Yan Guo

Sun Yat-Sen University of Medical Sciences, Shengcheng, Guangdong, China

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Publications (15)15.47 Total impact

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    ABSTRACT: OBJECTIVE. The purpose of this study was to determine an optimal multiparametric MRI protocol for characterizing tumors of low versus high grade and differentiating tumors as T1 versus T2 for preoperative staging of bladder urothelial carcinoma. SUBJECTS AND METHODS. Thirty-nine patients underwent MRI within 1 week before surgery. Three image sets-T2-weighted plus diffusion-weighted MRI (DWI), T2-weighted plus dynamic contrast-enhanced MRI (DCE-MRI), and T2-weighted plus DCEMRI plus DWI-were independently interpreted by two readers at 2-week intervals. ROC curves were plotted for both readers to compare the diagnostic efficacy of the three sets for detrusor muscle invasion for each reader, and the areas under the ROC curve were compared by use of the Bonferroni test. The apparent diffusion coefficient (ADC) values were correlated with histopathologic grade. RESULTS. A total of 49 category T1 and T2 lesions were analyzed. The average ADC of 11 low-grade tumors (1.141 ± 0.164 × 10(-3) mm(2)/s) was significantly (p < 0.05) higher than that of 20 high-grade malignant tumors (0.766 ± 0.091 × 10(-3) mm(2)/s). Neither reader considered T1 tumors as probably having muscle invasion (category T2) in the T2-weighted plus DWI image sets or the T2-weighted plus DWI plus DCE-MRI image sets. Using the T2-weighted plus DCE-MRI sets, the two readers overstaged 13 and 15 of 36 tumors by misdiagnosing category T1 as T2. With the cutoff ADC value of 0.899 × 10-3 mm(2)/s, the sensitivity and specificity for differentiating high- and low-grade bladder urothelial carcinoma were 100% and 95%. CONCLUSION. Multiparametric MRI with T2-weighted plus DWI plus DCE technique is the optimal protocol for preoperative staging of organ-confined bladder urothelial carcinoma. The ADC of low-grade tumors is significantly higher than that of high-grade tumors with 100% sensitivity and 95% specificity at a cutoff ADC value of 0.899 mm(2)/s.
    American Journal of Roentgenology 02/2015; 204(2):330-334. DOI:10.2214/AJR.14.13147 · 2.74 Impact Factor
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    ABSTRACT: Purpose: To assess the feasibility of diffusion tensor imaging (DTI) of normal kidneys and the influence of hydration state. Materials and Methods: Ten healthy volunteers underwent renal DTI after fasting for 12 hours and 4 hours, without fasting, and following water diuresis. Medullary and cortical apparent diffusion coefficient (ADC) and fractional anisotropy (FA) values were measured and compared in the four different states of hydration. DTI was performed with a 3T magnetic resonance imaging (MRI) system using fat-saturated single-shot spin-echo echo planar imaging sequence. Results: ADC of normal cortex (2.387 +/- 0.081 x 10(-3) mm 2/s) was significantly higher (t = 20.126, P = 0) than that of medulla (1.990 +/- 0.063 10(-3) mm(2)/s). The FA value of normal cortex (0.282 +/- 0.017) was significantly lower (t = 42.713, P = 0) than that of medulla (0.44760.022). The ADC and FA values of the left renal cortex (2.40460.082 x 10 (-3) mm(2)/s, 0.282 +/- 0.017) and medulla (2.002 +/- 0.081 x 10(-3) mm(2)/s, 0.452 +/- 0.024) were not significantly different (P > 0.05) from those of right renal cortex (2.369 +/- 0.080 x 10(-3) mm(2)/s, 0.283 +/- 0.018) and medulla (1.978 +/- 0.039 x 10(-3) mm(2)/s, 0.443 +/- 0.019). Values for ADC (x10(-3) mm(2)/s) and FA in the 12-hour fasting, 4-hour fasting, nonfasting, and water diuresis states were 2.372 +/- 0.095 and 0.278 +/- 0.018, 2.387 +/- 0.081 and 0.282 +/- 0.017, 2.416 +/- 0.051 and 0.279 +/- 0.023, 2.421 +/- 0.068, and 0.270 +/- 0.021, respectively, in cortex, 1.972 +/- 0.084 and 0.438 +/- 0.014, 1.990 +/- 0.063 and 0.447 +/- 0.022, 2.021 +/- 0.081 and 0.450 +/- 0.031, 2.016 +/- 0.076 and 0.449 +/- 0.028, respectively, in medulla. The ADC and FA values in different hydration states were not significantly different (P> 0.05). Conclusion: DTI of normal kidneys is feasible with reproducible ADC and FA values independent of hydration states.
    Journal of Magnetic Resonance Imaging 11/2014; 40(5). DOI:10.1002/jmri.24450 · 2.79 Impact Factor
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    ABSTRACT: Mixed neuroendocrine and non-neuroendocrine type of tumor in renal pelvis is rare and presents a high-grade malignancy. We present a case report that a 57-year-old man had no history of small cell cancer but presented a high-grade neuroendocrine carcinoma with focal squamous metaplasia and multiple stones simultaneously in the right renal pelvis. The patient underwent nephroureterocystectomy 9 months before this presentation, with evidence of multiple metastatic tumors in various parts of the body. The case of mixed neuroendocrine tumor with stones in the renal pelvis carries a poor prognosis and poses a therapeutic challenge to urologists.
    05/2014; 2(3):93–96. DOI:10.1016/j.eucr.2013.12.004
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    ABSTRACT: To investigate the relationship of apparent diffusion coefficient (ADC) and fractional anisotropy (FA) values with renal function on 3T diffusion tensor imaging (DTI) in chronic kidney disease. Twenty healthy volunteers and 29 patients with CKD underwent DTI. The relationship among ADC, FA, and renal function was analyzed. Cortical and medullary ADC and FA values of patients with chronic kidney disease were lower than those of healthy volunteers (P = 0.000). Both the renal ADC and FA values correlated inversely with serum creatinine and blood urea nitrogen (P < 0.05). DTI is a feasible and non-invasive means to reflect the severity of renal function damaged.
    Abdominal Imaging 03/2014; 39(4). DOI:10.1007/s00261-014-0116-y · 1.73 Impact Factor
  • Huanjun Wang, Yan Guo
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    ABSTRACT: PURPOSE To investigate the efficacy of diffusion weighted MRI on differentiating recurrent tumor from chronic inflammation and fibrosis after cystectomy or transurethral resection of bladder cancer. METHOD AND MATERIALS 11 consecutive patients suspected of bladder tumor recurrence at 3 months to 2 years after single TURBT (6), 3 months to 3 years after repeated TURBT (4), 1 year after partial cystectomy (1), or 2 years after unilateral nephro-ureterectomy and partial cystectomy (1) were performed pelvic MRI scanning using a 3-T MR system and phased-array pelvic coil which including high spatial resolution T2-weighted imaging, DWI in axial and sagittal planes and DCE MRI using three-dimensional volumetric spoiled gradient-echo sequence before and after Gd-DTPA injection. The DWI and DCE MR images were independently interpreted by two uroradiologists (Y.G. and D.Y.) blinded to the results of TURBT and cystoscopy.The apparent diffusion coefficients (ADC) of lesions and gluteus muscles were manually measured in solid portions of the lesions and muscles on ADC maps for three times by one uroradiologist (H.J.W.) and normalized average ADC of lesions were obtained as ratios of ADClesion and ADCgluteus.. Diagnosis was histologically confirmed in all patients by transurethral or cystoscopic resection of 27 lesions within two weeks of MR examinations. RESULTS The accuracies, sensitivities, specificities, and positive predict values of DWI (92.6%, 100%, 81.8%, and 88.9%) were higher than those of DCE MRI (59.3%, 81.3%, 27.3%, and 54.2%) for detecting recurrent tumors. Using receiver operating characteristic analysis, the accuracy of DWI was significantly higher than that of DCE MRI (P<0.05) with areas under the ROC curves of 0.909 and 0.517 respectively. There was no significant difference between DWI diagnosis and histopathology ((χ2=0.5, P>0.05)) whereas difference between diagnosis of DCE MRI and histopathology was significant (χ2=6.125, P<0.05) by McNemar test. The normalized ADC value of recurrent tumors (0.697±0.219) were significantly (P<0.05) lower than those of post-operative inflammation or fibrosis (1.019±0.143). CONCLUSION DWI is superior to DCE MRI for differentiating recurrent bladder tumors from benign changes after resection. DWI can be included in the follow-up MRI protocol after bladder cancer surgery. CLINICAL RELEVANCE/APPLICATION Be much valuable in the following-up for patients with bladder carcinoma after tumor resection.
    Radiological Society of North America 2013 Scientific Assembly and Annual Meeting; 12/2013
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    ABSTRACT: To investigate the efficacy of diffusion-weighted MRI (DWI) in differentiating recurrent tumor from chronic inflammation and fibrosis after cystectomy or transurethral resection of bladder cancer. Eleven patients with suspected tumor recurrence underwent pelvic DWI and dynamic contrast-enhanced (DCE) MRI at 3 months to 7 years following bladder cancer resection. The diagnosis was histologically confirmed in all patients by transurethral or cystoscopic resection of 27 lesions within 2 weeks of MR examinations. The accuracies, sensitivities, specificities, and positive predict values of DWI (92.6%, 100%, 81.8%, and 88.9%) were higher than those of DCE MRI (59.3%, 81.3%, 27.3%, and 54.2%) for detecting recurrent tumors. Using receiver operating characteristic analysis, the accuracy of DWI was significantly higher than that of DCE MRI (P < 0.05). There was no significant difference between DWI diagnosis and histopathology (P > 0.05), whereas the difference between diagnosis of DCE MRI and histopathology was significant (P < 0.05). The normalized apparent diffusion coefficients of recurrent tumors (0.697 ± 0.219) were significantly (P < 0.05) lower than those of postoperative inflammation or fibrosis (1.019 ± 0.143). DWI is superior to DCE MRI for differentiating recurrent bladder tumors from postoperative inflammation or fibrosis. DWI can be included in the follow-up MRI protocol after bladder cancer surgery.
    Abdominal Imaging 09/2013; 39(1). DOI:10.1007/s00261-013-0038-0 · 1.73 Impact Factor
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    ABSTRACT: This study aims to analyze magnetic resonance imaging (MRI) features of ejaculatory duct obstruction, and to provide an accurate diagnostic imaging approach for surgical planning of minimally invasive procedures treating ejaculatory duct obstruction. A total of 18 men with ejaculatory duct obstruction were enrolled in the study. The patients were admitted to our hospital and had undergone MRI examination and surgical treatment from January 2003 to February 2011. The data was collected by searching keywords ('ejaculatory duct obstruction') from our PACS. Patients suspected having ejaculatory duct obstruction according to the manifestations through MRI examinations and further being confirmed by surgery were included. The MRI features of ejaculatory duct obstruction in these patients were summarized. Five cases with ejaculatory duct cysts were detected by MRI, ranging in size from 4 mm × 4 mm × 7 mm to 4 mm × 4 mm × 9 mm and located in the paramedian line; ejaculatory duct dilation near the median line, with the internal diameter ranging from 5 mm to 30 mm was detected in nine cases; and among thirteen cases who underwent both non-contrast enhanced and contrast enhanced MRI scanning, significant enhancement of the wall of the ejaculatory duct on enhanced scanning was observed in three cases. Mullerian duct cysts complicated with dilation of the ejaculatory duct and seminal vesicles were detected in four cases; in these cases, the cysts were located in the median line, ranging in size from 4 mm × 5 mm × 6 mm to 34 mm × 35 mm × 44 mm, tear-drop appearance, with the tip pointing toward the area of the seminal colliculus. Findings of MRI were confirmed by the observations during the surgery. MRI is more accurate at displaying the ejaculatory duct. We recommend that ejaculatory duct diameter of > 2 mm can be used as a diagnostic criterion with MRI image analyses for ejaculatory duct dilation.
    Journal of X-Ray Science and Technology 01/2013; 21(1):141-146. DOI:10.3233/XST-130361 · 1.46 Impact Factor
  • Journal of Cancer Therapy 01/2013; 04(02):504-512. DOI:10.4236/jct.2013.42062
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    ABSTRACT: To explore the feasibility of multi-slice spiral computed tomography (CT) with a lower dose as one-off examination for the preoperative morphology evaluation and the quantification of unilateral renal glomerular filtration rate of living renal donors. A total of 36 living renal donors at our hospital from May 2008 to June 2009 were examined by 64-slice spiral CT and single photon emission computed tomography (SPECT). Living renal donors were examined with a plain scan and three-phase enhancement CT scan. Also there were two inserted dynamic scans, one after the injection of contrast agent and the other between cortex and parenchymal phases. Image reconstructions were performed to observe renal parenchyma, renal vessels and collecting system. Comparisons were made with intra-operative findings. And the known Patlak equation was used simultaneously. The glomerular filtration rate (GFR) in a single kidney was calculated on CT and SPECT respectively. The GFRs of two groups were analyzed to investigate the Pearson correlation and simple linear regression between them. Twenty of 36 renal living donor kidneys underwent the operation, variations of morphology detected by CT were all corresponded with the operation. The GFR values estimated from CT were (42.4 ± 8.9) ml/min (left) and 43.2 ± 8.4) ml/min (right). While GFR of SPECT 47.4 ± 9.3) ml/min (left) and 48.2 ± 8.5) ml/min (right). Linear trend was found between the GFRs of CT and SPECT. Pearson's product-moment correlation coefficient r = 0.753 (left) (P < 0.01), r = 0.709 (right) (P < 0.01). These values indicated that the GFR from CT was positively correlated with the GFR from SPECT. During the preoperative evaluation, multi-slice spiral CT may provide both anatomic information and the GFR of living renal donors.
    Zhonghua yi xue za zhi 10/2011; 91(38):2697-701.
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    ABSTRACT: Primary adenocarcinoma of the renal pelvis is rarely reported in the literature. Here we present a case of primary mucinous adenocarcinoma of the renal pelvis with elevated serum carcinoembryonic antigen (CEA) and carbohydrate antigen 19-9 (CA19-9) levels. A 56-year-old woman was referred to our center with intermittent fever and left-sided back pain for 1 month. Computed tomography showed bilateral nephrolithiasis, mild right hydronephrosis and left pyonephrosis accompanied with ambiguous soft tissues. A radionucleorenogram showed that the glomerular filtration rate of the left and right kidney was 0 and 79 ml/min, respectively. Left nephrectomy was performed without lymph node dissection. Histopathology revealed mucinous adenocarcinoma and elevated serum CEA and CA19-9 levels were found. She died of multiorgan metastasis after 5 months. A review of the literature is also reported.
    Urologia Internationalis 09/2011; 87(4):484-8. DOI:10.1159/000329767 · 1.15 Impact Factor
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    ABSTRACT: We designed to investigate the feasibility of multi-detector row computerized tomography (CT) as a "one-stop" examination for the simultaneous preoperative evaluation of the morphology and function of living renal donors. 21 living renal donors were examined by 64-slice spiral CT with a three-phase enhancement CT scan and two inserted dynamic scans. The maximum intensity projection (MIP), multi-planar reformation (MPR), and volume reconstruction (VR) procedures were performed to compare the renal parenchyma, renal vessels, and collecting system with operational findings. The known Patlak equation was used to calculate the glomerular filtration rate (GFR); exact GFR information was acquired by single photon emission computed tomography (SPECT). Our results as following, there were 3 cases of artery variation and 3 cases of vein variation. CT findings all corresponded with the operation, and the sensitivity, positive predictive value, specialty, and negative predictive value of CT were all 100%. The r of the GFR values estimated from CT is 0.894 (left) (P < 0.001) and 0.881 (right) (P < 0.001). In conclusions, our findings demonstrate that 64-slice spiral CT may offer a "one-stop" examination to replace SPECT in the preoperative evaluation of living renal donors to simultaneously provide information regarding both anatomy and the GFR of living renal donors.
    Abdominal Imaging 02/2011; 36(1):86-90. DOI:10.1007/s00261-009-9595-7 · 1.73 Impact Factor
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    ABSTRACT: ObjectiveThe aim of our study was to investigate the feature of minimal fat renal angiomyolipoma with sufficient blood supply using CT scans and improve the diagnosis accuracy required to differentiate it from clear cell renal carcinoma. MethodsRetrospective analysis of 24 cases of post-surgery confirmed angiomyolipoma with sufficient blood supply (total of 25 tumors) in our hospital that were used for a pathological comparison study. ResultsAmong the 24 patients diagnosed with angiomyolipoma, nobody had bloody urine. Of the 96 patients diagnosed with clear cell renal cancer, 14 had bloody urine (14.6%). In our studied group, the size of angiomyolipomas with sufficient blood supply was between 1.5 cm × 2.0 cm to 8.0 cm × 10.0 cm. During CT scan analysis, twenty tumors had similar density, and five of them had higher density. Only one tumor had a few dots of calcification (4%). Adipose tissue was not visible in 9 tumors, while 16 tumors had visible dots of adipose tissue, as visualized by CT scan. Intensive scanning indicated that all of the tumors showed a strong enhancement in the renal corticomedullary phase. Twenty tumors had significant heterogeneous enhancement in the early phase, while another set of five cases had homogenous prolonged enhancement. Nineteen patients had surgery to remove the angiomyolipomas, while six patients had single side kidney removal due to misdiagnosis for renal cancer in cases where the tumor severely compromised the renal parenchyma and sinus. All 25 cases were classified as renal angiomyolipoma by pathological analysis. Within the 96 cases of clear cell renal cancer, 64 tumors had relatively low density, 29 tumors had equal density, and 3 cases had relatively higher density. Fourteen of the tumors had calcification (14.6%), and none of them had visualized adipose tissue. Enhanced CT scans indicated that 69 cases of renal cancer showed significant enhancement in the renal corticomedullary phase, which had the abnormal pattern of “fast-in-and-fast-out”. Additionally, 27 cases had slow and prolonged enhancement. ConclusionSimilar to clear cell renal carcinomas, angiomyolipomas with sufficient blood supply also appear to exhibit abnormal enhancement with a pattern of “fast-in-and-fast-out” during the early phase, which is easily misdiagnosed as renal cancer. It is difficult to differentiate them merely through CT scans; the key to differentiating them is to identify the adipose tissue within the tumor. Therefore, it is helpful to use thin-layer CT scans to locate the adipose tissue. Key wordsrenal tumor, angiomyolipoma, minimal fat–clear cell renal carcinoma–CT scan
    The Chinese-German Journal of Clinical Oncology 01/2011; 10(1):35-39. DOI:10.1007/s10330-011-0731-9
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    ABSTRACT: Prostate tuberculosis is an uncommon disease of the prostate, which usually involves the upper urinary tract. In the elderly patients, it may be mistaken for prostate carcinoma, both clinically and by conventional radiology. However, magnetic resonance spectroscopy can provide more information to differentiate prostate tuberculosis from prostate cancer.
    Urology 09/2009; 75(5):1065-6. DOI:10.1016/j.urology.2009.06.069 · 2.13 Impact Factor
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    ABSTRACT: To assess the value of three dimensional proton magnetic resonance spectroscopy (3D 1H-MRS) with body coil at 3T in the differential diagnosis of prostate cancer. Forty patients suspected of prostate cancer underwent MRI and MRS examinations, and then transrectal ultrasound guided prostate biopsy for pathological diagnosis. The MRI and MRS features of benign prostate hyperplasia, prostate cancer and prostatic intraepithelial neoplasia (PIN) were analyzed in comparison with the pathological reports, and the receiver operating characteristic curve was drawn for the diagnosis of cancer from peripheral zones. The examinations were accomplished for all the patients. The mean ratios of (Cho + Cre)/Cit in the interstitial and glandular hyperplasia tissues, the cancer tissue of the central and peripheral glands, the healthy peripheral gland and PIN were 0.75 +/- 0.23, 0.59 +/- 0.14, 1.79 +/- 0.90, 1.18 +/- 0.95, 0.46 +/- 0.18, and 0.97 +/- 0.10, respectively, with statistically significant differences between the cancer and normal prostate tissues (P < 0.01). The optimum threshold for the diagnosis of prostate cancer in the peripheral zone was 0.68 with a sensitivity of 88.6% and a specificity of 88.7%. The 3D 1H-MRS with body coil at 3T has a high sensitivity and specificity in the differential diagnosis of prostate cancer, and can provide valuable information for the diagnosis of PIN.
    Zhonghua nan ke xue = National journal of andrology 05/2009; 15(5):431-6.
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    ABSTRACT: ObjectiveTo investigate the efficiency of helical CT comparing with contrast-enhanced ultrasound, and to improve the diagnosis efficiency of renal cell carcinoma (RCC). MethodsThirty RCCs confirmed pathologically were studied retrospectively. The un-enhanced CT scan and the triphasic enhanced helical CT scan were performed in all cases, the gray-scale US and angiosonography with SonoVue were performed in all cases meantime. Results22 cases (73.3%) were diagnosed correctly by helical CT alone before operation. 7 cases (23.3%) were suspected as RCC with helical CT. One case (3.3%) was misdiagnosed with helical CT. 25 cases (83.3%) were diagnosed correctly with contrast-enhanced ultrasound alone pre-operation. One case (3.3%) was suspected as RCC with angiosonography. Four cases (13.3%) were misdiagnosed with angiosonography alone. 29 cases (96.7%) were diagnosed correctly by helical CT combining with angiosonography before operation, one case (3.3%) was diagnosed as renal mass with both helical CT and angiosonography. ConclusionContrast-enhanced ultrasound is sensitive in detecting blood flow, it can detect the enhancement of the tumor which cannot be detected by helical CT. CT and angiosonography have strong complement each other in the diagnosis of RCC.
    The Chinese-German Journal of Clinical Oncology 01/2008; 7(2):93-97. DOI:10.1007/s10330-007-0158-5