Yasuo Takehara

Recently, time-resolved 3D phase contrast magnetic resonance imaging (4D-flow) allows flow dynamics in patients with pulmonary arterial hypertension to be measured. Abnormal flow dynamics, such as vortex blood flow pattern in the pulmonary artery (PA), may reflect progression of pulmonary arterial hypertension (PAH). Some reports suggested that abnormal blood flow parameters including wall shear stress (WSS) could be markers of PAH. However, it was not fully assessed clinical usefulness of these variables. We aimed to assess whether these flow dynamic parameters, such as vortex formation time (VFT) and WSS, were associated with right ventricular (RV) function. Fifteen subjects, nine with PAH and six healthy volunteers, underwent 4D-flow. Differences of Blood flow patterns, blood flow velocities and WSS between PAH patients and healthy volunteers were evaluated. We also assessed the association between VFT, WSS and RV function in PAH patients. Both vortex blood flow patterns and early systolic retrograde flow in the main PA were observed in all patients with PAH. The PA flow velocities and WSS in patients with PAH were lower than those in healthy volunteers, but that blood flow volumes in the MPA, RPA and LPA and SV in the MPA were broadly comparable between the groups. The mean VFT was 35.0 ± 16.6 % of the cardiac cycle. The VFT significantly correlated with RV ejection fraction, RV end systolic volume, and RV end systolic volume index (RVEF = 75.1 + (−85.7)·VFT, p = 0.003, RVESV = 12.4 + 181.8·VFT, p = 0.037 and RVESVI = 10.6 + 114.8·VFT, p = 0.038, respectively) in PAH patients, whereas WSS did not correlate with RV function. We confirmed that abnormal blood flow dynamics, including the vortex formation and the early onset of retrograde flow, low WSS in the PA were characteristics of PAH. The VFT may be associated with right ventricular dysfunction, whereas WSS was not. Our results suggest that 4D-flow is an effective means of detecting right heart failure as well as diagnosing PAH. Clinical trial registration URL: https://upload.umin.ac.jp/cgi-open-bin/ctr/ctr.cgi . Unique identifier: UMIN000011128

Institutional Review Board (IRB)-approved prospective study was conducted to test whether objective and quantitative hemodynamic markers wall shear stress (WSS) and oscillatory shear index (OSI) measured by three-dimensional (3D) cine phase-contrast (PC) can reflect pulmonary arterial hypertension (PAH). Seventeen consecutive patients of suspected secondary PAH were examined for pulmonary artery pressures (PAPs) with right heart catheterization (RHC) and three-dimensional (3D) cine PC MR. Based on the RHC data, patients were subdivided into two groups of 12 non-PAH (median age of 74.5 years) and 5 PAH (median age of 77 years) patients. Based on 3D cine PC magnetic resonance (MR), hemodynamic parameters including spatially averaged systolic WSS (sWSS), diastolic WSS (dWSS), mean WSS (mWSS), OSI and blood vessel section area (BVSA) at the pulmonary arterial trunk were calculated. Streamline images in the pulmonary arteries were also assessed. All the parameters were compared between non-PAH and PAH groups. sWSS (N/m(2)) and mWSS (N/m(2)) of PAH group was lower than that of non-PAH group (0.594 ± 0.067 vs. 0.961 ± 0.590, P = 0.001), (0.365 ± 0.035 vs. 0.489 ± 0.132, P = 0.027). OSI of PAH group was higher than that of non-PAH (0.214 ± 0.026 vs. 0.130 ± 0.046, P = 0.001). sWSS, mWSS, and dWSS were inversely correlated and OSI was positively correlated to mean PAP or systolic PAP with r values of -0.638 (P = 0.005), -0.643 (P = 0.005), -0.485 (P = 0.049), and 0.625 (P = 0.007); or -0.622 (P = 0.008), -0.629 (P = 0.007), -0.484 (P = 0.049), and 0.594 (P = 0.012), respectively. sWSS was also inversely correlated to BVSA with r value of -0.488 (P = 0.049), and OSI was correlated to BVSA with r value of 0.574 (P = 0.016). Vortex or helical flows were observed more frequently in PAH patients. The low sWSS and mWSS as well as high OSI measured with 3D cine PC MR could be potential hemodynamic markers for the increased PAP in suspected secondary PAH patients.

Diagnostic imaging is undoubtedly important in modern medicine, and final clinical decisions are often made based on it. Fortunately, Japan has the highest numbers of diagnostic imaging instruments, such as CT and MRI devices, and boasts easy access to them as well as a high level of diagnostic accuracy. In consequence, a very large number of imaging examinations are performed, but diagnostic instruments are installed in so many medical facilities that expert management of these examinations tends to be insufficient. Particularly, in order to avoid risks, clinicians have recently become indifferent to indications of imaging modalities and tend to rely on CT or MRI resulting in increasing the number of imaging examinations in Japan. This is a serious problem from the viewpoints of avoidance of unnecessary exposure and medical economy. Under these circumstances, the Japan Radiological Society and Japanese College of Radiology jointly initiated the preparation of new guidelines for diagnostic imaging. However, the field of diagnostic imaging is extremely wide, and it is impossible to cover all diseases. Therefore, in drafting the guidelines, we selected important diseases and focused on “showing evidence and suggestions in the form of clinical questions (CQs)” concerning clinically encountered questions and “describing routine imaging techniques presently considered to be standards to guarantee the quality of imaging examinations”. In so doing, we adhered to the basic principles of assuming the readers to be “radiologists specializing in diagnostic imaging”, “simultaneously respecting the global standards and attending to the situation in Japan”, and “making the guidelines consistent with those of other scientific societies related to imaging”. As a result, the guidelines became the largest ever, consisting of 152 CQs, nine areas of imaging techniques, and seven reviews, but no other guidelines in the world summarize problems concerning diagnostic imaging in the form of CQs. In this sense, the guidelines are considered to reflect the abilities of diagnostic radiologists in Japan. The contents of the guidelines are essential knowledge for radiologists, but we believe that they are also of use to general clinicians and clinical radiological technicians. While the number and contents of CQs are still insufficient, and while chapters such as those on imaging in children and emergency imaging need to be supplemented, the guidelines will be serially improved through future revisions. Lastly, we would like to extend our sincere thanks to the 153 members of the drafting committee who authored the guidelines, 12 committee chairpersons who coordinated their efforts, six members of the secretariat, and affiliates of related scientific societies who performed external evaluation.

Purpose: 1) To assess the usefulness of an elastic belt bracing the upper abdomen for reducing the miscalculated areas of the pancreas on 3.0T magnetic resonance elastography (MRE); 2) to test whether MRE can detect difference of stiffness between normal pancreas and the focal pancreatic diseases.Materials and Methods: Using an initial eight normal volunteers, miscalculated areas were compared between MRE with the elastic belt and without the belt on 3.0T MRI. Then, using the belt, MRE of the normal pancreas was measured using 14 volunteers and 11 patients with focal pancreatic lesions.Results: The median (95% confidence interval [CI]) percentages of correctly calculated areas were 57.4% (32.9–63.0) with the elastic belt and 35.3% (11.4–60.4) without the belt (P = 0.0078). The stiffness of each pancreatic segment of the normal volunteers (mean ± SE) was 2.37 ± 0.16 kPa for the head, 2.46 ± 0.17 kPa for the body, and 2.58 ± 0.26 kPa for the tail. The stiffness of seven pancreatic cancers was 6.06 ± 0.49 kPa, which was higher than the overall pancreatic stiffness of the normal volunteers (2.47 ± 0.11 kPa, P < 0.0001). Stiffness of the pancreatic lesions in the head of 6.03 ± 0.42 kPa, body of 5.57 ± 0.82 kPa, and tail of 5.9 ± 1.9 kPa were also higher than those of corresponding segments of the normal volunteers (P = 0.0011, 0.0029, and 0.029, respectively).Conclusion: With the elastic belt, miscalculation of the pancreatic stiffness was reduced. MRE showed differences of stiffness between normal pancreas and pancreatic lesions. J. Magn. Reson. Imaging 2016;43:384–390.

Background: The blood flow from pulmonary veins (PVs) to left ventricle (LV) through left atrium (LA) changes under various conditions, and affects global cardiac function and thrombogenesis. We aimed to clarify the velocity vectors in LA and the blood particles movement from PVs to LV using 4D-Flow MRI. Methods: Thirty two patients with and without organic heart diseases (59±14 years, mean±SD) underwent 4D-Flow with routine MRI and echocardiography. We set a plane traversing each exit of PV, and the velocity vectors in LA were post-processed to delineate streamline images (Fig. A). The percentage of blood particles that reached LV (%LV particles) was also analyzed during a cardiac cycle (Fig. B: initial phase and Fig. C: last phase). Results: (1) The streamline images revealed intra-LA vortex formation in 20 patients but did not in 12 patients. All the vortices showed characteristic counter-clockwise flow patterns in the cranial view. (2) The LV end-diastolic and end-systolic volume, and the LA volume were less in patients with vortex than in those without vortex (104±34 vs. 155±67 ml, 46±28 vs. 88±59 ml, and 41±19 vs. 75±31 ml, pConclusions: 4D-Flow MRI can visualize the intra-LA vortex formation and flow dynamics from PVs to LV. The vortex formation may be dependent on the LV and LA volume, and may affect the flow dynamic from PVs to LV. The blood flow from left PVs seems to be more stagnant within LA than that from right PVs.

The performance of a newly developed potential tumor‐seeking magnetic resonance (MR) contrast agent α‐Aqua‐13,17‐bis(1‐carboxypropionyl) carbamoylethyl‐3,8‐bis(1‐phenethyloxyethyl)‐β‐hydroxy‐2,7,12,18‐tetramethyl‐porphyrinato manganese (III) (HOP‐8P) was tested using a mouse model. Tumor‐bearing (SCC‐VII) mice were imaged using a 1.5T MR imager before and after intravenous administration of 0.1 mmol/kg of HOP‐8P. A biodistribution analysis was performed using an optical emission spectrometer. Significant enhancement of the transplanted tumor was observed in MR images 24 h after intravenous injection of HOP‐8P. The biodistribution assessment of manganese also correlated with the results of the imaging study. During the 24‐h period following contrast administration, HOP‐8P was consistently cleared from the circulation, liver, kidneys, and muscle; however, it was progressively accumulated within the tumor. HOP‐8P is a promising tumor‐seeking metalloporphyrin MR contrast agent with a wide imaging window. Magn Reson Med 47:549–553, 2002.

Our objective was to implement a non-invasive magnetic resonance imaging (MRI) technique combined with concentrated milk ingestion for depicting the gastrointestinal (GI) tract and detecting gastrointestinal motility and transit. The half-Fourier SSFSE (single-shot fast spin echo) sequence was optimized on the basis of a phantom study. In order to determine the feasibility of milk ingestion as a substitute for contrast medium, ten human volunteers were examined with SSFSE after two types of liquid ingestion (i.e., milk and water). The snapshot images provided subsecond data acquisition for each coronal plane, allowing visualization of peristalsis in the gastrointestinal tract in an almost real-time fashion, without motion-related image degradation, as would normally be seen using conventional MRI. There was no significant difference between concentrated milk and water in terms of depiction of the upper gastrointestinal tract; however, 10 min and 30 min after ingestion, concentrated milk showed better delineation of the intestine than that observed after water ingestion (p < 0.01). MR gastrointestinal imaging is a non-invasive method that allows gastrointestinal depiction as well as analysis of motility and passage. Especially with concentrated milk ingestion, the distal intestines were well depicted with adequate contrast filling and distention.