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Biomedical subjects

Diego Jaramillo

Publications and source records attributed to Diego Jaramillo.

At least 19 recordsLinked to original sources
PubMed2007

Early ischemia in growing piglet skeleton: MR diffusion and perfusion imaging.

PURPOSE: To determine whether diffusion changes with ischemia of increasing duration, whether diffusion magnetic resonance (MR) imaging provides different information than does gadolinium-enhanced imaging, and which structural and/or biochemical changes are potentially responsible for any changes in diffusion. MATERIALS AND METHODS: Ischemia was surgically induced in one hip of each piglet (n=8) after approval from the Subcommittee on Research Animal Care; the other hip served as a control. Piglets were imaged at approximately 48 hours and 1, 2, 4, and 8 weeks after surgery at 1.5 T by using line-scan diffusion and dynamic gadolinium-enhanced MR imaging. Apparent diffusion coefficients (ADCs) and enhancement ratios (ERs) were calculated. Significant differences in ADC and ER values over time were evaluated by using the Student t test (P<.05). At 8 weeks, piglets were sacrificed for histologic evaluation. RESULTS: MR images of ischemic hips showed essentially no flow 48 hours after surgery. Spontaneous partial reperfusion was observed 1-4 weeks after surgery (ischemic ER/control ER=66%+/-35 [standard deviation]), and the ER of the ischemic hips was well above that of the control hips at 8 weeks. The ADC of ischemic hips was elevated above that of control hips before reperfusion 1 week after surgery by 47%+/-12 and remained elevated despite flow restoration. Gross structural abnormalities on MR images appeared to coincide with reperfusion. Histologic findings revealed abnormal epiphyseal cartilage thickening, cartilaginous islands within ossified tissue, and less fatty marrow in ischemic hips than in control hips; all of these factors could explain elevated ADC. CONCLUSION: Diffusion is sensitive to early ischemia and follows a different time course than that of changes observed with gadolinium enhancement. ADC remained elevated in this model of severe, prolonged ischemia despite the spontaneous partial restoration of blood flow seen on gadolinium-enhanced images.

Animals↗
PubMed2006

Gadolinium-enhanced MR images of the growing piglet skeleton: ionic versus nonionic contrast agent.

PURPOSE: To determine whether there are differences in the distribution of ionic and nonionic gadolinium-based contrast agents by evaluating contrast enhancement of the physis, epiphyseal cartilage, secondary ossification center, and metaphysis in the knees of normal piglets. MATERIALS AND METHODS: Following approval from the Subcommittee on Research Animal Care, knees of 12 3-week-old piglets were imaged at 3-T magnetic resonance (MR) imaging after intravenous injection of gadoteridol (nonionic contrast agent; n = 6) or gadopentetate dimeglumine (ionic contrast agent; n = 6). Early enhancement evaluation with gradient-echo MR imaging was quantified and compared (Student t test) by means of enhancement ratios. Distribution of contrast material was assessed and compared (Student t test) by means of T1 measurements obtained before and at three 15-minute intervals after contrast agent administration. The relative visibility of the physis, epiphyseal cartilage, secondary ossification center, and metaphysis was qualitatively assessed by two observers and compared (Wilcoxon signed rank test). Differences in matrix content and cellularity that might explain the imaging findings were studied at histologic evaluation. RESULTS: Enhancement ratios were significantly higher for gadoteridol than for gadopentetate dimeglumine in the physis, epiphyseal cartilage, and secondary ossification center (P < .05). After contrast agent administration, T1 values decreased sharply for both agents-but more so for gadoteridol. Additionally, there was less variability in T1 values across structures with this contrast agent. Gadoteridol resulted in greater visibility of the physis, while gadopentetate dimeglumine resulted in greater contrast between the physis and metaphysis (P < .05). CONCLUSION: The results suggest different roles for the two gadolinium-based contrast agents: The nonionic contrast medium is better suited for evaluating perfusion and anatomic definition in the immature skeleton, while the ionic contrast medium is better for evaluating cartilage fixed-charge density.

Animals↗
PubMed2006

Fetal sheep development on ultrasound and magnetic resonance imaging: a standard for the in utero assessment of models of congenital abnormalities.

OBJECTIVE: To establish normative data for the size, conspicuity, and imaging characteristics of normal developing fetal sheep organs on ultrasound (US) and magnetic resonance (MR) imaging. METHODS: US and MR images of ten normal pregnant sheep, at 40, 65, 90, 115, and 140 gestational days (term = 145 days), were scored for organ conspicuity and imaging characteristics. Imaging biometry was correlated with specimens. Gestational age-based growth parameters were modeled using regression. RESULTS: Imaging biometry showed excellent correlation with specimens. Kidney, bladder, stomach, lung, liver, and spine were seen well from 65 days to term by US. More organs were consistently visible from 90 days to term by MR than by US. Most organ imaging characteristics tended not to change throughout gestation. CONCLUSION: Normal fetal sheep biometry, organ conspicuity, and imaging characteristics are established for US and MR and have potential use for the in utero assessment of sheep models of congenital abnormalities.

Animals↗
PubMed2006

MDCT of the elbow in pediatric patients with posttraumatic elbow effusions.

OBJECTIVE: The purpose of this study was to determine the performance characteristics of MDCT in the detection of fractures in children with posttraumatic elbow effusions and to assess the effect of MDCT findings on clinical management. SUBJECTS AND METHODS: Unenhanced MDCT of the elbow was prospectively performed without sedation on 31 children 20 months to 16 years old who had posttraumatic elbow effusions. Two blinded reviewers independently and in consensus characterized all MDCT scans as positive or negative for the presence of fracture. Level of interobserver agreement was determined with the kappa statistic. Sensitivity, specificity, positive predictive value, and negative predictive value of MDCT for fracture detection were determined for the consensus MDCT interpretations with follow-up radiographs as the reference standard. Patients were treated with casts and instructed to return in 2-3 weeks for clinical and radiographic follow-up unless a change in management was indicated on the basis of MDCT findings. The frequency of alteration of management was determined. RESULTS: Both reviewers detected fractures in 15 (48%) of the patients individually and in 16 (52%) of the patients by consensus. Interobserver agreement for fracture detection with MDCT was excellent (kappa = 0.85). The sensitivity, specificity, positive predictive value, and negative predictive value of MDCT in the detection of fractures were 92%, 79%, 79%, and 92%, respectively. Four (13%) of the children had changes in management based on the MDCT findings. CONCLUSION: MDCT is a sensitive means of evaluating for radiographically occult fractures in children with posttraumatic elbow effusions. It has a high negative predictive value and a high level of interobserver agreement. MDCT findings may lead to alteration of treatment of children with nondisplaced lateral condylar and radial head fractures.

Adolescent↗
PubMed2005

Which MRI sequence of the spine best reveals bone-marrow metastases of neuroblastoma?

BACKGROUND: MRI is an effective tool in evaluating bone marrow metastases. However, no study has defined which MRI sequences or image characteristics best correlate with bone-marrow metastases in neuroblastoma. OBJECTIVE: To identify and refine MRI criteria and sequence selection for the diagnosis of bone-marrow metastases in children with neuroblastoma. MATERIALS AND METHODS: Ninety-one children (mean age: 3.2 years; standard deviation: 2.8 years) enrolled in the RDOG IV study participated in our study. Forty-five children had bone metastases determined by bone-marrow aspiration or biopsy (n=4), radionuclide imaging (n=2), or both (n=39). Spine lesions were characterized using coronal T1-weighted (T1W) sagittal short tau inversion recovery (STIR) and coronal gadolinium-enhanced T1-weighted (GAD) MR sequences. Contingency table analysis was performed to determine which MRI sequences and characteristics were associated with metastases. The MRI criteria for metastatic disease were then developed for each imaging sequence. The sensitivity, specificity, predictive values, and accuracy of these criteria were determined for the whole group, children younger than 12 months old, and children 12 months and older. RESULTS: The MR characteristics that had significant (P<or=0.05) associations with metastases were homogeneous low T1-signal intensity, homogeneous high STIR-signal intensity, and heterogeneous pattern on T1, STIR, or GAD. Homogeneous low T1-signal had the highest sensitivity (88%), but a specificity of 62% for detecting metastases. A heterogeneous pattern on GAD was highly specific (97%), but relatively insensitive (65%) for detecting metastases. These MR characteristics were most accurate in children 12 months and older. CONCLUSION: The combination of non-contrast-enhanced T1W and GAD sequences can be used to determine the presence of spinal metastases in children with neuroblastoma, particularly those children who are 1 year and older.

Bone Marrow Neoplasms↗
PubMed2005

Low-dose CT colonography in children: initial experience, technical feasibility, and utility.

BACKGROUND: CT colonography (CTC) is utilized as a diagnostic tool in the detection of colon polyps and early colorectal cancer in adults. Large studies in the literature, although focused on adult populations, have shown CTC to be a safe, accurate, non-invasive technique. OBJECTIVE: We evaluated the technical feasibility of CTC in children using a low-dose technique. MATERIALS AND METHODS: From November 2001 to April 2004 we evaluated eight patients (3-17 years) with non-contrast CTC. Seven of the patients had CTC, followed by standard colonoscopy (SC) the same day; in one patient, CTC followed a failed SC. CTC results were compared to results of SC. The estimated effective dose from each CTC was calculated and compared to that of standard barium enema. RESULTS: CTC results were consistent with those of SC. Sensitivity for polyps 5-10 mm was 100%, and sensitivity for polyps 10 mm and larger was 66.7%. The estimated mean effective dose was 2.17 mSv for CTC, compared to the 5-6 mSv for a standard air-contrast barium enema in a small child. CONCLUSION: Our initial experience shows CTC in children is well-tolerated, safe, and useful. The procedure can be performed successfully with a low radiation dose, and preliminary results compare well with SC.

Adenomatous Polyposis Coli↗
PubMed2005

Multidetector row CT in pediatric musculoskeletal imaging.

The proliferation of multidetector row CT (MDRCT) has had a significant effect on imaging of the musculoskeletal system. An increasing number of such examinations is being performed in children. We reviewed our experience using such examinations in children during a period of 20 months. In this review, we discuss MDRCT techniques and issues regarding the radiation dose of these examinations. We present the effect of newer scanning techniques and their incorporation into our scanning protocols.

Child↗
PubMed2005

Imaging of the pediatric hand: soft tissue abnormalities.

This review attempts to demonstrate the spectrum of soft tissue masses encountered in the child's hand. The diagnosis may be suggested by the combination of physical exam and radiographs. Frequently the etiology of a soft tissue mass cannot be established by conventional radiographs and further imaging is necessary. MRI by virtue of its ability to provide detailed soft tissue characterization is the preferred method of imaging the problematic soft tissue mass.

Connective Tissue↗
PubMed2005

MR imaging of congenital/developmental and acquired disorders of the pediatric hip and pelvis.

This article reviews the MR imaging findings of some of the more common congenital and acquired disorders of the pediatric hip and pelvis,with the intent of increasing the awareness of radiologists and facilitating early and accurate diagnosis and treatment. The importance of MR imaging in the pediatric population is underscored by its ability to evaluate these disorders well and without the use of ionizing radiation.

Adolescent↗
PubMed2005

Superficial neurofibroma: a lesion with unique MRI characteristics in patients with neurofibromatosis type 1.

OBJECTIVE: Our aim was to test the hypothesis that in neurofibromatosis type 1 (NF1), superficial plexiform neurofibromas have different MRI characteristics than deep plexiform neurofibromas. SUBJECTS AND METHODS: Sixty-six patients (median age, 15 years) with superficial plexiform neurofibromas were compared with 56 patients with deep plexiform neurofibromas (median age, 12 years). All patients underwent axial STIR and coronal or sagittal STIR images. RESULTS: Superficial neurofibromas were more likely to be asymmetric (p = 0.004) and extend to the skin surface (p < 0.001). Lesion borders were poorly defined with similar frequency in both superficial and deep groups (77% vs 68%, p = 0.31). The morphology of superficial neurofibromas was more likely diffuse (64% vs 11%, p < 0.001), whereas deep neurofibromas were more likely nodular or fascicular. Of neurofibromas that were nodular or fascicular in morphology, superficial lesions had a smaller maximal fascicle-nodule diameter (mean, 10.3 mm) than deep lesions (mean, 13.4 mm) (p = 0.013). Signal characteristics of deep neurofibromas were more likely to be targetlike (75%) compared with superficial neurofibromas (21%) (p < 0.001). Superficial neurofibromas had a smaller mean volume than deep neurofibromas (180 vs 444 cm(3), p = 0.002). CONCLUSION: Unlike the typical targetlike lesions along the course of major nerves seen in deep plexiform lesions, superficial plexiform neurofibromas in NF1 tend to be asymmetric, have nontargetlike signal intensity, lack nodular or fascicular morphology, and are likely to involve skin.

Adolescent↗
PubMed2005

16-MDCT of the posttraumatic pediatric elbow: optimum parameters and associated radiation dose.

OBJECTIVE: Our objective was to investigate a low-radiation-dose protocol for 16-MDCT of the posttraumatic pediatric elbow using z-axis automatic tube-current modulation, based on optimum scanning parameters determined in a porcine fracture model, and to report the radiation dose from this technique in nine children with acute elbow trauma. CONCLUSION: For the posttraumatic pediatric elbow, 16-MDCT using z-axis automatic tube-current modulation was optimal at 100 kVp with a noise index of 20 and a minimum amperage of 25 mA.

Adolescent↗
PubMed2004

Malrotation with midgut volvulus: CT findings of bowel infarction.

Midgut volvulus, the most common serious complication of malrotation, can be diagnosed using conventional contrast fluoroscopy, US or CT. CT is a quick and comprehensive examination in the evaluation of complex acute abdominal pathology in children. Contrast-enhanced CT can readily help the radiologist recognize perfusion abnormalities of the bowel, which is vital for reducing morbidity and mortality in affected children. Our case emphasizes and demonstrates additional CT features of bowel infarction in a child with a proven malrotation with midgut volvulus.

Abdomen, Acute↗
PubMed2004

MR imaging of abdominopelvic involvement in neurofibromatosis type 1: a review of 43 patients.

BACKGROUND: Plexiform neurofibromas are a frequent complication of neurofibromatosis type 1. This article discusses MR imaging findings and distribution of plexiform neurofibromas in the abdomen and pelvis. OBJECTIVE: To define the most prevalent patterns of involvement and MR imaging findings in abdominopelvic neurofibromatosis type 1. MATERIALS AND METHODS: We reviewed the MR appearance of abdominopelvic lesions in 23 male and 20 female patients (median age: 16 years) with type 1 neurofibromatosis. The patients were part of a multi-institutional study of 300 patients. Imaging included coronal or sagittal, and axial short tau inversion recovery images. RESULTS: The most common abdominopelvic involvement was in the abdominopelvic wall (n=28, 65%) and lumbosacral plexus (n=27, 63%). Retroperitoneal involvement was frequent (n=15, 35%). Lesions were less often intraperitoneal (21%) (P=0.001). Pelvic disease (n=27, 63%), neural canal involvement (n=18, 42%), and hydronephrosis (n=4, 9%) were also noted. Target-like appearance of plexiform lesions was noted in more than half the patients. CONCLUSION: Abdominopelvic involvement in neurofibromatosis type 1 is primarily extraperitoneal. Although lesions are most prevalent in the abdominopelvic wall and lumbosacral plexus, retroperitoneal and pelvic involvement is common and usually affects important organs. MR imaging added information in the initial and follow-up clinical evaluation of these patients.

Abdomen↗
PubMed2004

Skeletal development in fetal pig specimens: MR imaging of femur with histologic comparison.

PURPOSE: To evaluate the magnetic resonance (MR) imaging features of the developing femur in fetal pig specimens. MATERIALS AND METHODS: MR images of 15 fetal pig femurs, which were categorized into three groups of specimens representing each third of the gestational period, were used to compare increasing femoral length (as an indication of gestational age) with epiphyseal growth in multiple dimensions by using Pearson product moment correlation. Physeal-epiphyseal demarcation, visibility of the secondary ossification center and its physis, prominence of the perichondrial structures (ie, groove of Ranvier and bone bark), metaphyseal undulation, and corticomedullary differences were evaluated qualitatively. These features were also evaluated on histologic sections. RESULTS: With femoral length measurements used as indications of gestational age, there were three, five, and seven fetal pig specimens in each gestation group. During fetal development, the cartilaginous epiphysis of the distal femur transformed from an oval to a bicondylar structure, with most of the growth occurring sagittally (P < .001). Physeal-epiphyseal demarcation, visibility of the secondary ossification center and its physis, and metaphyseal undulation increased later in gestation. Detection of perichondrial structures, however, was greatest during the middle third of gestation and decreased thereafter. During the fetal period, the perichondrial groove of Ranvier and the bone bark were easily identifiable at MR imaging. Marrow cavitation increased with gestation. CONCLUSION: MR imaging depicts fetal pig skeletal features that can be confirmed histologically and that may prove to be useful at human prenatal skeletal imaging.

Animals↗
PubMed2004

Imaging of articular disorders in children.

This article reviews aspects of arthritis imaging that are specific to children. The pediatric skeleton is unique and responds in characteristic ways to articular inflammation. Epiphyseal and physeal cartilage are affected by joint diseases, and disturbances of growth and maturation are sometimes the cardinal manifestations of arthritis. The target joints of pediatric articular diseases differ considerably from those of diseases in adults. Imaging techniques should be tailored to the children being studied.

Adolescent↗
PubMed2004

Acute injury of the articular cartilage and subchondral bone: a common but unrecognized lesion in the immature knee.

OBJECTIVE: We studied the prevalence of injuries of the articular cartilage and subchondral bone after acute trauma in skeletally immature knees using high-resolution MRI. MATERIALS AND METHODS: We reviewed knee MRIs of 126 young children and adolescents suspected to have internal knee derangement, including 82 with open physes and a control group of 44 who were skeletally mature. High-resolution proton density and T2-weighted pulse sequences were used in all patients. The prevalence of common injuries in the two groups was compared using chi-square analysis. Levels of interobserver agreement for evaluation of chondral lesions in the skeletally immature group were determined using the kappa statistic. RESULTS: In the skeletally immature group, chondral lesions were the most prevalent injuries (prevalence = 0.34, p = 0.009) followed by meniscal and anterior cruciate ligament injuries (prevalence = 0.23 and 0.24, respectively). No significant difference in the prevalence of chondral injury before and after physeal closure was seen (p = 0.45). There was no significant difference in the prevalence of anterior cruciate ligament injuries between the two groups, but meniscal injuries were more prevalent in the skeletally mature patients (prevalence = 0.41, p = 0.037). Interobserver agreement for chondral injuries in the group with open physes was good (weighted kappa = 0.45-0.51). CONCLUSION: The most common injuries occurring as a result of acute trauma to the immature knee were chondral. In patients with open physes, chondral injuries were significantly more prevalent than anterior cruciate ligament and meniscal injuries.

Adolescent↗
PubMed2004

Age-related vascular changes in the epiphysis, physis, and metaphysis: normal findings on gadolinium-enhanced MRI of piglets.

OBJECTIVE: We sought to study the normal enhancement patterns seen on MRIs of the epiphysis, physis, and metaphysis and age-related vascular changes in piglets using gadoteridol, a nonionic gadolinium chelate. MATERIALS AND METHODS: We quantitatively and qualitatively analyzed the normal changes on sequential T1-weighted images after the IV administration of gadoteridol. In an investigation approved by the research animal care committee at our hospital, we studied the proximal and distal femurs of 26 piglets 1-6 weeks old and correlated the enhanced images with findings on intermediate-weighted, T2-weighted, and gradient-recalled echo images and at histologic examination. RESULTS: We observed early enhancement of the epiphyseal vascular canals, the main physis, the physis of the secondary ossification center, and a metaphyseal band adjacent to the physis. Enhancement of the epiphyseal and metaphyseal marrow and of the epiphyseal cartilage was slower. In the epiphyseal cartilage, we saw three phases of enhancement: vascular, canalicular, and cartilaginous. As the piglets matured, enhancement of the epiphyseal cartilage decreased, and the epiphyseal vascular canals were less conspicuous. Physeal enhancement was greatest during the first week of life, declined at 3 weeks, and subsequently increased again as the physis came to lie adjacent to a larger segment of the epiphyseal ossification center. CONCLUSION: Gadoteridol-enhanced MRIs showed multiple cartilaginous and vascular structures of the growing skeleton. With maturity and progressive epiphyseal ossification, epiphyseal cartilage enhancement decreased, and physeal cartilage enhancement increased.

Aging↗