development of X-ray CT in 1973 played an important role in stimulating interest in NMR as an imaging tool, resulting in the birth of magnetic resonance imaging (MRI). Since its invention in the early 1970s, the development of MRI has been among the most active and exciting areas in science, technology, and medicine. Over the past twenty years, MRI has become one of the most important imaging modalities available to clinical medicine. In addition to its role as a routine imaging technique with a growing range of clinical applications, the pace of development in MRI methodology remains rapid, and new ideas with significant potential emerge on a regular basis. This article presents a brief history of the development of MRI. (author)

[en] Recent technical developments in neuroradiology include diffusion tensor imaging (DTI), statistical analysis of imaging, high-field MR imaging, multidetector-row CT (MDCT), perfusion CT and MR, contrast enhanced MR angiography (MRA), plaque imaging, and others. White matter fibers now can be visualized by diffusion tensor tractography and can be quantitatively evaluated. DTI and other recent techniques are discussed in this review. (author)

[en] Malignant lymphomas are a heterogeneous group of lympho-proliferative disorders, mainly originating in lymphoid tissues and other extranodal organs, with different patterns of behavior. Prognoses depend on the genomic/pathologic types identified in the WHO classification (2001), prognostic factors, and treatment strategy. According to the WHO classification, the malignant lymphomas are divided into three clinical groups: the indolent lymphomas (follicular lymphoma, marginal zone B-cell lymphoma, etc.), Hodgkin lymphomas, and the aggressive lymphomas (diffuse large B-cell lymphoma, peripheral T-cell lymphoma, etc.). Indolent lymphomas and Hodgkin lymphomas have good prognoses, with median survival as long as 10 years, and the patients with early-stage (I and II) disease can be treated with radiation therapy alone, with 70-90% 5-year overall survival rates. The aggressive lymphomas have shorter natural histories, but the number of patients cured with intensive chemotherapy is increasing. In general, overall survival at 5 years is approximately 50-60%. Patients with aggressive lymphomas of stage I and contiguous stage II enjoy excellent survival rates when treated with a combined modality that includes chemotherapy (CHOP) and radiation therapy. The radiation dose for lymphomas varies from 25-50 Gy and is dependent on genomic/pathologic type and the organs at risk. Radiation fields are basically limited to involved regions or extended to the immediate adjacent sites. Localized presentations of the extranodal lymphomas can be treated with significant success using involved-field techniques. However, long-term adverse reactions must be given careful consideration. (author)

[en] Gadolinium-ethoxybenzyl-diethylene-triamine-pentaacetic acid (Gd-EOB-DTPA, Primovist) is a recently developed hepatobiliary-specific contrast material for magnetic resonance imaging (MRI). Gd-EOB-DTPA is taken up by hepatocytes and then excreted into the bile ducts in normal liver. Hepatic focal lesions with abnormal hepatobiliary function can be definitely depicted compared to background liver on the hepatobiliary phase of Gd-EOB-DTPA-enhanced MR imaging (EOB-MRI). The enhancement ratio on EOB-MRI would reflect the balance of the uptake and excretion function of the lesions. In a rat experimental study, the hepatic uptake transporter of Gd-EOB-DTPA was confirmed to be an organic anion transporting polypeptide 1 (Oatp1), and the export transporter was multidrug resistance-associated protein 2 (Mrp2). The substrates transported by rat oatp1 can be taken up by human OATP1B1, OATP1B3 and OATP2B1, which are expressed on the sinusoidal side of hepatocytes. The substrates of rat Mrp2 can be exported by MRP2 on the canalicular side and MRP1/MRP3 on the sinusoidal side of human hepatocytes. Those transporters carry many kinds of intrinsic or extrinsic molecules, for example bilirubin glucuronides, bile acids, hormones and several drugs. Some of these transporters should be involved in the uptake and excretion of Gd-EOB-DTPA in human normal hepatocytes and tumor cells. During the hepatobiliary phase of EOB-MRI, most hepatocellular carcinomas (HCCs) classically show a low enhancement ratio, but a high enhancement ratio is shown in several percent of lesions. We analyzed the expression of uptake and excretion transporters (OATPs and MRPs) in HCCs correlated with the signal intensity on the hepatobiliary phase of EOB-MRI. As a result, the expressions of uptake transporter OATP1B3 and sinusoidal excretion transporter MRP3 significantly increased in hyperintense HCCs compared to hypointense HCCs. Therefore, we thought OATP1B3 and MRP3 (not canalicular transporter MRP2) are the most probable uptake transporter and export transporter of Gd-EOB-DTPA in human HCC cells, respectively. On histological examination, a pseudoglandular proliferation pattern with bile plugs is observed with significantly high frequency in hyperintense HCCs. This indicates increased bile production in the tumor, because OATP1B3 can transport some components of bile. EOB-MRI has the potential to provide more information in addition to detecting nodular lesions. The enhancement ratio during the hepatobiliary phase of EOB-MRI would reflect the hepatobiliary function (transporter expression) of chronic liver diseases. It is important to understand the uptake and excretion mechanism of transporters for precise evaluation of EOB-MRI. Further studies on the correlation between transporters and EOB-MRI are expected. (author)

[en] Superparamagnetic iron oxide (SPIO) is the only tissue-specific MR agent currently available in Japan. It is quickly taken up by Kupffer cells at the first pass (either arterial or portal) and becomes clustered in the lysosome, providing characteristic T2^* and T2 shortening effects that suppresses the signal of normal or non-tumorous liver tissue. SPIO has dramatically changed the diagnostic algorithm of liver metastasis in clinical practice, now serving as the gold standard instead of CT during arterial portography (CTAP). Its role in the diagnosis of hepatocellular carcinoma (HCC), however, is somewhat complicated, owing to its heterogeneous uptake by the background cirrhotic liver, as well as by some of the HCCs themselves. It has been shown to be useful in the diagnosis of pseudolesions (arterioportal shunts) and some benign hepatocellular lesions (focal nodular hyperplasia or adenoma) by their complete or partial uptake of SPIO, in contrast to an absence of uptake by true liver lesions. It has also been suggested that the histological grade of HCC affects the degree of SPIO uptake. Thus, SPIO serves as a complementary tool to the primary modalities of vascular survey, namely, dynamic CT/MR and CT during hepatic arteriography (CTHA)/CTAP, in the diagnosis of HCC. Gadolinium ethoxybenzyl diethylenetriaminepentaacetic acid (Gd-EOB-DTPA) is a novel hepatobiliary contrast agent that is not yet available but is supposed to be approved by the Ministry of Health, Labour, and Welfare of Japan in the near future. It is taken up by hepatocytes and excreted into the bile, providing a T1-shortening effect that enhances the normal or non-tumorous liver tissue. It has also been shown to have the effect of positive enhancement of hypervascular liver tumors on the arterial phase, just like the usual extracellular contrast agent (gadopentetate dimeglumine: Gd-DTPA). Thus, Gd-EOB-DTPA was once thought to be an ideal contrast agent for liver tumors, providing information on both tumor vascularity and precise location. Unfortunately, however, its performance in depicting tumor vascularity was suggested to be less than that of multi detector row CT (MDCT) or dynamic MR using Gd-DTPA. Further investigation is needed to determine the true usefulness of Gd-EOB-DTPA in the imaging diagnosis of liver tumors. A number of other promising tissue-specific contrast agents currently are under development, including blood pool agents, lymphatic or lymph nodal agents, blood vessel wall agents, and so on. We, as radiologists, should keep in mind that the true efficacy and roles of these tissue-specific agents need to be evaluated not only from the viewpoint of diagnostic accuracy but also with reference to their socioeconomic aspects, particularly in this era of the Diagnosis-Related Group/Prospective Payment System. (author)

[en] This paper describes the anatomical outline of liver vasculature and related matters including vascular architecture revealed by imaging. The related matters contain the embryonic development of the organ and its vasculature, channel to mesentery and ducts/vessels (shown also by images of the digital subtraction angiography, dynamic CT and CT with multi projection volume reconstruction), morphology of the liver involving its modification and surrounding structures, and functional segments like Healey/Schroys', Couinaud's and Ryu/Shos'. Japanese classification of segmental and lobular vasculature is essentially based on the above Couinaud's concept. According to 3D CT maximum intensity projection (MIP) images, the origin of intrahepatic portal vein is distinguished in 3 types (normal branching 71-90% and others 4-17%). The vein revealed by multi detector (MD) CT often exhibits various modifications. Hepatic veins are important at liver transplantation and also have been shown to exhibit many variations by CTMIP. Hepatic arteries are similar. Exact anatomy of liver has not been fully elucidated hitherto because of difficulty to deal with multiple cases but MDCT is promising for the problem, and for which, to understand the concept of segments and to identify their regional vasculature are thought meaningful. (K.T.)

[en] Although radiation therapy plays a significant role in the treatment of head and neck malignancy, the clinical outcome of this single modality remains insufficient. Radiation therapy has the advantage of organ and functional preservation compared with surgery, but is at a disadvantage in curing locally advanced lesions. In this decade, several factors such as combinations of anti-cancer drugs, technological developments in radiation techniques, and the clinical application of particle therapy, have markedly improved the clinical results of radiation therapy. Chemoradiotherapy is thought to be promising because of its enhancement of the radiation effect in advanced lesions, and meta-analysis has indicated its usefulness. When the method of combining the anti-cancer agent and radiation is used, both concurrent and alternating settings should be recommended. These two methods can provide significant improvement of both local control and survival; however, this improvement is accompanied with increasingly significant acute toxicity. New agents including molecular target agents are under now active investigation to refine treatment outcome. Recent technological revolutions have led to the clinical utilization of intensity modulated radiation therapy (IMRT), which makes it possible to escalate radiation dose while reducing radiation exposure to normal tissue. With the aid of IMRT, more refined radiation results will be achieved in the future. (author). 121 rets

[en] Prostate cancer is increasing rapidly in Japan. Surgery and conformal radiotherapy, intensity modulated radiation therapy (IMRT), heavy particle therapy, and brachytherapy are the most widely accepted curative options for patients with early-stage prostate cancer. All of these local treatments have been refined, resulting in comparable cure rates; however, they all have different profiles in terms of side effects. The decision on how to treat is based on complications after treatment and the grade of maintenance of quality of life (QOL). Although permanent implantation of ¹²⁵I seeds has just begun in Japan, it seems likely that the procedure will become widespread. (author)

[en] The advent of multi-slice CT is one of the quantum leaps in computed tomography since the introduction of helical CT. Multi-slice CT can rapidly scan a large longitudinal (z-axis) volume with high longitudinal resolution and low image artifacts. The rapid volume coverage speed of multi-slice CT can increase the difficulty in optimizing the delay time between the beginning of contrast material injection and the acquisition of images and we need accurate knowledge about optimal temporal window for adequate contrast enhancement. High z-axis resolution of multi-slice can improve the quality of three-dimensional images and MPR images and we must select adequate slice thickness and slice intervals in each case. We discuss basic considerations for adequate contrast enhancement and scanning protocols by multi-slice CT scanner in the upper abdomen. (author)

[en] The dynamic Magnetic Resonance Imaging (MRI) of the whole liver was examined for the detection of hepatocellular carcinoma (HCC) in 362 patients with chronic liver disease such as cirrhosis. We used warmed Gd-DTPA at 37degC. Most patients felt more comfortable than in the previous examination with cold Gd-DTPA. All patients were examined under the ceased respiration within 30 minutes (median sixteen minutes) per patient. The diagnosis of HCC was characterized by high intensity in the early phase and low intensity in the late phase determined by the dynamic MRI. The sensitivity of the detection of HCC was 81% determined by the dynamic MRI. The sensitivity of the detection of cavernous hemangioma of the liver was 96% determined by the dynamic MRI. The six (2%) regenerative nodules showed the high intensity in the early phase of the dynamic study. The dynamic MRI of the whole liver has the high sensitivity and specificity for the detection of HCC in patients with chronic liver disease. The dynamic MRI of the whole liver using the injector and warmed contrast medium is a suitable examination for the screening of HCC in patients with chronic liver disease. (author)