Xiaozhou Ma

Harvard Medical School, Boston, Massachusetts, United States

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Publications (5)8.88 Total impact

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    ABSTRACT: The purpose of this study was to compare enhancement quality, performance efficiency, technologists' satisfaction, and operation costs between 2 different power injectors (PIs) in an outpatient setting. In this prospective study, 275 consecutive outpatients (135 men, 140 women) scheduled for contrast-enhanced CT (CECT) were randomized and scanned using either of 2 multidetector CT scanners (16 adjacently placed detectors) fitted with a dual-syringe contrast injector or a syringeless contrast injector. The corresponding CECT studies were subjectively reviewed by 2 radiologists in consensus to rate the quality of contrast enhancement in each study. The equipment preparation time (contrast media [CM], saline loading), releasing time (unloading of saline and CM), and CM wastage incurred for each PI were recorded by one operator. Technologists' satisfaction with the use of the PIs was rated on a 10-point scale. Statistical analyses were performed using Student's t tests. A total of 140 patients were examined using the dual-syringe system, and 135 with the syringeless system, and CECT examination quality was comparable for both PI systems (P > .05). Equipment preparation time and releasing time per examination for dual-syringe and syringeless PIs were 139 ± 39 and 32 ± 14 seconds and 48 ± 31 and 8 ± 3 seconds, respectively (P < .001). On average, 11 mL CM wastage per examination was observed with the dual-syringe PI and 0 mL with the syringeless PI (P < .001). Technologists had higher satisfaction with the syringeless PI than the dual-syringe system (9.3 vs 6.3, P < .01). Because of improved efficiency, 2.6 additional patients per day were examined in the room using the syringeless PI. Given comparable CECT examination quality, the syringeless PI was more user-friendly and improved outpatient CT workflow and CT throughput while allowing 11-mL CM saving per examination compared with the dual-syringe injector.
    Journal of the American College of Radiology: JACR 08/2012; 9(8):578-82.
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    ABSTRACT: Imaging techniques can detect small liver lesions, although these are a challenge to biopsy, particularly in cirrhotic liver. The authors assessed the diagnostic success of image-guided biopsies collected from small (≤ 3 cm) focal liver lesions. This single-center, retrospective study included 374 patients (199 men; mean age, 62 ± 15). Eighteen-gauge core biopsy and 22-gauge fine needle aspiration (FNA) samples were collected from small focal liver lesions. Samples were compared by histology versus cytology, malignant versus benign, from lesions smaller versus larger than 1.5 cm, from livers with versus without cirrhosis, collected by computed tomography (CT) guidance versus ultrasound, and from different locations in the liver. The combined accuracy of core biopsy plus FNA analysis was 95.5%; core biopsy alone characterized 93.3% of samples, and FNA alone characterized 72.5% (P < .001). Biopsy successfully characterized 94.5% of malignant lesions and 98.8% of benign lesions (P > .05). Biopsy characterized 95.3% (102 of 107) lesions ≤ 1.5 cm. The success in cirrhotic livers was 94.8%, for CT-guided biopsies was 95%, and for ultrasound-guided biopsies was 95.8% (P > .05). The success rate was lower in liver caudate lobe than in other locations (P < .05). Image-guided biopsy of small (≤ 3 cm) focal liver lesions is highly reliable with the use of core biopsy alone. Neither size ≤ 1.5 cm nor presence of cirrhosis is an impediment to biopsy. CT and ultrasound guidance produce similar rates of success.
    Journal of vascular and interventional radiology: JVIR 10/2010; 21(10):1539-47; quiz 1547. · 1.81 Impact Factor
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    ABSTRACT: Fatty liver disease comprises a spectrum of conditions (simple hepatic steatosis, steatohepatitis with inflammatory changes, and end-stage liver disease with fibrosis and cirrhosis). Hepatic steatosis is often associated with diabetes and obesity and may be secondary to alcohol and drug use, toxins, viral infections, and metabolic diseases. Detection and quantification of liver fat have many clinical applications, and early recognition is crucial to institute appropriate management and prevent progression. Histopathologic analysis is the reference standard to detect and quantify fat in the liver, but results are vulnerable to sampling error. Moreover, it can cause morbidity and complications and cannot be repeated often enough to monitor treatment response. Imaging can be repeated regularly and allows assessment of the entire liver, thus avoiding sampling error. Selection of appropriate imaging methods demands understanding of their advantages and limitations and the suitable clinical setting. Ultrasonography is effective for detecting moderate or severe fatty infiltration but is limited by lack of interobserver reliability and intraobserver reproducibility. Computed tomography allows quantitative and qualitative evaluation and is generally highly accurate and reliable; however, the results may be confounded by hepatic parenchymal changes due to cirrhosis or depositional diseases. Magnetic resonance (MR) imaging with appropriate sequences (eg, chemical shift techniques) has similarly high sensitivity, and MR spectroscopy provides unique advantages for some applications. However, both are expensive and too complex to be used to monitor steatosis.
    Radiographics 01/2009; 29(5):1253-77. · 2.79 Impact Factor
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    ABSTRACT: The purpose of this study is to estimate the optimal time delay before the initiation of arterial phase scanning for detection of hypervascular hepatocellular carcinoma (HCC) on 16-MDCT when a rapid bolus injection of contrast medium is administered. In this prospective study, 25 patients (19 men and six women; mean age, 63.5 years; age range, 50-81 years) with pathologically confirmed HCC were included. Dynamic 16-MDCT imaging was performed in cine mode using 70 mL of nonionic iodinated contrast medium (300 mg I/mL) at an injection rate of 7 mL/s. Four consecutive 5-mm-thick slices at the maximum diameter of the HCC were selected as the region of interest. Time-attenuation curves were generated by region of interest drawn on the aorta, tumor, and liver. Qualitative assessments of conspicuity for contrast medium wash-in, peak, and wash-out of aorta and tumor were performed. There were 108 arterial phase enhancing lesions (mean [+/-SD], 4.9 +/- 2.4 cm; range, 0.7-12.9 cm) in the 25 patients. The maximum Hounsfield value of aorta, tumor, and background liver parenchyma were 463.8 +/- 98 HU, 106.5 +/- 19 HU, and 98.3 +/- 14 HU, respectively. At the time of onset of peak tumor enhancement, the difference between tumor density and background liver density was 38.2 +/- 19 HU. The time-attenuation curve showed that the mean times of contrast enhancement start, peak, and end were 9.2 +/- 2.7 seconds, 19.4 +/- 2.1 seconds, and 38 +/- 13.5 seconds, respectively, for the aorta, and 15.5 +/- 2.6 seconds, 26.3 +/- 2.9 seconds, and 57.7 +/- 14.4 seconds, respectively, for 25 pathologically confirmed hepatocellular carcinomas. Qualitatively, the mean times of contrast enhancement wash-in, peak, and washout were 10.2 +/- 2.8 seconds, 19.9 +/- 3 seconds, and 39.9 +/- 9.2 seconds, respectively for the aorta, and 18 +/- 4.2 seconds, 27 +/- 3 seconds, and 55.7 +/- 21 seconds, respectively, for tumor. There were no differences between quantitative and qualitative measurements of wash-in and peak time for the aorta (p = 0.00017, p = 0.00016) and tumor (p = 0.00163, p = 0.00040). When using 70 mL of 300 mg I/mL of contrast medium with an injection rate of 7 mL/s in 16-MDCT scanning, the optimal time to initiate scanning for HCC is 26.3 +/- 2.9 seconds (range, 24.0-34.5 seconds) after contrast medium administration.
    American Journal of Roentgenology 10/2008; 191(3):772-7. · 2.90 Impact Factor
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    ABSTRACT: To evaluate the degree of contrast enhancement, image quality, and accuracy of predicting resectability of pancreatic neoplasm with 16-row multiple-detector computed tomography (MDCT) angiography using low- and high-concentration (300 and 370 mg of iodine per milliliter, respectively) contrast media (CMs). Forty patients who had undergone pancreatic CT angiography (CTA) on 16-MDCT scanner and had surgery were included. Contrast medium of 2 iodine concentrations (group A, 300 mg/mL, n = 20; group B, 370 mg/mL, n = 20) from the same vendor (Isovue; Bracco Diagnostics), with iodine dose of 550 to 600 mg/kg of body weight, was injected at a rate of 5 mL/s. Dual-phase 16-row MDCT was performed using 1.25- and 5-mm collimation for the arterial and portal phases, respectively. For the quantitative analysis, Hounsfield units values in the aorta, superior mesenteric artery, portal vein, and pancreas during arterial and venous phases were measured. Two readers subjectively rated the overall image enhancement, 3-dimensional image quality, and lesion and pancreatic duct conspicuity. Accuracy of lesion resectability was also established for each patient. The data were compared using Student t test for statistical analysis. The quantitative analysis for the degree of enhancement (Hounsfield unit) of the aorta, superior mesenteric artery, and pancreas during the arterial phase demonstrated similar values in groups A (low-concentration CM) and B (high-concentration CM), with no statistically significant difference with each other (P > 0.05). During the portal venous phase, we found superior enhancements in the superior mesenteric and portal veins in group A (P < 0.05). The qualitative assessments of the overall image enhancement and 3-dimensional image quality on a 5-point scale were 4.3 and 4.65, respectively (P < 0.05), in group A and 4.6 and 4.75, respectively, in group B, whereas on a 3-point scale, the pancreatic duct display and lesion conspicuity were 2.75 and 2.85, respectively, in group A and 2.9 and 2.9, respectively, in group B. The accuracy for lesion resectability was 95% (19/20) in group A and 100% (20/20) in group B (P > 0.05). Both CMs demonstrated comparable performance for 16-row MDCT of the pancreas for presurgical planning. However, high-concentration CM (370 mg of iodine per milliliter) provides higher overall enhancement and superior-quality 3-dimensional images with a shorter injection duration.
    Journal of computer assisted tomography 01/2008; 32(4):511-7. · 1.38 Impact Factor