Cross-sectional and Longitudinal Analyses of Factors Contributing to the Progressive Loss of the β-cell Function in Type 2 Diabetes

OBJECTIVE

Type 2 diabetes is a progressive disease characterized by insulin resistance and insulin secretory dysfunction. In this study, we assessed the factors contributing to an insulin secretory defect in type 2 diabetes patients.

METHODS

The subjects consisted of 382 patients with type 2 diabetes, aged 57±13 years. We estimated the β-cell function using 6-min post-glucagon increments in C-peptide (ΔCPR).

RESULTS

A significant inverse correlation was observed between the time since the diagnosis of diabetes and ΔCPR. A simple liner regression analysis showed that ΔCPR decreases at a rate of 0.056 ng/mL/year. According to a multiple regression model, body mass index (BMI) and log (triglyceride) were positively correlated with ΔCPR. Time since the diagnosis of diabetes, diabetes in 1st degree relatives, the presence of diabetic retinopathy, and HbA1c were inversely correlated with ΔCPR. In 50 patients who underwent the glucagon stimulation test twice, the ΔCPR decreased from 2.27±1.47 to 1.72±1.08 ng/mL over a period of 6.5±0.9 years. A multiple regression analysis revealed the BMI and fasting plasma glucose level to be significant contributing factors to the decline in ΔCPR.

CONCLUSION

The duration of diabetes, a low BMI, genetic factors, and the presence of microangiopathy may be associated with β-cell dysfunction in diabetic patients. The observations in this study suggest that obese subjects showed a rapid decline in the β-cell function despite an initial high CPR response. Environmental factors causing insulin resistance and glucotoxicity may therefore be involved in progressive β-cell failure.

Prevalence and clinical characteristics of unremembered nocturnal eating in diabetic subjects: Kurume sleep trouble in obesity and metabolic disorders (KUSTOMED) study

Nighttime food intake is associated with weight gain and higher HbA1c levels. We experienced night eaters who have no memory of their nocturnal eating in the morning. In this study, the curious night eating behavior was designated as "unremembered nocturnal eating syndrome (UNES)". We screened 1,169 patients with diabetes for sleep quality and abnormal eating behavior at night using the Pittsburgh Sleep Quality Index questionnaire with an additional question regarding UNES. When abnormal nocturnal eating behavior was noted, detailed clinical information was extracted from interviews with the patients. We identified 9 patients who experienced UNES. They had a higher BMI compared with subjects who reported no such episodes. Among them, 6 patients who consumed food at night without memory 2-5 times per month or more had significantly higher HbA1c levels. Continuous glucose monitoring in a patient with type 1 diabetes revealed an abrupt elevation of glucose levels from midnight when some foods were consumed. Eight of the 9 patients were taking benzodiazepine and/or non-benzodiazepine hypnotic agents when they experienced the episodes. The prevalence of UNES was 0.8% in all subjects and 4% in those taking hypnotic drugs. The ratio of hypnotic drug use in subjects with UNES was significantly higher than for individuals without UNES (89% vs. 17%, p<0.0001). Although UNES seems to be etiologically heterogeneous, hypnotics-induced parasomnia and/or anterograde amnesia may be associated with the behavior. UNES is not rare in diabetic patients on hypnotic medicine and may be a hidden cause of unexpected morning hyperglycemia.

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.

Fast breath-hold T2-weighted MRI of the kidney by means of half-Fourier single-shot turbo spin echo: comparison with high resolution turbo spin echo sequence

PURPOSE

The value of the fast half-Fourier single-shot turbo spin echo (HASTE) sequence in T2-weighted MRI of the kidney was evaluated as a substitute for the conventional turbo spin echo (TSE) sequence.

METHOD

Forty-five patients with suspected abnormalities of the kidney underwent MRI with a 1.5 T system. Breath-hold HASTE and respiratory-triggered TSE sequences were performed. Qualitative and quantitative analyses were performed for comparison of these sequences.

RESULTS

The signal-to-noise ratio (SNR) with HASTE was higher than that with TSE. The lesion-to-kidney contrast-to-noise ratio for solid masses with HASTE was almost equal to that with TSE. For cystic masses, the CNR with HASTE was significantly higher than that with TSE (p < 0.05). Respiratory and chemical shift artifacts were significantly smaller on HASTE than on TSE (p < 0.01). However, the blurring artifact was higher on HASTE than on TSE (p = 0.01).

CONCLUSION

The HASTE sequence generates high contrast images and is free of motion and chemical shift artifacts, with much better time efficacy. The sequence provides comparable diagnostic information to TSE sequences.

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.

Abdomen, pelvis, and extremities: diagnostic accuracy of dynamic contrast-enhanced turbo MR angiography compared with conventional angiography-initial experience

To determine the value of contrast material-enhanced three-dimensional turbo magnetic resonance (MR) angiography compared with conventional cut-film or digital subtraction angiography for evaluating arterial stenosis in the abdomen, pelvis, and extremities. For detection of significant stenosis, MR angiography had 91% sensitivity and 89% specificity. This technique is highly sensitive in lesion detection, but stenosis tended to be overestimated.

Diffuse perfusion abnormality of the liver parenchyma on angiography-assisted helical CT in relation to cirrhosis and previous treatments: a potential diagnostic pitfall for detecting hepatocellular carcinoma

We evaluated diffuse perfusion abnormality of the liver parenchyma in relation to cirrhosis and previous treatments and estimated its potential limitation in detecting hepatocellular carcinomas (HCCs) on CT arterial portography (CTAP) and CT hepatic arteriography (CTHA). Sixty-one patients of liver cirrhosis with or without HCC received both CTAP and CTHA. Irregular defects of enhancement of the liver parenchyma on CTAP were noted in 37 of 61 patients (60.7%) and compensatory arterial perfusion in these defects on CTHA was noted in 30 of 37 patients (81.1%). Most patients had segmental or mixed patterns of enhancement. In patients with severe cirrhosis, irregular enhancement was often noted. The irregularity was also more often in patients who had had previous treatments. Four of 40 HCC nodules in 18 patients with severe irregular perfusion were not detected on CTAP and CTHA. Diffuse perfusion abnormalities of the liver parenchyma on CTAP and CTHA would decrease the accuracy of tumor detection in HCC patients.

[Clinical application of endoscopic ultrasonography (EUS) for gastrointestinal diseases]

Endoscopic mucosal resection (EMR) has been widely employed as a minimally invasive surgical procedure for early digestive cancers. Moreover, many recent reports emphasize the usefulness of endoscopic ultrasonography (EUS) for diagnosis of early gastrointestinal cancers. Generally, the normal gastrointestinal wall is visualized as having five layers by endosonographic probes of 7.5, 12, or 20 MHz. Delineation of these layers is the most important point for feature of EUS. Only mucosal cancers that are disclosed as hypoechoic masses within the first to second layer are indicated for EMR. The development of further extracorporeal applications such as color Doppler, 3-D, and aspiration biopsy EUS will contribute to the increased use of EUS in the near future.

Improved tissue characterization of focal liver lesions with ferumoxide-enhanced T1 and T2-weighted MR imaging

The purpose of our study was to evaluate the potential value of ferumoxide-enhanced T1-weighted magnetic resonance (MR) imaging for tissue characterization of focal liver lesions when combined with T2-weighted sequences. Images were acquired within 30 minutes after the end of ferumoxide administration, when ferrite particles were not totally cleared from the intravascular compartment. Thirty-eight patients with 47 focal liver lesions underwent T1-weighted gradient-echo (TR/TE 150/4.1 msec) and T2-weighted fast spin-echo (3180-8638/90 msec) MR imaging at 1.5 T before and after intravenous administration of ferumoxides (10 micromol/kg body weight). A qualitative and quantitative analysis was performed. During the early phase after infusion of ferumoxide, blood vessels showed hypersignal intensity on T1-weighted fast low-angle shot (FLASH) images, while liver signal decreased. Hemangiomas showed both homogeneous and inhomogeneous enhancement patterns, and liver metastasis most typically showed ring enhancement. Hypervascular tumors (hepatocellular carcinomas and focal nodular hyperplasias) showed a slight degree of homogeneous enhancement. Quantitatively, the degree of enhancement and lesion-to-liver contrast on ferumoxide-enhanced images were significantly different among these tumors. Our results demonstrate that distinct enhancement patterns obtained on ferumoxide-enhanced T1-weighted MR imaging improve tissue characterization of focal liver lesions when combined with T2-weighted images.

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.

Delineation of simulated vascular stenosis with Gd-DTPA-enhanced 3D gradient echo MR angiography: an experimental study

PURPOSE

The purpose of this experimental study was to evaluate the influence of contrast material concentration and flow velocity on pulsatile flow in Gd-DTPA-enhanced 3D gradient echo MR angiographic sequence.

METHOD

In vivo flow experiments were performed in Plexiglas phantoms with artificial stenosis (50% stenotic ratio and 20 mm stenotic length) attached to a cardiac pump that generated physiological pulsatile flow similar to that of the bloodstream in a closed circuit. We used a steady-state gradient echo sequence with different TEs (6, 3, and 1.4 ms). A TR of 15 ms was used for all parameters. The concentration of Gd-DTPA varied from 0 to 2.0 mmol/L and flow velocities from 25 to 80 cm/s. We measured the degree of stenosis and length of stenosis in comparison with the actual values.

RESULTS

The degree and length of stenosis on 3D gradient echo MR angiographic images were markedly influenced by the velocity of the flow and concentration of Gd-DTPA. The degree of stenosis was overestimated when the flow was fast or when the concentration of Gd-DTPA was low. When the concentration of Gd-DTPA was low, stenosis was elongated. These effects were less prominent on short TE (1.4 ms) sequence.

CONCLUSION

The stenotic lesions were markedly overestimated on MR angiographic images obtained with Gd-DTPA-enhanced fast 3D gradient echo sequence. Spin dephasing can be compensated for almost entirely by a high concentration of Gd-DTPA and/or a short TE sequence.

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.

Balloon-occluded retrograde transvenous embolization of a pelvic arteriovenous malformation

We successfully performed embolization therapy for a pelvic arteriovenous malformation by the retrograde transvenous approach using a liquid embolic material. This malformation was unique in that it had a single draining vein, which allowed this technique employing an occlusion balloon.

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.

Local extension of pancreatic carcinoma: assessment with thin-section helical CT versus with breath-hold fast MR imaging--ROC analysis

PURPOSE

To compare contrast material-enhanced thin-section helical CT with breath-hold contrast-enhanced MR imaging for sensitivity in the detection of pancreatic adenocarcinoma and for accuracy in local tumor staging.

MATERIALS AND METHODS

Fifty-seven patients (37 men, 20 women aged 42-28 years) suspected of having pancreatic adenocarcinoma were examined. The final diagnosis was confirmed at surgery to be pancreatic cancer in 31 patients; the other 26 patients were deemed not to have pancreatic cancer. All patients underwent both CT and MR imaging (turbo spin-echo and fast low-angle shot) studies. Image quality and pancreatic enhancement were subjectively evaluated. All CT scans and MR images were assessed by two independent observers by using a five-point scale for the detection of tumor and of invasion into the peripancreatic tissue, portal vein, and/or peripancreatic artery. Receiver operating characteristic curves for CT and MR imaging were analyzed.

RESULTS

At visual analysis, pancreatic enhancement at CT and at MR imaging was comparable, but depiction of vessels was superior at helical CT. Detectability of tumor was comparable. Helical CT was significantly superior to MR imaging in diagnostic imaging of invasion into the peripancreatic tissue, portal vein, and/or peripancreatic artery (P < .01).

CONCLUSION

Thin-section dynamic CT is more sensitive than MR imaging for detection of peripancreatic and vascular invasion in patients with pancreatic cancer.

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.

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.

CT evaluation of gastric lesions with three-dimensional display and interactive virtual endoscopy: comparison with conventional barium study and endoscopy

OBJECTIVE

This study was undertaken to assess the feasibility of three-dimensional (3D) CT rendering using shaded-surface display (SSD) and ray sum display and virtual endoscopic images of the stomach for simultaneous evaluation of intraluminal and extraluminal abnormalities compared with conventional upper gastrointestinal barium studies and endoscopy.

SUBJECTS AND METHODS

Our prospective study consisted of 39 patients with gastric lesions (17 gastric carcinomas, nine gastric polyps, five gastric varices, five gastric submucosal tumors, one lymphoma, one case of Menetrier's disease, and one gastric erosion) detected by endoscopy and barium study. All 3D CT images were reconstructed using SSD, ray sum display, and virtual endoscopic techniques. Three-dimensional images were evaluated for ability to reveal the range and morphologic features of the gastric lesions.

RESULTS

All SSD, ray sum display, and virtual endoscopic images successfully revealed five of the eight early-stage gastric carcinomas and all nine advanced-stage gastric carcinomas. Submucosal tumors were revealed on 3D CT approximately as well as on conventional endoscopy. Interactive evaluation of virtual endoscopic images and multiplanar reconstructions provided useful information regarding intraluminal and submucosal gastric involvement by gastric varices, submucosal tumor, advanced gastric carcinomas, and lymphoma. This kind of information could not be obtained by conventional endoscopy or double-contrast study.

CONCLUSION

Three-dimensional CT used in conjunction with virtual CT endoscopy proved helpful in identifying gastric lesions. Also, virtual CT endoscopic images with the interactive display of multiplanar reconstructions proved useful in identifying both intraluminal and submucosal components.

Pitfalls in image reconstruction of helical CT angiography: an experimental study

This study was undertaken to evaluate the effects of the object related factors: background tissue and the direction of vessels on the morphological reproducibility of helical CT angiography. Cylindrical tubes filled with a diluted contrast medium were prepared to obtain vascular phantoms. The scan was performed within various background tissues. For the evaluation of the direction of the vessels, two types of vascular phantoms were prepared. The phantoms were scanned by varying beam collimations and scan pitches. Reconstructed CT images were markedly affected by the background tissue. The reconstructed images were also affected by the direction of vessels.

Power Doppler sonography assessment of tumor recurrence after chemoembolization therapy for hepatocellular carcinoma

OBJECTIVE

This study was undertaken to determine the value of power Doppler sonography in the evaluation of recurrent hepatocellular carcinomas after transcatheter arterial chemoembolization therapy.

SUBJECTS AND METHODS

Forty-five patients (age range, 45-81 years; mean age, 61 years) with hepatocellular carcinomas prospectively underwent power Doppler sonography, helical CT, and intraarterial digital subtraction angiography before and after transcatheter arterial chemoembolization therapy to evaluate for tumor recurrence. Three to 6 months after transcatheter arterial chemoembolization therapy, the Doppler signal, its location, and shape were evaluated. The results were compared with tumor vascularity as determined on helical CT and intraarterial digital subtraction angiography, which were used as the gold standards (n = 142).

RESULTS

A sonographic signal was seen in 80 of 142 lesions with power Doppler sonography. Flow signal in lesions tended to be more difficult to detect in the left lobe (sensitivity, 74%) than in the right lobe (sensitivity, 93%). The location of the color signal was in the tumor's center, on its periphery, or both. No correlation between tumor recurrence and the location of a signal within a tumor was found. Power Doppler sonography had a sensitivity of 87%, a specificity of 85%, and an accuracy of 86% in revealing tumor recurrence after transcatheter arterial chemoembolization therapy. All lesions that showed linear signals in the center or at the periphery of the tumors proved to be recurring tumors (n = 20). In lesions with spotty signals, tumor recurrence was not revealed in nine of 60 lesions.

CONCLUSION

Power Doppler sonography can be used for follow-up studies after transcatheter arterial chemoembolization therapy as a sensitive and cost-effective imaging technique. Although spotty signals were frequently seen, linear signals appeared to be specific for tumor recurrence.

Comparison of ultrafast half-Fourier single-shot turbo spin-echo sequence with turbo spin-echo sequences for T2-weighted imaging of the female pelvis

So that we might evaluate the ultrafast half-Fourier single-shot turbo spin-echo (HASTE) sequence in T2-weighted MRI of the female pelvis and compare it with the turbo spin-echo (TSE) sequence, we prospectively studied 60 consecutive females with suspected abnormalities of the pelvis. For all MR examinations, we used a 1.5-T superconductive magnet with a phased array coil. The HASTE sequence was applied with TR/effective TE/echo train = infinity/90/64 and a 128 x 256 matrix (acquisition time: .3 sec/slice), conventional TSE imaging with 3,400 to 5,000/132/15 and a 128 x 256 matrix (mean acquisition time: 2 min 4 sec), and high-resolution TSE imaging with 3,400 to 5,000/132/15 and a 300 x 512 matrix (6 min 4 sec). Although the lesion conspicuity for the HASTE sequence was less than that for the high-resolution TSE sequences, artifacts (including ghosting, bowel motion, susceptibility difference, and chemical shift) were negligible on HASTE images of all patients. The lesion conspicuity for the HASTE sequence was significantly better than for the conventional TSE sequence. In spite of the very short acquisition time, the subjective scoring of the overall image quality for the HASTE sequence was significantly higher than for the conventional TSE sequence (P < .01) and were slightly lower than for the high-resolution TSE sequence. Compared with high-resolution TSE, HASTE provided clearer visualization of large leiomyomas and ovarian tumors but slightly poorer visualization of uterine cancer. In occlusion, HASTE sequence generates higher contrast and is free from motion and chemical shift artifact with much higher time efficacy. Because of limited image resolution, the HASTE sequence should be used when the high-resolution TSE imaging is suboptimal.

CT appearance of hepatic tumors after microwave coagulation therapy

OBJECTIVE

The purpose of this study was to evaluate the changes in treated lesions and surrounding parenchyma of the liver as well as associated findings on CT in patients who underwent microwave coagulation therapy for hepatic tumors.

MATERIALS AND METHODS

We retrospectively reviewed the findings on helical dynamic CT scans obtained before and after percutaneous or intraoperative microwave coagulation therapy for 74 lesions in 63 patients with hepatocellular carcinoma or metastatic hepatic tumors. Indications for microwave coagulation therapy included primary hepatic tumors in 54 patients and hepatic metastasis in nine patients. Sixty percent nonionic contrast material, infused at 3 ml/sec, was followed by sequential arterial phase, portal venous phase, and equilibrium phase helical CT of the entire liver in all patients.

RESULTS

All lesions were hypodense and extended to the liver capsule. The lesions treated with percutaneous microwave coagulation therapy were teardrop-shaped, whereas those treated with intraoperative microwave coagulation therapy were round. Peripheral enhancement was seen on contrast-enhanced CT in 93% of the treated lesions immediately after microwave coagulation therapy; however, such enhancement disappeared on follow-up CT. Hemorrhage within the lesions and pleural effusion were found in nine patients. Complications detected on CT included intratumoral abscess (n = 4), subcapsular hematoma (n = 2), tumor dissemination (n = 3), ascites (n = 5), and portal vein thrombosis (n = 1).

CONCLUSION

CT of the liver in patients undergoing microwave coagulation therapy showed findings that were dependent on the technique of therapy. Thus, CT scans must be carefully analyzed to avoid confusing results of therapy with findings that indicate complications requiring further treatment.

Three-dimensional high-resolution dynamic contrast-enhanced MR angiography of the pelvis and lower extremities with use of a phased array coil and subtraction: diagnostic accuracy

In this study, our purpose was to compare the high-resolution contrast-material-enhanced three-dimensional subtraction MR angiography with conventional angiography for occlusive disease in the pelvic and lower extremity arteries. A three-dimensional fast-imaging with steady precession (FISP) sequence with a 256 x 512 matrix was obtained on 1.5T MR unit using a phased array coil. Twenty patients with arteriosclerotic obstructive disease underwent subtraction dynamic contrast-enhanced MR angiography. In 15 patients, three regions (pelvis, upper knee, and lower knee) were sequentially obtained after repeated injection of gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA). In the other five patients, one region was imaged (total of 50 examinations); a maximum-intensity projection (MIP) algorithm was used for subtracted images. All patients also underwent conventional angiography. Angiographic images were divided into several anatomical segments. Three blinded radiologists independently graded a total of 50 anatomic segments with stenotic or obstructive diseases and 90 segments without disease. Subtracted images allowed resolution of small branch vessels in all examinations, although misregistration was seen in eight examinations of five patients. All arteries larger than 1 mm in diameter were visualized on subtracted images. For detection of significant stenosis (>50%), MR angiography had 96% sensitivity and 83% specificity. The correlation coefficient of degree of agreement between MR angiography and conventional angiography was .92. Stenotic vessels tended to be overestimated. We conclude that high-resolution dynamic contrast-enhanced three-dimensional MR angiography is capable of depicting small vessel anatomy of the pelvis and lower extremities. Sequential MR angiography of different regions was feasible by repeated injection of Gd-DTPA and subtraction. This technique is highly sensitive in detecting lesions, but stenosis tended to be overestimated.

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.

High resolution breath-holding MR imaging of the abdomen with a phased-array multicoil

We prospectively compared standard resolution and high resolution breath-hold T1- and T2-weighted images of the upper abdomen with use of a body phased-array multicoil in 30 patients. The image quality of high resolution T1-weighted FLASH sequence was equal to that of standard resolution sequence, while the quality of high resolution T2-weighted turbo spin-echo sequence was slightly inferior to that of standard resolution sequence. The merit of high resolution image is appreciated especially on a T1-weighted FLASH sequence.

The value of respiratory triggered T2-weighted turbo spin-echo imaging of the liver using a phased array coil

The purpose of this study was to evaluate the value of the respiratory triggered turbo spin-echo (TSE) technique for T2-weighted MRI of liver lesions. Fifty-nine patients (32 men, 27 women; mean age, 63.3 years) with focal hepatic lesions were prospectively studied with MRI at 1.5 T with use of a body phased array coil. In the first 15 patients, breath-hold TSE, respiratory triggered TSE, and conventional nonrespiratory triggered TSE T2-weighted imaging were compared. Because nonrespiratory triggered TSE imaging was significantly inferior (P < .01) to breath-hold or respiratory triggered images, breath-hold and respiratory triggered TSE T2-weighted images were compared in the remaining 44 patients. Images were analyzed quantitatively by measuring the liver signal-to-noise ratio and the lesion-liver and spleen-liver contrast-to-noise ratios and qualitatively by evaluating the lesion conspicuity, liver parenchymal homogeneity, and sharpness of intrahepatic vessels. The imaging time was 26 seconds for breath-hold TSE imaging, 49 to 219 seconds (mean, 149 seconds) for the respiratory triggered TSE imaging, and 79 to 379 seconds (mean, 239 seconds) for the nonrespiratory triggered TSE imaging. Quantitatively, the signal-to-noise ratio of the liver for breath-hold imaging was comparable to that for respiratory triggered imaging. The lesion-liver and liver-spleen contrast-to-noise ratios for the respiratory triggered images were greater by 37% and 39%, respectively, than for the breath-hold T2-weighted TSE images. Qualitatively, the respiratory triggered images showed lower frequency of image artifact, better lesion conspicuity, and greatly superior depiction of intrahepatic structures compared with the breath-hold T2-weighted TSE images. The respiratory triggered T2-weighted TSE technique provides better quality liver images than the breath-hold TSE technique or nonrespiratory triggered technique within a reasonable acquisition time.

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.

Hepatic parenchymal perfusion abnormalities after pancreaticobiliary surgery. Evaluation with dynamic helical CT

PURPOSE

To evaluate perfusion abnormalities of the liver after pancreaticobiliary surgery.

MATERIAL AND METHODS

We retrospectively evaluated 128 patients with pancreaticobiliary malignant tumors who had been examined both before and after surgery by means of helical CT of the liver. An infusion of 3 ml/s of 60% nonionic contrast material was followed by helical CT of the liver in a sequential arterial phase, portal venous phase, and equilibrium phase.

RESULTS

Of 128 patients, we followed 97. In 21 patients (22%) we found 47 lesions with perfusion abnormalities that were detected 1-33 months (mean 6.6 months) after the operation. All patients were asymptomatic. The shape of each perfusion abnormality was characterized as geographic (n = 23, 47%), wedge-shaped (n = 21, 45%), or round (n = 3, 8%). The abnormalities were seen in the arterial phase in 46 lesions (98%), in the portal venous phase in 18 lesions (38%), and in the equilibrium phase in 1 lesion (0.2%). In all lesions, the size either decreased spontaneously, or it remained unchanged for more than one year.

CONCLUSION

Perfusion abnormalities of the liver may occur in patients who undergo pancreaticobiliary surgery. This findings should not be confused with hypervascular metastases.

Sonographic comparison of intraarterial CO2 and helium microbubbles for detection of hepatocellular carcinoma: preliminary observations

PURPOSE

To evaluate the usefulness of helium gas microbubbles in the detection of small hepatocellular carcinoma (HCC) lesions relative to that of CO2 microbubbles.

MATERIALS AND METHODS

Ultrasonography (US) enhanced with both CO2 microbubbles and helium microbubbles was performed in 15 patients. CO2 microbubbles were injected into the proper hepatic artery under US observation. Next, helium microbubbles were injected. Duration and degree of enhancement with the two types of microbubbles were compared. Ten minutes after helium injection, the whole liver was examined with US to detect additional tumors. When new lesions were detected, biopsy was performed.

RESULTS

Duration of enhancement with the helium microbubbles (mean, 37.2 minutes) was significantly longer than that with the CO2 microbubbles (mean, 3.6 minutes; P < .001). The degree of enhancement with helium was greater than that with CO2. Thirteen additional lesions were detected after injection of helium gas. All these lesions proved to be HCC at biopsy.

CONCLUSION

The duration of enhancement is significantly longer with helium than with CO2 microbubbles. Therefore, helium microbubbles can be used for examination of the whole liver for detection of additional tumors.

Helium gas microbubbles. Experimental study on a new ultrasound contrast material

PURPOSE

To evaluate histological changes and duration of enhancement after the intra-arterial injection of helium gas microbubbles in comparison with conventionally used carbon dioxide (CO2) microbubbles at US.

MATERIAL AND METHODS

Four different doses of helium gas microbubbles (0, 0.1, 0.2 and 0.5 ml/kg) mixed with normal saline and own blood were injected into the celiac artery of 8 rabbits. After one week, autopsies were performed on all animals and histological changes in the liver, stomach and spleen were studied on hematoxylin-eosin stains. In addition, VX-2 tumor strains were transplanted into the femoral muscle in 5 other rabbits. Four weeks after transplantation, we catheterized the femoral artery and either CO2 or helium gas microbubbles were injected under US observation. We evaluated the duration of enhancement in the tumors with the two types of microbubbles.

RESULTS

On histological evaluation, damage in hepatic cells as well as multiple areas of gastritis in the stomach were seen when a dose of 0.5 ml/kg of helium gas was used. Damage in the liver and stomach was slight at a dose of 0.2 ml/kg. The spleen was not damaged at doses of under 0.5 ml/kg. In the evaluation of tumor enhancement, the duration of enhancement with helium gas microbubbles ranged from 28 to 45 min (average 36 min) while that with CO2 ranged from 4 to 12 min (average 9 min) (p<0.01 at paired t-test).

CONCLUSION

Intra-arterial injection of helium gas should not exceed 0.2 ml/kg: a dose of 0.5 ml/kg may cause damage to the liver and stomach. The duration of enhancement with helium gas microbubbles is significantly longer than that with CO2 microbubbles.

Spiral CT of the pancreas. The value of small field-of-view targeted reconstruction

PURPOSE

To compare the value of a retrospective targeted high-resolution spiral CT to the standard reconstruction technique in the assessment of pancreatic diseases.

MATERIAL AND METHODS

Spiral CT pancreatic images of a standard-size reconstruction protocol were compared prospectively with those of a retrospective targeted high-spatial-resolution reconstruction protocol in 30 patients. Prior to clinical evaluation, a phantom study was performed to evaluate the spatial resolution and signal-to-noise ratio of both protocols.

RESULTS

The high-resolution protocol achieved a good signal-to-noise ratio with acceptable spatial resolution. Phantom studies revealed increased image noise (+17%) with an increase in spatial resolution (+100%). In patients studied with the high-resolution protocol, the increase in noise was not significant but there was a marked improvement in the definition of small details.

CONCLUSION

Images obtained with a targeted high-spatial-resolution reconstruction protocol showed superior lesion definition and vascular opacification compared with those obtained with a standard-size reconstruction protocol. This technique may have potential in the evaluation of small pancreatic abnormalities.

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.

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.

Multiple-phase helical CT of the liver for detecting small hepatomas in patients with liver cirrhosis: contrast-injection protocol and optimal timing

OBJECTIVE

Helical CT scanners allow multiple-phase sequential scans of the entire liver to be obtained during a single bolus injection of contrast material. The purpose of this study was to compare two injection protocols and to establish timing that would optimize detection of hepatomas less than 3 cm in diameter.

SUBJECTS AND METHODS

Triple-phase helical CT of the liver was evaluated in 217 patients who had liver cirrhosis and were referred for known or suspected hepatomas. Proof of individual neoplasms was based on biopsy results, surgical findings, or findings of other imaging studies. Sixty percent nonionic contrast material, infused at 2 or 4 ml/sec, was followed by sequential arterial-phase, portal-venous phase, and equilibrium-phase helical scans of the liver. Aortic and hepatic enhancement curves were constructed by measuring CT attenuation. The CT attenuation values of individual tumor lesions were also measured. We compared the degree of enhancement of normal structures and tumors obtained with four scan protocols (injection at 2 ml/sec with a 30-sec scan delay [n = 54], injection at 2 ml/sec with a 35-sec scan delay [n = 47], injection at 4 ml/sec with a 20-sec scan delay [n = 56], and injection at 4 ml/sec with a 25-sec scan delay [n = 60] and determined the optimal injection protocol and timing for CT acquisition.

RESULTS

Peak aortic and hepatic enhancement was obtained earlier with the 4-ml/sec protocol (at 24 sec and 61 sec versus 36 sec and 90 sec for the 2-ml/sec protocol). The peak attenuation value of the aorta was higher with the 4-ml/sec protocol (330 H versus 186 H for the 2-ml/sec protocol). However, peak hepatic attenuation was similar for both protocols (98 H for the 4-ml/sec protocol versus 92 H for the 2-ml/sec protocol). Liver-tumor contrast was highest in the arterial phase with both protocols. The next highest contrast was obtained during the equilibrium phase. Liver-tumor contrast in the portal-venous phase was significantly lower than that in the other two phases. Tumor enhancement was significantly higher in scans obtained using the 4-ml/sec protocol with a delay time of 25 sec than those obtained with a delay time of 20 sec. In 109 hepatomas, 35 tumors were only seen or were most conspicuous during the arterial phase, four tumors were most conspicuous during the equilibrium phase, and one tumor was most conspicuous during the portal-venous phase.

CONCLUSION

Arterial-phase helical CT of the liver after 4-ml/sec injection of contrast material significantly improves detection of hepatomas less than 3 cm in diameter when performed in addition to delayed scanning. Portal-venous phase helical CT is of limited value in detecting small hepatomas.

Small hepatocellular carcinoma in patients with chronic liver damage: prospective comparison of detection with dynamic MR imaging and helical CT of the whole liver

PURPOSE

To compare contrast material-enhanced dynamic magnetic resonance (MR) imaging with helical computed tomography (CT) for the detection of small hepatocellular carcinoma (HCC) in patients with chronic liver damage.

MATERIALS AND METHODS

Fifty patients with chronic hepatitis or liver cirrhosis underwent dynamic contrast-enhanced fast low-angle shot MR imaging and multiple-phase helical CT. Arterial, portal-venous, and delayed-phase images were compared. Diagnostic ability with both techniques was evaluated by means of receiver operating characteristic (ROC) analysis; images in patients with (n = 27) and those without (n = 15) HCC in whom the same anatomic levels were available for both examinations were assessed. Seventy-two lesions were evaluated, and tumor diameter ranged from 0.5 to 3.0 cm (mean, 1.9 cm).

RESULTS

ROC analysis showed that the arterial-phase images obtained with both techniques allowed better detection of HCC. Diagnostic ability was significantly better with arterial-phase MR imaging (mean area under the ROC curve [Az] = 0.96) than arterial-phase CT (Az = 0.87) or with images from any other phase (P < .05). For the delayed phase, diagnostic capability was significantly better with CT (Az = 0.84) than with MR imaging (Az = 0.77) (P < .05).

CONCLUSION

Arterial-phase dynamic MR imaging is superior to helical CT for the detection of HCC in patients with chronic liver damage.

MR findings in two presumed cases of mild central pontine myelinolysis

The authors describe two patients with presumed central pontine myelinolysis whose clinical symptoms were mild despite extensive intrapontine lesions evident on MR imaging. Enhancement of the lesions with Gd-DTPA was not observed in either case. It is suggested that the severity of findings on MR imaging does not necessarily reflect the severity of clinical symptoms of the disease.