Hale Ersoy

Biochemical Safety Profiles of Gadolinium-Based Extracellular Contrast Agents and Nephrogenic Systemic Fibrosis

Gadolinium (Gd)‐based paramagnetic contrast agents are relatively safe when used in clinically recommended doses. However, with the rapidly expanding body of literature linking Gd‐based paramagnetic contrast agents and nephrogenic systemic fibrosis (NSF), awareness of the potential side effects and adverse reactions from Gd is now an important requirement for practicing radiologists. In addition to the ongoing accumulation and analyses of clinical NSF data, it is also essential for the practicing radiologist to understand the biochemical characteristics of the extracellular Gd‐chelates. The purpose of this review is to consolidate and update the available information on known side effects, adverse reactions, and toxicity of the Gd chelates, with particular emphasis on the potential mechanisms of NSF. J. Magn. Reson. Imaging 2007;26:1190–1197.

Time-Resolved MR Angiography: A Primary Screening Examination of Patients with Suspected Pulmonary Embolism and Contraindications to Administration of Iodinated Contrast Material

OBJECTIVE The purpose of this study was to evaluate the efficiency and reproducibility of a single-breath-hold time-resolved 3D MR angiographic technique in the diagnosis of pulmonary embolism. MATERIAL AND METHODS Twenty-seven consecutively registered patients with clinically suspected pulmonary embolism and contraindication to administration of iodinated contrast agents underwent imaging by time-resolved 3D MR angiography at 1.5 T. Bolus timing was not required. Two reviewers independently analyzed MR angiograms for overall image quality and evidence of pulmonary embolism. Additional imaging techniques, including pulmonary embolism CT angiography, ventilation-perfusion (V/Q) lung scanning, venous duplex sonography for deep venous thrombosis, and echocardiography for right ventricular strain, and 30-day and 3-month clinical follow-up were used to confirm the MR angiographic findings. RESULTS Image quality was sufficient for diagnosis in the cases of 98% of lobar, 92-93% of segmental, and 94-95% of all vessel parts from the main pulmonary artery though the segmental branches with excellent interobserver agreement. Findings on MR angiography were concordant with the anatomic distribution of abnormalities for all pulmonary embolism CT angiographic examinations (n = 2) and four of seven V/Q lung scans. Screening with time-resolved 3D MR angiography allowed confident exclusion or inclusion of pulmonary embolism in 96% of patients. CONCLUSION Time-resolved 3D MR angiography provides high temporal resolution (nine phases, one phase per 3.3 seconds) and consistently yields arterial phase only images. As found with clinical follow-up, confident diagnosis of pulmonary embolism from the main pulmonary artery through the segmental branches can be incorporated into a clinical service as a screening examination of patients with contraindications to the use of iodinated contrast material.

MR Angiography of the Lower Extremities

OBJECTIVE Current MRI technology and postprocessing tools have enabled 3D contrast-enhanced MR angiography (MRA) to evolve into a first-line noninvasive diagnostic tool to evaluate vascular disorders. CONCLUSION In this article, 3D MRA techniques, bolus timing issues, new IV contrast agents allowing a steady-state acquisition, principals of postprocessing, and unenhanced MRA techniques are reviewed and how to effectively use 3D gadolinium-enhanced MRA for peripheral arterial imaging is described.

Imaging features of intramural hematoma of the aorta

Intramural Hematoma (IMH) is defined as localized hemorrhage within the aortic wall and is included in the acute aortic syndrome spectrum with aortic dissection and penetrating aortic ulcer. The mortality from IMH is similar to classic aortic dissection (21%). 16% of patients with IMH will evolve to classic aortic dissection over time. Despite this confusion exists regarding the precise definitions and radiologic features of IMH versus penetrating ulcers with mural thrombus and overt aortic dissection.

Surgical planning for composite tissue allotransplantation of the face using 320-detector row computed tomography.

We report initial surgical planning computed tomographic protocols for composite tissue allotransplantation of the face. This complex procedure replaces missing facial structures with anatomically identical tissues, restoring form and function. Achieved results are superior to those accomplished with conventional techniques. As a growing number of patients/recipients have undergone multiple reconstructions, vascular imaging plays an increasingly critical role in surgical planning and successful execution of the operation.

In vivo differentiation of two vessel wall layers in lower extremity peripheral vein bypass grafts: Application of high‐resolution inner‐volume black blood 3D FSE

Lower extremity peripheral vein bypass grafts (LE‐PVBG) imaged with high‐resolution black blood three‐dimensional (3D) inner‐volume (IV) fast spin echo (FSE) MRI at 1.5 Tesla possess a two‐layer appearance in T1W images while only the inner layer appears visible in the corresponding T2W images. This study quantifies this difference in six patients imaged 6 months after implantation, and attributes the difference to the T2 relaxation rates of vessel wall tissues measured ex vivo in two specimens with histologic correlation. The visual observation of two LE‐PVBG vessel wall components imaged in vivo is confirmed to be significant (P < 0.0001), with a mean vessel wall area difference of 6.8 ± 2.7 mm2 between contrasts, and a ratio of T1W to T2W vessel wall area of 1.67 ± 0.28. The difference is attributed to a significantly (P < 0.0001) shorter T2 relaxation in the adventitia (T2 = 52.6 ± 3.5 ms) compared with the neointima/media (T2 = 174.7 ± 12.1 ms). Notably, adventitial tissue exhibits biexponential T2 signal decay (P < 0.0001 vs monoexponential). Our results suggest that high‐resolution black blood 3D IV‐FSE can be useful for studying the biology of bypass graft wall maturation and pathophysiology in vivo, by enabling independent visualization of the relative remodeling of the neointima/media and adventitia. Magn Reson Med, 2009.

High‐resolution peripheral vein bypass graft wall studies using high sampling efficiency inner volume 3D FSE

A 3D inner‐volume fast spin echo (3D IV‐FSE) sequence was developed for ECG‐gated, black‐blood, T1‐ and T2‐weighted vessel wall imaging of peripheral vein bypass grafts (PVBG). The sequence utilizes nonselective refocusing excitations to minimize echo spacings and a highly selective IV excitation scheme to minimize the need for oversampling of z‐encode slice selections. The method was tested in eight PVBG patients who also underwent 2D FSE graft imaging. High‐quality 3D imaging was achieved in all subjects, with significant spatial resolution and volume coverage gains compared to the more conventional 2D FSE sequences normalized for signal‐to‐noise ratios (SNRs) and scan times. Compared to previously proposed 3D IV‐FSE methods, nonselective refocusing resulted in a more than 20% FSE echo train sampling efficiency increase while the use of highly selective IV excitation resulted in a 30% improvement in slice oversampling efficiency. Magn Reson Med, 2008.

Metastatic aortic intimal sarcoma: The use of PET/CT in diagnosing and staging

A 67-year-old woman presented with acute cold left foot. Her medical history was remarkable for intermittent bilateral leg pain, abdominal pain, nausea, vomiting, and progressive weight loss. She underwent left superficial femoral artery embolectomy and fasciotomy. Histopathology of the emboli revealed sheets of necrosis with small foci of poorly differentiated malignant neoplasm consistent with intimal sarcoma (*areas of necrosis; black arrows are representative viable tumor cells) (Panel A). Thoracoabdominal CT angiography was performed to determine the source of the tumor emboli. CT angiography revealed a short segment of polypoid mass with amorphic calcifications in the distal descending thoracic aorta wall (Panel B-1, white arrow), focal wall thickening in the infrarenal aortic wall without significant enhancement on the arteriovenous phase, and could not be differentiated from mural thrombus or atherosclerotic plaques (Panel B-2, black arrow). The left renal artery was enlarged and did not enhance, which was suspicious for bland thrombosis and there were several hypodense (white open arrow), non-enhancing liver lesions (*) (Panel B-3). Whole-body fluorodeoxyglucose positron emission tomography (FDG PET) was performed, which showed intense FDG uptake in the thoracic aorta lesion (Panel B-4, white arrow), in the focal wall thickening in the infrarenal aorta (Panel B-5, black arrow), at the left renal artery ostium (Panel B-6, black open arrow) and in the liver lesions (Panel B-6, *). Vascular lesions thought to be multifocal intimal sarcoma or drop metastasis from thoracic aorta primary, and the liver lesions were considered as metastasis. Primary intimal sarcoma is an extremely rare vascular tumor with poor prognosis, and there are fewer than a hundred reported cases in the literature.1–3 In this case, we have demonstrated the clinical value of the FDG PET in the diagnosis and the staging of the intimal sarcoma in addition to CT angiography.

The Role of Noninvasive Vascular Imaging in Splanchnic and Mesenteric Pathology

Traditionally, catheter angiography (CA) has been the mainstay of diagnosis for mesenteric arterial diseases. However, CA is invasive and is associated with complications that result from the procedure itself, depending on the experience of the operators, site of vascular access, ionized radiation that could be significant when combined with interventional procedures, and administered contrast material. During the past 2 decades, technical improvements in computed tomography (CT) and magnetic resonance hardware and methods have contributed new, noninvasive tools, specifically CT angiography (CTA) and 3-dimensional gadolinium-enhanced magnetic resonance angiography (3D Gd-MRA). This article outlines the current applications, strengths, and weaknesses of CTA and 3D Gd-MRA in imaging of the mesenteric vessels.

Contrast Agents for Cardiovascular MRI

In the last two decades, magnetic resonance imaging (MRI) has revolutionized clinical cardiovascular imaging. Its major advantages over other noninvasive diagnostic modalities are its safety, operator-independent reproducibility, and multiplanar two-dimensional (2D) and three-dimensional (3D) imaging capability with high spatial and temporal resolution. MRI does not deliver ionizing radiation and does not utilize inherently nephrotoxic iodinated contrast media. The intrinsic tissue contrast offered by MRI has been even further expanded by the introduction of paramagnetic magnetic resonance (MR) contrast agents. These agents improve the image signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR), thereby increasing the sensitivity, specificity, and accuracy of MRI.