Andres Kohan

N staging of lung cancer patients with PET/MRI using a three-segment model attenuation correction algorithm: initial experience.

AbstractObjectivesEvaluate the performance of PET/MRI at tissue interfaces with different attenuation values for detecting lymph node (LN) metastases and for accurately measuring maximum standardised uptake values (SUVmax) in lung cancer patients.Materials and MethodEleven patients underwent PET/CT and PET/MRI for staging, restaging or follow-up of suspected or known lung cancer. Four experienced readers determined the N stage of the patients for each imaging method in a randomised blinded way. Concerning metastases, SUVmax of FDG-avid LNs were measured in PET/CT and PET/MRI in all patients. A standard of reference was created with a fifth experienced independent reader in combination with a chart review. Results were analysed to determine interobserver agreement, SUVmax correlation between CT and MRI (three-segment model) attenuation correction and diagnostic performance of the two techniques.ResultsOverall interobserver agreement was high (κ = 0.86) for PET/CT and substantial (κ = 0.70) for PET/MRI. SUVmax showed strong positive correlation (Spearman’s correlation coefficient = 0.93, P < 0.001) between the two techniques. Diagnostic performance of PET/MRI was slightly inferior to that of PET/CT, without statistical significance (P > 0.05).ConclusionsPET/MRI using three-segment model attenuation correction for LN staging in lung cancer shows a strong parallel to PET/CT in terms of SUVmax, interobserver agreement and diagnostic performance.Key Points•F18-FDG PET/MRI shows similar performance to F18-FDG PET/CT in lung cancer N staging. •PET/MRI has substantial interobserver agreement in N staging. •A three-segment model attenuation correction is reliable for assessing the mediastinum.

Qualitative and Quantitative Performance of 18F-FDG-PET/MRI versus 18F-FDG-PET/CT in Patients with Head and Neck Cancer

BACKGROUND AND PURPOSE: MR imaging and PET/CT are integrated in the work-up of head and neck cancer patients. The hybrid imaging technology 18F-FDG-PET/MR imaging combining morphological and functional information might be attractive in this patient population. The aim of the study was to compare whole-body 18F-FDG-PET/MR imaging and 18F-FDG-PET/CT in patients with head and neck cancer, both qualitatively in terms of lymph node and distant metastases detection and quantitatively in terms of standardized uptake values measured in 18F-FDG-avid lesions. MATERIALS AND METHODS: Fourteen patients with head and neck cancer underwent both whole-body PET/CT and PET/MR imaging after a single injection of 18F-FDG. Two groups of readers counted the number of lesions on PET/CT and PET/MR imaging scans. A consensus reading was performed in those cases in which the groups disagreed. Quantitative standardized uptake value measurements were performed by placing spheric ROIs over the lesions in 3 different planes. Weighted and unweighted κ statistics, correlation analysis, and the Wilcoxon signed rank test were used for statistical analysis. RESULTS: κ statistics for the number of head and neck lesion lesions counted (pooled across regions) revealed interreader agreement between groups 1 and 2 of 0.47 and 0.56, respectively. Intrareader agreement was 0.67 and 0.63. The consensus reading provided an intrareader agreement of 0.63. For the presence or absence of metastasis, interreader agreement was 0.85 and 0.70. The consensus reading provided an intrareader agreement of 0.72. The correlations between the maximum standardized uptake value in 18F-FDG-PET/MR imaging and 18F-FDG-PET/CT for primary tumors and lymph node and metastatic lesions were very high (Spearman r = 1.00, 0.93, and 0.92, respectively). CONCLUSIONS: In patients with head and neck cancer, 18F-FDG-PET/MR imaging and 18F-FDG-PET/CT provide comparable results in the detection of lymph node and distant metastases. Standardized uptake values derived from 18F-FDG-PET/MR imaging can be used reliably in this patient population.

Initial experience of MR/PET in a clinical cancer center.

Magentic Resonance/positron emission tomography (PET) has been introduced recently for imaging of clinical patients. This hybrid imaging technology combines the inherent strengths of MRI with its high soft‐tissue contrast and biological sequences with the inherent strengths of PET, enabling imaging of metabolism with a high sensitivity. In this article, we describe the initial experience of MR/PET in a clinical cancer center along with a review of the literature. For establishing MR/PET in a clinical setting, technical challenges, such as attenuation correction and organizational challenges, such as workflow and reimbursement, have to be overcome. The most promising initial results of MR/PET have been achieved in anatomical areas where high soft‐tissue and contrast resolution is of benefit. Head and neck cancer and pelvic imaging are potential applications of this hybrid imaging technology. In the pediatric population, MR/PET can decrease the lifetime radiation dose. MR/PET protocols tailored to different types of malignancies need to be developed. After the initial exploration phase, large multicenter trials are warranted to determine clinical indications for this exciting hybrid imaging technology and thereby opening new horizons in molecular imaging. J. Magn. Reson. Imaging 2014;39:768–780.

Amyloid PET/MRI in the differential diagnosis of dementia.

The potential of brain imaging has grown rapidly with new modalities, hybrid combinations of existing modalities, and novel metabolic tracers. F-florbetapir is an amyloid plaque-binding molecule labeled to F that allows positron imaging of the amyloid deposition in the brain. This protein deposition is known to be one of the features in Alzheimer disease and therefore can be of interest in the differential diagnosis of dementia. We present 2 cases combining the new hybrid imaging modality PET/MRI, which offers molecular and morphological information, with F-florbetapir in the differential diagnosis of dementia.

PET/MRI: Applications in Clinical Imaging

PET/MRI is a new hybrid modality which is increasingly being used in clinical settings, although both clinical evaluation and technical optimization are still an ongoing process. Initial experience with this new imaging device proves promising for oncologic applications. Other clinical indications in the field of cardiac imaging and neuroimaging are also being explored. This article aims to review the current status of PET/MRI and its value in oncologic applications, and summarizes our own preliminary experience in this field.

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 in oncologic diseases of the male and female pelvis.

Introduction Thehuman pelvis harbors a variety of organs and structures that can be at the origin of developing neoplasms. The clinical and diagnostic workup, the staging, and the appropriate treatment and disease follow-up of these neoplasms are diverse and complex anddependon the organ and tumor type, among other factors. Similarly, the individual diagnostic algorithms and the value of imaging in these algorithms vary between organs and tumor types. The possibility to directly access the target tissue and organ via percutaneous, transrectal, transvaginal, or transurethral approaches offers many options for the diagnosis and staging of the disease and may make one think that imaging is a less requested diagnostic tool. At the same time, a large variety of imaging modalities are nowadays available to assist in the diagnostic workup of oncologic diseases in general and in the diseases of the pelvis in particular. Although constantly improving imaging technology and newly developing imaging techniques are at the disposition of the clinician, oftentimes their diagnostic effect and evidence-based value seem underestimated or remain to be determined. Conversely, for many oncologic diseases of the pelvis, the value of imaging in diagnosing and staging is well established, documented, and accepted knowledge. Ultrasound (US) of the female pelvis, as an example, is a cost-effective and widely and readily available imaging tool, providing comprehensive information in most instances, despite being operator dependent. The endovaginal approach significantly improves its diagnostic performance. Computed tomography (CT) is the standard of care to assess the metastatic spread of disease for pelvic malignancies. To complement the diagnostic value of CT with functional

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

PET/MR in Colorectal Cancer

Colorectal cancer (CRC) is the third most common malignant neoplasm in mankind with slightly less than 1.2 million new cases and more than 600,000 deaths worldwide in 2008 [1, 2]. Colorectal cancer is frequently associated with metastatic disease – either synchronous or metachronous – with the highest number of metastases to the lymph nodes and liver. In CRC patients’ early detection of metastases has a strong impact on prognosis since effective interventional as weall as surgical treatment options can be offered leading to relatively high survival rates [3]. If disease course is followed closely with imaging, survival can be significantly improved [4].

PET/MRI of the Liver

Current imaging methods for liver disease include the use of US, CT, MRI and PET/CT. While US and CT are the initial and more cost-effective imaging methods worldwide, MR imaging has become the modality of choice for liver imaging due to its high sensitivity and specificity in characterizing liver lesions. Introduction of liver-specific MR contrast agents has further increased the role of MR imaging of liver in primary and secondary liver malignancy lesion detection, treatment planning, and follow-up. Similarly, 18 FDG PET/CT imaging has established a place in staging and follow-up of liver malignancies, especially of liver metastases. Due to decreased sensitivity of 18FDG PET in primary hepatocellular carcinoma, focus is being made on introduction of new radiotracers.