Photoacoustic tissue scanning (PATS)

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Experimental Multicenter and Multivendor Evaluation of the Performance of PET Radiomic Features Using 3-Dimensionally Printed Phantom Inserts

The sensitivity of radiomic features to several confounding factors, such as reconstruction settings, makes clinical use challenging. To investigate the impact of harmonized image reconstructions on feature consistency, a multicenter phantom study was performed using 3-dimensionally printed phantom inserts reflecting realistic tumor shapes and heterogeneity uptakes. Methods: Tumors extracted from real PET/CT scans of patients with non-small cell lung cancer served as model for three 3-dimensionally printed inserts. Different heterogeneity pattern were realized by printing separate compartments that could be filled with different activity solutions. The inserts were placed in the National Electrical Manufacturers Association image-quality phantom and scanned various times. First, a list-mode scan was acquired and 5 statistically equal replicates were reconstructed. Second, the phantom was scanned 4 times on the same scanner. Third, the phantom was scanned on 6 PET/CT systems. All images were reconstructed using EANM Research Ltd. (EARL)-compliant and locally clinically preferred reconstructions. EARL-compliant reconstructions were performed without (EARL1) or with (EARL2) point-spread function. Images were analyzed with and without resampling to 2-mm cubic voxels. Images were discretized with a fixed bin width (FBW) of 0.25 and a fixed bin number (FBN) of 64. The intraclass correlation coefficient (ICC) of each scan setup was calculated and compared across reconstruction settings. An ICC above 0.75 was regarded as high. Results: The percentage of features yielding a high ICC was largest for the statistically equal replicates (70%-91% for FBN; 90%-96% for FBW discretization). For scans acquired on the same system, the percentage decreased, but most features still resulted in a high ICC (FBN, 52%-63%; FBW, 75%-85%). The percentage of features yielding a high ICC decreased more in the multicenter setting. In this case, the percentage of features yielding a high ICC was larger for images reconstructed with EARL-compliant reconstructions: for example, 40% for EARL1 and 60% for EARL2 versus 21% for the clinically preferred setting for FBW discretization. When discretized with FBW and resampled to isotropic voxels, this benefit was more pronounced. Conclusion: EARL-compliant reconstructions harmonize a wide range of radiomic features. FBW discretization and a sampling to isotropic voxels enhances the benefits of EARL-compliant reconstructions

Interobserver Reproducibility of Diffusion-Weighted MRI in Monitoring Tumor Response to Neoadjuvant Therapy in Esophageal Cancer

OBJECTIVE: To investigate the reproducibility of diffusion-weighted magnetic resonance imaging (DW-MRI) in assessing tumor response early in the course of neoadjuvant chemoradiotherapy in patients with operable esophageal cancer. METHODS: Eleven male patients (mean age 54.8 years) with newly diagnosed esophageal cancer underwent DW-MRI before and 10 days after start of chemoradiotherapy. Reproducibility of apparent diffusion coefficient (ADC) measurements by manual (freehand) and semi-automated volumetric methods was assessed. RESULTS: Interobserver reproducibility for the assessment of mean tumor ADC by the manual measurement method was good, with an ICC of 0.69 (95% CI, 0.36 to 0.85; P = 0.001). Interobserver reproducibility for the assessment of mean tumor ADC by the semi-automated volumetric measurement method was very good, with an ICC of 0.96 (95% CI, 0.91 to 0.98; P<0.001). CONCLUSION: Semi-automated volumetric ADC measurements have higher reproducibility than manual ADC measurements in assessing tumor response to chemoradiotherapy in patients with esophageal adenocarcinoma

Box plots show the distribution of mean pretreatment ADC values (A) and percentage change in ADC value (B), as measured by the manual method, for patients with and without tumor response.

<p>Box plots show the distribution of mean pretreatment ADC values (A) and percentage change in ADC value (B), as measured by the manual method, for patients with and without tumor response.</p

Interobserver reproducibility using the manual measurement method.

<p>Measurements from both the first and second MRI scan were included in this analysis. Bland-Altman plot shows the difference between measurements of two observers (R.F.A.V. and S.S.) against the average measurement, with mean absolute difference (continuous line) and 95% CI of the mean difference (dashed lines).</p

Scatter plots of percentage change in mean tumor ADC value between the first and second MRI scan (x-axis) and TRG score (y-axis), both for the manual (A) and semi-automated measurements (B).

<p>Scatter plots of percentage change in mean tumor ADC value between the first and second MRI scan (x-axis) and TRG score (y-axis), both for the manual (A) and semi-automated measurements (B).</p

Details of the MRI protocol.

<p>DWI: diffusion-weighted imaging.</p><p>EPI: echo planar imaging.</p><p>FOV: field of view.</p><p>NA: not applicable.</p><p>NSA: number of signal averages.</p><p>SE: spin-echo.</p><p>STIR: short TI inversion recovery.</p><p>TSE: turbo spin-echo.</p

Scatter plots of mean pretreatment tumor ADC value (x-axis) and TRG score (y-axis), both for the manual (A) and semi-automated measurements (B).

<p>Scatter plots of mean pretreatment tumor ADC value (x-axis) and TRG score (y-axis), both for the manual (A) and semi-automated measurements (B).</p

Manual measurement method.

<p>T2-weighted (A) and b1000 DW (B) images, and corresponding ADC map (C and D). An esophageal tumor can be depicted as thickening of the esophageal wall (arrow in (A) with high signal intensity on the corresponding b1000 DW image (arrow in B) and low signal intensity on the corresponding ADC map (arrow in C). An ROI was manually drawn in the tumor on the ADC map (red circular region in D) to calculate the tumor ADC value.</p

Timing of neoadjuvant therapy, surgery, and MRI (timing of MRI scans is indicated by asterisks and arrowheads).

<p>Timing of neoadjuvant therapy, surgery, and MRI (timing of MRI scans is indicated by asterisks and arrowheads).</p