John D. MacKenzie

Diffusion-weighted and diffusion tensor imaging for pediatric musculoskeletal disorders

Diffusion-weighted imaging (DWI) is a powerful tool that has recently been applied to evaluate several pediatric musculoskeletal disorders. DWI probes abnormalities of tissue structure by detecting microscopic changes in water mobility that develop when disease alters the organization of normal tissue. DWI provides tissue characterization at a cellular level beyond what is available with other imaging techniques, and can sometimes identify pathology before gross anatomic alterations manifest. These features of early detection and tissue characterization make DWI particularly appealing for probing diseases that affect the musculoskeletal system. This article focuses on the current and future applications of DWI in the musculoskeletal system, with particular attention paid to pediatric disorders. Although most of the applications are experimental, we have emphasized the current state of knowledge and the main research questions that need to be investigated.

MRI of HAGL lesions: four arthroscopically confirmed cases of false-positive diagnosis.

OBJECTIVE The purpose of this article is to present the cases of four consecutive patients with preoperative MR diagnosis of humeral avulsion of the glenohumeral ligament (HAGL) who had no evidence of HAGL at arthroscopy. CONCLUSION These four cases suggest that the diagnosis of HAGL should be reserved for arthroscopy and illustrate the difficulty in distinguishing HAGL from other abnormalities of the inferior glenohumeral ligament complex with MRI. Thus, MRI findings classically associated with HAGL should be more broadly described as defects of the inferior glenohumeral ligament complex. This terminology more accurately describes the abnormalities of the inferior glenohumeral ligament complex that may be depicted by MRI.

Sol-gel coatings for the protection of brass and bronze

The effectiveness of sol-gel Ormosil coatings as barriers coatings has already been demonstrated, and it is natural to assume that such coatings can play a unique role in art conservation, where object corrosion and decay are often a major issue. The main feature of ormosil coatings that would make them preferable to polymers is their potentially higher stability to ultra-violet radiation, controlled porosity and good adhesion to many different substrates. The permeability to various gases can also be tailored with changes in the chemical structure. In previous work, we have applied the sol-gel process as part of a multiplayer coating in the conservation of the Last Judgment mosaic in Prague. In the present work, we explore the use of sol-gel organic-inorganic hybrid coatings on various copper alloy substrates frequently encountered in art conservation.

Detection of Inflammatory Arthritis by Using Hyperpolarized 13C-Pyruvate with MR Imaging and Spectroscopy

PURPOSE To examine the feasibility of using magnetic resonance (MR) spectroscopy with hyperpolarized carbon 13 ((13)C)-labeled pyruvate to detect inflammation. MATERIALS AND METHODS The animal care and use committee approved all work with animals. Arthritis was induced in the right hind paw of six rats; the left hind paw served as an internal control. The lactate dehydrogenase-catalyzed conversion of pyruvate to lactate was measured in inflamed and control paws by using (13)C MR spectroscopy. Clinical and histologic data were obtained to confirm the presence and severity of arthritis. Hyperpolarized (13)C-pyruvate was intravenously injected into the rats before simultaneous imaging of both paws with (13)C MR spectroscopy. The Wilcoxon signed rank test was used to test for differences in metabolites between the control and arthritic paws. RESULTS All animals showed findings of inflammation in the affected paws and no signs of arthritis in the control paws at both visible inspection (clinical index of 3 for arthritic paws and 0 for control paws) and histologic examination (histologic score of 3-5 for arthritic paws and 0 for control paws). Analysis of the spectroscopic profiles of (13)C-pyruvate and converted (13)C-lactate showed an increase in the amount of (13)C-lactate in inflamed paws (median lactate-to-pyruvate ratio, 0.50; mean lactate-to-pyruvate ratio ± standard deviation, 0.52 ± 0.16) versus control paws (median lactate-to-pyruvate ratio, 0.27; mean lactate-to-pyruvate ratio, 0.32 ± 0.11) (P < .03). The ratio of (13)C-lactate to total (13)C was also significantly increased in inflamed paws compared with control paws (P < .03). CONCLUSION These results suggest that alterations in the conversion of pyruvate to lactate as detected with (13)C-MR spectroscopy may be indicative of the presence of inflammatory arthritis.

Advances in pediatric MR imaging.

This article describes the considerable technical achievements that have been made in MR imaging in the evaluation of pediatric patients. The latest techniques in improving signal intensity, resolution, and speed are discussed. The multitude of new options for pediatric MR imaging are illustrated, including higher field strength imaging, multi-channel coil technology coupled with parallel imaging, and new pulse sequence designs. Several future directions in the field of pediatric body and musculoskeletal imaging also are highlighted.

Techniques and Tactics for Optimizing CT Dose in Adults and Children: State of the Art and Future Advances

With growing concern over radiation exposure from CT, dose reduction and optimization have become important considerations. Many protocol factors and CT technologies influence this dose reduction effort, and as such, users should maintain a working knowledge of developments in the field. Individual patient factors and scanner-specific details also require care and expertise, which are vital to the success of any dose reduction effort. The authors review the content of the Virtual Symposium on Radiation Safety in Computed Tomography (University of California Dose Optimization and Standardization Endeavor), specifically that pertaining to the more practical aspects of dose optimization. These range from prescan tips to postscan factors, as well as protocol definition itself. Topics discussed include localizer radiograph acquisition, tube current modulation, reconstruction methods, and pediatric considerations, with the content biased toward a CT technologist or protocol manager. Near-term innovations, including new iterative reconstruction methods, tube potential modulation, and dual-energy CT, are presented, and their capability for dose reduction is briefly discussed.

Radiation dose reduction in pediatric CT-guided musculoskeletal procedures.

BackgroundComputed-tomography-guided interventions are attractive for tissue sampling of pediatric bone lesions; however, it comes with exposure to ionizing radiation, inherent to CT and magnified by multiple passes during needle localization.ObjectiveWe evaluate a method of CT-guided bone biopsy that minimizes ionizing radiation exposure by lowering CT scanner tube current (mAs) and voltage (kVp) during each localization scan.Materials and methodsWe retrospectively reviewed all CT-guided bone biopsies (n = 13) over a 1-year period in 12 children. Three blinded readers identified the needle tip on the reduced-dose CT images (mAs = 50, kVp = 80) during the final localization scan at biopsy and rated the image quality as high, moderate or low.ResultsThe image quality of the reduced-dose scans during biopsy was rated as either high or moderate, with needle tip visualized in 12 out of 13 biopsies. Twelve of 13 biopsies also returned sufficient sample for a pathological diagnosis. The average savings in exposure using the dose-reduction technique was 87%.ConclusionOur results suggest that a low mAs and kVp strategy for needle localization during CT-guided bone biopsy yields a large dose reduction and produces acceptable image quality without sacrificing yield for biopsy diagnosis.

Shooting a moving target: use of real-time cine magnetic resonance imaging in assessment of the small bowel.

ABSTRACT The chronic nature of inflammatory bowel disease (IBD) creates a lifelong effect on the morbidity of children affected by the disease. The ability to confidently identify and characterize complications resulting from IBD in the pediatric patient is of critical importance. Magnetic resonance enterography (MRE) is especially valuable in the diagnostic assessment of IBD; however, precise elucidation of complications including strictures can be difficult with standard MRE sequences. The recent development of faster MRI pulse sequences provides rapid, real-time imaging of the intestinal tract. In this review, we describe how the addition of cine MRE confidently pinpoints areas of stricture, aids in lesion detection and diagnosis, and provides valuable information on intestinal motility.

A Deep Learning Approach for Semantic Segmentation in Histology Tissue Images

To make reliable diagnosis, pathologists often need to identify certain special regions in medical images. In inflammatory bowel disease (IBD) diagnosis via histology tissue image examination, muscle regions are known to have no immune cell infiltration, and thus are ignored by pathologists. Also, messy regions (e.g., due to distortion and poor staining) are low in diagnostic yield. Hence, excluding muscle and messy regions to focus on vital regions is crucial for accurate diagnosis of IBD. In this paper, we propose a novel deep neural network based on fully convolutional networks (FCN) to identify muscle and messy regions, in an end-to-end fashion. First, we address the challenge of having limited medical training data, for training our deep neural network (a common problem for medical image processing, which may impede the application of the powerful deep learning method). Second, to deal with target regions of largely different sizes and arbitrary shapes, our deep neural network explores multi-scale information and structural information. Experimental results on clinical images show that our approach outperforms the state-of-the-art FCN for semantic segmentation of muscle and messy regions. Our approach may be readily extended to identify other types of regions in a variety of medical imaging applications.

Nonanesthesia magnetic resonance enterography in young children: feasibility, technique, and performance.

Objectives: The aim of the present study was to demonstrate the effectiveness and cost savings of a nonanesthesia approach to magnetic resonance enterography (MRE) in 14 young pediatric patients (age 4–7 years) with clinically suspected early-onset inflammatory bowel disease using an MRE protocol. Methods: MRE was performed using a combination of an abbreviated imaging protocol, magnetic resonance imaging video goggles, and Child Life Services support. MRE results were correlated with both colonoscopy and pathology results using Pearson correlation coefficient. Sensitivity, specificity, and positive and negative predictive values were calculated. Results: MRE was performed successfully in 13 of 14 patients (age range 4 years 0 months to 7 years 6 months). MRE findings matched with results in 12 of 13 patients in whom colonoscopy was successfully performed. Both MRE and colonoscopy demonstrated a high specificity (100%) and a positive predictive value (100%), but a low sensitivity (43%) and a negative predictive value (50%). Conclusions: MRE can be successfully performed in children ages 4 to 7 years using this approach. In addition to decreased risks to the child, the lack of anesthesia also offers a potential overall cost reduction.