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Kazuo Awai

Publications and source records attributed to Kazuo Awai.

46 records · Page 3Linked to original sources
PubMed2004

Endometrial carcinoma in adenomyosis: assessment of myometrial invasion on T2-weighted spin-echo and gadolinium-enhanced T1-weighted images.

OBJECTIVE: The aim of our study was to compare T2-weighted and contrast-enhanced dynamic T1-weighted images with histologic findings in assessing the depth of myometrial invasion by endometrial carcinoma in adenomyosis. MATERIALS AND METHODS: We retrospectively reviewed the MRIs of 11 patients who had a total of 12 lesions of endometrial carcinoma within adenomyosis. T2-weighted and contrast-enhanced dynamic T1-weighted images were compared with the histologic findings separately. We assessed the extent of myometrial invasion by endometrial carcinomas. The depth of myometrial invasion seen on MRI was classified as stage S (superficial invasion), stage D (deep invasion), or undetectable. The staging accuracies of each sequence were assessed. The tumor-myometrium contrast-to-noise ratios were calculated for each sequence. RESULTS: The histologic specimens revealed that myometrial invasion was deep in seven of 12 lesions and superficial in five. On T2-weighted images the depth of invasion was underestimated in two lesions and impossible to determine in five lesions. On dynamic T1-weighted images the depth of invasion was overestimated in one lesion and underestimated in one lesion. The staging accuracy on dynamic T1-weighted images (83%) was significantly higher than that on T2-weighted images (42%). The contrast-to-noise ratio was significantly higher on dynamic T1-weighted studies during the early phase (mean +/- SD, 2.68 +/- 0.94) than it was on T2-weighted studies (1.74 +/- 1.05) and during the delayed phase (2.01 +/- 0.86). CONCLUSION: When adenomyosis coexists with endometrial cancer at the same site on T2-weighted images, contrast-enhanced dynamic T1-weighted imaging improves the accuracy of staging.

Adult↗
PubMed2004

[Interaction between a ceiling pendent-type lead acrylic protective board for use in IVR and scattered radiation].

Scattered radiation was measured following the application of a ceiling pendent-type lead acrylic protective board (protective board) for use in IVR, and the dose-reduction rate was obtained. As a result of the interaction between the protective board and the scattered radiation, the dose reduction rate in the space between the protective board and floor surface became negative, resulting in an increase in scattered radiation. It was demonstrated that the increase in scattered radiation could be prevented by installing an added filter. This report presents a method to evaluate the effect of a protective board on scattered radiation by converting its property to that of a material with a similar effective density, and explains the experimental results. This report also shows that a conventional method, which calculates scattered radiation on the basis of lead equivalent, carries the risk of underestimating the effect on scattered radiation. The necessity of training operators based on the above findings is also emphasized.

Acrylates↗
PubMed2004

[Radiation exposure doses in medical procedures].

An investigation was conducted concerning long-term changes of patients' radiation exposure doses in medical procedures such as chest X-ray and CT scans. The result of the investigation compelled consideration of methods for reducing the exposure doses. While the exposure doses have decreased in chest X-ray compared with 30 years ago, they have remained unchanged in CT scan compared with 20 years ago. The following address possible causes of unchanged doses for CT scan: Measuring doses is difficult. Technology to reduce patients' doses has yet to be used effectively. It is important to take deterministic causes into consideration. More research and attention to the issue are needed.

Humans↗
PubMed2003

Effect of contrast injection protocol with dose tailored to patient weight and fixed injection duration on aortic and hepatic enhancement at multidetector-row helical CT.

The aim of this study was to investigate the effect of a contrast material injection protocol with dose and injection rate of contrast material tailored to patient weight (dose tailored to patient weight and fixed injection duration). Hepatic helical CT was performed in 92 patients with chronic liver damage with a dose of 1.4 ml (518 mgI) at a rate of 0.056 ml/s per kilogram body weight of Iopamidol 370. Attenuation values of liver and aorta were measured for calculation of maximum aortic and hepatic enhancement, time to maximum hepatic enhancement, and end of hepatic arterial phase. Correlation coefficients between the injection rate and the four parameters were r=0.008, 0.057, 0.167, and 0.036, and there were no statistically significant correlations between the injection rates and the four parameters. In our injection protocol, uniform temporal scan window may be achieved and the injection rate can be reduced in lighter patients without reducing the degree of enhancement in the aorta and the liver.

Aged↗
PubMed2002

Solitary necrotic nodule of the liver.

Solitary necrotic nodule of the liver is a rare benign lesion; only 22 cases have been reported to date. An unsolved problem in treating these lesions involves the difficulties in differential diagnosis; specific features of necrotic nodule of the liver in preoperative examinations have not been identified. Here, we report a patient with resected solitary necrotic nodule of the liver with preoperative features shown on ultrasound (US), computed tomography (CT), and magnetic resonance imaging (MRI) examinations. A 48-year-old woman was referred to our hospital on December 13, 1999 because a hypoechoic lesion in Couinaud's segment VIII of the liver had been incidentally detected on US. A CT scan confirmed the presence of a round hypodense lesion, measuring 2 cm in diameter. No significant enhancement was recognized on dynamic MRI study. T1-Weighted MRI examinations demonstrated a low intensity showing a triple-layered pattern with low-iso-low intensity in the lesion, while T2-weighted images demonstrated a slightly high intensity in the lesion. These features suggested fibrous tissue. Histological examinations following partial resection of the liver revealed a solitary necrotic nodule of the liver. Combination studies, including MRI examinations, would be useful for the preoperative diagnosis of a solitary necrotic nodule of the liver.

Female↗
PubMed2002

Aortic and hepatic enhancement and tumor-to-liver contrast: analysis of the effect of different concentrations of contrast material at multi-detector row helical CT.

PURPOSE: To investigate the effect of different iodine concentrations of contrast material on aortic and hepatic enhancement and the detectability of hypervascular hepatocellular carcinoma (HCC) with multi-detector row computed tomography (CT) and a uniphasic contrast material injection technique. MATERIALS AND METHODS: Two hundred one patients with known or who were suspected of having HCC underwent multi-detector row CT; 58 patients with hypervascular HCC were identified. First-, second-, and third-phase scanning was started with the aortic arrival times plus 15 seconds, plus 30 seconds, and plus 105 seconds, respectively. All patients were assigned randomly into two groups. Patients in groups A and B received iopamidol with an iodine concentration of 300 mg/mL and 370 mg/mL, respectively, with the same total iodine load per patient per body weight. The liver and aorta enhancement and tumor-to-liver contrast (TLC) were measured. Depiction of hepatic arteries was evaluated visually by two radiologists. RESULTS: During the first phase, aortic enhancement was significantly (P <.01) higher in group B, with no significant difference in hepatic enhancement between the two groups. During the second phase, aortic enhancement was significantly (P <.01) higher in group A, with no significant difference in hepatic enhancement. The TLC was significantly (P <.01) higher in group B during the first phase, but there was no significant difference between the two groups during the second phase. There was no significant difference in any parameters between the two groups during the third phase. Depiction of the hepatic arteries in group B was significantly (P <.05) superior to that in group A. CONCLUSION: In the arterial phase, administration of a higher concentration of contrast material is effective for a significantly higher TLC.

Adult↗
PubMedDate not supplied

Evaluation of hypervascular hepatocellular carcinoma in cirrhotic liver by means of helical CT: comparison of different contrast medium concentrations within the same patient.

PURPOSE: To compare enhancement of the aorta, portal vein, liver, and tumor with contrast medium of a higher iodine concentration to that with one of a standard iodine concentration for liver dynamic CT within the same patient with known liver cirrhosis and hepatocellular carcinoma (HCC). MATERIALS AND METHODS: Fifty-three patients with known cirrhosis and HCC underwent repeat computed tomographic (CT) examinations within three months, the first with either 300 (n=26) or 370 mgI/ml (n=27) of nonionic contrast material. In the second examination, only concentration was altered. In 28 patients, weight was equal to or more than 65 kg, and in 25 patients it was less than 65 kg. The CT numbers (HU) of the aorta, portal vein, liver, and tumor were obtained, and CT attenuation was compared between the two concentration studies. The degree of enhancement was scored qualitatively. RESULTS: Mean enhancement values of the aorta, liver, portal vein, and tumor were greater with the 370 mgI/ml injections than with the 300 mgI/ml injections throughout the study. In visual analysis, the difference in aortic, portal venous, liver, and tumor enhancement was not statistically significant between the two groups in patients weighing less than 65 kg. However, in patients weighing 65 kg or more, strong aortic and portal venous enhancement (rated as good or excellent) occurred more frequently with the 370 mgI/ml injections than with the 300 mgI/ml injections. CONCLUSION: Higher contrast enhancement was achieved in patients who received 370 mgI/ml of contrast material, resulting in better tissue contrast between liver parenchyma and HCCs. However, this difference was not visually significant in patients weighing less than 65 kg.

Aged↗
PubMedDate not supplied

Role of preoperative helical CT before laparoscopic cholecystectomy: evaluation of gallbladder and peritoneal adhesion.

OBJECTIVE: The purpose of this study was to assess the value of preoperative helical CT for the detection of adhesion of the gallbladder or surrounding peritoneum. SUBJECTS AND METHODS: Dynamic-enhanced helical CT of the abdomen was obtained before laparoscopic cholecystectomy in 47 patients. Images were reconstructed with a 5-mm interval. Appearances on CT images were correlated with operative findings, and useful findings for predicting gallbladder or peritoneal adhesion were determined by univariate and multivariate analysis. RESULTS: Patients with gallbladder or peritoneal adhesion often have gallbladder wall thickening, gallbladder wall enhancement, and increased density of the pericholecystic fat more frequently than patients without adhesion on both precontrast and postcontrast CT. Each of these findings was significant on univariate analysis. On multivariate analysis, increased density of the pericholecystic fat and focal attenuation increase in the liver were significant factors for predicting gallbladder or peritoneal adhesion. CONCLUSION: Increased density or stranding of pericholecystic fat and transient focal hepatic attenuation increase at dynamic arterial-phase CT indicates gallbladder and peritoneal adhesion.

Cholecystectomy, Laparoscopic↗
PubMedDate not supplied

Contrast enhancement for whole-body screening using multidetector row helical CT: comparison between uniphasic and biphasic injection protocols.

OBJECTIVE: To investigate which is more suitable for whole-body screening with multidetector row CT (MDCT) during one breathhold, a uniphasic or biphasic injection protocol for contrast material. SUBJECTS AND METHODS: Sixty patients received a volume of 1.7 mL x weight (kg) with iopamidol 300 mg iodine/mL. The patients were randomized into two injection protocols: A) a fixed injection rate of 2.0 mL/sec with a 70 sec delay, B) administration of 80% of the contrast material in 40 sec, then administration of the remaining 20% in 20 sec with an 80 sec delay. A helical scan from the apex of the lung to the base of the pelvic cavity was performed during one breathhold. CT attenuation values of the thoracic aorta, pulmonary artery, abdominal aorta, portal vein, superior vena cava (SVC), suprarenal and infrarenal inferior vena cava (IVC), liver, and pancreas were measured. Two radiologists visually assessed the degree enhancement of the IVC. In addition, the two radiologists visually assessed artifacts caused by contrast material in the subclavian vein and SVC using a four-point scale. RESULTS: Enhancement of the SVC in protocol A was significantly better than that in protocol B (p=0.04). Enhancement of the infrarenal IVC and liver in protocol B was significantly better than that in protocol A (p<0.01, p<0.01). Renal enhancement in protocol B was significantly better than that in protocol A (p=0.02). In all patients with both protocols A and B, enhancement of the suprarenal IVC was visually graded as acceptable or good. In all patients with protocol B, enhancement of the infrarenal IVC was graded as acceptable or good. In only 2/3 of patients with protocol A, enhancement of the infrarenal IVC was graded as acceptable or good. There was no significant difference in artifacts in the subclavian vein between the two protocols (p=0.77). Artifacts in the SVC in protocol B were significantly fewer than those in protocol A (p<0.01). CONCLUSION: Protocol B was more suitable for whole-body screening than protocol A, because of better enhancement of the liver and infrarenal IVC and fewer artifacts in the SVC.

Artifacts↗