Munemasa Okada

Magnetic resonance imaging features of aortic diseases.

The usefulness of magnetic resonance imaging (MRI) for aortic diseases is discussed, with special attention given to the MRI features of aortic dissection and Takayasu arteritis. Computed tomography (CT) and MRI provide excellent visualization of vessels and their relationship to surrounding structures; however, CT depicts the vessel lumen optimally only when contrast enhancement is used. MRI, with its inherent multiplanar imaging capability, is well suited for evaluation of the thoracic and abdominal aorta and can be used with or without contrast enhancement. Basic technical considerations in cardiac imaging, which include conventional spin-echo, fast spin-echo, cine gradient, and echo-planar imaging, with time-of-flight and phase-contrast methods, are discussed and applied to aortic aneurysm, aortic dissection, and Takayasu arteritis. The diagnostic capacity of spin-echo MRI in patients with suspected aortic dissection is enhanced when it is combined with cine MRI. Despite the ability of CT and MRI to demonstrate luminal and mural changes of aortic abnormalities, conventional angiography still may be necessary at first admission for selected patients in the late occlusive phase to provide additional information on the degree and extent of the arteritis. CT angiography and MR angiography are promising imaging techniques that will overcome difficulties in visualizing distal branch vessel lesions and obviate the need for conventional angiography in the near future.

Regional lung functional impairment in acute airway obstruction and pulmonary embolic dog models assessed with gadolinium-based aerosol ventilation and perfusion magnetic resonance imaging.

Suga K, Ogasawara N, Okada M, et al. Regional lung functional impairment in acute airway obstruction and pulmonary embolic dog models assessed with gadolinium-based aerosol ventilation and perfusion magnetic resonance imaging. Invest Radiol 2002;37:281–291. rationale and objectives. Gadolinium diethylenetriaminepentaacetic acid (Gd-DTPA)-based aerosol ventilation and perfusion magnetic resonance (MR) images were used to define regional functional impairment in acute airway obstruction (AO) and pulmonary embolic (PE) dog models. methods. The aerosol study was performed in 10 anesthetized normal dogs in a supine position during 20-minute spontaneous inhalation of an aerosol of 100- or 200-mmol-Gd/L Gd-DTPA solute produced by an ultrasonic nebulizer in an open-circuit delivery system, combined with a dynamic perfusion study after a 3-second intravenous bolus injection of a 0.1 mmol/kg dose of Gd-DTPA. These MR studies were also performed in the same 10 dogs approximately 30 minutes after obstructing the segmental (n = 6) or lobar (n = 4) bronchus with a balloon catheter, and in another six dogs after segmental (n = 6) and lobar (n = 4) pulmonary arterial embolization with enbucrilate. Regional lung enhancement was assessed on time-signal intensity (SI)-curves and ventilation- and perfusion-weighted images produced by a subtraction technique. results. The normal lungs were gradually and gravity-dependently enhanced with time after Gd-DTPA aerosol inhalation regardless of the respiratory SI changes, except for three animals with the fastest breathing rate. The averaged maximal relative lung SI increase against the baseline in the successful animals was significantly greater in the slowly and deeply breathing animals than in the fast and shallow breathing animals, regardless of the difference in Gd-concentration (100 mmol Gd/L: 153.3% ± 69.7% vs. 54.2% ± 23%;P < 0.001; and 200 mmol Gd/L: 189.7% ± 68.0% vs. 75.6% ± 42.2%;P < 0.0001, respectively). There was an additional enhancement of 382% ± 101 in the ventral lung and 722% ± 160 in the dorsal lung on the pulmonary arterial phase perfusion image even in the slowly and deeply breathing animals who inhaled 200-mmol-Gd/L aerosol, and the enhancement effect was significantly greater compared with that with the aerosol (P < 0.0001). The ventilation- and perfusion-weighted images clearly defined the regionally matched perfusion-ventilation deficits in all the AO models, and the regionally mismatched perfusion-ventilation in all the PE models. conclusion. Gd-based aerosol can provide efficient lung enhancement in spontaneously and adequately breathing animals, using a relatively noninvasive aerosol delivery system. The combined use of Gd-based perfusion MR imaging may be acceptable for defining regionally impaired function associated with acute AO and PE.

Correlation between diffusion in lumbar intervertebral disks and lumbar artery status: evaluation with fresh blood imaging technique.

To evaluate the correlation of the lumbar artery status with the diffusion values in lumbar vertebral disks in patients with low back problems using a fresh blood imaging (FBI) technique.

Added value of lung perfused blood volume images using dual-energy CT for assessment of acute pulmonary embolism

PURPOSE To investigate the added value of lung perfused blood volume (LPBV) using dual-energy CT for the evaluation of intrapulmonary clot (IPC) in patients suspected of having acute pulmonary embolism (PE). MATERIALS AND METHODS Institutional review board approval was obtained for this retrospective study. Eighty-three patients suspected of having PE who underwent CT pulmonary angiography (CTPA) using a dual-energy technique were enrolled in this study. Two radiologists who were blinded retrospectively and independently reviewed CTPA images alone and the combined images with color-coded LPBV over a 4-week interval, and two separate sessions were performed with a one-month interval. Inter- and intraobserver variability and diagnostic accuracy were evaluated for each reviewer with receiver operating characteristic (ROC) curve analysis. RESULTS Values for inter- and intraobserver agreement, respectively, were better for CTPA combined with LPBV (ICC=0.847 and 0.937) than CTPA alone (ICC=0.748 and 0.861). For both readers, diagnostic accuracy (area under the ROC curve [Az]) were also superior, when CTPA alone (Az=0.888 [reader 1] and 0.912 [reader 2]) was compared with that after the combination with LPBV images (Az=0.966 [reader 1] and 0.959 [reader 2]) (p<0.001). However, Az values of both images might not have significant difference in statistics, because Az value of CTPA alone was high and 95% confidence intervals overlapped in both images. CONCLUSION Addition of dual-energy perfusion CT to CTPA improves detection of peripheral IPCs with better interobserver agreement.

Assessment of lung perfusion impairment in patients with pulmonary artery‐occlusive and chronic obstructive pulmonary diseases with noncontrast electrocardiogram‐gated fast‐spin‐echo perfusion MR imaging

To evaluate the ability of noncontrast electrocardiogram (ECG)‐gated fast‐spin‐echo (FSE) perfusion MR images for defining regional lung perfusion impairment, as compared with technetium (Tc)‐99m macroaggregated albumin (MAA) single‐photon emission computed tomography (SPECT) images.

Visualization of normal and interrupted lymphatic drainage in dog legs with interstitial MR lymphography using an extracellular MR contrast agent, gadopentetate dimeglumine.

PurposeThe capability of the interstitial magnetic resonance lymphography (MR-LG) using a widely available extracellular contrast agent, gadopentetate dimeglumine, for the visualization of normal and interrupted lymphatic drainage was tested in dog legs. Materials and methodsWith a 7-day interval, 1 mL and 2 mL undiluted gadopentetate dimeglumine were injected intradermally into the dorsal foot of both hind legs of 12 dogs. T1-weighted 3-dimensional (3D) spoiled gradient-echo (repetition time/echo time = 6.7/1.6 ms) and maximum intensity projection (MIP) images covering the legs and pelvic region were acquired at 1.5 T for 10 minutes after 30 seconds gentle massage at the injection sites. These dogs also underwent the MR-LG with 2 mL of this contrast agent 7 days after surgical ligation of the popliteal lymphatic vessels. ResultsIn the normal dogs, the interstitial MR-LG quickly and consistently visualized the direct connection of the lymphatic vessels and lymph nodes draining from the injection sites up to the inguinal region, without any late adverse effects. The enhancement effect was significantly greater with a 2-mL dose than with a 1-mL dose. After lymphatic obstruction, the MR-LG clearly revealed the anatomic compromises of the lymphatics, such as poor enhancement of the affected lymphatic vessels and lymph nodes, collateral lymphatic vessels, abnormal soft-tissue enhancement, and delayed lymphatic migration of the contrast agent. The topographic 3D images provided a comprehensive anatomy of these normal and compromised lymphatic drainage. ConclusionAlthough gadopentetate dimeglumine is not lymphotropic, the interstitial MR-LG using this T1-contrast agent appears to have potential for quick and sufficient mapping of the lymphatic drainage from the injection sites and for the characterization of interrupted lymph flow.

Potential of magnetic resonance lymphography with intrapulmonary injection of gadopentetate dimeglumine for visualization of the pulmonary lymphatic basin in dogs: preliminary results.

Purpose:To evaluate a new approach of magnetic resonance (MR) lymphography with intraalveolar injection of a conventional extracellular contrast agent (gadopentetate dimeglumine) for imaging lymphatic basin draining from specific portions of the lung. Methods:Three-dimensional T1-weighted spoiled gradient-recalled echo MR sequence images were acquired serially before and for 40 minutes after intraalveolar injection of gadopentetate dimeglumine in a total of 14 anesthetized beagle dogs. Six of these dogs received 1 mL undiluted and low-concentration (75%) contrast agent into the same portion of the right caudal lobe during a 7-day interval. In all dogs, including these 6 dogs, MR lymphography was repeated with injection of the low-concentration contrast agent into different lung regions at 7-day intervals to evaluate the differences of the visualized draining lymphatic station. Lymphatic enhancement was quantified by percent increases of signal intensity against precontrast. Postmortem examination of the lymphatic anatomy was performed in 7 of these animals. Results:In all dogs, the lymphatic station draining from the injection sites was visualized within 5 minutes after contrast injection. The maximum percent increase of signal intensity of the same middle tracheobronchial lymph nodes was significantly greater with a low-concentration (75%) contrast agent than with an undiluted one in the same 6 dogs (n = 6, 247.6 ± 30.5% vs. 204.2 ± 33.8%; P < 0.01). Different lymphatic stations draining from the different injection sites were visualized in all dogs. In a total of 12 MR studies that showed extended nodal enhancement after injection of the low-concentration contrast agent, the enhancement peak of the most proximal nodes (n = 12) from the injection sites appeared earlier than that of their distant nodes (n = 12), with a maximum percent increase of signal intensity of 249.8 ± 42.4%. The visualized lymph nodes were found in the appropriate locations postmortem, with significant correlation for nodal sizes (r = 0.965; P < 0.0001). Conclusion:MR lymphography with low-concentration gadopentetate dimeglumine can quickly and sufficiently visualize the drainage lymphatic station from specific lung portions, and may have the potential of sentinel node mapping in lung cancer.

Volumetric evaluation of dual-energy perfusion CT for the assessment of intrapulmonary clot burden

AIM To evaluate the volumetric values of intrapulmonary clots (IPCs) using 64-section dual-energy perfusion computed tomography (DEpCT). MATERIALS AND METHODS A total of 174 patients suspected of having acute pulmonary embolism (PE) underwent DEpCT, and acute PE was diagnosed in 48 of these patients. DEpCT images were three-dimensionally reconstructed with four threshold ranges: 1-120 HU (V₁₂₀), 1-15 HU (V₁₅), 1-10 HU (V₁₀), and 1-5 HU (V₅). Each relative value per V₁₂₀ was expressed as %V₁₅, %V₁₀ and %V₅. These values were compared with the d-dimer, pulmonary arterial (PA) pressure, right ventricular (RV) diameter, RV/left ventricular diameter ratio, PA diameter, and CT angiographic obstruction index (CTOI). RESULTS In patients with IPCs, PA pressure, d-dimer and volumetric values of DEpCT were significantly higher (p < 0.001). Relative volumetric values at DEpCT had better correlations with the PA pressure, PA diameter, and CTOI than absolute ones, and %V₅ especially had good correlations with PA pressure (r = 0.44, p = 0.02), PA diameter (r = 0.40, p = 0.005), and CTOI (r = 0.38, p = 0.009). CONCLUSION The relative volumetric evaluation of DEpCT images with a lower attenuation threshold range may be helpful for assessing right heart strain, because these values had good correlation with CTOI, pulmonary pressure, and diameter in suggesting right heart load.

Coronary vasodilation by the use of sublingual nitroglycerin using 64-slice dual-source coronary computed tomography angiography

BACKGROUND Sublingual nitroglycerin capsules or spray is routinely used to treat anginal attacks and to maximally dilate the epicardial coronary arteries during coronary angiography. These dilated coronary vessels have an advantage, but increased heart rates were disadvantageous for coronary computed tomography angiography (CTA). PURPOSE The influence of applying nitroglycerin was analyzed regarding the coronary diameter, coronary luminal attenuation, evaluable number of coronary segments, heart rate (HR), HR variability, the optimal reconstruction phase, and image scoring of CTA in the same patients using a 64-slice dual-source CT. METHODS AND SUBJECTS Fifty-two patients with atypical chest pain underwent coronary CTA before and after the administration of sublingual nitroglycerin without heart rate control. The coronary diameter and luminal attenuation were measured on short-axial images in each coronary segment. The coronary vasodilation ratios (VRs) were calculated from the coronary diameters at the same location before and after the use of nitroglycerin. The local institutional review board approved this study and written informed consent was obtained from all the patients. RESULTS No significant differences were noted in the HR variability or optimal reconstruction phase, despite an increase in HR after the use of nitroglycerin. Nitroglycerin significantly enlarged the coronary artery diameter, and VRs of each coronary segment ranged from 7.54% to 22.26%. As compared with baseline coronary diameter, VRs of minor segments (16.91%) were significantly larger than those of major segments (11.35%), and the magnitude of VR correlated with the baseline coronary diameter (r=-0.48, p<0.001). Coronary luminal attenuation significantly increased due to additional administration of contrast material after the use of nitroglycerin (p<0.01), but no significant difference was noted in the image quality after the use of nitroglycerin. CONCLUSION Sublingual nitroglycerin significantly enlarged the coronary diameters, especially in peripheral small coronary arteries, and increased the evaluable number of coronary segments on coronary CTA.

Superselective Intra-arterial Chemotherapy for Advanced Maxillary Sinus Cancer: An Evaluation of Arterial Perfusion With Computed Tomographic Arteriography and of Tumor Response

Objective: The purpose of our study was to elucidate the relationship between arterial perfusion in advanced maxillary sinus cancer which was opacified by superselective intra-arterial computed tomographic arteriography (IA-CTA) and the tumor response to intra-arterial chemotherapy. Methods: Superselective IA-CTA was performed to identify the feeding arteries and their perfusion in advanced maxillary sinus cancer in 10 patients. Cisplatin was selectively infused into these feeding arteries, except for the internal carotid artery. Results: The results were assessed in 9 of the 10 patients, and a complete response was achieved in 5 patients in whom either the entire tumor, or most of the tumor, was perfused by the branches of the external carotid artery. In 4 patients with a partial response, the residual tumors were seen in the territory of the perfusion defect or in the perfusion territory of the internal carotid artery. Conclusion: Superselective IA-CTA is a useful technique to correctly identify the intratumoral perfusion and to predict tumor response to the intra-arterial chemotherapy of advanced maxillary sinus cancer.