Camilo Jaimes

Osteoid osteomas: a pain in the night diagnosis

Osteoid osteoma is a common benign bone-forming lesion that is composed of a nidus of vascular osteoid tissue and woven bone lined by osteoblasts. It is frequently associated with considerable surrounding inflammation. The diagnosis is usually straightforward when imaging reveals a radiolucent nidus surrounded by variable degrees of reactive sclerosis. However, the diagnosis can be elusive when osteoid osteomas occur in atypical locations, as they may have a nonspecific and misleading appearance on different imaging modalities, particularly on MRI. The purpose of this pictorial essay is to review the typical and atypical features of osteoid osteomas on different imaging modalities, and the appearance of osteoid osteomas in different locations. We also review growth disturbances caused by osteoid osteomas and potential mimickers, with imaging characteristics that can aid in diagnosis.

Taking the Stress out of Evaluating Stress Injuries in Children

Pediatric stress injuries result from a mismatch between (a) the burden of activity on growing bone and cartilage and (b) their intrinsic biomechanical properties. Although the presentation of stress injuries varies with the specific physical activity and the site of injury, in children it varies primarily with the degree of skeletal maturation. During the past several years, there has been a substantial increase in the incidence of pediatric stress injuries. The differential diagnosis of a stress injury in a child or adolescent can be challenging because the injury sometimes can appear aggressive at imaging assessment. Awareness of the spectrum of imaging features of stress injuries can help the radiologist to reach the correct diagnosis and prevent unnecessary anxiety. This review depicts the range of stress injuries in children and adolescents in various anatomic locations, with emphasis on their appearances at magnetic resonance imaging.

MR Imaging of Normal Epiphyseal Development and Common Epiphyseal Disorders

During infancy and childhood, multiple developmental changes occur in the epiphysis. Initially the epiphysis is composed entirely of hyaline cartilage. As skeletal maturation progresses, one or several secondary ossification centers (SOCs) develop within the epiphyseal cartilage. The SOCs enlarge by endochondral ossification and undergo marrow transformation in a process analogous to that of the primary physis and metaphysis. Magnetic resonance (MR) imaging can be used to evaluate vascularity, marrow, and cartilage and plays a critical role in the assessment of epiphyseal disorders in children. In cases of shoulder and hip dysplasia, MR imaging demonstrates unossified structures and helps guide treatment. In cases of trauma, the intracartilaginous pathway of fractures, the degree of physeal involvement, and early bridge formation can be assessed. With the use of intravenous gadolinium-based contrast material, avascular necrosis and reperfusion can be characterized. This article reviews the normal structure of the epiphysis, its appearance at MR imaging, and age-related changes to the epiphysis. Common conditions that lead to epiphyseal damage in children are reviewed, with an emphasis on the role of MR imaging in diagnosis, prognosis, and treatment.

Vasa Vasorum Enhancement on Computerized Tomographic Angiography Correlates With Symptomatic Patients With 50% to 70% Carotid Artery Stenosis

Background and Purpose— Significant stenosis of the internal carotid artery (ICA) is an established stroke risk factor. Recent evidence suggests that features within the atherosclerotic plaque also have prognostic value. The purpose of this study was to correlate the enhancement of the vasa vasorum (VV) overlying the carotid artery plaque with acute neurological symptoms in patients with 50% to 70% ICA stenosis. Methods— We conducted a 4-year retrospective computerized tomographic angiographic review to identify patients with 50% to 70% stenosis of the ICA. Three types of plaques were identified: enhancing VV, calcified, and nonenhancing-noncalcified. Medical records were reviewed for cardiovascular risk factors and neurological status, and imaging was reviewed for signs of a recent stroke. Results— We identified a total of 428 patients with 50% to 70% ICA stenosis: 103 (24.1%) had enhancing VV, 202 (47.2%) calcified, and 123 (28.7%) nonenhancing-noncalcified arteries; 97 were symptomatic and 331 asymptomatic. Thirty-three (34%) symptomatic subjects demonstrated enhancing VV, 42 (20%) had calcified arterial plaques, and 22 (17%) had nonenhancing-noncalcified arterial plaques. Fisher exact tests revealed that the proportion of symptomatic individuals with enhancing VV plaque was double that of the other groups combined (P=0.015; odds ratio, 1.92; 95% confidence interval, 1.17–3.16). Regression analyses confirmed this association as independent from other known cardiovascular risk factors. Conclusions— In patients with 50% to 70% ICA stenosis, VV enhancement recognized on computed tomographic angiography is strongly associated with acute neurological symptoms compared with calcified and nonenhancing-noncalcified arterial plaques. This finding may aid in the identification of patients at increased risk for ischemic stroke within populations with the same degree of stenosis.

Strategies to minimize sedation in pediatric body magnetic resonance imaging

The high soft-tissue contrast of MRI and the absence of ionizing radiation make it a valuable tool for assessment of body pathology in children. Infants and young children are often unable to cooperate with awake MRI so sedation or general anesthesia might be required. However, given recent data on the costs and potential risks of anesthesia in young children, there is a need to try to decrease or avoid sedation in this population when possible. Child life specialists in radiology frequently use behavioral techniques and audiovisual support devices, and they practice with children and families using mock scanners to improve child compliance with MRI. Optimization of the MR scanner environment is also important to create a child-friendly space. If the child can remain inside the MRI scanner, a variety of emerging techniques can reduce the effect of involuntary motion. Using sequences with short acquisition times such as single-shot fast spin echo and volumetric gradient echo can decrease artifacts and improve image quality. Breath-holding, respiratory triggering and signal averaging all reduce respiratory motion. Emerging techniques such as radial and multislice k-space acquisition, navigator motion correction, as well as parallel imaging and compressed sensing reconstruction methods can further accelerate acquisition and decrease motion. Collaboration among radiologists, anesthesiologists, technologists, child life specialists and families is crucial for successful performance of MRI in young children.

Multimodality imaging manifestations of the Meckel diverticulum in children.

Meckel diverticulum is the most common congenital abnormality of the gastrointestinal (GI) tract, occurring in approximately 2% of the general population. The lifetime complication rate from a Meckel diverticulum is 0.5%–2%. The most common complications include bleeding, obstruction, inflammation and perforation. However, the clinical manifestations of a Meckel diverticulum are frequently nonspecific. As a result, complications secondary to Meckel diverticulitis can mimic a variety of more common intra-abdominal processes, such as appendicitis, inflammatory bowel disease and any other cause of small bowel inflammation or obstruction. The radiologist should be aware of potential manifestations of the disease on different imaging modalities. In this pictorial essay, we illustrate several complications related to the Meckel diverticulum, in multiple modalities.

Magnetic Resonance Imaging of the Pediatric Shoulder

Magnetic resonance (MR) imaging is a modality widely used to assess shoulder abnormalities in children. A thorough understanding of the development of the shoulder and adequate MR techniques are crucial in the radiologic evaluation. The immature skeleton is particularly vulnerable to insults such as trauma, infection, and inflammation, and responds in unique ways. The pediatric shoulder can also be affected by complex congenital deformities such as brachial plexus injuries. In addition, certain neoplasms can be seen specifically in the young patient. MR imaging plays a critical role in the initial diagnostic evaluation and in assessing posttreatment responses.

The diagnostic performance of classical molecular tests used for detecting human papillomavirus

Cervical samples were evaluated for human papillomavirus (HPV) presence using the hybrid capture-2 (HC2) assay and the polymerase chain reaction (PCR) with three different primer sets (GP5+/6+, MY09/11 and pU1M/2R). PCR results were compared to HC2 and results of all assays were compared to cytological and colposcopy findings. Post-test probability was assessed in individual assays and test combinations. HPV-DNA prevalence was 36.5% with HC2 and 55.2% with PCR. MY09/11 detected HPV-DNA in 38% of samples, GP5+/6+ in 19.1% and pU1M/2R in 16.4%. pU1M/2R and HC2 had the highest concordance (75.31%, k=0.39 in the whole population; 74.1%, k=0.5 in women with abnormal cytology). pU1M/2R had the best diagnostic performance, including optimal post-test probabilities and cervical abnormality detection (individually or in a panel of tests). Women positive for pU1M/2R may be at higher risk of disease progression; the assay performance when combined with a Pap smear in cervical cancer screening programs should be evaluated.

Dynamic Gadolinium-Enhanced MRI of the Proximal Femur: Preliminary Experience in Healthy Children

OBJECTIVE The purpose of this study is to use dynamic contrast-enhanced MRI to evaluate the perfusion characteristics of the proximal femur in the growing skeleton. MATERIALS AND METHODS We evaluated 159 subjects (mean age, 5.67 years) who underwent a well-controlled protocol of contrast-enhanced MRI of the abdomen and hips. Perfusion and permeability parameters (enhancement ratio peak, AUC, time to peak, and rate of extraction) for six regions of the proximal femur were calculated. RESULTS A decrease with age was found for all contrast kinetics parameters in all regions (p < 0.001). Perfusion parameters differed between the regions (p < 0.001). The highest perfusion and permeability parameters were found in the metaphyseal spongiosa, metaphyseal marrow, and periosteum. The metaphyseal spongiosa had a highly vascular pattern of enhancement and showed the highest enhancement ratio peak, AUC, and rate of extraction and the lowest time to peak. The metaphyseal marrow showed a vascular pattern of enhancement with a lower peak compared with the metaphyseal spongiosa. The periosteum showed prompt nonvascular contrast enhancement that reached a plateau that remained elevated. CONCLUSION The highest enhancement was seen in areas involved with growth: the metaphyseal spongiosa, which is related to endochondral ossification, and the periosteal cambium, which is related to membranous ossification. The enhancement characteristics are radically different: in the spongiosa; enhancement is brisk and declines, with a vascular pattern, whereas contrast uptake increases with time in the periosteum. Recognition of normal enhancement patterns of the proximal femur is important for distinguishing normal development from pathologic processes.

The trochlear pre-ossification center: a normal developmental stage and potential pitfall on MR images

BackgroundThe hypertrophic changes that occur in the cartilage of an epiphysis prior to the onset of ossification are known as the pre-ossification center. Awareness of the appearance of the pre-ossification center on MR images is important to avoid confusing normal developmental changes with pathology.ObjectiveThe purpose of this study was to determine the characteristics of the trochlear pre-ossification center on MR imaging and examine age and gender differences.Materials and methodsWe retrospectively analyzed MR images from 61 children. The trochleas were categorized into three types on the basis of signal intensity (SI). Trochlear types were compared to age and gender.ResultsThere was no significant difference between the ages of boys and girls. Type 1 trochleas showed homogeneous SI on all pulse sequences. Type 2 trochleas demonstrated a focus of high SI in the epiphyseal cartilage on fat-suppressed water-sensitive sequences, with high or intermediate SI on gradient-echo images (pre-ossification center). Type 3 trochleas showed low SI on fat-suppressed water-sensitive sequences and gradient-echo images. Thirty-seven trochleas were described as type 1, sixteen as type 2 and eight as type 3. ANOVAs confirmed a statistically significant difference in the age of children with type 3 trochleas and those with types 1 and 2 (P < 0.001). Spearman rank correlations determined a positive relationship between trochlear type and age of the children (r = 0.53).ConclusionDevelopment-related changes in the trochlea follow a predictable pattern. The signal characteristics of the pre-ossification center likely reflect normal chondrocyte hypertrophy and an increase in free water in the matrix.