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Biomedical subjects

Jun Aoki

Publications and source records attributed to Jun Aoki.

30 records · Page 2Linked to original sources
PubMed2003

[Whether and under what conditions FDG-PET might be cost-effective in evaluating solitary pulmonary nodules depicted on lung cancer screening in Japan].

PURPOSE: To determine whether and under what conditions fluorine-18 fluorodeoxyglucose positron emission tomography (FDG-PET) may be cost-effective in evaluating solitary pulmonary nodules depicted on lung cancer screening in Japan. MATERIALS AND METHODS: Three decision models for differentiating lung cancer from benign nodules were compared: CT alone, PET alone, and CT plus PET. The various paths of each strategy were dependent on variables determined from a review of the medical literature. Costs were based on Japanese health insurance. RESULTS: The prevalence of lung cancer among solitary pulmonary nodules detected on lung cancer screening was less than 10%. For this prevalence, the CT-plus-PET model was the cost-effective alternative to the CT-alone model (cost savings were yen 64,000 per patient) and provided greater accuracy (0.90 vs. 0.84). Both of these effects were the result of reducing the number of candidates who undergo unnecessary CT-guided or bronchofiberscopic biopsies or thoracotomy for a benign pulmonary nodule. CONCLUSION: The CT-plus-PET strategy is accurate and cost-effective for the characterization of solitary pulmonary nodules detected on lung cancer screening in Japan.

Cost-Benefit Analysis↗
PubMed2002

P-glycoprotein inhibition by the multidrug resistance-reversing agent MS-209 enhances bioavailability and antitumor efficacy of orally administered paclitaxel.

PURPOSE: Recent studies in humans and mice have demonstrated that intestinal P-glycoprotein plays a causative role in the limited absorption of orally administered paclitaxel. Multidrug resistance (MDR)-reversing agents, such as cyclosporin A and PSC 833, are known to increase the systemic exposure to orally administered paclitaxel by enhancing absorption in the intestinal tract and decreasing elimination via the biliary tract. In this study, we demonstrated that coadministration of the MDR-reversing agent MS-209, which is known to inhibit P-glycoprotein function by direct interaction, improved the bioavailability of orally administered paclitaxel and consequently enhanced its antitumor activity. METHODS: The pharmacokinetics of paclitaxel were examined by measuring [(3)H]paclitaxel in plasma drawn from rats and mice given the drug with or without MS-209. The influence of MS-209 on the intestinal transport of [(3)H]paclitaxel was studied using a human colorectal cancer cell line, Caco-2. The in vivo efficacy of orally administered paclitaxel in combination with MS-209 was further evaluated in B16 melanoma-bearing mice. RESULTS: The plasma concentration of [(3)H]paclitaxel following oral administration was significantly increased by coadministration of MS-209 at 100 mg/kg in both rats and mice. In rats, the AUC of [(3)H]paclitaxel following oral administration was strikingly increased (1.9-fold) by coadministration of MS-209, whereas the AUC of [(3)H]paclitaxel following i.v. injection was slightly increased (1.3-fold) by MS-209. The increase in apparent bioavailability of oral paclitaxel due to MS-209 was 1.4-fold. To demonstrate this enhancing action in vitro, we studied the influence of MS-209 on the transport of [(3)H]paclitaxel using Caco-2 cells, which is a well-known model of intestinal efflux. The transport of [(3)H]paclitaxel across the Caco-2 monolayer was markedly inhibited in the presence of MS-209, and the apparent K(i)of MS-209 for the active transport of [(3)H]paclitaxel was 0.4 microM. Moreover, paclitaxel administered orally at 100 mg/kg per day with MS-209 at 100 mg/kg per day showed significant antitumor activity in B16 melanoma-bearing mice, whereas paclitaxel administered orally alone at the same dose showed no antitumor activity. These results suggest that the coadministration of MS-209 improved low systemic exposure to paclitaxel through inhibition of P-glycoprotein, which is involved in drug excretion via the intestinal tract, resulting in a clear antitumor activity of paclitaxel administered orally. CONCLUSION: The present study suggests that coadministration of MS-209 may be a useful way to improve the bioavailability of drugs not suitable for oral administration due to elimination via the intestinal tract.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2002

Evaluation of hepatic lesions and hepatic parenchyma using diffusion-weighted reordered turboFLASH magnetic resonance images.

PURPOSE: To determine whether the centric reordered snapshot fast low-angle shot (reordered turboFLASH) magnetic resonance (MR) images with no, low, and high motion-probing gradients (MPGs) were useful to evaluate hepatic lesions and hepatic parenchyma. MATERIALS AND METHODS: The measured diffusion coefficient (D), deviation factor (f), and apparent diffusion coefficient for flowing spin (D*) values for 92 hepatic lesions (33 hepatocellular carcinomas (HCCs), 17 metastases, 27 hemangiomas, and 15 cysts) and the nonlesion-bearing regions of parenchyma in 74 livers (46 noncirrhotic and 28 cirrhotic) were approximately calculated from the reordered turboFLASH images (modified for diffusion sensitivities of b = 0, 50.2, and 295 seconds/mm(2)). RESULTS: These groups, listed in order of decreasing D* and f values, were cysts, noncirrhotic livers, cirrhotic livers, hemangiomas, metastases, and HCCs. The order on the basis of D values was cysts, hemangiomas, metastases, HCCs, cirrhotic livers, and noncirrhotic livers. Noncirrhotic livers showed higher D* and f values, and lower D values than HCCs and metastases (P < 0.04). CONCLUSION: The D* and f values, in addition to the D value, may be useful for evaluating the nature of diffusion and flowing spins in hepatic lesions and hepatic parenchyma.

Adult↗
PubMed2002

Development of perfusion CT software for personal computers.

RATIONALE AND OBJECTIVES: The authors developed software for creating quantitative maps of arterial and portal perfusion in the upper abdominal organs on personal computers. The image quality of these perfusion computed tomographic (CT) images was visually evaluated. MATERIALS AND METHODS: In 58 patients (38 men, 20 women; mean age, 63.9 years +/- 11.9; range, 22-85 years) with various diseases of the upper abdomen, 91 single-section dynamic CT studies were obtained. The data were transferred on-line to a personal computer, and quantitative maps of arterial and portal perfusion were created by means of the maximum-slope method. Perfusion CT images were reviewed by a radiologist and a radiation technologist, and image quality was rated according to a four-category scoring system (1 = good quality, 2 = moderate, 3 = poor, 4 = images could not be created). RESULTS: Arterial perfusion CT images could be created in 81 (89%) of 91 examinations, and 74 images (81%) were scored as 1 or 2. Portal perfusion CT images could be created in 60 (68%) of 88 examinations, in which a portal trunk was included in the section, and 33 of them (38%) were scored as 1 or 2. Patient motion during dynamic CT sequences resulted in poor image quality in seven arterial and 27 portal perfusion images. CONCLUSION: Perfusion CT can combine quantitative perfusion maps with good anatomic detail in one image, although patient movement frequently degrades image quality in portal perfusion CT.

Abdomen↗
PubMed2002

Effect of contrast-enhanced computed tomography on diagnosis and management of acute abdomen in adults.

AIM: To determine the impact of computed tomography (CT) on the diagnosis and treatment plan in patients with acute abdominal pain. MATERIALS AND METHODS: A prospective study was undertaken in 125 adult patients presenting with acute abdominal pain (74 men and 51 women; 40.2 +/- 19.3 years; range, 18-92). Changes in diagnosis, gain in percentage diagnostic certainty and changes of treatment plan of the surgeons in the emergency department before and after CT were evaluated. Pre- and post-CT diagnoses were compared with the final diagnoses. RESULTS: CT findings changed the initial diagnosis in 40 (32.0%) patients. The diagnostic certainty was 58.3 +/- 22.9% before CT, and its gain after CT was 21.9 +/- 18.5 points (P < 0.0001). Post-CT diagnoses were consistent with the final diagnosis in 116 patients (92.8%), while pre-CT diagnoses were correct in 89 patients (71.2%; P < 0.0001). Initial treatment plans were changed in 31 (24.8%) patients after CT. In 57 (45.6%) patients, CT information changed diagnoses and/or treatment plans. No significant differences were observed in the diagnosis, diagnostic certainty and treatment plan among four surgeons. CONCLUSION: Contrast-enhanced CT frequently changed the clinical diagnoses with increased diagnostic certainty and the initial treatment plans.

Abdomen, Acute↗
PubMed2002

Atypical growth plate closure: a possible chronic Salter and Harris Type V injury.

Salter-Harris Type V epiphyseal injury is relatively uncommon. The authors present a case involving the proximal tibia diagnosed both by radiologic and histologic findings. The findings suggest that Salter-Harris Type V injury can be a possible outcome when the disappearance of the physeal plate is reported in a patient who has great physical activity in childhood, even if the patient has suffered from no major injury.

Adolescent↗
PubMed2002

Which concentration of the inhibitor should be used to predict in vivo drug interactions from in vitro data?

When the metabolism of a drug is competitively or noncompetitively inhibited by another drug, the degree of in vivo interaction can be evaluated from the [I]u/Ki ratio, where [I]u is the unbound concentration around the enzyme and Ki is the inhibition constant of the inhibitor. In the present study, we evaluated the metabolic inhibition potential of drugs known to be inhibitors or substrates of cytochrome P450 by estimating their [I]u/Ki ratio using literature data. The maximum concentration of the inhibitor in the circulating blood ([I]max), its maximum unbound concentration in the circulating blood ([I]max,u), and its maximum unbound concentration at the inlet to the liver ([I]in,max,u) were used as [I]u, and the results were compared with each other. In order to calculate the [I]u/Ki ratios, the pharmacokinetic parameters of each drug were obtained from the literature, together with their reported Ki values determined in in vitro studies using human liver microsomes. For most of the drugs with a calculated [I]in,max,u/Ki ratio less than 0.25, which applied to about half of the drugs investigated, no in vivo interactions had been reported or "no interaction" was reported in clinical studies. In contrast, the [I]max,u/Ki and [I]max/Ki ratio was calculated to be less than 0.25 for about 90% and 65% of the drugs, respectively, and more than a 1.25-fold increase was reported in the area under the concentration-time curve of the co-administered drug for about 30% of such drugs. These findings indicate that the possibility of underestimation of in vivo interactions (possibility of false-negative prediction) is greater when [I]max,u or [I]max values are used compared with using [I]in,max,u values.

Binding, Competitive↗
PubMedDate not supplied

Evaluation of hemangioma by positron emission tomography: role in a multimodality approach.

PURPOSE: The relative utility of various preoperative diagnostic imaging modalities for the evaluation of hemangioma of the extremities, including positron emission tomography (PET) (using 18F-fluoro-2-deoxy-D-glucose [FDG] and fluorine-18 alpha-methyltyrosine [FMT]), computed tomography (CT), magnetic resonance imaging (MRI), and digital subtraction angiography (DSA), was investigated. METHODS: Imaging findings in 16 patients with 16 histopathologically documented hemangiomas of the extremities were retrospectively reviewed. Preoperative imaging included: FDG-PET (n = 16), FMT-PET (n = 12), MRI (n =16), CT (n =11), and DSA (n =14). RESULTS: All 16 lesions examined by PET with FDG and/or FMT showed accumulation. The standardized uptake values (SUVs) for FDG-PET for the 16 examined tumors ranged from 0.7 to 1.67; for FMT-PET, they ranged from 0.14 to 1.00. The SUVs with both tracers indicated the benign nature of the tumor. Computed tomography demonstrated variable attenuation and phleboliths in two patients. The MRI signal characteristics were relatively consistent: heterogeneous signals were slightly higher than those of skeletal muscle on T1-weighted images and brighter than those of subcutaneous fat on T2-weighted images. The pooling and cotton-wool staining depicted in DSA was found to be significantly correlated with FDG accumulation, suggesting that localized blood retention-induced ischemia may accelerate anaerobic glycolysis, which leads to high FDG uptake. CONCLUSION: Although plain radiography, CT, MRI, and angiography may provide anatomic extent and be pathognomonic, FDG-PET and FMT-PET may be the most reliable among the studied imaging modalities for differentiating benign hemangiomas from other soft tissue tumors, especially malignant neoplasms.

Adolescent↗
PubMedDate not supplied

Early diagnosis and radical surgical treatment of Budd-Chiari syndrome.

We report a 26-year-old woman who was diagnosed with Budd-Chiari syndrome following consultation for a skin nodule in the lower extremity. Histopathological examination of a biopsy specimen showed features of erythema induratum. As part of the diagnostic work-up, chest roentgenography performed to rule out possible tuberculosis showed enlarged right lower mediastinum. Computed tomography identified a dilated azygos vein and obstruction of the inferior vena cava near the liver. Liver function tests and blood cell counts were all within normal limit and no sign of portal hypertension was noted except for mild splenomegaly. Although angioplasty by balloon catheter resulted in recanalization of the obstructed inferior vena cava, obstruction of the inferior vena cava appeared again 2 months later. One-stage surgical reconstruction of the vascular abnormalities affecting inferior vena cava and hepatic vein using autologous pericardial patch was performed 11 months after angioplasty, which resulted in normalization of blood flow. Examination of a liver biopsy obtained intraoperatively revealed hepatic fibrosis compatible with early-stage Budd-Chiari syndrome. No complications were noted postoperatively and the nodular lesion in the lower extremity disappeared after surgery.

Adult↗
PubMedDate not supplied

The combination of multi-voxel MR spectroscopy with MR imaging improve the diagnostic accuracy for localization of prostate cancer.

BACKGROUND: We assessed the usefulness of combined multi-voxel magnetic resonance spectroscopy (MRS) and MR imaging (MRI) in the diagnosis of prostate cancer localization. PATIENTS AND METHODS: MRS and MRI were performed in 21 patients with prostate cancer. On T2-weighted images, tumor localization was based on low signal intensity in the peripheral zone. At MRS, cancer patterns were diagnosed when the ratio of choline plus creatine to citrate was greater than 0.86. The results were analyzed with reference to pathological confirmation of prostate cancer at bilateral or unilateral lobe. RESULTS: Six out of 11 patients with unilateral positive biopsy specimens were diagnosed as unilateral cancer, and 9 of 10 patients with bilateral positive biopsy specimens were diagnosed as bilateral cancer on MRI. Two of 4 patients with unilateral cancer, who were not detected on MRI alone, were diagnosed as unilateral cancer on combined MRI and MRS. The accuracy of MRI alone was 71.4%, while that of combined MRI and MRS was 81.0%. CONCLUSION: Combined MRI and MRS improved the diagnostic accuracy for localization of prostate cancer.

Adenocarcinoma↗