Biomedical subjects

T Namimoto

Publications and source records attributed to T Namimoto.

At least 19 recordsLinked to original sources

PubMed2001

Adrenal masses: quantification of fat content with double-echo chemical shift in-phase and opposed-phase FLASH MR images for differentiation of adrenal adenomas.

PURPOSE: To quantify fat content in adrenal lesions with double-echo chemical shift magnetic resonance (MR) imaging in a phantom study and to differentiate adrenal adenomas from other adrenal masses by assessing fat content in a clinical study. MATERIALS AND METHODS: The study consisted of two parts: a phantom study and a clinical study. To explore the effect of the T1 value on in- and opposed-phase MR images of fat-containing tissues, phantom models with various proportions of fat and gadopentetate dimeglumine concentrations were implemented. Signal intensity (SI) indexes ([SI in-phase - SI opposed-phase]/SI in-phase) were calculated with double-echo fast low-angle shot (FLASH) MR imaging. In the clinical study, 23 patients with 28 adrenal masses (16 adrenal adenomas, nine adrenal metastases, and three pheochromocytomas) underwent double-echo FLASH MR imaging, and SI indexes were calculated. RESULTS: SI index reached a maximum of 0.87 at 53% fat fraction for gadopentetate dimeglumine concentration at 0.5 mmol/L as the simulated T1 of the adrenal mass. The SI indexes of the adrenal adenomas, adrenal metastases, and pheochromocytomas, respectively, were 0.36, -0.15, and -0.07, and estimated fat fraction from the phantom study was 26.5%, 0%, and 0%. All adrenal adenomas contained fat on double-echo FLASH images. There was no overlap in SI index between adenomas and other tumors. CONCLUSION: Preliminary experience indicates that quantitative measurement of the fat fraction of adrenal masses is possible with the double-echo chemical shift FLASH technique and allows for differentiating adrenal adenomas from other adrenal masses.

Adenoma↗

PubMed2000

Intraductal papillary tumors of the pancreas. Histopathologic correlation of MR cholangiopancreatography findings.

PURPOSE: To evaluate MR cholangiopancreatography (MRCP) findings of intraductal papillary tumors of the pancreas and correlate them with histopathology. MATERIAL AND METHODS: Seventeen patients with intraductal papillary tumor of the pancreas underwent MRCP before surgery. MRCP findings were correlated to histopathology with regard to the presence of septa and excrescent nodules in the cystic lesion, communication between the cystic lesion and the main pancreatic duct (MPD), degree of dilatation of MPD, and dilatation of the common bile duct (CBD). RESULTS: MRCP demonstrated septa in 17 cases (100%), excrescent nodules in 8 cases (47.1%), communication between the intraductal papillary tumor and the MPD in 14 cases (82.3%), dilatation of MPD over 50% in 6 cases (35.3%), and dilatation of CBD in 3 cases (17.6%). These findings showed excellent correlation with histopathology. The septum on MRCP corresponded with a layer of connective tissue with pancreatic duct epithelium. Excrescent nodules in the carcinomas consisted not only of malignant cells, but also of dysplasia and adenoma. Excrescent nodules in adenomas were consistent not only with minimal papillary growth of adenoma, but also with proliferation of fibrosis, and hematoma and organized fibrin with minimal fibrosis. Pancreatic tissue was affected by chronic pancreatitis in all cases. Cases with dilatation of CBD on MRCP were due to microscopic invasion by the carcinoma. CONCLUSION: MRCP appearances of intraductal papillary tumors are well correlated with the findings at histopathology.

Adenocarcinoma, Papillary↗

PubMed2000

Diagnostic accuracy of helical CT arterial portography and CT hepatic arteriography for hypervascular hepatocellular carcinoma in chronic liver damage. An ROC analysis.

PURPOSE: To evaluate the detectability of hypervascular hepatocellular carcinomas (HCCs) in chronic liver damage with helical CT arterial portography (CTAP) and CT hepatic arteriography (CTHA). MATERIAL AND METHODS: Thirty-nine HCC patients who underwent CTAP and CTHA were studied. Diagnostic abilities of CTAP alone, CTHA alone, or combined CTAP and CTHA were evaluated by receiver operating characteristic (ROC) analysis. Fifty-three images with 53 HCC nodules were evaluated. Tumor size ranged from 5 to 90 mm (mean 22.8 mm). Sensitivities and specificities for all techniques were calculated. RESULTS: ROC analysis showed the diagnostic ability significantly better with combined CTAP and CTHA (mean area under the ROC curve (Az)=0.95), or CTHA alone (Az=0.93) than CTAP alone (Az=0.87) (p<0.01). Combined CTAP and CTHA showed the best sensitivity (95.0%), followed by CTHA alone (88.1%) and CTAP alone (85.5%). The specificities of all three imaging techniques were relatively low (54.1% for combined CTAP and CTHA, 71.1% for CTHA alone, and 54.1% for CTAP alone) because of perfusion abnormalities of the liver parenchyma. CONCLUSION: The combination of CTAP and CTHA is superior to CTAP alone for detection of hypervascular HCCs. However, its specificity was relatively low in chronic liver damage.

Aged↗

PubMed2000

Pancreaticobiliary ductal system: value of half-Fourier rapid acquisition with relaxation enhancement MR cholangiopancreatography for postoperative evaluation.

PURPOSE: To assess the usefulness of half-Fourier rapid acquisition with relaxation enhancement (RARE) magnetic resonance cholangiopancreatography (MRCP) for evaluation of postoperative changes in the pancreaticobiliary ductal system. MATERIALS AND METHODS: The study included 34 patients (20 men, 14 women; mean age, 65.5 years) who underwent surgery of the pancreaticobiliary ductal system. Half-Fourier RARE MRCP images were obtained after surgery. Qualitative evaluation included ratings by two observers for depiction of postoperative anatomy and for artifacts, as well as analysis of postoperative complications. Direct cholangiographic, computed tomographic, and ultrasonographic findings and 6-month follow-up results were the reference standard. Sensitivity, specificity, and accuracy were calculated for the evaluation of postsurgical complications seen at half-Fourier RARE MRCP. RESULTS: The sensitivity, specificity, and accuracy of MRCP for the evaluation of postsurgical complications were each 100% for ductal dilatation; 100%, 87%, and 89%, respectively, for choledochoenteric anastomotic stricture; 100%, 86%, and 87%, respectively, for pancreaticoenteric anastomotic stricture; 100% each for intraductal stones and anastomotic leakage; and 80%, 100%, and 94%, respectively, for cholangitis. CONCLUSION: Half-Fourier RARE MRCP is a reliable imaging technique for the evaluation of anatomy and of complications associated with a surgically altered pancreaticobiliary ductal system.

Adult↗

PubMed1999

Measurement of the apparent diffusion coefficient in diffuse renal disease by diffusion-weighted echo-planar MR imaging.

The purpose of this study was to determine the relationship between the apparent diffusion coefficient (ADC) and diffuse renal disease by diffusion-weighted echolanar magnetic resonance (MR) imaging (EPI). Thirty-four patients were examined with diffusion-weighted EPI. The average ADC values were 2.55 x 10(-3) mm2/sec for the cortex and 2.84 x 10(-3) mm2/sec for the medulla in the normal kidneys. The ADC values in both the cortex and medulla in chronic renal failure (CRF) kidneys and in acute renal failure (ARF) kidneys were significantly lower than those of the normal kidneys. In renal artery stenosis kidneys, the ADC values in the cortex were significantly lower than those of the normal and the contralateral kidneys. In the cortex, ADC values were above 1.8 x 10(-3) mm2/sec in all 32 normal kidneys, ranging from 1.6 to 2.0 x 10(-3) mm2/sec in all 8 ARF kidneys, and below 1.5 x 10(-3) mm2/sec in 14 of 15 CRF kidneys. In the medulla, there was considerable overlap in the ADC values of the normal and diseased kidneys. There was a linear correlation between ADC value and sCr level in the cortex (r = 0.75) and a weak linear correlation in the medulla (r = 0.60). Our results show that diffusion-weighted MR imaging may be useful to identify renal dysfunction.

Adolescent↗

PubMed1999

Optimal protocol for injection of contrast material at MR angiography: study of healthy volunteers.

Forty healthy volunteers, matched for age and body weight, underwent abdominal magnetic resonance angiography with gadopentetate dimeglumine administered by using a power injector. Injection rates were 0.3, 1.0, 2.0, or 3.0 mL/sec. Contrast material doses were 0.1 (single dose) or 0.2 (double dose) mmol/kg. Increased contrast enhancement in the aorta and minimum arteriovenous overlap can be achieved with high flow rate and double-dose injection.

Adult↗

PubMed1999

Detection of hepatocellular carcinoma arising in cirrhotic livers: comparison of gadolinium- and ferumoxides-enhanced MR imaging.

OBJECTIVE: We prospectively compared the detectability of hepatocellular carcinoma (HCC) arising in cirrhotic livers using dynamic gadolinium-enhanced fast low-angle shot (FLASH), ferumoxides-enhanced T2-weighted turbo spin-echo, and ferumoxides-enhanced T2*-weighted FLASH MR imaging. SUBJECTS AND METHODS: Fifty-three patients with HCC (32 men and 21 women) who were 33-86 years old (mean, 63 years old) were enrolled in a prospective MR study to assess hepatic lesions using both gadopentetate dimeglumine and ferumoxides. Dynamic gadolinium-enhanced imaging was obtained before and 30, 60, and 180 sec after rapid bolus injection of gadopentetate dimeglumine (0.1 mmol/kg). Ferumoxides-enhanced T2-weighted turbo spin-echo imaging and ferumoxides-enhanced T2*-weighted FLASH imaging were performed between 30 min and 2 hr after i.v. infusion of ferumoxides (10 micromol/kg). Images were analyzed qualitatively and quantitatively. A receiver operating characteristic curve study was performed to compare the diagnostic value of gadolinium-enhanced imaging with that of ferumoxides-enhanced imaging for the detection of HCC. RESULTS: Quantitative analysis revealed a significantly higher percentage of signal-intensity loss and higher liver-lesion contrast-to-noise ratio on ferumoxides-enhanced T2*-weighted FLASH imaging than on ferumoxides-enhanced T2-weighted turbo spin-echo imaging. The percentage of signal-intensity loss and liver-lesion contrast-to-noise ratio on ferumoxides-enhanced images was significantly higher in patients with mild liver cirrhosis (Child's class A) than in patients with severe liver cirrhosis (Child's class C). Qualitative analysis showed that dynamic gadolinium-enhanced images revealed significantly higher lesion conspicuity than did ferumoxides-enhanced T2-weighted turbo spin-echo images. According to receiver operating characteristic analysis, dynamic gadolinium-enhanced FLASH imaging achieved the highest sensitivity, and ferumoxides-enhanced T2*-weighted FLASH imaging was the second most sensitive. We found that ferumoxides-enhanced turbo spin-echo imaging was the least valuable technique for revealing HCC lesions. Gadolinium-enhanced imaging revealed more HCC lesions than did ferumoxides-enhanced imaging, particularly for lesions smaller than 2 cm in diameter. CONCLUSION: Ferumoxides-enhanced imaging revealed fewer findings, such as lesion conspicuity of HCCs arising in cirrhotic livers, than did gadolinium-enhanced FLASH imaging.

Adult↗

PubMed1998

Carcinoma of the uterine cervix. High-resolution turbo spin-echo MR imaging with contrast-enhanced dynamic scanning and T2-weighting.

PURPOSE: To compare high-resolution contrast-enhanced (Gd-DTPA) dynamic MR imaging with T2-weighted turbo spin-echo (TSE) imaging in the evaluation of uterine cervical carcinoma. MATERIAL AND METHODS: Thirty-two patients with cervical carcinoma underwent MR imaging on a 1.5 T superconductive unit to have the extension of the disease assessed before treatment. A phased-array coil was used in all patients. In 25 patients, surgical confirmation of the diagnosis was obtained after imaging. Radiation therapy was selected for the remaining 7 patients with advanced carcinoma. Qualitative and quantitative image analyses were also performed. RESULTS: The cervical carcinomas showed maximum contrast in the cervical stroma and myometrium in the early dynamic phase. The tumor/cervical-stroma contrast in the early dynamic phase obtained with the T1-weighted TSE technique (contrast-to-noise ratio 22.6) was significantly higher than that obtained in T2-weighted TSE imaging (contrast-to-noise ratio 4.3). In the evaluation of parametrial invasion, the accuracy of T2-weighted imaging was 71.8% and contrast-enhanced dynamic imaging 81.2%. CONCLUSION: High-resolution contrast-enhanced (Gd-DTPA) dynamic MR imaging in cervical cancer offers improved tumor/cervical-stroma contrast and provides useful information on parametrial invasion.

Adult↗

PubMed1998

MR imaging of the liver: comparison between single-shot echo-planar and half-Fourier rapid acquisition with relaxation enhancement sequences.

PURPOSE: To evaluate single-shot T2-weighted magnetic resonance sequences and their role in clinical practice in patients with hepatic lesions. MATERIALS AND METHODS: Prospective comparison of echo-planar and half-Fourier rapid acquisition with relaxation enhancement (RARE) imaging was performed in 80 patients with focal hepatic lesions. Spin-echo (SE) single-shot echo-planar (echo times, 47 and 80 msec) and half-Fourier RARE (echo time, 59 msec) images were compared with turbo SE (repetition time msec/echo time msec = 3,200-7,600/90) images. Quantitative, qualitative, and receiver operating characteristic (ROC) analyses were performed. RESULTS: For liver, signal-to-noise ratios on half-Fourier RARE images were significantly higher than those on echo-planar images (P < .01). For cystic lesions, contrast on half-Fourier RARE and echo-planar images was slightly higher than that on turbo SE images. For solid lesions, contrast on echo-planar images was better than that on half-Fourier RARE or turbo SE images. Artifacts including ghosting, bowel motion, susceptibility difference, and chemical shift were negligible on half-Fourier RARE images in all patients, whereas susceptibility difference and chemical shift of various degrees were seen on all echo-planar images. On the basis of ROC analyses, tumor detection rates were significantly higher with half-Fourier RARE and turbo SE images than with echo-planar images (P < .01). CONCLUSION: Echo-planar images provide sufficient contrast to allow detection of both solid and cystic masses, but severe artifacts preclude routine use. Half-Fourier RARE images are free from artifacts (chemical shift and susceptibility) and diagnostic performance with them is similar to that with turbo SE images.

Adult↗

PubMed1998

Mucin-producing tumor of the pancreas: diagnostic value of diffusion-weighted echo-planar MR imaging.

PURPOSE: To determine whether diffusion-weighted echo-planar magnetic resonance (MR) imaging can help differentiate mucin-producing tumors of the pancreas from other cystic lesions. MATERIALS AND METHODS: Diffusion-weighted echo-planar 1.5-T MR imaging was performed in patients with mucin-producing tumor (n = 15), pseudocyst (n = 15), or serous microcystic tumor (n = 2). Images were obtained with diffusion-sensitizing gradients of 30 and 300 sec/mm2. The apparent diffusion coefficient (ADC) was calculated. RESULTS: At 30 sec/mm2, all cystic lesions had very high signal intensity. The dilated main pancreatic duct was depicted in eight patients with mucin-producing tumor and in six with pseudocyst. The mean (+/- standard deviation) ADCs of mucin-producing tumors (2.7 x 10(-3) mm2/sec +/- 0.9 x 10(-3)) and pseudocysts (3.2 x 10(-3) mm2/sec +/- 1.0 x 10(-3) were significantly lower (P < .01) than those of serous cysts or cerebrospinal fluid (5.8 x 10(-3) mm2/sec +/- 2.0 x 10(-3)). At 300 sec/mm2, cysts and the main pancreatic ducts had high signal intensity in cases of mucin-producing tumor, indicative of the presence of mucinous products in both the cystic cavity and the main pancreatic duct. The signal intensity of cystic fluid in pseudocysts was high on diffusion-weighted images, but that of the pancreatic duct was decreased (ADC = 5.1 x 10(-3) mm2/sec +/- 1.7 x 10(-3)). CONCLUSION: Diffusion-weighted MR imaging can help characterize cystic lesions of the pancreas. Findings-suggestive of viscous fluid in mucin-producing tumors are present on such images.

Adenocarcinoma, Mucinous↗

PubMed1997

Liver T2-weighted MR imaging: comparison of fast and conventional half-Fourier single-shot turbo spin-echo, breath-hold turbo spin-echo, and respiratory-triggered turbo spin-echo sequences.

PURPOSE: T2-weighted spin-echo (SE) magnetic resonance imaging in the liver was compared with four sequences: fast and conventional half-Fourier single-shot turbo SE (HASTE) and breath-hold and respiratory-triggered turbo SE. MATERIALS AND METHODS: In 58 patients with focal liver lesions, imaging was performed with a 1.5-T magnet and a phased-array coil. Images obtained with fast HASTE conventional HASTE, breath-hold turbo SE, and respiratory-triggered turbo SE were compared. Results of quantitative, qualitative, and receiver operating characteristic analyses were compared. RESULTS: Lesion-to-liver contrast for solid tumors was significantly higher with the fast HASTE and respiratory-triggered turbo SE sequences than with the conventional HASTE and breath-hold turbo SE sequences (P < .01) and for cystic lesions was significantly higher with the conventional and fast HASTE sequences than with the breath-hold or respiratory-triggered turbo SE sequences (P < .01). Artifacts were negligible on all fast and conventional HASTE images. In receiver operating characteristic analyses, diagnostic performance was significantly higher with the fast HASTE and respiratory-triggered turbo SE sequences than with the conventional HASTE and breath-hold turbo SE sequences (P < .01). CONCLUSION: Images obtained with the fast HASTE sequence were free from motion artifacts, and observer diagnostic performance was similar to that with the respiratory-triggered turbo SE sequence.

Adolescent↗

PubMed1997

Focal liver masses: characterization with diffusion-weighted echo-planar MR imaging.

PURPOSE: To evaluate diffusion-weighted echo-planar magnetic resonance (MR) imaging for improving the specificity of characterization of liver tumors. MATERIALS AND METHODS: Diffusion-weighted echo-planar imaging was performed with a 1.5-T whole-body imager with use of a body phased-array coil in 51 patients with 59 hepatic masses (41 malignant tumors, nine hemangiomas, and nine cysts). Apparent diffusion coefficient (ADC) values were obtained with two motion-probing gradients (b = 30 and 1,200 sec/mm2) during each of the breath-hold periods, and an ADC map was constructed. The T2 was derived from spin-echo echo-planar images with echo times of 47 and 99 msec. RESULTS: The ADC value of malignant masses (1.04 x 10(-3) mm2/sec) was significantly lower (P < .01) than that of benign masses (hemangiomas [1.95 x 10(-3) mm2/sec] and cysts [3.05 x 10(-3) mm2/sec]), although the T2s showed considerable overlap. A small amount of overlap in ADC values occurred among malignant tumors, hemangiomas, and cysts. ADC values of two cystic masses from ovarian carcinomas were within the range of those of hemangiomas. CONCLUSION: These preliminary results indicate that diffusion-weighted MR imaging can be useful in characterizing focal liver masses. With the exception of cystic metastatic tumors, the technique may be especially useful in tumors that appear markedly hyperintense on T2-weighted images due to a long T2.

Adult↗

PubMed1997

MR imaging of the fetus by a HASTE sequence.

OBJECTIVE: The value of a half-Fourier acquisition single-shot turbo spin-echo (HASTE) sequence, in which high-resolution heavily T2-weighted images can be obtained within 2 sec, was evaluated in the imaging of the fetus during the second or third trimester. MATERIALS AND METHODS: Eighteen women with complicated pregnancies as revealed on a sonogram during the second and third trimesters (16-36 weeks' gestation) were studied with a 1.5-T superconductive MR imaging unit that used a body phased-array coil. After informed consent, T1-weighted fast low-angle shot images, T2-weighted turbo spin-echo images, and HASTE images were obtained without any premedication. Images were analyzed with regard to image quality, degree of blurring, visualization of the normal fetal organs, and visualization of fetal and maternal abnormalities. RESULTS: On HASTE sequences, visualization of the fetal brain, visceral organs (lung, heart, liver, kidney, and bladder), extremities, and umbilical cord were significantly better than on fast low-angle shot or turbo spin-echo sequences (p < .01). In the brain, the white matter-gray matter distinction, gyrus formation, and myelination of the brain were clearly revealed by the HASTE sequence. Pathologic processes including fetal abnormalities (anomalies of the central nervous systems [n = 5], placenta previa [n = 1], and transverse lie in the third trimester [n = 1]) and maternal abnormalities (leiomyoma [n = 5], ovarian tumors [n = 3], and hydronephrosis [n = 1]) were clearly seen on HASTE imaging. The peak specific absorption rate for RF exposure in these studies was less than 1.5 W/kg. CONCLUSION: In situations when sonography is suggestive but not definitive, MR imaging with a HASTE sequence allows clear fetal imaging with high T2-weighted contrast.

Adult↗

PubMed1996

Gadolinium-enhanced breath-hold three-dimensional MR angiography of the portal vein: value of the magnetization-prepared rapid acquisition gradient-echo sequence.

The authors evaluated magnetic resonance (MR) angiography of the portal vein performed with a breath-hold, gadolinium-enhanced, magnetization-prepared rapid acquisition gradient-echo sequence in five volunteers and 24 patients. The main portal vein and its branches and the liver were depicted clearly in all images. The hepatic vein was clearly depicted in 21 of the 24 patients. MR angiography performed with this sequence allowed high-quality imaging of the portal and hepatic veins.

Adult↗

PubMed1996

Embolization for ruptured superior mesenteric artery aneurysms.

Superior mesenteric artery (SMA) aneurysms are very uncommon. They are difficult to detect until they rupture and cause hypovolaemic shock. We performed embolization in four cases of aneurysm of branches of the superior mesenteric artery, succeeding in three cases without the need for surgical treatment. In the first case, the aneurysm was excised because of migration of a microcoil into the left hepatic artery. It was not retrieved because sufficient blood flow to the liver was shown on angiography after migration and no ischaemic change of liver was detected on laparotomy. In the second case, the aneurysm arose from the anterior pancreaticoduodenal artery. In the third case, the patient had two SMA aneurysms; one had been resected at surgery, another was revealed on follow-up angiography and embolized with microcoils. The fourth patient had a jejunal artery aneurysm with extravasation; haemostasis was achieved by packing it. In all four cases, no major complications were observed in the clinical course after embolization. Microcoils were considered to be the desirable embolic material, in order to prevent post-therapeutic ischaemic change. Embolization should be the treatment of choice for SMA aneurysms, because it is less invasive and takes less time than surgical treatment.

Adult↗

PubMed1996

The value of MR urography that uses HASTE sequences to reveal urinary tract disorders.

OBJECTIVE: Breath-hold MR urography using half-Fourier acquisition single-shot turbo spin-echo (HASTE) sequences was evaluated as a noninvasive alternative to excretory urography in healthy volunteers and in patients with disorders of the urinary tract. SUBJECTS AND METHODS: Twenty healthy volunteers and 45 patients with disorders of the urinary tract underwent HASTE MR urography on a 1.5-T MR imaging unit. Imaging time was 2 sec for single-thick-slice (20- to 60-mm slice thickness) technique and 10-18 sec for multislice technique. In the latter, images were postprocessed with maximum-intensity-projection technique and visualized in an arbitrary plane. Obstruction and its level were determined solely by excretory urography in eight patients, by excretory urography with other imaging techniques (CT, retrograde pyelography, or sonography) in 27 patients, and by sonography alone in the 20 normal volunteers, seven pregnant women, and three patients who were allergic to iodinated contrast media. We evaluated whether HASTE MR urograms showed obstruction, showed the level of obstruction, and showed the cause of obstruction. RESULTS: In all 20 healthy volunteers and all 45 patients, the upper, middle, and lower group of renal calices and the pelvis were clearly revealed by HASTE MR urography. In patients whose urinary tracts were seen on excretory urography (n = 31), the accuracy of HASTE MR urography in revealing urinary tract dilatation and level of obstruction completely correlated with that of excretory urography, although functional information about the obstructed collecting system was not obtained. However, MR urography revealed nonfunctioning urinary tracts that were invisible on excretory urography (n = 6). In patients with extrinsic obstruction (n = 27), MR urography also revealed the obstructing lesions. Small stones within the ureter were more clearly seen on single-shot or source images. With HASTE MR urography, hydronephrosis in pregnant women (n = 7) was clearly shown. CONCLUSION: HASTE MR urography can be used as an alternative to excretory urography to obtain high-quality images of the dilated urinary tract and adjacent abnormalities. HASTE MR urography allows rapid acquisition of images, thus overcoming the drawbacks of earlier MR urography techniques.

Adolescent↗

PubMedDate not supplied

Phased array breath-hold versus non-breath-hold MR imaging of focal liver lesions: a prospective comparative study.

This study was undertaken to determine whether phased array breath-hold T1- and T2-weighted sequences can replace non-breath-hold spin echo (SE) sequences in the imaging of focal liver lesions by comparing overall image quality, liver-lesion contrast, and artifact. Both breath-hold and non-breath-hold T1-weighted and T2-weighted imagings of focal liver lesions were prospectively compared in 120 patients with suspected focal liver lesions imaged at 1.5 T with use of a body phased array multicoil. Breath-hold images were acquired with T1-weighted fast low-angle shot (FLASH) and T2-weighted turbo spin echo (TSE) sequences, and non-breath-hold images were made with conventional T1- and T2-weighted SE sequences. Qualitative image analysis was done by three blinded readers, and quantitative analysis was done. The highest signal-to-noise ratios were obtained with breath-hold T1-weighted FLASH sequence. The signal-to-noise ratios of breath-hold T2-weighted TSE sequence were slightly inferior to those of non-breath-hold SE sequence. Both T1-weighted and T2-weighted breath-hold sequences had less image artifact. Overall image quality of breath-hold sequences was better than that of non-breath-hold sequences for both T1- and T2-weighted sequences (P < .01). The tissue contrast of T1-weighted FLASH sequence was superior to that of SE sequence (P < .01). On T2-weighted imaging, tissue contrast of solid lesions was better on conventional SE sequence than that on breath-hold TSE sequence (P < .01). Respiratory ghost artifact was less prominent on T1-weighted FLASH sequence, although this artifact was occasionally seen on breath-hold T2-weighted TSE sequence. In a state-of-art MR unit with use of a phased array multicoil, conventional T1-weighted can be replaced by breath-hold sequences. On T2-weighted imaging, because solid tumor-liver contrast on breath-hold TSE imaging is inferior to that on non-breath-hold SE image, breath-hold imaging may not replace conventional non-breath-hold T2-weighted SE sequence.

Adult↗

PubMedDate not supplied

Gadolinium-enhanced breath-hold three-dimensional time-of-flight MR angiography of the abdominal and pelvic vessels: the value of ultrafast MP-RAGE sequences.

MR angiography (MRA) was performed in 50 consecutive subjects (mean age, 59 years), who had been referred for abdominal MRA, on a 1.5-T superconductive unit that used a body phased-array coil. Three breath-hold three-dimensional sequences were evaluated both in phantom and clinical studies: (a) standard fast three-dimensional gradient-echo sequence (TR = 15, TE = 6; imaging time, 32 seconds), (b) ultrafast three-dimensional gradient-echo sequence (TR = 8.2, TE = 3; imaging time, 18 seconds), and (c) ultrafast magnetization-prepared (MP) rapid acquisition gradient echo (RAGE) (TR = 5.8, TE = 2.9, inversion time [TI] = 20; imaging time, 15 seconds). The initial 30 patients were randomized into three groups by three separate sequences. For the remaining 20 patients, ultrafast-gradient-echo and ultrafast MP-RAGE sequences were performed. Conventional angiography was performed on 36 patients. Signal measurements of the phantom and clinical images of the aorta, visceral branches of the aorta, iliac arteries, inferior vena cavae, and portal veins were performed. The overall image quality and background fatty tissue contrast of the vessels were rated subjectively. Comparison of images between MRA and conventional angiography also was performed. The contrast between the vessels and background fatty tissue was significantly higher in the ultrafast MP-RAGE sequence in both quantitative and qualitative analysis, and image-quality ultrafast MP-RAGE was superior to the other two sequences (P < .01). The aorta and iliac arteries could be visualized in all pulse sequences, and abnormalities of these vessels were diagnosed correctly. The renal artery was visualized more clearly with the two ultrafast sequences.

Angiography↗