Walter Kucharczyk

Palliative Treatment of Painful Bone Metastases with MR Imaging–guided Focused Ultrasound

PURPOSEnTo evaluate the safety and initial efficacy of magnetic resonance (MR) imaging-guided focused ultrasound for the palliation of pain caused by bone metastases in patients in whom standard available treatments had been ineffective or not feasible.nnnMATERIALS AND METHODSnInformed consent was obtained in 11 patients (seven women, four men; average age, 58.6 years) with pain related to non-weight-bearing bone metastases who were subsequently treated with MR imaging-guided focused ultrasound in this research and ethics board-approved study. Efficacy was evaluated by changes in visual analog scale (VAS) scores, in pain medication usage, and in quality of life. Safety of the device was evaluated by recording incidence and severity of treatment-related adverse events up to 3 months after treatment at physical examination and follow-up imaging. Follow-up imaging included contrast material-enhanced MR imaging and unenhanced computed tomography (CT) 1 month after treatment and contrast-enhanced MR imaging 3 months after treatment. Imaging studies were assessed for changes in tumor imaging characteristics and any adverse events associated with MR imaging-guided focused ultrasound treatment.nnnRESULTSnTwelve lesions were treated in 11 patients. All patients reported progressive decrease in pain in treated regions and reduction in pain medication usage during the 3-month follow-up period. VAS scores averaged 6.0 before treatment and decreased to 0.5 at 3 months (decrease in pain scores, 92%; P < .01). No adverse events were recorded at physical examination or follow-up imaging. The majority of patients with osteolytic metastases had varying degrees of necrosis of the enhancing medullary component of the metastasis at follow-up enhanced MR imaging. Five patients had increased bone density at the site of treated osteolytic metastases at follow-up unenhanced CT at 3 months after MR imaging-guided focused ultrasound.nnnCONCLUSIONnMR imaging-guided focused ultrasound is a noninvasive technique that allows palliative treatment of bone metastases with little or no morbidity.

Risk factors for NSF: a literature review.

Emerging evidence linking gadolinium‐based contrast agents (GBCAs) to nephrogenic systemic fibrosis (NSF) has changed medical practice patterns toward forgoing GBCA‐enhanced magnetic resonance imaging (MRI) or substituting other imaging methods, which are potentially less accurate and often radiation‐based. This shift has been based on reports of high NSF incidence at sites where a confluence of risk factors occurred in patients with severe renal dysfunction. This review article explores the factors that affect NSF risk, compares risks of alternative imaging procedures, and demonstrates how risk can be managed by careful selection of GBCA dose, timing of injection with respect to dialysis, and other factors. Nearly half of NSF cases are a milder form that does not cause contractures or reduce mobility. It appears that eliminating even a single risk factor can reduce NSF incidence/risk at least 10‐fold. Elimination of multiple risk factors by using single‐dose GBCA, dialyzing dialysis patients quickly following GBCA administration, avoiding GBCA in acute renal failure while serum creatinine is rising, and avoiding nonionic linear GBCA in renal failure patients may reduce NSF risk more than a thousand‐fold, thereby allowing safe GBCA‐enhanced MRI in virtually all patients. J. Magn. Reson. Imaging 2009;30:1298–1308.

Brain Tumor Surgery with the Toronto Open Magnetic Resonance Imaging System: Preliminary Results for 36 Patients and Analysis of Advantages, Disadvantages, and Future Prospects

OBJECTIVEnFrameless navigation systems represent a huge step forward in the surgical treatment of intracranial pathological conditions but lack the ability to provide real-time imaging feedback for assessment of postoperative results, such as catheter positions and the extent of tumor resections. An open magnetic resonance imaging system for intracranial surgery was developed in Toronto, by a multidisciplinary team, to provide real-time intraoperative imaging.nnnMETHODSnThe preliminary experience with a 0.2-T, vertical-gap, magnetic resonance imaging system for intraoperative imaging, which was developed at the University of Toronto for the surgical treatment of patients with intracranial lesions, is described. The system is known as the image-guided minimally invasive therapy unit.nnnRESULTSnBetween February 1998 and March 1999, 36 procedures were performed, including 21 tumor resections, 12 biopsies, 1 transsphenoidal endoscopic resection, and 2 catheter placements for Ommaya reservoirs. Three complications were observed. All biopsies were successful, and the surgical goals were achieved for all resections. Problems included restricted access resulting from the confines of the magnet and the imaging coil design, difficulties in working in an operating room that is less spacious and familiar, inconsistent image quality, and a lack of nonmagnetic tools that are as effective as standard neurosurgical tools. Advantages included real-time imaging to facilitate surgical planning, to confirm entry into lesions, and to assess the extent of resection and intraoperative and immediate postoperative imaging to confirm the extent of resections, catheter placement, and the absence of postoperative complications.nnnCONCLUSIONnIntraoperative magnetic resonance imaging has great potential as an aid for intracranial surgery, but a number of logistic problems require resolution.

Magnetic resonance imaging of temperature changes during interstitial microwave heating: A phantom study

Changes in magnetic resonance (MR) signals during interstitial microwave heating are reported, and correlated with simultaneously acquired temperature readings from three fiber-optic probes implanted in a polyacrylamide gel phantom. The heating by a MR-compatible microwave antenna did not interfere with simultaneous MR image data acquisition. MR phase-difference images were obtained using a fast two-dimensional-gradient echo sequence. From these images the temperature-sensitive resonant frequency of the 1H nuclei was found to decrease approximately by 0.008 ppm/ degree C. The method and results presented here demonstrate that noninvasive MR-temperature imaging can be performed simultaneously with interstitial microwave thermal treatment.

Nephrogenic Systemic Fibrosis : Review of 370 Biopsy-Confirmed Cases

Discovery of an association between gadolinium-based contrast agents (GBCAs) and nephrogenic systemic fibrosis (NSF) has led to less use of GBCA-enhanced magnetic resonance imaging in dialysis patients and patients with severe renal failure at risk of NSF, and the virtual elimination of new cases of NSF. But shifting patients with renal failure to alternative imaging methods may subject patients to other risks (e.g., ionizing radiation or iodinated contrast). This review paper examines 370 NSF cases reported in 98 articles to analyze NSF risk factors. Eliminating multiple risk factors by limiting GBCA dose to a maximum of 0.1 mmol/kg, dialyzing patients undergoing dialysis quickly following GBCA administration, delaying GBCA in acute renal failure until after renal function returns or dialysis is initiated, and avoiding nonionic linear GBCA in patients with renal failure especially when there are proinflammatory conditions may substantially reduce the risk of NSF.

Physics of MRI: a primer.

This article is based on an introductory lecture given for the past many years during the “MR Physics and Techniques for Clinicians” course at the Annual Meeting of the ISMRM. This introduction is not intended to be a comprehensive overview of the field, as the subject of magnetic resonance imaging (MRI) physics is large and complex. Rather, it is intended to lay a conceptual foundation by which magnetic resonance image formation can be understood from an intuitive perspective. The presentation is nonmathematical, relying on simple models that take the reader progressively from the basic spin physics of nuclei, through descriptions of how the magnetic resonance signal is generated and detected in an MRI scanner, the foundations of nuclear magnetic resonance (NMR) relaxation, and a discussion of the Fourier transform and its relation to MR image formation. The article continues with a discussion of how magnetic field gradients are used to facilitate spatial encoding and concludes with a development of basic pulse sequences and the factors defining image contrast. J. Magn. Reson. Imaging 2012;35:1038‐1054.

NSF prevention in clinical practice: Summary of recommendations and guidelines in the United States, Canada, and Europe

In this article we summarize recommendations and guidelines for the prevention of NSF from the United States, Canada, and Europe. J. Magn. Reson. Imaging 2009;30:1357–1363.

Acute Hyperammonemic Encephalopathy in Adults: Imaging Findings

If you work in the hospital where organ transplants are done, you have probably seen this condition (even if you did not recognize it!). Unless identified and treated early, this encephalopathy has significant morbidity and mortality. In this short retrospective review, 4 patients with liver failure and plasma ammonia levels ranging from 55-168 umol/L were studied with MR imaging. The findings were significantly similar to those seen with anoxia, that is, diffuse gray and subcortical white matter involvement. The abnormalities were more pronounced in the insular cortex and cingulate gyri, a finding that helps distinguish acute hyperammonemic encephalopathy from other diseases. BACKGROUND AND PURPOSE: Acute hyperammonemic encephalopathy has significant morbidity and mortality unless promptly treated. We describe the MR imaging findings of acute hyperammonemic encephalopathy, which are not well-recognized in adult patients. MATERIALS AND METHODS: We retrospectively reviewed the clinical and imaging data and outcome of consecutive patients with documented hyperammonemic encephalopathy seen at our institution. All patients underwent cranial MR imaging at 1.5T. RESULTS: Four patients (2 women; mean age, 42 ± 13 years; range, 24–55 years) were included. Causes included acute fulminant hepatic failure, and sepsis with a background of chronic hepatic failure and post–heart-lung transplantation with various systemic complications. Plasma ammonia levels ranged from 55 to 168 μmol/L. Bilateral symmetric signal-intensity abnormalities, often with associated restricted diffusion involving the insular cortex and cingulate gyrus, were seen in all cases, with additional cortical involvement commonly seen elsewhere but much more variable and asymmetric. Involvement of the subcortical white matter was seen in 1 patient only. Another patient showed involvement of the basal ganglia, thalami, and midbrain. Two patients died (1 with fulminant cerebral edema), and 2 patients survived (1 neurologically intact and the other with significant intellectual impairment). CONCLUSIONS: The striking common imaging finding was symmetric involvement of the cingulate gyrus and insular cortex in all patients, with more variable and asymmetric additional cortical involvement. These specific imaging features should alert the radiologist to the possibility of acute hyperammonemic encephalopathy.

Magnetically‐assisted remote control (MARC) steering of endovascular catheters for interventional MRI: A model for deflection and design implications

Current applied to wire coils wound at the tip of an endovascular catheter can be used to remotely steer a catheter under magnetic resonance imaging guidance. In this study, we derive and validate an equation that characterizes the relationship between deflection and a number of physical factors: θ∕sin(γ-θ)=nIABL∕EIA, where θ is the deflection angle, n is the number of solenoidal turns, I is the current, A is the cross-sectional area of the catheter tip, B is the magnetic resonance (MR) scanner main magnetic field, L is the unconstrained catheter length, E is Youngs Modulus for the catheter material, and IA is the area moment of inertia, and γ is the initial angle between the catheter tip and B. Solenoids of 50, 100, or 150 turns were wound on 1.8F and 5F catheters. Varying currents were applied remotely using a DC power supply in the MRI control room. The distal catheter tip was suspended within a phantom at varying lengths. Images were obtained with a 1.5T or a 3T MR scanner using real-time MR pulse sequences. Deflection angles were measured on acquired images. Catheter bending stiffess was determined using a tensile testing apparatus and a stereomicroscope. Predicted relationships between deflection and various physical factors were observed (R2=0.98-0.99). The derived equation provides a framework for modeling of the behavior of the specialized catheter tip. Each physical factor studied has implications for catheter design and device implementation.

Silent subtype 3 pituitary adenomas are not always silent and represent poorly differentiated monomorphous plurihormonal Pit-1 lineage adenomas

Originally classified as a variant of silent corticotroph adenoma, silent subtype 3 adenomas are a distinct histologic variant of pituitary adenoma of unknown cytogenesis. We reviewed the clinical, biochemical, radiological, immunohistochemical and ultrastructural features of 31 silent subtype 3 adenomas to clarify their cellular origin. Among 25 with clinical and/or radiological data, all were macroadenomas; there was cavernous sinus invasion in 30% of cases and involvement of the clivus in 17% of cases. Almost 90% of patients were symptomatic; 67% had mass effect symptoms, 37% were hypogonadal and 8% had secondary adrenal insufficiency. Significant hormonal excess in 29% of cases included hyperthyroidism in 17%, acromegaly in 8% and hyperprolactinemia above 150u2009μg/l in 4%. Two individuals with hyperprolactinemia who were younger than 30 years had multiple endocrine neoplasia type 1. Immunohistochemically, all 31 tumors were diffusely positive for the pituitary lineage-specific transcription factor Pit-1. Although three only expressed Pit-1, others revealed variable positivity for one or more hormones of Pit-1 cell lineage (growth hormone, prolactin, thyroid-stimulating hormone), as well as alpha-subunit and estrogen receptor. Most tumors exhibited perinuclear reactivity for keratins with the CAM5.2 antibody; scattered fibrous bodies were noted in five (16%) tumors. The mean MIB-1 labeling index was 4% (range, 1–9%). Fourteen cases examined by electron microscopy were composed of a monomorphous population of large polygonal or elongated cells with nuclear spheridia. Sixty-five percent of patients had residual disease after surgery; after a mean follow-up of 48.4 months (median 41.5; range=2–171) disease progression was documented in 53% of those cases. These data identify silent subtype 3 adenomas as aggressive monomorphous plurihormonal adenomas of Pit-1 lineage that may be associated with hyperthyroidism, acromegaly or galactorrhea and amenorrhea. Our findings argue against the use of the nomenclature ‘silent’ for these tumors. To better reflect the characteristics of these tumors, we propose that they be classified as ‘poorly differentiated Pit-1 lineage adenomas’.