Biomedical subjects

T Nishiharu

Publications and source records attributed to T Nishiharu.

17 recordsLinked to original sources

PubMed2001

[Usefulness of enhanced ultrasonography after administration of intravenous contrast agent in the evaluation of therapeutic effect in treatment of hepatocellular carcinoma, and efficacy of percutaneous ethanol injection therapy (PEIT) for residual tumor].

PURPOSE: To investigate the usefulness of enhanced ultrasonography after the administration of intravenous contrast agent in the evaluation of therapeutic effect in the treatment of hepatocellular carcinoma (HCC) comparison with dynamic CT, and to examine the efficacy of percutaneous ethanol injection therapy (PEIT) for residual tumor. MATERIALS AND METHODS: Thirty patients (22 men, 8 women; age range, 42-76 years; mean age 60 years) underwent enhanced ultrasonography with the intravenous ultrasonographic agents Levovist, after transcatheter arterial embolization (TAE) (n = 15, size range 23-35 mm, mean 25.3 mm) or PEIT (n = 15, 15-35 mm, mean 24.5 mm), to compare the therapeutic effect with dynamic CT. If residual lesions were detected by enhanced ultrasonography, we performed additional PEIT. RESULTS: The evaluation of enhanced ultrasonography correlated almost completely with that of dynamic CT. Two residual lesions could not be detected by dynamic CT due to lipiodol, but enhanced ultrasonography and dynamic MRI showed them clearly. In total, eight residual tumors (3-15 mm, mean 8.3 mm) were seen. We performed PEIT on seven lesions and obtained good control for six months. CONCLUSION: Enhanced ultrasonography with Levovist could be performed to evaluate the therapeutic effect of treatment for HCC, and could serve as be a good marker for additional US-guided therapy.

Adult↗

PubMed1999

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.

Adenocarcinoma↗

PubMed1999

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.

Aged↗

PubMed1998

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.

Adult↗

PubMed1998

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.

Animals↗

PubMed1998

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.

Aged↗

PubMed1998

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.

Carbon Dioxide↗

PubMed1998

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.

Aged↗

PubMed1997

Percutaneous microwave coagulation therapy in liver tumors. A 3-year experience.

PURPOSE: Percutaneous microwave coagulation therapy (PMCT) is an interventional alternative for inoperable malignant liver tumors. In this paper, we report the results of our 3-year experience of PMCT in order to establish suitable indications for this treatment. MATERIAL AND METHODS: We studied a total of 27 inoperable liver tumors in 24 patients. Histology of the tumors showed 20 hepatocellular carcinomas (HCCs) (13 well differentiated, 4 moderately differentiated, and 3 poorly differentiated) and 7 metastases. These tumors were treated by PMCT and were followed for 4-40 months (average 18 months). Under US guidance, the tumors were coagulated by microwaves emitted from an electrode. The changes of tumor size after PMCT were evaluated by CT. When the tumors disappeared or were reduced in size after treatment, PMCT was regarded as effective. Complications from PMCT were also evaluated. The patient survival rate was obtained by means of the Kaplan-Meier method. RESULTS: In tumors of 30 mm or less, treatment response was obtained in 70% of cases, while 55% of tumors larger than 30 mm responded. The tumor became smaller or disappeared in 85% of the well differentiated HCCs, and in 25% of the moderately differentiated HCCs, but none of the poorly differentiated HCCs responded. In metastatic tumors, PMCT was effective in 57% of cases. Slight pain (24%), fever (20%) and subcutaneous hematoma (8%) were experienced immediately after PMCT. In 2 poorly differentiated HCCs, needle tract seeding was observed. No case of liver dysfunction was seen after PMCT. The overall survival rate was 83.1% at 1 year and 68.7% at 2 years. CONCLUSION: Good therapeutic results were achieved with PMCT in lesions of 30 mm or less, and in well differentiated HCCs.

Aged↗

PubMed1996

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.

Aged↗

PubMed1996

Detection of hepatocellular carcinoma by intraarterially enhanced ultrasonography with CO2 microbubbles. Comparison with DSA, dynamic CT, and Lipiodol CT.

PURPOSE: To evaluate the diagnostic value of contrast-enhanced US with CO2 microbubbles (EU) for HCCs. Detectability was compared with DSA, dynamic CT, and Lipiodol CT. MATERIAL AND METHODS: Forty-seven histologically proven HCCs detected with US were evaluated with EU, DSA, and dynamic CT. In 23 patients (35 lesions), Lipiodol CT was also performed. The size of the tumors ranged from 8 to 71 mm (average 28.1 mm); 24 lesions were smaller than 20 mm and 23 lesions were larger than 20 mm. RESULTS: Overall detection was possible in 40 of 47 lesions (85%) by EU, in 32 of 47 (68%) by DSA, in 33 of 47 (74%) by dynamic CT, and in 27 of 35 (77%) by Lipiodol CT. In tumors smaller than 20 mm, detection was possible in 21 of 24 lesions (88%) by EU, 14 of 24 (58%) by DSA, 14 of 24 (58%) by dynamic CT, and 11 of 17 (65%) by Lipiodol CT. CONCLUSION: EU has significant diagnostic value for detection of HCCs, particularly tumors smaller than 20 mm.

Angiography, Digital Subtraction↗

PubMed1996

Detection of pseudocapsule of renal cell carcinoma with MR imaging and CT.

OBJECTIVE: A pseudocapsule surrounding a renal cell carcinoma is a pathologic feature seen frequently in the early stages of this disease. Partial nephrectomy or simple enucleation may be indicated when a pseudocapsule is detected. The purpose of this study is to analyze the roles of MR imaging and CT in showing the pseudocapsule in renal cell carcinomas. SUBJECTS AND METHODS: MR imaging and CT appearances of the kidneys in 52 patients with 54 renal cell carcinomas--and 40 patients with 45 other renal masses for comparison--were prospectively analyzed and correlated with pathologic results. The frequency of a pseudocapsule in renal cell carcinomas and in various renal tumors was analyzed. We compared the detectability of a pseudocapsule in renal cell carcinomas with MR imaging on T1-weighted spin-echo, T2-weighted spin-echo, and contrast-enhanced T1-weighted spin-echo sequences, and on contrast-enhanced CT. RESULTS: At pathologic evaluation, a pseudocapsule was seen in 66% (19 of 29) of tumors 4 cm or less in diameter and in 28% (7 or 25) of tumors larger than 4 cm in diameter. All tumors with a pseudocapsule were low histologic grade. Large renal cell carcinomas and other tumors appeared expansile but not encapsulated. A rim corresponding to the pseudocapsule was seen around the tumor in seven lesions on T1-weighted images, 26 lesions on T2-weighted images, and 11 lesions on postcontrast T1-weighted images. T2-weighted imaging was the most sensitive technique for visualization of the pseudocapsule (sensitivity, 68%; specificity, 91%). All pseudocapsules detected on T1-weighted images or postcontrast T1-weighted images could be detected on T2-weighted images. With postcontrast images, enhancement of the pseudocapsule resulted in poor contrast relative to the surrounding tissue. At contrast-enhanced CT, the pseudocapsule was not visible in any tumors. In all MR imaging sequences and in CT, a pseudocapsule were not found in other pathologic conditions except oncocytoma. CONCLUSION: A pseudocapsule was seen in 66% of renal cell carcinomas 4 cm in diameter or smaller. T2-weighted MR imaging is the most sensitive technique for showing this feature.

Adult↗

PubMed1996

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.

Carcinoma, Hepatocellular↗

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↗

PubMed1995

Hepatocellular carcinoma in cirrhotic livers: detection with unenhanced and iron oxide-enhanced MR imaging.

PURPOSE: To evaluate diagnostic accuracy with unenhanced and superparamagnetic iron oxide (SPIO)-enhanced magnetic resonance (MR) imaging for detection of hepatocellular carcinoma (HCC) in cirrhotic livers. MATERIALS AND METHODS: Fifteen patients with 26 histologically proved HCCs associated with liver cirrhosis underwent imaging with T1-, T2-, and proton-density-weighted spin-echo (SE) and fast low-angle shot (FLASH) sequences. Lesion-to-liver contrast-to-noise ratios were measured in all sequences. Diagnostic performance of the imaging techniques was assessed by using receiver operating characteristic analysis. RESULTS: Enhanced SE and FLASH sequences were significantly more accurate (P < .005) for the detection of small HCCs. Among the unenhanced pulse sequences, the accuracy of tumor localization was highest with the T2-weighted SE sequences; however, 25% of the lesions were located incorrectly. Compared with unenhanced images, lesions were correctly located more often when SPIO-enhanced SE and FLASH sequences were used. CONCLUSION: SPIO-enhanced MR imaging with proton-density-weighted or FLASH sequences was more accurate in the detection of small HCCs in cirrhotic livers.

Biopsy↗

PubMedDate not supplied

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.

Angiography↗

PubMedDate not supplied

Percutaneous microwave coagulation therapy: an experimental study.

PURPOSE: Microwave coagulation therapy (MCT) is a surgical alternative for inoperable hepatocellular carcinomas (HCCs). We have recently developed a percutaneous method for using MCT under ultrasound guidance. The purpose of this study was to investigate the feasibility of percutaneous MCT (PMCT) in an animal model and correlate the ultrasound findings with histological results. MATERIALS AND METHODS: Microwaves were administered for 30, 45, 60 and 90 seconds to 12 cadaveric porcine livers in vivo one hour after sacrificing them, to determine the most suitable coagulation time for the percutaneous method. The cadaveric livers were then subjected to histologic evaluation. The temperature around the electrode was measured in both cadaveric and living livers during PMCT. Ultrasound-guided MCT was also performed in nine rabbits. The histological findings after PMCT were evaluated in the cadaveric and living livers, and the areas of coagulation necrosis were correlated with the ultrasound findings. RESULTS: After microwave emission, coagulation necrosis of a spindle shape occurred primarily from the base of the electrode. The maximum area of coagulation was obtained at 60 seconds. The maximum temperature of cadaveric liver under PMCT was 95 degrees at 3 mm from the electrode; that of living liver was 85.1 degrees at 5 mm. Ultrasound revealed hyperechoic areas after PMCT in both cadaveric and living livers. On microscopy, parenchymal necrosis of the liver was observed only in living livers one month after MCT. Hyperechoic areas measured with ultrasound were significantly larger than the actual necrotic areas (p < 0.01), probably due to air bubbles which developed within the tissue. CONCLUSIONS: PMCT completely coagulated the liver tissue around the electrode. These preliminary results indicate that PMCT should be an effective treatment for hepatic neoplasms. In terms of clinical application, the hyperechoic areas observed during PMCT appear to be considerably larger than the areas actually treated.

Animals↗