Biomedical subjects

Duo Liu

Publications and source records attributed to Duo Liu.

9 recordsLinked to original sources

PubMed2006

Pulmonary nodules: estimation of malignancy at thin-section helical CT--effect of computer-aided diagnosis on performance of radiologists.

PURPOSE: To evaluate the effect of a computer-aided diagnosis (CAD) system on the diagnostic performance of radiologists for the estimation of the malignancy of pulmonary nodules on thin-section helical computed tomographic (CT) scans. MATERIALS AND METHODS: The institutional review board approved use of the CT database; informed specific study-related consent was waived. The institutional review board approved participation of radiologists; informed consent was obtained from all observers. Thirty-three (18 malignant, 15 benign) pulmonary nodules of less than 3.0 cm in maximal diameter were evaluated. Receiver operating characteristic (ROC) analysis with a continuous rating scale was used to compare observer performance for the estimation of the likelihood of malignancy first without and then with the CAD system. The participants were 10 board-certified radiologists and nine radiology residents. RESULTS: For all 19 participants, the mean area under the best-fit ROC curve (A(z)) values achieved without and with the CAD system were 0.843 +/- 0.097 (standard deviation) and 0.924 +/- 0.043, respectively. The difference was significant (P = .021). The mean A(z) values achieved without and with the CAD system were 0.910 +/- 0.052 and 0.944 +/- 0.040, respectively, for the 10 board-certified radiologists (P = .190) and 0.768 +/- 0.078 and 0.901 +/- 0.036, respectively, for the nine radiology residents (P = .009). CONCLUSION: Use of the CAD system significantly (P = .009) improved the diagnostic performance of radiology residents for assessment of the malignancy of pulmonary nodules; however, it did not improve that of board-certified radiologists.

Adenocarcinoma↗

PubMed2006

Ectopic cervical thymus in an infant.

We report a case of accessory cervical thymus presenting as a unilateral neck mass in a 2-month-old boy. Ultrasonography (US) showed a mass isoechogenic to muscle in the left neck. Computed tomography (CT) revealed a well-defined, mildly enhanced mass located anterior to the sternocleidomastoid muscle, anterolateral to the carotid sheath, and posterior to the submandibular gland. On magnetic resonance imaging (MRI), the mass was isointense to muscle on T1-weighted images and hyperintense to muscle on T2-weighted images. Diffusion-weighted images showed relatively low apparent diffusion coefficient (ADC) values, and the mass was slightly enhanced after administration of contrast material. We suspected ectopic thymus, but we could not exclude the possibility of a malignant lesion. Therefore, the tumor was surgically resected. The histological diagnosis was ectopic cervical thymus. Ectopic thymus should be included in the differential diagnosis of a submandibular or cervical mass in infants. US and MRI can provide useful information for the diagnosis of ectopic cervical thymus.

Biomarkers, Tumor↗

PubMed2006

Improvement of low-contrast detectability in low-dose hepatic multidetector computed tomography using a novel adaptive filter: evaluation with a computer-simulated liver including tumors.

PURPOSE: The purpose of this study was to investigate how much radiation dose can be reduced without loss of low-contrast detectability with a newly developed adaptive noise reduction filter in hepatic multidetector computed tomography (MDCT) scans by using a computer-simulated liver phantom. MATERIALS AND METHODS: Simulated CT images, including liver and intrahepatic tumors, were mathematically constructed using a computer workstation to evaluate low-contrast detectability by the observer performance test. Milliampere second for construction of simulated images were 60, 80, 100, and 120 mAs (low dose) and 160 mAs (standard dose) at 120 kVp. Images with 60, 80, 100, and 120 mAs were postprocessed with the adaptive noise reduction filter. A total of 432 images were prepared and receiver operating characteristic (ROC) analysis was performed by 5 radiologists. The detectability of simulated tumor by radiologists was estimated with the area under the ROC curves (Az values). In addition, we visually evaluated CT images of 15 patients with chronic liver damage for graininess of the liver parenchyma, sharpness of the liver contour, conspicuity and marginal sharpness of the liver tumors, and overall image quality. RESULTS: The mean Az value at 0.777 (60 mAs), 0.828 (80 mAs), and 0.844 (100 mAs) without filter was significantly lower than that of 160 mAs without filter (P < 0.001, 60 mAs; P = 0.010, 80 mAs; P = 0.040, 100 mAs). There was no statistical difference between the mean Az value at 80 mAs with and 160 mAs without the adaptive noise reduction filter (P = 0.220) and 100 mAs with and 160 mAs without the adaptive noise reduction filter (P = 0.979). In the visual evaluation of patient livers, there was no statistical difference in the graininess and sharpness of the liver, the conspicuity and marginal sharpness of the tumor, and the overall image quality between standard-dose and filtered low-dose images (Wilcoxon signed rank test, P > 0.05). CONCLUSION: The radiation dose can be reduced by 50% without loss of nodule detectability by applying the adaptive noise reduction filter to simulated and patient liver images obtained at MDCT.

Aged↗

PubMed2006

Simulation of aortic peak enhancement on MDCT using a contrast material flow phantom: feasibility study.

OBJECTIVE: The objective of our study was to develop a flow phantom simulating aortic peak enhancement after the injection of contrast material on CT and to investigate the validity of the flow phantom by comparing the time-enhancement curves obtained for the flow phantom and humans. MATERIALS AND METHODS: We developed a flow phantom simulating the enhancement pattern of the aorta after the injection of contrast material. In protocols 1, 2, and 3 of the phantom study, 90, 102, and 150 mL of iohexol, respectively, was administered over 35 sec. In protocol 4, 102 mL of iohexol was administered over 25 sec. In phantom protocols 1', 2', and 3', the dose and contrast injection duration were the same as in protocols 1, 2, and 3; however, saline (10 mL) was injected during the 20 sec after contrast delivery. In the human study, 20 patients were randomized into four groups: Groups A, B, and C received 1.5, 1.7, and 2.5 mL of iohexol per kilogram of body weight, respectively, over 35 sec; and group D received 1.7 mL/kg over 25 sec. In patient groups A, B, C, and D, phantom protocols 1, 2, 3, and 4 were used, respectively. Single-level serial CT scans were obtained using a 16-MDCT scanner on the simulated and real aortas after the injection of contrast material. Time-enhancement curves of simulated and real aortas were generated, and aortic peak times and aortic peak enhancement values were calculated. RESULTS: Aortic peak enhancement and aortic peak times in protocols 1-4 and 1'-3' of the phantom study were 2-8% larger and 6-18% longer, respectively, than in the corresponding patient study. The shape of the time-enhancement curves before aortic peak time in protocols 1-3 and 1'-3' of the phantom study closely resembled that of the corresponding patient study. After the aortic peak time, the shape of time-enhancement curves in protocols 1, 2, and 3 of the phantom study was different from the corresponding patient study; however, it was similar in phantom protocols 1'-3' and the corresponding patient study. In all four phantom protocols, the difference between maximal and minimal aortic peak enhancement was less than the SD of the corresponding patient study. CONCLUSION: The level of peak aortic enhancement and the time to peak aortic enhancement were similar in the phantom and human studies when we used our different contrast injection protocols for MDCT.

Aged↗

PubMed2006

Lower tube voltage reduces contrast material and radiation doses on 16-MDCT aortography.

OBJECTIVE: The purpose of our study was to compare aortic CT angiography performed at a low tube voltage and reduced dose of contrast material with standard-voltage, standard-contrast-dose CT angiography. SUBJECTS AND METHODS: We evaluated 74 patients for aortic disease on MDCT angiography (collimation, 16 x 1.5 mm; beam pitch, 0.9). In 36 patients, we used the standard tube voltage (120 kVp) and a contrast dose of 100 mL (300 mg I/mL) (protocol 1), and in the remaining 38 patients we applied a reduced tube voltage (90 kVp) and a contrast dose of 40 mL (300 mg I/mL) (protocol 2). The patients' weights, CT attenuation of the aorta, visualization of the celiac axis and renal artery, and graininess and streak artifacts on transverse CT scans were evaluated and recorded for each data set. The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were also measured. For statistical analysis, we used the two-tailed Student's t test and logistic regression; agreement between measurements recorded independently by two blinded reviewers was assessed using Cohen kappa statistics. RESULTS: In both protocols a negative correlation was seen between patient weight and CT attenuation. In three protocol 1 patients weighing more than 70 kg, CT attenuation was less than 200 H. No difference was seen between the two protocols with respect to mean attenuation of the aorta (p = 0.13) or visualization of the celiac axis and renal artery (p = 0.35 and 0.60, respectively). Although the SNR and CNR were significantly higher in protocol 1 than in protocol 2, qualitative evaluation of graininess and streak artifacts showed no statistically significant difference (p = 0.15 and 0.48, respectively). Interobserver agreement for quality assessments was within an acceptable range (kappa = 0.42-0.80). CONCLUSION: Low-contrast and low-voltage scans are appropriate for lighter patients (< 70 kg in body weight) with aortic disease. Moreover, this method is particularly valuable for follow-up studies of heavier patients (> 70 kg) with renal dysfunction.

Adult↗

PubMed2005

Temporary ectopic implantation for salvage of amputated lower extremities: case reports.

Two cases of temporary ectopic implantation of a complex amputated foot, followed by replantation to its anatomic position, are reported. Both cases of amputated foot were complicated by devastating soft-tissue injuries in the proximal stump of the amputation, fracture of the femur, and hemorrhagic shock, which ruled out the possibility of primary foot replantation. Both feet were temporarily ectopically implanted onto the contralateral legs, with microvascular anastomoses of the vessels to the recipient posterior tibial artery and saphenous vein. When the patient's general condition allowed, and the soft-tissue defects were repaired, the ectopic implanted feet were replanted to their anatomic positions. Both feet survived the temporary ectopic implantation and second-stage replantation. The length of the injured legs was maintained, and the feet regained their function in 4- and 6-month follow-ups. We conclude that temporary ectopic implantation of amputated parts provides an innovative procedure for the salvage of amputated extremities under special circumstances. A contralateral healthy extremity is an ideal recipient site for temporary ectopic implantation. The temporary ectopic implantation and second-stage replantation of an amputated foot and distal leg with indications can obtain satisfactory results.

Amputation, Traumatic↗

PubMed2004

Allelotypic characteristics of thorotrast-induced intrahepatic cholangiocarcinoma: comparison to liver cancers not associated with thorotrast.

To elucidate the genetic alterations that are specific to Thorotrast-induced liver cancers and their possible roles in tumorigenesis, we analyzed loss of heterozygosity (LOH) at 37 loci. Our previous study of liver cancers that were not associated with Thorotrast found LOH at 9 of these loci to be characteristic of intrahepatic cholangiocarcinoma (ICC), at 19 to be characteristic of hepatocellular carcinoma (HCC), and at 9 to be common to both ICC and HCC. LOH analysis was also performed in tissues of cholangiolocellular carcinoma, which is thought to originate from a common stem cell progenitor of hepatocytes and bile duct epithelial cells. We found frequent LOH at D4S1538, D16S2624 and D17S1303 to be common to all the subtypes of liver cancers, independent of the specific carcinogenic agent. In contrast, LOH at D4S1652 generally was not observed in Thorotrast-induced ICC. LOH analysis revealed that Thorotrast-induced ICC shares some LOH features with both ICC and HCC that were not induced by Thorotrast; however, it is more similar to ICC than to HCC in terms of genetic changes. This study could narrow down the crucial chromosomal loci whose deletions are relevant to hepatobiliary carcinogenesis irrespective of the carcinogenic agent. The study of LOH at loci other the those crucial ones may help us understand how the phenotype of liver cancers is determined.

Aged↗

PubMed2002

Microsatellite instability in thorotrast-induced human intrahepatic cholangiocarcinoma.

Thorotrast, a colloidal suspension of radioactive (232)ThO(2) that emits alpha particles, was used as a radiographic contrast during World War II. It is known to induce liver cancers, most frequently ICC, decades after injection. Since radiation induces genomic instability, we analyzed MSI in Thorotrast-induced ICC. The frequency of MSI(+) cases was 62.5% in Thorotrast ICC, whereas it was 22.7% in non-Thorotrast ICC. However, frameshift mutations of mononucleotide repeats were not observed in Thorotrast ICC. In addition, the MSI(+) phenotype was not associated with the quantity of Thorotrast deposited or the latency period of ICC induction. Promoter regions of both the hMLH1 and the hMSH2 MMR genes tended to be hypermethylated in the tumor part compared to the adjacent nontumor part in Thorotrast ICC. Methylation of the hMLH1 promoter was associated with the MSI(+) phenotype in Thorotrast ICC. In contrast, methylation status of these promoter regions was not related to MSI in non-Thorotrast ICC cases. These findings suggest that MSI induced by exposure to Thorotrast mainly reflects clonal expansion of cancer cells and is partly due to inactivation of hMLH1 by hypermethylation.

Adaptor Proteins, Signal Transducing↗

PubMed2002

Microdistribution of alpha particles in pathological sections of tissues from thorotrast patients detected by imaging plate autoradiography.

Thorotrast is a colloidal suspension of radioactive (232)ThO(2) that naturally emits alpha particles (90%), beta particles and gamma rays (10%). Thorotrast was used as a radiographic contrast agent in the 1930s-1950s; it caused liver cancer several decades after injection because of its life-long deposition and exposure. Determination of the amount and the distribution of radioactive thorium are essential for assessment of radiation risks. We visualized alpha particles on ordinary archival tissue sections using an imaging plate and a BAS5000 image analyzer. Furthermore, we confirmed that the imaging system is sensitive enough to detect alpha particles and accurate in measuring the total amount of thorium deposited in the organ from a single tissue section. This method revealed that the amount of thorium deposited in tumor tissue is correlated to that in non-tumor tissue. Thorotrast deposition was not associated with DNA damage determined by histochemistry. In combination with histological findings, it is suggested that radioactive thorium always migrates within the deposited organs by macrophages, and that the organs are evenly exposed to alpha particles.

Aged↗