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Ivan Pedrosa

Publications and source records attributed to Ivan Pedrosa.

At least 19 recordsLinked to original sources
PubMed2006

Part I: preparing first-year radiology residents and assessing their readiness for on-call responsibilities.

RATIONALE AND OBJECTIVES: The aim of the study is to evaluate the effectiveness of an Emergency Radiology (ER) Core Curriculum training module and a Digital Imaging and Communications in Medicine (DICOM)-based interactive examination system to prepare first-year (postgraduate year 2 [PGY-2]) radiology residents and assess their readiness for taking overnight radiology call. MATERIALS AND METHODS: Institutional review board approval was obtained, and the study was compliant with Health Insurance Portability and Accountability Act (HIPAA) regulations. A dedicated month-long ER curriculum was designed to prepare new radiology residents for overnight radiology call that includes interpretation of off-hour urgent and emergent studies without immediate direct attending supervision. Lectures of the curriculum, provided by department staff, were based on the American Society of Emergency Radiology core curriculum. The lecture series was implemented after PGY-2 residents had completed formal introductory resident rotations during their first 6 months of training. A DICOM-based interactive computer-based testing module was developed and administered at the end of the lecture series. The module consisted of 19 actual emergency department cases with entire series of images, simulating an on-call setting. Tests were scored by two staff members blinded to resident identifying information. Upper-level residents also were tested, and comparison was made between first-year and upper-level resident test scores to determine the effectiveness of the test in determining first-year resident preparedness for call. Statistical analysis of results was performed by using t-test (P < .05). RESULTS: All residents in the residency program present during the month (nine PGY-2, six PGY-3, seven PGY-4, seven PGY-5 residents) attended the lecture series and finished the testing module at the end of the lecture series. Of 19 actual emergency cases on the testing module, five cases were neuroradiology, three cases were thoracic imaging, eight cases were body imaging, and three cases were musculoskeletal. PGY-2 residents scored an average of 73.0% (range, 63.2%-81.6%) of total points possible. PGY-3 residents scored an average of 76.8% (range, 68.4%-86.8%); PGY-4 residents scored an average of 77.4% (range, 65.8%-100%), and PGY-5 residents scored an average of 81.2% (range, 68.4%-94.7%). There was no statistically significant difference in scores according to level of training. CONCLUSION: First-year radiology residents who underwent 6 months of formal radiology training followed by an intensive ER lecture series before taking overnight call had scores similar to upper-level colleagues on an interactive computer-based ER simulation module.

Curriculum↗
PubMed2006

Part II: preparing and assessing first-year radiology resident on-call readiness technical implementation.

RATIONALE AND OBJECTIVES: The effectiveness of using a Digital Imaging and Communications in Medicine (DICOM)-based interactive examination system in evaluating the readiness of first year radiology residents before taking overnight call in the emergency department (ED) was reported in part I of this article. This report describes technical aspects for the design and implementation of this system. MATERIALS AND METHODS: The examination system consists of two modules: Data Collection and Image Viewing. The Data Collection module was a personal computer (PC)-based DICOM storage server based on a free public domain software package, the Mallinckrodt Central Test Node. The Image Viewing module was a Java-based DICOM viewer created using another freeware package: zDicom ActiveX component. RESULTS: The examination takes place once a year at the end of the first 6-month rotation. Cases selected for the examination were actual clinical cases according to the American Society of Emergency Radiology core curriculum. In the 3-hour timed examination, each resident was required to read the cases and provide clinical findings and recommendations. Upper-level residents also participated in the examination to serve as a control. Answers were scored by two staff radiologists. CONCLUSION: We have been using this examination system successfully in our institution since 2003 to evaluate the readiness of the first-year residents before they take overnight call in the ED. This report describes a step-by-step procedure for implementing this system into a PC-based platform. This DICOM viewing software is available as freeware to other academic radiology institutions. The total cost for implementing this system is approximately 2000 US dollars.

Curriculum↗
PubMed2006

Ischemic colitis in marathon runners: a case-based review.

In the United States over 450,000 participants finished a marathon in 2002. Some of them will present to an Emergency Department (ED) with a variety of gastrointestinal complaints. The diagnosis of ischemic colitis should be considered in patients who present with bloody diarrhea. We describe three patients who presented to our ED with abdominal pain and bloody diarrhea after a marathon. Gastrointestinal complaints with emphasis on mesenteric ischemia and ischemic colitis are discussed.

Adult↗
PubMed2006

MR imaging evaluation of acute appendicitis in pregnancy.

PURPOSE: To retrospectively assess the diagnostic performance of magnetic resonance (MR) imaging in pregnant patients suspected of having acute appendicitis. MATERIALS AND METHODS: The study was approved by the committee on clinical investigations and was HIPAA compliant. The informed consent requirement was waived. MR images were obtained in 51 consecutive pregnant patients (mean age, 28.3 years) who were clinically suspected of having acute appendicitis. In this protocol for pregnant patients, MR imaging is performed when findings at ultrasonography (US) are inconclusive or additional information is needed. Four patients had appendicitis, which was confirmed at surgery in three patients and at follow-up computed tomography in one patient. Initial interpretations were used for patient care and to calculate diagnostic accuracy. The appendix was considered normal at MR imaging if its diameter was less than or equal to 6 mm or if it was filled with air, oral contrast material, or both. An enlarged fluid-filled appendix (>7 mm in diameter) was considered an abnormal finding. An appendix with a diameter of 6-7 mm was considered an inconclusive finding; in those cases, the presence of periappendiceal inflammation was used for the final diagnosis. Three radiologists retrospectively assessed the visualization of the appendix by using a 5-point scale. Statistical analysis was performed by using the median and Fisher exact tests and the Spearman correlation coefficient. RESULTS: MR images were positive for appendicitis in four patients and inconclusive in three. In the three patients with inconclusive results, the appendix was not seen in two patients and was borderline enlarged (7 mm in diameter) in the third. The overall sensitivity, specificity, prevalence-adjusted positive and negative predictive values, and accuracy for MR imaging was 100%, 93.6%, 1.4%, 100%, and 94.0%, respectively. CONCLUSION: MR imaging is an excellent modality for use in excluding acute appendicitis in pregnant women who present with acute abdominal pain and in whom a normal appendix is not visualized at US.

Acute Disease↗
PubMed2006

MDCT angiography of acute chest pain: evaluation of ECG-gated and nongated techniques.

OBJECTIVE: The objective of our study was to compare MDCT angiography protocols used in patients with acute chest pain caused by vascular, nonvascular, and cardiac abnormalities. SUBJECTS AND METHODS: In four groups of 20 patients with chest pain each, four MDCT protocols were used based on monitoring vascular attenuation: pulmonary embolism (150 H at pulmonary artery), aortic dissection (200 H at aortic arch), chest pain (200 H at pulmonary artery), and chest pain with ECG gating (150 H at pulmonary artery). Vascular enhancement was assessed by attenuation measurements taken from locations in the pulmonary artery (n = 3) and thoracic aorta (n = 4). The appearance of the coronary artery in regard to opacification and motion was assessed on a scale of 1 to 5 (best). RESULTS: The mean pulmonary artery and aorta attenuation (372 H and 352 H, respectively) was significantly higher (p < 0.005, Student's t test) and the number of vessel attenuation points measuring less than 200 H (1/140) was significantly smaller (p < 0.001, chi-square test) in the chest pain compared with the dissection (318 H, 310 H; 16/140), gated chest pain (304 H, 286 H; 17/14), and pulmonary embolism (302 H, 220 H; 28/140) groups. The median coronary artery visualization score was 4; the proximal regions received a significantly (p < 0.005, Mann-Whitney test) higher grade compared with the middle and distal regions (medians, 5, 4, and 2, respectively). Artifacts were noted on the gated scans. CONCLUSION: The chest pain protocol can be used to assess both the pulmonary arteries and the thoracic aorta, whereas the ECG-gating protocol appears to be a promising adjunct for a comprehensive single chest pain protocol.

Acute Disease↗
PubMed2005

Short breath-hold, volumetric coronary MR angiography employing steady-state free precession in conjunction with parallel imaging.

An ECG-gated, 3D steady-state free precession (SSFP) technique in conjunction with sensitivity encoding (SENSE)-based parallel imaging was implemented for short breath-hold, volumetric coronary MR angiograpy (CMRA). Two parallel imaging acquisition strategies (employing 1 R-R and 2 R-R intervals, respectively) were developed to achieve 1) very short breath-hold times (12 s for a heart rate of 60 bpm), and 2) small acquisition windows to minimize sensitivity to physiologic motion. Both strategies were examined in CMRA applications over a range of heart rates. A four-point scale blinded reading (with 4 indicating the most desirable features) revealed substantial image quality improvements for the accelerated data as compared to the nonaccelerated approach. The 1 R-R interval scheme yielded an image score of 3.39 +/- 0.60, and was found to be particularly suitable for low heart rates (P = 0.0008). The 2 R-R interval strategy yielded an image score of 3.35 +/- 0.64, and was more appropriate for higher heart rates (P = 0.03). The results demonstrate that 3D SSFP combined with parallel imaging is a versatile method for short breath-hold CMRA while maintaining high spatial resolution. This strategy permits imaging of the major coronary artery distributions in two to three breath-holds using targeted slabs, and offers the potential for single breath-hold, large-volume CMRA.

Adult↗
PubMed2005

Is true FISP imaging reliable in the evaluation of venous thrombosis?

OBJECTIVE: The objective of our study was to evaluate the accuracy of true fast imaging with steady-state precession (FISP) in the diagnosis of venous thrombosis using gadolinium-enhanced 3D T1-weighted gradient-echo images and correlative imaging as the gold standard. MATERIALS AND METHODS: Twenty-five MR examinations were retrospectively reviewed independently by two radiologists to rule out thrombosis in the central veins of the body. The presence of venous thrombus was assessed separately in 80 veins using true FISP and gadolinium-enhanced T1-weighted images. Diagnosis was confirmed by another imaging technique (sonography, CT, and/or conventional venography) in all positive cases. Negative examinations were confirmed using imaging, clinical follow-up, or both. RESULTS: Venous thrombosis was present in 25 veins in 18 patients. True FISP images had a lower sensitivity (66%) and specificity (70.9%) for the diagnosis of venous thrombosis than gadolinium-enhanced MR images (p < 0.01). CONCLUSION: True FISP images have lower sensitivity and specificity in the diagnosis of venous thrombosis than gadolinium-enhanced T1-weighted gradient-echo images. True FISP images should not be used exclusively for the diagnosis of venous thrombosis.

Adolescent↗
PubMed2004

Decreases in free cholesterol and fatty acid unsaturation in renal cell carcinoma demonstrated by breath-hold magnetic resonance spectroscopy.

Increased utilization of cross-sectional imaging has resulted in increased detection of incidental renal tumors. The noninvasive characterization of renal tissue has important implications for the diagnosis of renal malignancies and treatment monitoring. Recently, multiple breath-hold averaged proton magnetic resonance spectroscopy ((1)H-MRS) performed at high field has enabled the use of this noninvasive metabolic profiling technique for the investigation of the abdomen. Multiple breath-hold averaged (1)H-MRS at high field (3T) was obtained in the kidneys of 10 healthy volunteers and in renal cell carcinoma tumors of 14 patients. The spectra of normal kidneys showed four main groups of resonances: 1) at 5.4-5.6 ppm, attributed to C6 of cholesterol and the unsaturated parts of the olefinic region of fatty acids; 2) at 4.7 ppm, attributed to the residual water signal; 3) at 3.2 ppm, attributed to trimethylamine moiety of choline metabolites; and 4) at 1.3 and 0.9 ppm, attributed to the methylenes and terminal methyls of lipids. The ratio of the signal at 5.4 ppm to that of 1.3 ppm was 19-fold lower in renal cell carcinomas than in healthy kidneys, tied P = 0.0003 Mann-Whitney U-test, suggesting a decrease in both free cholesterol and the degree of unsaturation of fatty acids in the malignant tissue. This metabolic shift is in agreement with previous ex vivo studies of human renal cell carcinoma. The ability to detect renal metabolic shifts noninvasively may improve the specificity of preoperative renal tissue characterization and may provide a new modality for treatment monitoring.

Adult↗
PubMed2004

Pancreatic sarcoidosis: MRI features.

Pancreatic sarcoidosis is a rare entity, and few reports in the literature describe the CT aspects of the disease. We report the MR features of a pathologically-confirmed case of pancreatic sarcoidosis, which presented as multiple pancreatic masses with low signal intensity on T1-weighted images, mild high signal intensity on T2-weighted images, and decreased enhancement compared to the normal pancreas after administration of gadolinium. Pancreatic sarcoidosis should therefore be included in the differential diagnosis of multiple pancreatic masses with these MRI features.

Adult↗
PubMed2004

MR imaging of the prostate at 3 Tesla: comparison of an external phased-array coil to imaging with an endorectal coil at 1.5 Tesla.

RATIONALE AND OBJECTIVES: To qualitatively compare the image quality of torso phased-array 3-Tesla (3T) imaging of the prostate with that of endorectal 1.5-Tesla imaging. MATERIALS AND METHODS: Twenty cases of torso phased-array prostate imaging performed at 3-Tesla with FSE T2 weighted images were evaluated by two readers independently for visualization of the posterior border (PB), seminal vesicles (SV), neurovascular bundles (NVB), and image quality rating (IQR). Studies were performed at large fields of view(FOV) (25 cm) (14 cases) (3TL) and smaller FOV (14 cm) (19 cases) (3TS). A comparison was made to 20 consecutive cases of 1.5-T endorectal evaluation performed during the same time period.Results. 3TL produced a significantly better image quality compared with the small FOV for PB (P = .0001), SV (P =.0001), and IQR (P = .0001). There was a marginally significant difference within the NVB category (P = .0535). 3TL produced an image of similar quality to image quality at 1.5 T for PB (P = .3893), SV (P = .8680), NB (P = .2684), and IQR (P = .8599). CONCLUSION: Prostate image quality at 3T with a torso phased-array coil can be comparable with that of endorectal 1.5-T imaging. These findings suggest that additional options are now available for magnetic resonance imaging of the prostate gland.

Adenocarcinoma↗
PubMed2004

3 Tesla magnetic resonance imaging of the prostate with combined pelvic phased-array and endorectal coils; Initial experience(1).

RATIONALE AND OBJECTIVES: High-resolution magnetic resonance imaging of the prostate at 1.5T has gained acceptance for pretherapeutic staging of prostate cancer. The aim of this study was to evaluate the potential clinical utility of combined pelvic phased-array and endorectal coils at 3T. MATERIALS AND METHODS: Six volunteers were examined on 1.5T and 3T scanners with pelvic phased-array surface coil combined with a disposable endorectal prostate coil. RESULTS: We were able to acquire T2-W fast spin echo images with 1.5 mm slices, field of view 12, matrix 320 x 192, (voxel size 0.35 mm(3)), with excellent anatomic detail and good T2 contrast. A 1.5 mm axial slice thickness permitted high-quality multiplanar reconstructions with clear visualization of small patho-anatomic structures. Dynamic contrast-enhanced gradient echo images showed excellent spatial resolution (voxel size, 0.38 mm(3)) and temporal resolution. With this level of anatomic information in dynamic images we could clearly distinguish between intracapsular and extracapsular contrast enhancement. CONCLUSION: Using modified T2-fast spin echo and dynamic contrast-enhanced gradient echo sequences, we obtained whole gland coverage with 35-38 microm(3) resolution, without interfering artifacts, in reasonable acquisition times and staying well below the specific absorption rate guidelines. The high spatial resolution in the axial plane allowed meaningful multiplanar reconstructions. The initial results show the clinical utility of endorectal 3T for the noninvasive evaluation of the prostate with image features and quality not achievable at 1.5 T.

Contrast Media↗
PubMed2004

Magnetic resonance mapping of transplanted endothelial progenitor cells for therapeutic neovascularization in ischemic heart disease.

OBJECTIVE: Intramyocardial transplantation of endothelial progenitor cells (EPCs) has been previously correlated with significant augmentation of vascularity and improvement of left ventricular function following myocardial ischemia. However, precise intramyocardial localization of the transplanted cells and the extent of in situ cell migration are unknown. We present a novel technique using magnetic resonance imaging (MRI) to localize transplanted EPCs in ischemic hearts. METHODS: CD34-positive cells were isolated from human peripheral blood by magnetic bead selection: CD34-positive cells adhere to CD34-negative antibody coated magnetic beads, while CD34-negative cells do not. All cells were labeled with fluorescent DiI-dye for histological localization. CD34-positive cells or CD34-negative cells (105, 1 x 106 and 2 x 106 cells) were transplanted into non-ischemic (n = 6) or ischemic myocardium (n = 2) of Sprague-Dawley rats. Rats were sacrificed 24 h after cell transplantation. The resected hearts were imaged ex vivo using 3 and 8.5 T magnets. Morphological correlation between the MRI findings and fluorescent microscopy for identification of retained CD34-positive cells was evaluated. RESULTS: CD34-positive cells were identified as areas of low signal intensity on T2*-weighted images within the myocardium. These areas increased in size with the gradual increase in the echo time due to susceptibility effect. The extent of the low signal intensity at a given echo time was proportional to cell dosage. No areas of low signal were identified in the CD34-negative cell transplanted hearts. Histological localization of DiI-labeled CD34-positive cells documented a direct anatomic correlation with the localization of transplanted cells on the MRI images. CONCLUSIONS: Magnetically labeled EPCs transplanted for therapeutic neovascularization in myocardial ischemia can be visualized with ex vivo MRI at high-field strengths.

Animals↗
PubMed2003

Shortening MR image acquisition time for volumetric interpolated breath-hold examination with a recently developed parallel imaging reconstruction technique: clinical feasibility.

A recently developed parallel magnetic resonance (MR) imaging technique, parallel imaging with an augmented radius in k space, was used to accelerate the volumetric interpolated breath-hold examination (VIBE) performed in 20 patients referred for clinical liver imaging. Nonaccelerated MR images were also acquired in these patients. A five-point scale was used to score the quality of the images. The acceleration resulted in reduced image quality: The nonaccelerated images had a significantly higher (P <.05) mean score--3.8 +/- 0.3 (SD), indicating good quality--than the accelerated images--3.0 +/- 0.3, indicating acceptable quality. However, for three patients who could not hold their breath for the duration necessary for nonaccelerated imaging, less severe breathing artifacts on the accelerated images resulted in improved quality compared with the quality of the nonaccelerated images. Parallel MR imaging-accelerated VIBE may be beneficial for patients who have difficulty sustaining a breath hold for the duration necessary to perform nonaccelerated imaging.

Adult↗
PubMed2003

The interrupted rim sign in acute cholecystitis: a method to identify the gangrenous form with MRI.

We present the imaging findings on MR of a patient with acute gangrenous cholecystitis that demonstrated patchy enhancement of the gallbladder mucosa on gadolinium-enhanced fat-saturated T1-weighted gradient echo images. This interrupted rim of mucosal enhancement correlated with patchy areas of necrosis and inflammation of the gallbladder mucosa on the histopathological examination.

Acute Disease↗
PubMed2003

MR techniques for renal imaging.

This article describes the principles, attributes, and pitfalls of the many MR imaging approaches available for assessment of renal-related disorders. Tables 1 and 2 summarize the specific approach and rationale.

Contrast Media↗
PubMed2003

MR imaging in abdominal emergencies.

The use of MR imaging in the emergency setting is evolving. Clear indications include situations in need of contrast media when iodinated contrast cannot be administered or to facilitate assessments in pregnant patients and children when exposure to ionizing radiation is considered unacceptable. The availability of rapid, motion-immune sequences now makes MR imaging a feasible study in less cooperative patients extending the range of patients for whom a diagnostic study can be achieved. Capitalizing on the unique benefits of MR imaging there is optimism that MR imaging can eliminate test redundancy and impact patient care in a cost-effective manner. Further investigations are needed to identify the diagnostic algorithms for which this favorable use holds true.

Abdomen, Acute↗