Hyo-Chun Yoon

Coronary artery calcium: Alternate methods for accurate and reproducible quantitation

RATIONALE AND OBJECTIVES The aim of this study was to determine a more precise and accurate method of quantitating coronary artery calcium (CAC) detected with electron-beam computed tomography (CT) in patients with low CAC scores. MATERIALS AND METHODS Two 40-section, 3-mm-collimation, electrocardiographically gated electron-beam CT examinations of the heart were performed in each patient. Fifty patients with average scores between 2 and 100, as determined with the conventional scoring algorithm, were selected. The modified conventional scoring algorithm was compared with two techniques: calculated calcium volume and approximated calcium mass. RESULTS The percentage difference between scans ranged from 37.2% for the conventional scoring method to 28.2% and 28.4% for volume- and mass-based methods, respectively. Increasing lesion size thresholds does not improve quantitative precision and reduces accuracy in patients with small amounts of CAC. CONCLUSION Quantification methods based on calcification volume or mass decrease score variation compared with the conventional scoring method, and increased size threshold does not improve accuracy.

Clinical Outcomes of Patients after a Negative Spiral CT Pulmonary Arteriogram in the Evaluation of Acute Pulmonary Embolism

PURPOSE To examine 6-month clinical outcomes of patients after acquisition of a spiral computed tomography (CT) pulmonary arteriogram interpreted as negative for acute pulmonary embolism (PE). MATERIALS AND METHODS A retrospective review was performed on a consecutive series of 143 patients who underwent spiral CT pulmonary arteriography for possible acute PE during a 19-month period. All studies were performed on a HiSpeed Scanner with use of 3-mm collimation with a pitch between 1.3 and 2.0, depending on patient size. All imaging was performed during dynamic contrast material injection at rates between 3.0 and 4.0 mL/sec, timed to peak pulmonary arterial enhancement. For the studies interpreted as negative for PE through the segmental (fourth order) pulmonary arteries, follow-up data were collected by telephone interviews with patients or surviving relatives, and by medical record reviews. RESULTS Among 143 patients, 22 studies (15%) were positive for PE, eight (6%) were suboptimal to exclude PE to the segmental artery level, and 113 (79%) were interpreted as negative for acute PE. Among the 113 negative studies, 13 patients were lost to follow-up, leaving a study population of 100 patients. Eighty-one patients were alive a minimum of 6 months after acquisition of a negative spiral CT pulmonary arteriogram (mean, 9 months; range, 6-24 months) and were without interim diagnosis of PE. Nineteen patients died within the follow-up period after a negative spiral CT pulmonary arteriogram (mean, 3 months; range, 0-8 months); however, in none of these cases was acute pulmonary embolus reported as the cause of death. No documented PE was identified by subsequent imaging studies or autopsy within the study population. CONCLUSION A series of 100 patients with a negative spiral CT pulmonary arteriogram did not experience significant morbidity and mortality as a result of pulmonary embolic disease within a 6-month follow-up period.

Gadolinium-enhanced Breathhold Three-dimensional Time-of-Flight Renal MR Angiography in the Evaluation of Potential Renal Donors☆

PURPOSE To evaluate the utility of gadolinium-enhanced three-dimensional (3D) time-of-flight (TOF) magnetic resonance angiography (MRA) of the renal arteries in the evaluation of potential renal donors. MATERIALS AND METHODS Fifty consecutive patients underwent gadolinium-enhanced 3D-TOF MRA of the renal arteries as part of their evaluation as possible renal donors. All imaging was performed on a 1.5-T system with use of a torso phased-array coil. Conventional T1-weighted axial spin-echo and T2-weighted axial fast spin-echo imaging was performed to evaluate the renal parenchyma. Coronal dynamic MRA was performed during bolus injection of 40 mL of gadolinium with use of a 3D-TOF sequence requiring a breathhold of approximately 30 seconds. Maximum-intensity-projection reconstructions were obtained of the renal arterial and venous anatomy. All studies were prospectively evaluated by a single radiologist experienced with body MRA. Intraoperative findings were used as the reference standard in 35 patients. To evaluate interobserver variability, each examination was evaluated for image quality, renal artery number, and anatomy by two radiologists experienced with MRA and blinded to the others interpretations and surgical results. RESULTS Ninety-eight percent of all MRAs were graded as diagnostic quality (Kappa value = 0.38; P < .05). Multiple renal arteries were identified in 29 (29%) of 100 kidneys. Four of 50 patients studied (8%) had renal parenchymal abnormalities identified with MR imaging. Sensitivity and specificity for accessory renal artery detection was 71% and 95%, respectively. Overall, accuracy for MRA in determining renal artery number was 90%. CONCLUSION Gadolinium-enhanced breathhold 3D-TOF renal MRA is sufficient to assess the renal arteries in potential donors.

Electron-beam CT: The effect of using a correction function on coronary artery calcium quantitation

PURPOSE The purpose of the study was to determine if use of a correction function derived from a phantom with known calcium density reduces variation in coronary artery calcium scores measured with electron-beam computed tomography (CT) and to evaluate the influence of body girth, as measured by body mass index (BMI), on coronary artery calcium-score variability in a clinical screening cohort. MATERIALS AND METHODS Two hundred fifty consecutive patients underwent two electron-beam CT examinations with a standardized phantom. Region-of-interest (ROI) measurements of the phantom were correlated with the patient BMI. In a subset of 28 patients with low but positive coronary artery calcium scores, ROI values of the phantom were used as a correction for signal attenuation. RESULTS Patient BMI was not significantly correlated to signal attenuation. Application of a correction function resulted in a small but insignificant decrease in interscan coronary artery calcium-score variation. The interscan coronary artery calcium score variation was 24.5% +/- 23.9; it decreased to 24.3% +/- 21.6 with use of the 75 mg/cm3 portion of the phantom and to 22.2% +/- 21.4 with use of the 150 mg/cm3 portion of the phantom. CONCLUSION The use of a coronary artery calcium phantom does not reduce interscan variation sufficiently to warrant regular clinical usage. Interscan variation in the coronary artery calcium score is not significantly influenced by patient BMI.

Fluoroscopically guided percutaneous placement of large-bore gastrostomy and gastrojejunostomy tubes: review of 109 cases.

PURPOSE To evaluate our experience with percutaneous placement, management, and complications of large-bore (20-24 F) gastrostomy and gastrojejunostomy feeding tubes. MATERIALS AND METHODS A retrospective review was performed on 109 consecutive patients who underwent placement of percutaneous large-bore feeding tubes between January 1994 and May 1998. Data were collected with respect to underlying illness, technical success, number of replaced tubes, and immediate and late complications. No patient had a small-bore tube placed during this series. RESULTS A total of 109 cases were reviewed. Immediate follow-up within the first 2 weeks was available for all 109. Follow-up after 2 weeks was available for 61 (56%) patients. Tubes were placed in patients aged 15 to 94 years. Neurologic dysfunction from a variety of causes was the most common underlying illness and occurred in 52% of patients. There were nine (8.3%) immediate, treatable complications: three major and six minor. There was one procedure-related death (0.9%). Persistent fistula tracts following tube removal occurred in three patients (4.9%). Balloon rupture was the most common reason for tube exchange (40.7%). CONCLUSION Percutaneous large-bore gastrostomy and gastrojejunostomy tubes are safe to place and have technical success, morbidity, and mortality rates comparable to those of tubes placed surgically or endoscopically as well as small-bore tubes placed with fluoroscopic guidance.

Refractory abdominal-cutaneous fistulas or leaks : Percutaneous management with a collagen plug

BACKGROUND We report the results of abdominal-cutaneous fistula tract occlusion with a collagen plug in a series of patients with fistulas or leaks refractory to conservative therapy. STUDY DESIGN Seven patients were found to have persistent fistula or leak after percutaneous drainage of abdominal pelvic fluid collections. All patients but one were refractory to surgical or percutaneous drainage. Under fluoroscopic guidance, modified Vasoseal (Datascope Inc, Montvale, NJ) collagen plugs were deployed into the fistulas using catheter-directed techniques. The plugs were split longitudinally to fit into an 8F or 9F peel-away sheath, placed into the fistula, and deployed. Results were tabulated and patients were followed up. RESULTS Six of seven patients undergoing fluoroscopically guided, catheter-directed tract occlusion had resolution of the fistula, with no evidence of fistula or abscess recurrence from 30 to 180 days after closure. There were no procedural complications. The technique was unsuccessful in dosing a gastrocutaneous fistula after removal of a large-bore gastrostomy tube; this failure was believed to be secondary to the short length and large caliber of the tract in a patient with hypercortisolemia. CONCLUSIONS Closure of abdominal-cutaneous fistula tracts by occlusion with a modified Vasoseal collagen plug shows promise in the management of fistulas refractory to catheter drainage.

PREVENTION OF HEMOBILIA DURING PERCUTANEOUS BILIARY DRAINAGE : LONG-TERM FOLLOW-UP

PURPOSE The authors evaluated a technique for the prevention of hemobilia when placing transhepatic biliary drainage catheters (THBDCs). MATERIALS AND METHODS Initially, 20 patients were randomized into two groups. In the control group, a THBDC was placed after blind needle passage without contrast material opacification of the needle tract. In the experimental group, the tract was studied and then abandoned if a major vascular structure was encountered. Once a tract was found that did not traverse a major vascular structure, a THBDC was placed. An additional 35 patients undergoing 40 procedures were studied with use of the technique as outlined for the original experimental group. The original experimental group patients and the additional 35 patients were followed for up to 3 years. RESULTS There were three cases of hemobilia in the initial control group. None of the patients in the initial experimental group experienced hemobilia. In the additional 35 patients, there were three cases of bloody drainage from the THBDC; however, the etiology of hemobilia was not secondary to transgression of a vascular structure. CONCLUSION Visualization of the tract prevents the usage of tracts that communicate with large vascular structures. This technique reduces the incidence of hemobilia when placing THBDCs.

Carotid MPRAGE Signal Is Associated with Acute Territorial Cerebral Ischemic Events Detected by Diffusion Weighted MRI

Background— Carotid intraplaque hemorrhage has been associated with symptomatic stroke and can be accurately detected with magnetization-prepared rapid acquisition with gradient-echo (MPRAGE). Currently, there are no studies analyzing carotid MPRAGE signal and territorial ischemic events defined by diffusion restriction in the acute setting. Our aim was to determine the association of carotid MPRAGE signal with acute territorial ischemic events using carotid MPRAGE and brain diffusion tensor imaging. Methods and Results— After the addition of the MPRAGE sequence to the neck MR angiographic protocol, 159 patients with suspected acute stroke were evaluated with both brain diffusion tensor imaging and carotid MPRAGE sequences over 2 years, providing 318 carotid artery and paired brain images for analysis. Forty-eight arteries were excluded due to extracarotid sources of brain ischemia and 4 were excluded due to carotid occlusion. Two hundred sixty-six arteries were eligible for data analysis. Carotid MPRAGE-positive signal was associated with an acute cerebral territorial ischemic event with a relative risk of 6.4 (P<0.001). The relative risk of a diffusion tensor imaging-positive territorial ischemic event with carotid MPRAGE-positive signal was increased in mild, moderate, and severe stenosis categories (10.3, P<0.001; 2.9, P=0.01; and 2.2, P=0.01, respectively). Conclusions— In the workup of acute stroke, carotid MPRAGE-positive signal was associated with an increased risk of territorial cerebral ischemic events as detected objectively by brain diffusion tensor imaging. The relative risk of stroke was increased in all carotid stenosis categories but was most elevated in the mild stenosis category.Background —Carotid intraplaque hemorrhage has been associated with symptomatic stroke and can be accurately detected with Magnetization-Prepared Rapid Acquisition with Gradient-Echo (MPRAGE). Currently, there are no studies analyzing carotid MPRAGE signal and territorial ischemic events defined by diffusion restriction in the acute setting. Our aim was to determine the association of carotid MPRAGE signal with acute territorial ischemic events using carotid MPRAGE and brain diffusion tensor imaging (DTI). Methods and Results —After the addition of the MPRAGE sequence to the neck MRA protocol, 159 patients with suspected acute stroke were evaluated with both brain DTI and carotid MPRAGE sequences over 2 years, providing 318 carotid artery and paired brain images for analysis. 48 arteries were excluded due to extracarotid sources of brain ischemia and 4 were excluded due to carotid occlusion. 266 arteries were eligible for data analysis. Carotid MPRAGE positive signal was associated with an acute cerebral territorial ischemic event with a relative risk of 6.4 (p<0.001). The relative risk of a DTI positive territorial ischemic event with carotid MPRAGE positive signal was increased in mild, moderate and severe stenosis categories (10.3 p<0.001, 2.9 p=0.01, and 2.2 p=0.01 respectively). Conclusions —In the workup of acute stroke, carotid MPRAGE positive signal was associated with an increased risk of territorial cerebral ischemic events as detected objectively by brain DTI. The relative risk of stroke was increased in all carotid stenosis categories, but was most elevated in the mild stenosis category.

Percutaneous delivery of a heparin-impregnated collagen stent-graft in a porcine model of atherosclerotic disease.

RATIONALE AND OBJECTIVES To develop collagen stent-grafts impregnated with heparin to improve the biocompatibility of endovascular stents and to design a percutaneous delivery system for graft deployment in a swine model. METHODS Heparin-impregnated collagen stent-grafts were deployed, and follow-up angiograms were obtained every 15 minutes for 90 minutes to assess acute thromboses and again at 2 and 4 weeks afterward to assess patency. If stenosis or occlusion was detected at the 2-week evaluation, guidewire passage across the lesion was attempted and angioplasty was performed. If stenosis or occlusion was present at the 4-week evaluation, only guidewire passage was attempted; thereafter, the animals were killed and the stent-grafts were harvested and reviewed by a vascular pathologist. RESULTS Group A represents a feasibility study to optimize the deployment method applied in groups B and C. Fifteen of 17 stent-grafts were successfully deployed using this method. In group B, 89% of grafts were successfully deployed; 12% were patent at 2 weeks and none at 4 weeks. In group C, a 10-minute inflation time was added to the deployment procedure; 88% of grafts were successfully deployed and 28% were patent at 2 weeks and 14% at 4 weeks. Extensive luminal thrombosis and myointimal hyperplasia were present in every case. CONCLUSIONS A method was developed for percutaneous implantation of collagen stent-grafts into peripheral vessels. The heparin-impregnated grafts did not prevent vessel restenosis. Modification of the graft-processing technique may improve patency.

Randomized Prospective Comparison of Alteplase versus Saline Solution for the Percutaneous Treatment of Loculated Abdominopelvic Abscesses

PURPOSE To determine if alteplase infusion for the treatment of loculated abdominopelvic abscesses requiring percutaneous catheter drainage was superior to saline solution infusion. METHODS AND MATERIALS This study was a single-center prospective randomized trial. Patients with loculated abdominopelvic abscesses unsuccessfully drained by initial catheter placement were randomized to receive the fibrinolytic agent alteplase or normal saline solution. The amount of alteplase used to treat abscesses was 2 mg or 4 mg based on infusion volumes of 0-50 mL or 51-100 mL, respectively. Infusions were administered twice daily for 3 days. Computed tomography was performed before initiation of therapy and immediately after 3 days of infusions. Success was defined by removal of the catheter after drainage without recurrent abscess or surgical intervention within 30 days. RESULTS A total of 20 patients were included in this study: 11 received alteplase and nine received normal saline solution. There was no significant difference in the distribution of sex (P = .08) or age (P = .29). Abscess resolution was achieved in nine of 11 alteplase-treated patients (80%) versus three of nine saline solution-treated patients (33%). However, one patient in each group required repeat intervention within 30 days, for overall success rates of 73% versus 22%, respectively (P = .02). Having observed a significant difference in the primary outcome variable, the study was terminated early. CONCLUSIONS A 3-day course of twice-daily alteplase infusion therapy is superior to normal saline solution for the treatment of loculated abdominopelvic abscesses.