Biomedical subjects
Publications and source records attributed to Huay-Ben Pan.
We report a 28-year-old man who presented with hematuria and intermittent flank pain. Conventional CT urography showed mild left hydronephrosis and an undetermined lesion in the left ureter. By virtual CT ureteroscopy, a fibroepithelial polyp (FEP) was preoperatively diagnosed. The patient had segmental resection of the ureter and pathological proof of FEP was obtained.
A temporal correlation (TC) mapping method is proposed to help bolus chasing during dynamic contrast-enhanced (DCE) MRI of complex pulmonary circulation (CPC) in patients with congenital heart disease. DCE-MRI was performed on five healthy male subjects (23-24 years old) and 25 patients (nine males and 16 females, 0.25-44 years old), and TC maps were generated by performing pixel-based computation of cross-correlations to the pulmonary artery with a series of time shifts in all subjects. Qualitative and quantitative evaluations were performed in comparison with original DCE images. TC maps exhibited a better signal-to-noise ratio (SNR) by factors of 4.3 and 1.3 in the lung parenchyma, pulmonary veins, and superior artery/vein; a better intraparenchymal contrast-to-noise ratio (CNR) by factors of 1.5-5.4; and a significantly higher conspicuity in all regions except the pulmonary arteries when graded with a five-point score. TC maps evaluated by two experienced clinicians significantly added relevant information (P<0.001), and in some cases affected the final diagnosis. We conclude that TC maps facilitate bolus chasing for DCE-MRI by reducing recirculation effects and interframe fluctuations, and hence complements morphological imaging of CPC in patients with complex congenital heart disease.
Ureteroarterial fistula is a rare but life-threatening cause of hematuria. The predisposing factors of a ureteroarterial fistula includes pelvic exenteration, radiation therapy, infection, primary vascular disease, vascular reconstructive surgery, and indwelling ureteral catheters or stents. We report a case of ureteroarterial fistula between the right ureter and a pseudoaneurysm originating from the right proximal external iliac artery in a female patient presenting with intermittent massive hematuria. She had previously undergone an operation for cervical cancer, radiation therapy, and ureteral stent placement. She was treated successfully by percutaneous endovascular stent graft placement to exclude the pseudoaneurysm. Percutaneous stent graft placement appears to be an effective and safe therapeutic alternative in the treatment of ureteroarterial fistula.
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OBJECTIVE: The objective of our study was to describe MRI features of contracture of the gluteus maximus muscle after providing a retrospective review of the MRI studies of 21 patients. CONCLUSION: Gluteal contracture manifests characteristic features on MRI, including an intramuscular fibrotic cord extending to the thickened distal tendon with atrophy of the gluteus maximus muscle and posteromedial displacement of the iliotibial tract. In advanced cases, medial retraction of the muscle and its tendon results in a depressed groove at the muscle-tendon junction and external rotation of the proximal femur. Clinical correlation and meticulous physical examination may confirm the MR diagnosis.
OBJECTIVE: Our purpose was to evaluate the safety and therapeutic efficacy of single-session prolonged alcohol sclerotherapy in treating large hepatic cysts. A therapeutic comparison between 4-hour and 2-hour retention techniques was also studied. MATERIALS AND METHODS: Twenty-seven patients with 31 hepatic cysts were enrolled in this study. Seventeen patients (18 cysts) were treated by alcohol retention for 4 hours (group 1) and 10 patients (13 cysts) for 2 hours (group 2). The mean diameter of the hepatic cysts was 12.4 cm (range, 8-23 cm) with a comparable size range in each group. The sclerosing agent used was 95% alcohol, and the maximum amount was limited to 200 mL. Patients changed position and vital signs were monitored every 10-15 minutes. The blood alcohol concentrations were checked hourly for 5 consecutive hours in the initial nine patients. The nonparametric Mann-Whitney U test was used to compare the difference in characteristics and treatment results of the subjects between these two groups. The level of statistical significance was set at a p value of less than 0.05. RESULTS: All but one patient in group 2 tolerated the entire course of sclerotherapy. The mean aspirated volume and mean injected alcohol volume of the hepatic cysts were 730 mL and 138.3 mL, respectively, in group 1 patients, and 931 mL and 139 mL, respectively, in group 2 patients. The mean maximum blood alcohol concentration was 128.2 mg/dL (range, 60-199 mg/dL) at 3-4 hours after alcohol instillation. The mean posttherapy residual cystic diameter was 2.5 cm (range, 0-6 cm), with an average volume reduction rate of 98.3% and 97.7%, respectively, for patients in group 1 and group 2 after a mean follow-up period of 29.6 months (9-59 months). No statistical differences of the mean reduction rate between the two groups were noted. CONCLUSION: Long retention of the alcohol in a single-injection technique is safe and effective. Two-hour alcohol retention has a comparable efficacy to that of 4-hour retention.
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BACKGROUND AND PURPOSE: Multi-detector computed tomographic (MDCT) angiography is a recently developed imaging technique that can study small vessels such as medullary arteries and veins. The purpose of this study was to evaluate MDCT angiography in diagnosing SDAVF. METHODS: Eight patients with initial magnetic resonance imaging (MRI) and clinical findings suggestive of spinal dural arteriovenous fistula (SDAVF) and 8 control subjects underwent MDCT angiography. Both MDCT angiography and catheter angiography were performed within 5 days in patients with SDAVFs. The results of MDCT angiography in patients with SDAVFs were compared with those of catheter angiography. RESULTS: MDCT angiography detected engorged perimedullary draining veins and correctly localized the fistula of the SDAVFs, and correlated well with catheter angiography. Fistula was at the thoracic level in 7 patients, and sacral level in 1 patient. MDCT angiography did not visualize the engorged perimedullary venous plexus in the control group. CONCLUSIONS: MDCT angiography correlated well with catheter angiography in diagnosing SDAVFs. It might play a role in shortening the length of the catheter angiography in diagnosing this disease.
BACKGROUND: Recent studies reveal that contrast-enhanced multidetector row computed tomography (MDCT) is a promising technique for noninvasive visualization of coronary artery stenoses. We investigated the safety and accuracy of MDCT for early assessment of the severity of residual stenosis of the infarct-related artery (IRA) and the number of diseased vessels in patients after acute myocardial infarction (AMI). METHODS AND RESULTS: Of 146 AMI cases admitted, 72 fit with criteria and underwent 16-slice MDCT (4 +/- 2 days after AMI) with beta-blockers. There were no complications except 1 patient who had from complete atrioventricular block. Results were compared with conventional coronary angiography (CCA) within 3 days. In 55 (73.3%) of 72 patients, all arteries were assessable. In total, the number of assessable arteries was 253 (87.8%), and 35 (12.2%) vessels were nonassessable, mostly because of motion artifacts and extensive calcification. Overall, 84 of the 115 lesions (> or = 50% lumen reduction) were correctly detected by MDCT (sensitivity 73.0%). The accuracy in classifying patients with nonsignificant, single-, or multiple-vessel diseases was 79.1%. The accuracy for residual lesions with >50% stenosis of IRA was 87.5%. There was a good correlation regarding the severity of residual stenosis of the IRA (0%, 1%-49%, 50%-89%, 90%-99%, or occlusion) between MDCT and CCA (Spearman correlation 0.94, P < .001). Lesions with 90% to 99% or occlusion of the IRA were accurately detected or ruled out in 31 of 36 cases (86.1%). CONCLUSIONS: With appropriate protocol, MDCT is safe and accurate in assessing the severity of IRA and the number of diseased vessels during the first week after AMI. It has the potential to provide triage for early management of patients after AMI.
BACKGROUND: Acute subarachnoid hemorrhage (SAH) has traditionally been diagnosed by computed tomography (CT); however, fluid-attenuated inversion recovery (FLAIR) is a magnetic resonance imaging (MRI) modality currently used to detect acute SAH. CT is insensitive in the detection of subacute or chronic SAH. The purpose of this study was to compare 4 MRI pulse sequences and CT in the detection of SAH in acute and subacute-to-chronic stages. METHODS: From 2001-2003, we collected data for 22 patients (12 men and 10 women, aged 35-80 years) with SAH due to ruptured aneurysm (n = 11), trauma (3), or unknown origin (8). All patients underwent MRI and CT examination, with an interval of less than 12 hours between the 2 procedures. We divided patients into 2 groups according to the time from symptom onset to MRI evaluation: patients with MRI performed < or = 5 days post-ictus had acute-stage illness, whereas patients with MRI performed from day 6-30 post-ictus had a subacute-to-chronic condition. MRI (1.5-T) pulse sequences comprised spin-echo T1-weighted, fast spin-echo T2-weighted, FLAIR, and gradient-echo (GE) T2*-weighted images. RESULTS: In the acute-stage group, SAH was seen as an area of high signal intensity compared with surrounding cerebrospinal fluid in 36.4% of cases on T1-weighted images, and in 100% on FLAIR images; low signal intensities were seen in 18.2% of cases on T2-weighted images, and in 90.9% on GE T2*-weighted images. High-attenuated SAH was seen on CT in 90.9% of cases. FLAIR (p = 0.008), GE T2*-weighted images (p = 0.012) and CT images (p = 0.012) were all statistically significant indicators of acute SAH. In the subacute/chronic-stage group, SAH was detected on T1-weighted images (36.4% of cases), FLAIR (33.3%), T2-weighted images (9.1%), GE T2*-weighted images (100%), and CT (45.5%). GE T2*-weighted images were significantly superior (p = 0.001) to other MRI pulse sequences and CT as indicators of subacute-to-chronic SAH. CONCLUSION: FLAIR and GE T2* MRI pulse sequences, and CT scans, are all statistically significant indicators of acute SAH. GE T2*-weighted images are statistically significant indicators of subacute-to-chronic SAH, whereas other MRI pulse sequences, and CT scans, are not.
Technical success rates for percutaneous restoration of thrombosed arteriovenous grafts are high. However, in thrombosed grafts without restorable original outflow veins, percutaneous salvage is usually not possible. In this situation, patients are referred for bypass grafting or recreation of their vascular access sites. This report describes a patient in whom the original outflow vein at the venous anastomosis was completely obliterated and in whom vascular access was successfully salvaged by percutaneously reanastomosing the venous stump of the thrombosed graft with an adjacent patent vein. This procedure is technically feasible for the salvage of a thrombosed graft.
OBJECTIVE: The objectives of our study were to evaluate the feasibility of ethanol sclerotherapy in treating simple renal cysts with prolonged ethanol retention and to compare the therapeutic results of 2- and 4-hr retention techniques. MATERIALS AND METHODS: We retrospectively reviewed 36 renal cysts in 33 patients treated by ethanol sclerotherapy with a single-session single-injection technique during the past 6 years. After complete aspiration of the cystic fluid, 95% ethanol was injected into the cyst and was retained for 4 hr in 14 cysts (group 1) and for 2 hr in 22 cysts (group 2). The average maximal diameter and aspirated volume of the cysts were 8.3 cm and 223 mL in group 1 patients and 7.9 cm and 167 mL in group 2, respectively. The ablated cysts were followed up regularly by sonography, CT, or both at 3- to 6-month intervals for at least 1 year. The nonparametric Mann-Whitney U test was used to compare differences in characteristics, treatment results, and laboratory data of the subjects in the two groups. The level of statistical significance was set at a p value of less than 0.05. RESULTS: Technically, all the patients tolerated the procedures. One patient had gross hematuria 10 days after the procedure. She underwent surgical deroofing treatment and was excluded in the later statistical analysis. After sclerotherapy, 14 cysts disappeared completely and 16 cysts showed marked regression with residual maximal diameter of less than 3 cm. The overall volume reduction rate was 97.6% in all 35 cysts. The mean residual longest diameters and average volume reduction rates of the treated cysts were 1.9 cm and 97.9% in group 1 patients and 1.1 cm and 97.3% in group 2 patients, respectively, which showed no statistical significance of volume reduction rate with a p value 0.149. CONCLUSION: The single-session prolonged ethanol-retention technique is safe and efficacious for the treatment of renal cysts. There is no statistical difference in therapeutic efficacy between 2- and 4-hr ethanol-retention techniques.
OBJECTIVE: The purpose of this study was to report our experience with metallic stent placement in the peripheral outflow veins in native arteriovenous fistula (A-V fistula) hemodialysis patients after insufficient balloon dilatation. MATERIALS AND METHODS: During the past 4 years, 12 A-V fistula dialysis patients in our hospital underwent metallic stent placement in the peripheral outflow veins to restore vascular access. The indications for metallic stent placement in our study included (1) recoil stenosis of outflow vein in six patients; (2) outflow venous rupture in two patients and dissection in one patient; and (3) large residual adherent thrombus in outflow aneurysms in three patients with thrombosed (arteriovenous) access. Self-expandable Wallstent or Jostent (Jomed, Abbott Laboratories) of appropriate size (6-10 mm in diameter) was chosen for use in these patients. Kaplan-Meier survival analysis was used to calculate the access patency rates. RESULTS: Twelve patients received stents. Eleven patients (92%) underwent successful dialysis after the procedure. One patient experienced complications due to incorrect positioning of the stent at the anastomotic site, causing flow compromise. The primary patency (+/- standard error) of the vascular access at 3, 6, 12, and 24 months was 92% +/- 8%, 81% +/- 12%, 31% +/- 17%, and 31% +/- 17%, respectively. The secondary patency of the vascular access at 3 months was 92% +/- 8%, and 82% +/- 12% at 6, 12, and 24 months each. CONCLUSION: Metallic stent placement is safe and effective in treating peripheral venous lesions in native A-V fistula hemodialysis patients after unsatisfactory balloon dilatation.
OBJECTIVE: The purpose of this study was to demonstrate CT voiding urethrography and CT virtual urethroscopy. Fourteen CT voiding urethrography examinations on 13 men (mean age, 30 years) were prospectively performed with 16-MDCT. The clinical diagnoses of those patients included urethral injury, urethral stricture, and hypospadia. The CT voiding urethrogram was obtained with transverse CT of the voiding, contrast-filled urethra and display of 2D multiplanar and 3D virtual images. CONCLUSION: The full urethral structure was clearly shown by CT voiding urethrography and virtual urethroscopy in all patients. The results of CT voiding urethrography and conventional methods correlated closely with the urethral diseases being imaged.
OBJECTIVE: A 26-year-old woman presented with urinary frequency. Findings were negative on voiding cystourethrography. Cystourethroscopy failed to reveal a urethral diverticulum. A new method of virtual CT urethroscopy was performed using a 16-MDCT scanner. The orifice of the diverticulum was identified clearly on 3D virtual urethroscopy. Intraoperatively, the diverticulum was identified, with the orifice location compatible with that seen on virtual urethroscopy. CONCLUSION: Virtual CT urethroscopy provides more information than conventional urethral examinations and is less invasive than conventional urethroscopy.
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The flow-sensitive alternating inversion recovery (FAIR) and the first-pass dynamic contrast-enhanced MR imaging (CE-MRI) techniques have both been shown to be effective in the assessment of human pulmonary perfusion. However, no comprehensive comparison of the measurements by these two methods has been reported. In this study, healthy adults were recruited, with FAIR and CE-MRI performed for an estimation of the relative pulmonary blood flow (rPBF). Regions of interest were encircled from the right and left lungs, with right-to-left rPBF ratios calculated. Results indicated that, on posterior coronal slices, the rPBF ratios obtained with the FAIR technique agreed well with CE-MRI measurements (mean difference = -0.02, intraclass correlation coefficient RI = 0.78, 95% confidence interval = [0.67, 0.86]). On middle coronal slices, however, FAIR showed a substantially lower rPBF by up to 43% in the right lung compared with CE-MRI (mean difference = -0.38, RI = 0.34, 95% confidence interval = [-0.09, 0.68]). The location-dependent discrepancy between measurements by FAIR and CE-MRI methods is attributed to tracer saturation effects of arterial inflow when the middle coronal slice contains the in-plane-oriented right pulmonary artery, whereas the left lung rPBF is less affected due to oblique orientation of the left pulmonary artery. Intrasequence comparison on additional subjects using FAIR at different slice orientations supported the above hypothesis. It is concluded that FAIR imaging for pulmonary perfusion in the coronal plane provides equivalent rPBF information with CE-MRI only in the absence of tracer saturation effects; hence, FAIR should be carefully exercised to avoid misleading interpretations.
Posterior reversible encephalopathy syndrome (PRES) is a potentially devastating neurologic syndrome, but timely treatment may lead to complete reversal of the disease course. We reviewed 12 cases of PRES and describe the clinical history and imaging findings, including conventional magnetic resonance imaging (MRI), diffusion-weighted imaging (DWI), and calculated apparent diffusion coefficient (ADC) maps, used to establish the diagnosis of PRES. Three male and nine female patients aged between 11 and 70 years (mean, 37 years) with clinical and imaging findings consistent with PRES were enrolled in the study. All patients had undergone conventional MRI and 10 had undergone additional DWI studies. Ten patients had follow-up MRI studies. DWI was performed using a 1.5T system with a single-shot spin-echo echoplanar pulse sequence. Initial and follow-up neuroimaging and clinical history were reviewed. Lesions were almost always present over the posterior circulation, mainly the parieto-occipital region, affecting primarily the white matter. The anterior circulation region, brainstem, cerebellum, deep cerebral white matter, and thalamus were also involved in five cases. Conventional MRI revealed hyperintensity on T2-weighted and fluid-attenuated inversion recovery images. DWI showed isointensity and increased signal intensity on ADC values in all cases, indicating vasogenic edema. Clinical and MRI follow-up showed that the symptoms and radiologic abnormalities could be reversed after appropriate treatment of the causes of PRES in most patients (9 of 10). In one patient, the ADC value was lower on follow-up images, indicating cytotoxic edema with ischemic infarct. DWI was a useful complement to MRI in the diagnosis of PRES.