Search PubMed⌕ Search

Biomedical subjects

H Hatabu

Publications and source records attributed to H Hatabu.

At least 55 records · Page 3Linked to original sources
PubMed1997

MR pulmonary angiography and perfusion imaging: recent advances.

Recent advances in MR pulmonary angiography and MR perfusion imaging are reviewed, focusing on two principal areas of technical development: (1) the availability of MR scanners equipped with enhanced gradient systems; and (2) new trends in MR angiography using gadolinium contrast agents or labeling of blood with an inversion recovery radiofrequency pulse in place of the more traditional methods using naturally flowing spins as the source of intravascular signal. These recent developments in MR have significant potential for clinical imaging of the pulmonary vasculature, particularly for the diagnosis of pulmonary embolism, and are now opening windows to functional MR imaging of the lung.

Animals↗
PubMed1997

Accuracy of bedside chest hard-copy screen-film versus hard- and soft-copy computed radiographs in a medical intensive care unit: receiver operating characteristic analysis.

PURPOSE: To compare the clinical diagnostic accuracy of hard-copy readings of screen-film bedside chest radiographs and both hard- and soft-copy readings of bedside chest computed radiographs obtained in a medical intensive care unit. MATERIALS AND METHODS: Two samples of 95 cases were assembled from chest images obtained in 541 patients with either screen-film radiography or computed radiography. The cases were stratified according to the clinical problem for which the examination was ordered; the corresponding diagnosis was verified by a panel of two or three radiologists. Four radiologists blindly read the hard-copy images obtained with screen-film or computed radiography. Six months later, the radiologists read the computed radiographs by using an 8-bit, 1,684 x 2,048-pixel display. The data were analyzed by using multireader-multicase receiver operating characteristic (ROC) analysis of variance. RESULTS: No statistically significant differences in the area under the ROC curve were found between any of the methods. CONCLUSION: The results provide some justification for using bedside chest computed radiography and for reading soft-copy images from a high-quality display.

Female↗
PubMed1996

Pulmonary perfusion: qualitative assessment with dynamic contrast-enhanced MRI using ultra-short TE and inversion recovery turbo FLASH.

The accurate assessment of pulmonary perfusion is especially important in the evaluation of patients with suspected pulmonary embolism, a common and potentially lethal disorder that can be treated by aggressive anticoagulation. In this study, we demonstrate for the first time the use of MR to image pulmonary perfusion in humans by using dynamic imaging after contrast administration. The technique, which uses an inversion recovery turbo FLASH sequence with ultrashort TE (1.4 ms) and 1-s temporal resolution, was tested in a series of eight healthy subjects and in a porcine model of pulmonary embolism. After the administration of gadopentetate dimeglumine in humans and animal models, there was serial enhancement of the systemic veins, right atrium, right ventricle, and pulmonary arteries. The pulmonary arterial tree was visualized beyond the segmental branches, followed by a gradual diffuse increase in signal intensity of the lung parenchyma over a period of 4.0-7.0 s. Pulmonary circulation times ranged from 3.0-3.4 s. Whereas a high dose (20 or 40 ml) of contrast agent tended to produce the most intense parenchymal enhancement, a low dose (5 ml) was best for showing recirculation. In the animal model, a perfusion defect due to a pulmonary embolus was clearly shown and confirmed by cine angiography. It is concluded that MRI of lung perfusion is feasible. With further development, perfusion MRI could eventually have a significant clinical role in the diagnostic evaluation of pulmonary embolism.

Animals↗
PubMed1996

Pulmonary MR angiography.

Recent technical improvements have made pulmonary MR angiography (MRA) feasible. The technique is attractive because it is noninvasive, provides a full three-dimensional (3D) display of the pulmonary vasculature, and potentially can be combined with MR venography of the lower extremities and pelvis for the comprehensive diagnosis of thromboembolism. Approaches to acquiring pulmonary MR angiograms are currently being developed and include both two-dimensional and 3D time-of-flight methods, breath-hold and non-breath-hold techniques, and the use of gadolinium-based contrast enhancement. The results of initial studies using pulmonary MRA for the detection of pulmonary embolism are encouraging, but they must be evaluated in conjunction with newly developed fast CT scanning techniques. This article reviews the state of development of pulmonary MRA, the current clinical applications of the technique, and the prospects for future development.

Humans↗
PubMed1996

Noninvasive assessment of regional ventilation in the human lung using oxygen-enhanced magnetic resonance imaging.

The imaging of regional ventilation in the lungs is essential for the evaluation of a variety of pathological conditions, such as emphysema, pneumonia and pulmonary embolism. We propose a novel approach for ventilation scanning, using magnetic resonance imaging (MRI) and inhaled molecular oxygen as a contrast agent, that directly depicts transfer of oxygen across the alveolus into the pulmonary vasculature. Molecular oxygen is only weakly paramagnetic but produces substantial signal changes in the lungs because of their large surface area. Ventilation defects were shown in a patient with bullous emphysema, and ventilation-perfusion mismatches were shown in two patients with pulmonary embolism.

Humans↗
PubMed1996

Liver masses: replacement of conventional T2-weighted spin-echo MR imaging with breath-hold MR imaging.

PURPOSE: To evaluate breath-hold magnetic resonance (MR) imaging with single-shot and multishot T2-weighted fast spin-echo (SE) and inversion-recovery (IR) SE echo-planar (EP) SE (IR-SE-EP) sequences compared with conventional T2-weighted SE imaging for detection of liver masses. MATERIALS AND METHODS: Imaging with all sequences was performed in 32 patients on a 1.5-T whole-body system. Images were compared on the basis of lesion-to-liver contrast-to-noise ratio (C/N), lesion conspicuity, and image quality. Image analysis was performed by two experienced radiologists in consensus. RESULTS: Lesion-to-liver C/Ns were highest on fat-suppressed-half-Fourier-single-shot-fast-SE images. For solid lesions, the lesion-to-liver C/Ns were highest with IR-fast-SE, which was significantly better (P < .05) than IR-SE-EP and conventional SE techniques and also produced the best image quality. Sensitivity with IR-fast-SE was 96%; with fat-suppressed-half-Fourier-single-shot-fast-SE, 92%; with fat-suppressed-fast-SE, 89%; with IR-SE-EP, 83%; and with conventional SE, 78%. CONCLUSION: T2-weighted breath-hold imaging, particularly IR-fast-SE imaging, was more sensitive for hepatic masses than conventional SE imaging, with a substantial reduction in acquisition time. Half-Fourier-single-shot-fast-SE imaging was especially useful in patients who were unable to hold their breath.

Adult↗
PubMed1996

Fetal anatomy revealed with fast MR sequences.

Although all the imaging studies in this pictorial essay were done for maternal rather than fetal indications, fetal anatomy was well visualized. However, when scans are undertaken for fetal indications, fetal motion in between scout views and imaging sequences may make specific image planes difficult to obtain. Of the different techniques described in this review, we preferred the HASTE technique and use it almost exclusively for scanning pregnant patients. The T2-weighting is ideal for delineating fetal organs. Also, the HASTE technique allows images to be obtained in 430 msec, limiting artifacts arising from maternal and fetal motion. MR imaging should play a more important role in evaluating equivocal sonographic cases as fast scanning techniques are more widely used. Obstetric MR imaging no longer will be limited by fetal motion artifacts. When complex anatomy requires definition in a complicated pregnant patient, MR imaging should be considered as a useful adjunct to sonography.

Female↗
PubMed1995

Multi-slice, breathhold imaging of the lung with submillisecond echo times.

The signal from the lungs is heavily attenuated by T2 and T2 decay in standard MR images of the thorax. The authors utilized the capabilities of a prototype fast gradient system to develop a multi-slice gradient echo sequence that can obtain images with an echo time of 0.7 ms. Images acquired in a single breath-hold are free from respiratory motion artifacts and clearly display signal from lung parenchyma. The use of fast gradients makes short echo times possible without the use of nonstandard RF pulses and spatial encoding techniques and their associated limitations.

Artifacts↗
PubMed1995

Carotid artery invasion by head and neck masses: prediction with MR imaging.

PURPOSE: To determine the value of magnetic resonance (MR) imaging in predicting resectability of head and neck neoplasms around the carotid arteries. MATERIALS AND METHODS: Forty-nine patients (28 male patients and 21 female patients aged 17-79 years; mean, 57.3 years) with head and neck masses and clinical evidence of carotid wall invasion underwent MR imaging. T1-weighted, T2-weighted, and gadolinium-enhanced T1-weighted images were analyzed to determine circumferential involvement of 53 arteries by tumor. RESULTS: More than 270 degrees of circumferential involvement was considered suggestive of unresectability of the malignant neoplasm; 270 degrees or less was considered lack of invasion. The sensitivity of MR imaging for determination of unresectable disease was 100% (12 of 12 cases), specificity was 88% (36 of 41), and accuracy was 91% (48 of 53). Accuracy was 100% for squamous cell carcinoma (n = 29). CONCLUSION: Tumor that encompasses more than 270 degrees of the carotid artery probably cannot be removed from the artery. Tumor that involves 270 degrees or less of the artery can be removed.

Adolescent↗
PubMed1995

Pulmonary thromboembolism: recent developments in diagnosis with CT and MR imaging.

Recent technical advances in computed tomography (CT; helical and electron beam) and magnetic resonance (MR) imaging have spurred a renewed interest in these modalities for the diagnosis of acute and chronic pulmonary embolism (PE). These techniques can enable accurate clot detection down to segmental pulmonary arteries, with CT currently allowing more accuracy than that with MR imaging. Ongoing technical advances, particularly in MR angiography, will likely increase diagnostic accuracy. Inability to reliably detect subsegmental acute emboli may not prove to be a clinically significant limitation if lung imaging is coupled with evaluation for deep venous thrombosis. MR imaging can potentially accomplish this within a single examination. Incorporation of CT and MR imaging into diagnostic algorithms for suspected PE can be cost-effective. Evaluation of these new modalities should be based on patient outcome, not solely on clot detectability. Well-designed clinical trials are warranted before CT and MR imaging can be used routinely in the diagnosis of acute PE.

Acute Disease↗
PubMed1994

Scintigraphic findings of the thyroid in hypothyroid patients with blocking-type TSH-receptor antibodies.

The present study was designed to analyse the scintigraphic appearance of the thyroid in hypothyroid patients with blocking-type TSH receptor antibodies (TRAbs). Eleven hypothyroid patients with autoimmune thyroiditis positive for TSH binding inhibitor immunoglobulins (TBII) [80% +/- 12 (SD)%; normal < 11%] and for thyroid stimulation-blocking antibodies (TSBAbs) (90% +/- 9%: normal < 32%) were studied. Thyroid scanning was performed using technetium-99m or iodine-123, when the patients were hypothyroid. Analysis of the scan images revealed the presence of localized functioning areas in six patients (group 1), and no visualization of the thyroid in the remaining five patients (group 2). Patients in group 1 showed significantly higher uptake of 99mTc than those in group 2 (P < 0.05). Interestingly, three patients in group 1 were positive for thyroid-stimulating antibodies (TSAbs) (249% +/- 17%; normal < 145%), which were not detected in the remaining eight patients. Antibodies against thyroglobulin and microsomal antigens were detected in nine nine (81.8%) and 11 (100%) patients, respectively, but neither of these titres correlated with the scan image. Three patients in group 1 underwent scintigraphy again after treatment with thyroxine, at which time the functioning lesion was not noted. Fourteen hypothyroid patients with negative TBII displayed no such scintigraphic findings. Chronic stimulation of the thyroid by TSAbs and/or TSH might be responsible for the presence of the functioning lesion, but clarification of the mechanism requires further studies. In summary (1) TSAbs were detected in three (27.3%) of 11 hypothyroid patients with blocking TRAbs; (2) thyroid scintigraphy revealed the presence of localized functioning area(s) in approximately half of these cases.

Adolescent↗
PubMed1994

MR imaging with spatial modulation of magnetization in the evaluation of chronic central pulmonary thromboemboli.

PURPOSE: To assess the diagnostic value of magnetic resonance (MR) imaging with SPAMM (spatial modulation of magnetization) in the identification of chronic central pulmonary thromboemboli. MATERIALS AND METHODS: Twelve patients with pulmonary hypertension and five healthy volunteers were prospectively studied with a 1.5-T MR imaging system. The SPAMM technique was integrated into a conventional cardiac-synchronized spin-echo (SE) sequence. Six of the 12 patients had central thromboemboli. RESULTS: In the healthy subjects, intravascular stripes in the central pulmonary arteries disappeared as a result of flow within 100 msec after the R wave. Areas of persistent stripes were identified in seven of eight central pulmonary arteries with thromboemboli. Conversely, in the 16 central pulmonary arteries without clot, intraluminal stripes disappeared despite the presence of flow-related signal (sensitivity = 88%, specificity = 100%, accuracy = 96%). CONCLUSION: SPAMM appears to be a simple and effective technique for differentiating central pulmonary arterial thromboemboli from flow-related signal frequently observed with pulmonary hypertension.

Adult↗
PubMed1993

Increased uptake of iodine-131 in metastases of differentiated thyroid carcinoma associated with less severe hypothyroidism following total thyroidectomy.

BACKGROUND: In an attempt to determine possible factors affecting the efficacy of iodine-131 (I-131) treatment for metastatic thyroid carcinoma, the authors focused their efforts on thyroid functions after total thyroidectomy. METHODS: Between 1980 and 1991, 47 patients with lung metastases of differentiated thyroid carcinoma were treated with I-131. Relationships of the images on post-therapy scans with various clinical features were studied. RESULTS: Among them, 28 (59.6%) showed I-131 uptake in the metastases on post-therapy scans. Younger patients had lesions that concentrated more radioactive iodine than did those of older patients. The amount of I-131 concentrated in the metastatic lesions correlated with serum triiodothyronine (T3), thyroxine (T4), and thyroglobulin levels and inversely with serum thyroid-stimulating hormone (TSH) levels determined at the time of therapy. Serum T3 and T4 levels were significantly higher in 28 patients with positive scans than in 19 patients with negative scans. Most patients who had metastases with markedly increased radioactivity were euthyroid or mildly hypothyroid, suggesting that thyroid hormones produced by tumor masses compensated for severe hypothyroidism after total thyroidectomy, and showed favorable responses to the treatment. In three patients successfully treated, decreases in serum thyroglobulin levels and the size of metastatic lesions were accompanied by the development of severe hypothyroidism. CONCLUSIONS: The presence of a large amount of metastatic functioning thyroid tissues responsive to I-131 treatment can be suspected in patients with less severe hypothyroidism after total thyroidectomy.

Adenocarcinoma↗
PubMed1993

Evaluation of pulmonary vascular anatomy and blood flow by magnetic resonance.

Rapidly evolving magnetic resonance (MR) imaging techniques provide noninvasive approaches to evaluating morphology and quantitative physiologic information about blood flow in the pulmonary circulation. Important clinical applications currently include the preoperative and postoperative evaluation of congenital abnormalities, assessment of vascular involvement by extrinsic and intrinsic tumors, identification of central thromboemboli, and diagnosis of vascular lung lesions. Ongoing refinements in pulmonary MR angiography may make it possible to use the technique for the noninvasive detection of acute pulmonary emboli in the near future. Quantitative measurements based upon MR flow-encoding sequences are promising for the evaluation of patients with abnormal degrees or distributions of pulmonary blood flow, for example, those with unilateral lung transplants or pulmonary arterial stenoses. MR contrast agents currently under development also show promise for quantitative measurements of regional pulmonary ventilation and perfusion. The coupling of high-resolution anatomic and functional images renders MR a uniquely attractive and powerful method for evaluating the pulmonary vasculature.

Humans↗
PubMed1993

Suspected pulmonary embolism: prospective evaluation with pulmonary MR angiography.

PURPOSE: To prospectively evaluate three magnetic resonance (MR) imaging techniques for detection of pulmonary embolism. MATERIALS AND METHODS: Eighteen patients in whom the presence of acute or chronic pulmonary emboli was suspected underwent examination with the following pulse sequences: cardiac-gated spin echo, cine spatial modulation of magnetization, and two-dimensional time-of-flight pulmonary breath-hold (PBH) MR angiography. Three radiologists independently and blindly reviewed each case and graded a total of 518 arterial segments for each pulse sequence with a continuous scale of 0%-100% for likelihood of pulmonary embolism. RESULTS: The overall sensitivity of PBH MR angiography for detection of acute pulmonary emboli was 0.85; for chronic emboli, which were smaller in anteroposterior (AP) diameter, the overall sensitivity was 0.42. Emboli larger than 1 cm in AP diameter were typically identified with > 75% confidence with all pulse sequences. CONCLUSION: Acute pulmonary emboli greater than 1 cm in AP diameter were as accurately identified on PBH MR angiograms obtained in 15 seconds as they were on MR images obtained with longer pulse sequences not dependent on breath holding.

Acute Disease↗