Andrew Sher

The impact of orthopedic metal artifact reduction software on interreader variability when delineating areas of interest in the head and neck

PURPOSE Metal artifacts during computed tomography (CT) hinder the evaluation of diagnostic images and impair the delineation of tumor volume in treatment planning. Several solutions are available to minimize these artifacts. Our objective was to determine the impact of one of those tools on the interreader variability when measuring head and neck structures in the presence of metal artifacts. METHODS AND MATERIALS Eleven patients were retrospectively selected from an institutional review board-approved study based on the presence of metallic artifacts in the head and neck region. CT raw data were postprocessed using a metal artifact reduction tool. A single matching CT slice from the filtered backprojection and postprocessed data sets was selected in the region of the metal artifact. Areas of selected anatomical structures were measured by independent readers, including an anatomical structure selected from a CT slice with no metal artifact in each patient as control. The intraclass correlation coefficient was calculated. RESULTS Two extreme outliers were identified and the intraclass correlation coefficient was performed with and without them. The intraclass correlation on filtered backprojection, postprocessed, and control images was 0.903, 0.948, and 0.985 with outliers and 0.884, 0.971, and 0.989 without outliers, respectively, for all readers. On the other hand, the intraclass correlation on filtered backprojection, postprocessed, and control images for experienced readers was 0.904, 0.979, and 0.976 with outliers and 0.934, 0.975, and 0.990 without outliers, respectively. CONCLUSIONS The interreader variability of areas measured in the presence of metal artifact was greatly decreased by the use of the metal artifact reduction tool and almost matched the variability observed in the absence of the metal artifact.

Positron emission tomography/magnetic resonance imaging of the breast.

Introduction Despite advances in the diagnosis and treatment of breast cancer, it remains a major cause of morbidity and mortality. In the United States, approximately 232,000 new cases of breast cancer and 40,000 cancer deaths were expected in 2013, and 1 in 8 women will develop breast cancer in her lifetime. Currently, mammography is the primary method of breast cancer screening; however, extensive controversy exists regarding the timing, frequency, and schedule of such screening. Mammography has its limitations, with reported sensitivities ranging from30%-96% and is influenced bymultiple factors, including age and breast tissue density. Given the known limitations of mammography, alternative modalities have been explored to aid in the diagnosis of breast cancer, including dynamic contract-enhanced magnetic resonance tomography (DCE-MRI), whole-breast ultrasound, andmolecular breast imaging using positron emission tomography (PET). Fluorodeoxyglucose (FDG)-PET/computed tomography (CT) has been used in patients with breast cancer as a tool to diagnose breast cancer as well as to detect metastasis and recurrence. This article reviews the current state of DCE-MRI and FDG-PET/CT in patients with breast cancer and then delves into the potential utilization of PET/MRI (Figs. 1-3).

Whole-Body Positron Emission Tomography-Magnetic Resonance in Breast Cancer

Whole-BodyMagnetic Resonance Technology Hybrid positron emission tomography (PET)-magnetic resonance (MR) technology has recently been introduced into the market, appearing in the clinical setting in 2007. Whether designed as a sequential or simultaneous system, the hybrid PET-MR produces high-resolution anatomical, biological, and functional imaging. Given the limited approved indications of PET/computed tomography (CT) in patients with breast cancer, it is understandable that the potential role of PET-MR in such patients remains to be determined. The impetus to develop whole-body MR imaging (WB-MRI) scanning techniques lies in its advantages over CT. Namely, MRI makes no use of ionizing radiation, provides exceptional soft tissue contrast, and offers the ability to perform multisequence andmultiplanar imaging, which allows for improved lesion characterization. The feasibility of a hybrid PET-MR scanner to evaluate the WB was dependent on the development of WB-MR sequences that could be conducted within a reasonable period while providing diagnostic images. The development of such sequences has been made possible by hardware innovations including multireceiver channel WB scanners as well as acquisition acceleration techniques. Such advances allow the assessment of multiple organ systems during 1 scan to be conducted in an efficient and clinically applicable manner. In terms of clinical applications, WBMRI holds promise in evaluating tumors with frequent metastatic spread to the bone, liver, and central nervous system, such as lung cancer, colorectal cancer, prostate cancer, melanoma, and definitively breast cancer. The recent advent

PET/MRI in Lung Cancer

Introduction Imaging plays an important role in the diagnosis and management of lung cancer, which is the leading cause of cancer-related death in the world. Radiography is often the initial modality of diagnosis, but detection depends on the size and density of nodules. The sensitivity of detection may be improved by using the dual-energy subtraction technique, which generates a soft tissue reconstruction that is free of overlapping chest wall and bony structures, or by using tomosynthesis. Computed tomography (CT) has become the established modality for the screening, diagnosis, and staging of lung cancers. Radiation and the use of potentially nephrotoxic contrast media are the risk factors associated with it. Magnetic resonance imaging (MRI) does not involve radiation, but its use in lung cancer is limited by intrinsic low proton spin density, magnetic field inhomogeneities, and motion artifacts from cardiac and respiratory motion. However, novel sequences show potential in the evaluation of lung cancer. Positron emission tomography (PET) with 18-fluorodeoxyglucose (FDG-PET) is useful in determining the metabolic activity of the lung tumor. False-negative results are seen in small tumors and in bronchoalevolar carcinoma, whereas falsepositive findings are seen in cases of infection or inflammation. The hybrid imaging modality of PET/CT is now the standard of care in the staging of lung cancers, combining the morphologic information of CT with the metabolic information of PET. PET/MRI is a novel hybrid imaging technology that involves the fusion of 2 powerful imaging modalities: PET and MRI. MRI provides tissue characterization capabilities

Early response monitoring of receptor tyrosine kinase inhibitor therapy in metastatic renal cell carcinoma using [F-18]fluorothymidine-positron emission tomography-magnetic resonance.

Introduction A 62-year-old man was admitted to the hospital with a 2-month history of left flank pain and hematuria. Unenhanced computed tomography (CT) demonstrated a large, solid mass within the lower pole of the left kidney measuring 10.9 9.5 cm (Fig. 1). The patient underwent radical nephrectomywith histopathology revealing a Fuhrman grade 2 clear cell renal cell carcinoma. A follow-up CT scan obtained 14 months later demonstrated a large lobulated soft tissue mass in the left nephrectomy bed measuring 12 14 9 cm as well as multiple mesenteric nodules suggestive of disease recurrence. Subsequently, the patient received 2 cycles of high-dose interleukin-2 before sunitinib malate (SUTENT, Pfizer Inc) was approved. Sunitinib is an oral, small-molecule, multitargeted receptor tyrosine kinase inhibitor affecting tumor angiogenesis and tumor cell proliferation by targeting receptors for platelet-derived growth factor and vascular endothelial growth factor receptors. The patient consented to participate in a research study using [F-18]fluorothymidine (FLT)-positron emission

MR based PET attenuation correction (MRAC) and anatomical localization ofhuman brain using an optimized UTE-mDixon pulse sequence

MR based Attenuation Correction (MRAC) is essential for PET quantitation and image quality assurance in PET/MR. Ultra-short TE (UTE) sequence is promising in generating positive contrast for cortical bone but its further adoption is limited by prohibitively long scan time, lack of soft tissue contrast, and potential ambiguity in a tissue classification due to MR imaging artifacts. In this investigation, we aimed to develop a new MRAC method that consists an optimized under-sampled UTE-mDixon sequence and an iterative voxel-based tissue classification algorithm to generate 4-compartment μ-map, including water, fat, bone and air cavity. In vivo UTE-mDixon images were acquired on 12 human subjects and the developed segmentation method was employed for tissue classification. Diagnostic quality of MR images and the tissue classification accuracy for MRAC was evaluated by three radiologists independently. As a unique advantage over other MRAC sequences, the under-sampled UTE-mDixon of whole brain with retrospective trajectory delay calibration can be finished within less than 3 minutes providing both high quality water/fat separation images for anatomical localization and UTE images for bone segmentation. Robust tissue classification was achieved in all subjects as evaluated by radiologists. The developed MR scan methodology together with tissue classification algorithm may provide a one-scan solution for attenuation correction and anatomical localization in PET/MR.

Management and Organization of Positron Emission Tomography/Magnetic Resonance Imaging

Introduction The decision to install a positron emission tomography/ magnetic resonance imaging (PET/MRI) system within a health care organization requires an understanding of the mission and vision for using the PET/MRI system. A critical question to consider is if the PET/MRI system will be used for research, routine clinical imaging, or both purposes. If the primary purpose of PET/MRI system is research, then an appropriate funding infrastructure needs to be in place to operate and maintain it. For clinical applications, it is essential that adult and pediatric referring clinicians, including those from medical oncology, radiation oncology, neurology, and cardiology departments, be engaged in discussions about the potential use. Regardless of the purpose, it is important to recognize that, from a financial perspective, a facility should not expect ideal annual growth and increasing net revenue until PET/MRI system development and deployment is more mature. Continued adoption of the PET/MRI modality may take several years and additional peer-reviewed evidence in its support before it is clinically accepted in the United States. The physical location of the system within the radiology department must simultaneously satisfy the requirements of patient workflow, radiation safety, radioactive materials security, and MRI safety. The Philips Ingenuity TF PET/MR system was installed in the University Hospitals Seidman Cancer Center in Cleveland, OH, in December 2011. The installation was the first Food and Drug Administration–approved sequential system designed for use in a clinical environment