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H Hatabu

Publications and source records attributed to H Hatabu.

At least 37 records · Page 2Linked to original sources
PubMed2000

Novel techniques for MR imaging of pulmonary airspaces.

Hyperpolarized gas- and molecular oxygen-enhanced MR imaging are two new techniques for high-resolution MR imaging of pulmonary airspaces. Both techniques produce excellent images in a safe, reproducible, and technically feasible manner. Because morphologic and functional information is obtained, and radiation is not used, these techniques may prove ideal for serially evaluating patients with a variety of lung diseases that affect pulmonary ventilation, such as cystic fibrosis, emphysema, asthma, or bronchiolitis obliterans syndrome in lung transplant recipients. At present, the greatest clinical experience is with hyperpolarized He-3-enhanced MR imaging. This technique is limited, however, by the limited availability of He-3, by its polarization requirements, and by the need to tune the MR system to the resonant frequency of the gas. There is less clinical experience with oxygen-enhanced MR imaging. Although this technique produces images with more inherent noise than hyperpolarized He-3 imaging, this problem can be overcome by signal averaging. Oxygen-enhanced imaging has the major advantages of lower cost and ready availability. For oxygen-enhanced imaging, the MR imaging system does not need to be readjusted; imaging is performed at the conventional hydrogen proton frequency.

Animals↗
PubMed1999

Demonstration of gravity-dependent lung perfusion with contrast-enhanced magnetic resonance imaging.

Imaging of lung perfusion using contrast-enhanced dynamic magnetic resonance (MR) was performed in both the supine and prone positions in six volunteers. Regions of interest (ROIs) were chosen in the dependent and non-dependent portions of the right lung. The percentage increase in signal intensity (SI) and the mean slope were calculated. In the supine position, the dorsal ROI had a greater increase in SI (236.0% vs. 156.9%, P < 0.05) and a faster rise in the slope of enhancement (55.1%/sec vs. 30.1%/sec, P < 0.05) than the ventral ROI. After changing to the prone position, higher peak enhancement (234.3% vs. 177.4%, P < 0.05) and faster slopes (59.6%/sec vs. 35.3%/sec, P < 0.05) shifted to the anterior ROI. We conclude that dynamic contrast-enhanced MR imaging is sensitive to demonstrate gravitationally dependent differences in lung perfusion.

Adult↗
PubMed1999

Oxygen-enhanced magnetic resonance ventilation imaging of the human lung at 0.2 and 1.5 T.

Lung ventilation imaging using inhaled oxygen as a contrast medium was performed using both a 0.2 and a 1.5 T clinical magnetic resonance (MR) scanner in eight volunteers. Signal-to-noise-ratios (SNRs) of the ventilation images as well as T1 values of the lung acquired with inhalation of 100% oxygen and room air were calculated. The SNR was 9.7 +/- 3.0 on the 0.2 T MR system and 69.5 +/- 28.8 on the 1.5 T system (P < 0.001). The mean T1 value on the 0.2 T MR system with subjects breathing room air was 632 +/- 54 msec; with 100% oxygen, it was 586 +/- 41 msec (P < 0.01). At 1.5 T, the mean values were 904 +/- 99 msec and 790 +/- 114 msec, respectively (P < 0.0001). We conclude that MR oxygen-enhanced ventilation imaging of the lung is feasible with an open configured 0.2 T MR system.

Adult↗
PubMed1999

Quantitative assessment of pulmonary perfusion with dynamic contrast-enhanced MRI.

The feasibility of qualitative assessment of pulmonary perfusion using dynamic contrast enhanced MRI with ultra-short TE has recently been demonstrated. In the current study, quantitative analysis was attempted based on the indicator dilution principle using a pig model of pulmonary embolism. The results were compared with the absolute pulmonary perfusion obtained with colored microspheres. The inverse of apparent mean transit time (1/tau(app)), distribution volume (V), and V/tau(app) were correlated well with the absolute lung perfusion. This study demonstrates that MR has the potential to evaluate pulmonary perfusion quantitatively. Magn Reson Med 42:1033-1038, 1999.

Adult↗
PubMed1999

Magnetic resonance imaging of the thorax. Past, present, and future.

Magnetic resonance is a valuable modality of extreme flexibility for specific problem-solving capability in the thorax. This article reviews MR applications in the imaging of great vessels, which are currently the most important applications in the thorax; other established applications in the thorax; and pulmonary functional MR imaging.

Aortic Diseases↗
PubMed1999

MR imaging of pulmonary parenchyma with a half-Fourier single-shot turbo spin-echo (HASTE) sequence.

OBJECTIVE: To evaluate the utility of a half-Fourier single-shot turbo spin-echo sequence (HASTE) at depicting lung parenchyma and lung pathology. METHODS AND PATIENTS: A HASTE sequence was applied to five normal volunteers and 20 patients with various pulmonary disorders to depict the lung parenchyma. Images were acquired with ECG-triggering and breath-holding. In three volunteers, signal intensity measurements from lung parenchyma were performed using four sequences: (a) HASTE; (b) conventional spin echo; (c) fast spin echo; and (d) gradient echo. T2 maps were produced using the HASTE acquisition. RESULTS: Minimal respiratory or cardiac motion artifacts were observed. The signal-to-noise ratios from lung parenchyma were 27.8 +/- 5.4, 22.0 +/- 3.0, 15.3 +/- 0.9, and 6.0 +/- 1.9 for HASTE, spin-echo, fast spin-echo, and gradient echo sequences, respectively. The scan time for HASTE was 302 ms for each slice. The T2 values in the right lung and the left lung were 61.2 +/- 4.1 and 79.1 +/- 8.9 ms in systole and 92.6 +/- 5.8 and 97.5 +/- 12.2 ms in diastole, respectively (P < 0.05 diastole versus systole). The HASTE sequence demonstrated clearly various pulmonary disorders, including lung cancer, hilar lymphadenopathy, metastatic pulmonary nodules as small as 3 mm, pulmonary hemorrhage, pulmonary edema and bronchial wall thickening in bronchiectasis. CONCLUSION: Our preliminary results indicate that the HASTE sequence provides a practical means for breath-hold MR imaging of lung parenchyma.

Adult↗
PubMed1999

T2* and proton density measurement of normal human lung parenchyma using submillisecond echo time gradient echo magnetic resonance imaging.

OBJECTIVE: To obtain T2* and proton density measurements of normal human lung parenchyma in vivo using submillisecond echo time (TE) gradient echo (GRE) magnetic resonance (MR) imaging. MATERIALS AND METHODS: Six normal volunteers were scanned using a 1.5-T system equipped with a prototype enhanced gradient (GE Signa, Waukausha, WI). Images were obtained during breath-holding with acquisition times of 7-16 s. Multiple TEs ranging from 0.7 to 2.5 ms were tested. Linear regression was performed on the logarithmic plots of signal intensity versus TE, yielding measurements of T2* and proton density relative to chest wall muscle. Measurements in supine and prone position were compared, and effects of the level of lung inflation on lung signal were also evaluated. RESULTS: The signal from the lung parenchyma diminished exponentially with prolongation of TE. The measured T2* in six normal volunteers ranged from 0.89 to 2.18 ms (1.43 +/- 0.41 ms, mean +/- S.D.). The measured relative proton density values ranged between 0.21 and 0.45 (0.29 +/- 0.08, mean +/- S.D.). Calculated T2* values of 1.46 +/- 0.50, 1.01 +/- 0.29 and 1.52 +/- 0.18 ms, and calculated relative proton densities of 0.20 +/- 0.03, 0.32 +/- 0.13 and 0.35 +/- 0.10 were obtained from the anterior, middle and posterior portions of the supine right lung, respectively. The anterior-posterior proton density gradient was reversed in the prone position. There was a pronounced increase in signal from lung parenchyma at maximum expiration compared with maximum inspiration. The ultrashort TE GRE technique yielded images demonstrating signal from lung parenchyma with minimal motion-induced noise. CONCLUSION: Quantitative in vivo measurements of lung T2* and relative proton density in conjunction with high-signal parenchymal images can be obtained using a set of very rapid breath-hold images with a recently developed ultrashort TE GRE sequence.

Artifacts↗
PubMed1999

Fast magnetic resonance imaging techniques.

This article reviews fast magnetic resonance (MR) techniques currently used for body imaging. Improvements in gradient performance have made very short repetition and echo times on clinical scanners feasible, thus enabling subsecond image acquisition. The article provides a fundamental overview of the technical aspects from the concept of k-space and k-space segmentation technique, fast MR imaging techniques including fast spin echo, fast gradient echo with or without magnetization preparation to echo planar and hybrid techniques. The article also addresses the use of different fat suppression techniques in MR imaging of the body and improvements in coil technology to obtain faster images and higher signal-to-noise.

Echo-Planar Imaging↗
PubMed1999

Fast magnetic resonance imaging of the lung.

The impact of fast MR techniques developed for MR imaging of the lung will soon be recognized as equivalent to the high-resolution technique in chest CT imaging. In this article, the difficulties in MR imaging posed by lung morphology and its physiological motion are briefly introduced. Then, fast MR imaging techniques to overcome the problems of lung imaging and recent applications of the fast MR techniques including pulmonary perfusion and ventilation imaging are discussed. Fast MR imaging opens a new exciting window to multi-functional MR imaging of the lung. We believe that fast MR functional imaging will play an important role in the assessment of pulmonary function and disease process.

Humans↗
PubMed1999

Magnetic resonance T2* measurements of the normal human lung in vivo with ultra-short echo times.

The objective of this study was to measure T2* values of the normal human lung in vivo during breathhold using a rapid gradient-echo sequence with ultra-short echo times (TE). A sagittal slice of the right lung was imaged in six volunteers with various TE ranging from 0.5 ms to 5 ms using a clinical 1.5 Tesla MR scanner. T2* values were calculated in a region of interest in the dependent and non-dependent lung. In the dependent lung, T2* values of 1.1 ms+/-0.15 ms were measured, and in the non-dependent lung, 0.86 ms+/-0.11 (p < 0.01). T2* measurements of the normal human lung during breathhold are feasible with a clinical MR unit. The short T2* values require the use of very short TE times (< 2.5 ms) in gradient-echo sequences to obtain adequate signal intensity from lung tissue.

Adult↗
PubMed1999

Rapid progression of pituitary hyperplasia in humans with primary hypothyroidism: demonstration with MR imaging.

PURPOSE: To use magnetic resonance (MR) imaging to evaluate the morphologic changes of the pituitary gland during the development of hypothyroidism. MATERIALS AND METHODS: Fourteen patients who had undergone thyroidectomy were evaluated before radioactive iodine 131 therapy. In each patient, MR imaging and measurement of serum hormone levels were performed twice: 5 weeks before 131I treatment as the "euthyroid state" with thyroid hormone supplementation and on the day of 131I treatment as the "hypothyroid state" after a 3-week depletion of thyroid hormone supplements. Nine healthy volunteers also underwent MR imaging twice at an interval of 5 weeks. Pituitary volume and the relative signal intensity ratio of the anterior pituitary to the pons were measured. The shape and signal intensity of the pituitary gland were also visually assessed. The paired Student t test was used to evaluate the significance of the data. A P value less than .05 indicated a statistically significant difference. RESULTS: The patients had significantly larger pituitary volume in the hypothyroid state than in the euthyroid state both quantitatively (P < .001) and visually. No significant differences were found in the relative signal intensity ratios of the anterior pituitary to the pons. In healthy volunteers, no significant differences in pituitary volumes or signal intensity were found between the two MR images. CONCLUSION: Rapid progression of hyperplasia of the anterior pituitary may occur with acute development of hypothyroidism.

Adult↗
PubMed1999

Pulmonary disorders: ventilation-perfusion MR imaging with animal models.

PURPOSE: To demonstrate the capability of magnetic resonance (MR) imaging to assess alteration in regional pulmonary ventilation and perfusion with animal models of airway obstruction and pulmonary embolism. MATERIALS AND METHODS: Airway obstruction was created by inflating a 5-F balloon catheter into a secondary bronchus. Pulmonary emboli were created by injecting thrombi into the inferior vena cava. Regional pulmonary ventilation was assessed with 100% oxygen as a T1 contrast agent. Regional pulmonary perfusion was assessed with a two-dimensional fast low-angle shot, or FLASH, sequence with short repetition and echo times after intravenous administration of gadopentetate dimeglumine. RESULTS: Matched ventilation and perfusion abnormalities were identified in all animals with airway obstruction. MR perfusion defects without ventilation abnormalities were seen in all animals with pulmonary emboli. CONCLUSION: Ventilation and perfusion MR imaging are able to provide regional pulmonary functional information with high spatial and temporal resolution. The ability of MR imaging to assess both the magnitude and regional distribution of pulmonary functional impairment could have an important effect on the evaluation of lung disease.

Airway Obstruction↗
PubMed1999

Ventilation-perfusion MR imaging of the lung.

The assessment of regional ventilation in human lungs is important for the diagnosis and evaluation of a variety of pulmonary disorders, including pulmonary emphysema, diffuse lung disease (e.g., sarcoidosis, and pulmonary fibrosis), lung cancer, and pulmonary embolism. This article introduces new MR imaging techniques of pulmonary ventilation and perfusion that will provide a framework for assessing regional pulmonary functions of the lung.

Adult↗
PubMed1998

Oxygen enhanced MR ventilation imaging of the lung.

The current work is a continuation of a new MRI technique that was proposed for the non-invasive assessment of regional lung ventilation using inhaled molecular oxygen as a T1 contrast agent. Several improvements of this technique are described in this work. The signal-to-noise ratio in the ventilation-scan images was optimized using a centrically reordered single-shot RARE sequence with a short effective echo time and short inter-echo spacing. The contrast-to-noise ratio was improved using an optimized inversion delay time. The optimized MR-ventilation-scan was successfully performed in healthy volunteers and in an animal model with airway obstruction. The experimental results demonstrate the feasibility and clinical potential of the MR ventilation imaging technique for assessment of regional pulmonary function.

Airway Obstruction↗