We developed a new approach to produce individual immobilization devices for the head based on MRI data and 3D printing technologies. The purpose of this study was to determine positioning accuracy with healthy volunteers. 3D MRI data of the head were acquired for 8 volunteers. In-house developed software processed the image data to generate a surface mesh model of the immobilization mask. After adding an interface for the couch, the fixation setup was materialized using a 3D printer with acrylonitrile butadiene styrene (ABS). Repeated MRI datasets (n=10) were acquired for all volunteers wearing their masks thus simulating a setup for multiple fractions. Using automatic image-to-image registration, displacements of the head were calculated relative to the first dataset (6 degrees of freedom). The production process has been described in detail. The absolute lateral (x), vertical (y) and longitudinal (z) translations ranged between -0.7 and 0.5 mm, -1.8 and 1.4 mm, and -1.6 and 2.4 mm, respectively. The absolute rotations for pitch (x), yaw (y) and roll (z) ranged between -0.9 and 0.8°, -0.5 and 1.1°, and -0.6 and 0.8°, respectively. The mean 3D displacement was 0.9 mm with a standard deviation (SD) of the systematic and random error of 0.2 mm and 0.5 mm, respectively. In conclusion, an almost entirely automated production process of 3D printed immobilization masks for the head derived from MRI data was established. A high level of setup accuracy was demonstrated in a volunteer cohort. Future research will have to focus on workflow optimization and clinical evaluation.

PURPOSE:Staging of lung cancer is typically performed with fluorodeoxyglucose-positron emission tomography-computed tomography (FDG-PET/CT); however, false positive PET scans can occur due to inflammatory disease. The CT scan is used for anatomic registration and attenuation correction. Herein, we evaluated x-ray attenuation (XRA) within nodes on CT and correlated this with the presence of malignancy in an orthotopic lung cancer model in rats.METHODS:1×10⁶ NCI-H460 cells were injected transthoracically in six National Institutes of Health nude rats and six animals served as controls. After two weeks, animals were sacrificed; lymph nodes were extracted and scanned with a micro-CT to determine their XRA prior to histologic analysis.RESULTS:Median CT density in malignant lymph nodes (n=20) was significantly higher than benign lymph nodes (n=12; P = 0.018). Short-axis diameter of metastatic lymph nodes was significantly different than benign nodes (3.4 mm vs. 2.4 mm; P = 0.025). Area under the curve for malignancy was higher for density-based lymph node analysis compared with size measurements (0.87 vs. 0.7).CONCLUSION:XRA of metastatic mediastinal lymph nodes is significantly higher than benign nodes in this lung cancer model. This suggests that information on nodal density may be useful when used in combination with the results of FDG-PET in determining the likelihood of malignant adenopathy.

Purpose The demand to optimize multidisciplinary treatment strategies in patients with benign and malignant diseases of the lung and other organs has led to the increased need of mechanistic proof-of-concept studies in preclinical small animal models using new non-invasive imaging methods. Therefore, we evaluated the role of microPET and microCT for mediastinal lymph node staging in an orthotopic lung cancer model in rats. Procedures Human lung cancer cells (NCI-H460) were injected transthoracically in nude rats (NIH-RNU). After 2 weeks of tumour growth, animals underwent multiphase contrast-enhanced microCT using ExiTron nano 12000 as a contrast agent and dynamic microPET using the tracer 2-deoxy-2-[ 18 F]fluoro- d -glucose ([ 18 F]FDG). Thereafter, animals were sacrificed for histological analysis. Results Late phase micro X-ray computed tomography (microCT) revealed the best delineation of lymph node metastases, as compared to earlier scans. In terms of an increased [ 18 F]FDG uptake over time, dynamic micro positron emission tomography (microPET) delineated lymph node metastases and enabled metabolic examinations of the induced lung cancer metastases. Conclusion The combination of contrast-enhanced microCT and dynamic microPET is feasible in rats for the visualization of mediastinal lymph node metastases.

In patients with lung cancer (LC), malignant melanoma (MM), gastroenteropancreatic neuroendocrine tumors (GEP NETs), and prostate cancer (PCA), lymph node (LN) staging is often performed by 18F-FDG PET/CT (LC and MM), 68Ga-DOTATOC PET/CT (GEP NET), and 68Ga-labeled prostate-specific membrane antigen PET/CT (PCA) but is sometimes not accurate because of indeterminate PET findings. To better evaluate malignant LN infiltration, additional surrogate parameters, especially in cases with indeterminate PET findings, would be helpful. The purpose of this study was to evaluate whether SUVmax in the PET examination might correlate with semiautomated density measurements of LNs in the CT component of the PET/CT examination. Methods: After approval by the institutional review board, 1,022 LNs in the PET/CT examinations of 148 patients were retrospectively analyzed (LC: 327 LNs of 40 patients; MM: 224 LNs of 33 patients; GEP NET: 217 LNs of 35 patients; and PCA: 254 LNs of 40 patients). PET/CT was performed before surgery, biopsy, chemotherapy, or internal or external radiation therapy, according to the clinical schedule; patients with prior chemotherapy or radiation therapy were excluded. SUVmax analyses were based on uptake 60 min after tracer injection, and volumetric CT histogram analyses were based on the unenhanced CT images of the PET/CT scan. Results: PET findings were considered positive or negative on the basis of SUVmax in the LN compared with that in the blood pool; histologic confirmation was not available. Of the 1,022 LNs, 331 were PET-positive (3 times the SUVmax of the blood pool), 86 were PET-indeterminate (1–3 times the SUVmax of the blood pool), and 605 were PET-negative (less than the SUVmax of the blood pool). PET-positive LNs had significantly higher CT densities than PET-negative LNs, irrespective of the type of cancer. Conclusion: CT density measurements of LNs in patients with LC, MM, GEP NET, and PCA correlated with18F-FDG uptake, 68Ga-DOTATOC uptake, and 68Ga-PSMA uptake, respectively, and might therefore serve as an additional surrogate parameter for differentiating between malignant and benign LNs. The use of a 7.5–Hounsfield unit CT density threshold to differentiate between malignant and benign LN infiltration and 20 Hounsfield units to exclude benign LN processes might be possible in clinical routine and would be especially helpful for PET-indeterminate LNs.

Mediastinal nodal (N)-staging done by integrated 2-deoxy-2-[18F]fluoro-d-glucose ([18F]FDG) positron emission tomography/x-ray computed tomography (PET/CT) in lung cancer patients is not always accurate. In order to reduce the need for invasive staging procedures, additional surrogate parameters for the detection of malignant lymph node infiltration would be helpful. The purpose of this study was to evaluate if radiomic semi-automated density profiling in mediastinal lymph nodes can improve preclinical N-staging, irrespective of the specific lung cancer entity.

PURPOSE:To compare lesion conspicuity in patients with liver metastases arising from gastroenteropancreatic neuroendocrine tumors (GEP-NETs) using MRI, PET and CT. MATERIALS AND METHODS:16 patients with GEP-NETs were evaluated using non-contrast MRI, contrast-enhanced (CE) MRI using Gd-EOB-DTPA and CE-(68)Ga-DOTATOC PET. Quantitative analyses were performed by two blinded readers using ROI-analyses quantifying contrast ratios (CR) between normal liver-tissue and GEP-NET-metastases. Qualitative analyses were performed evaluating primary visibility and spatial detectability of all lesions. RESULTS:103 of the same liver metastases were detected on all modalities. Qualitatively, lesion conspicuity was superior on CE-MRI imaging compared to non-contrast MR-sequences (T2, DWI, fl2D, fl3D), as well as arterial- and portal-venous phase CT. Concerning detectability of lesions, CE-MRI was superior to all other modalities. The quantitative ROI-analysis demonstrated improved CR for DWI compared to all other non-contrast MR-sequences (p<0.001). CE-MRI presented with higher CR-values compared to CE-(68)Ga-DOTATOC PET/CT (p<0.001). CONCLUSIONS:Anatomic imaging using non contrast MRI with fl2D-and fl3D-sequences in combination with the molecular imaging modality (68)Ga-DOTATOC PET is optimal for the assessment of liver lesions in GEP-NET-patients. Even though CE-MRI was superior to non-contrast MRI, non-contrast MRI is sufficient to detect and quantify liver metastases in daily routine, especially in combination with DW-Imaging.

Lung cancer often coexists with acute and chronic lung diseases such as chronic obstructive pulmonary disease. Therefore, mediastinal lymph nodes may be false-positive on 18F-FDG PET because of the inflammatory disease alone. Nevertheless, 18F-FDG PET/CT is the primary imaging modality used for staging patients with lung cancer, including nodal status. The purpose of this study was to evaluate whether volumetric CT histogram analysis can improve the characterization of lymph nodes on PET/CT staging of patients with lung cancer. Methods: Sixty histologically proven lymph nodes of 45 patients aged 43–76 y diagnosed with lung cancer were investigated. 18F-FDG PET/CT, contrast-enhanced CT, and nonenhanced CT were performed before surgery or biopsy as part of the clinical staging procedure. Lymph nodes were analyzed on the basis of the 18F-FDG standardized uptake value and volumetric CT histogram analysis. These findings were correlated to the gold standard of histopathology. Results: Histologic examination revealed 36 positive and 24 negative lymph nodes, which were also successfully analyzed by volumetric CT histogram. Median CT density was significantly higher for histologically positive lymph nodes (33.2 Hounsfield units [HU]; range, −29.8 to 59.1) than for histologically negative lymph nodes (10.1 HU; range, −21.0 to 87.4; P = 0.002). The incidence of malignancy was 88% above a cutoff value of 20 HU in the ten 18F-FDG–equivocal lymph nodes; the incidence of benign findings was 100% in the interval between −20 and +20 HU. Visual- and density-based analysis on contrast-enhanced CT failed to differentiate affected from nonaffected lymph nodes. Conclusion: Three-dimensional histogram analysis is a promising and potentially valuable imaging surrogate for N-stage stratification in patients with lung cancer with unclear glucose uptake during 18F-FDG PET imaging. In cases of equivocal 18F-FDG PET status, this technique might potentially bridge the diagnostic gap between noninvasive techniques and invasive lymph node sampling and could help improve the yield of core biopsies.

Poster: "ECR 2014 / C-1574 / Quantitative ROI-analysis of native Flash-2D, Flash-3D and hepatospecific contrast-enhanced VIBE MR imaging in liver metastases in patients with neuroendocrine cancer" by: "P. Flechsig, J. Schweiweis, C. Kratochwil, D. Rath, U. Haberkorn, H. U. Kauczor, F. L. Giesel; Heidelberg/DE"