Prostate specific membrane antigen (PSMA) ligands for diagnosis and therapy of prostate cancer

<p><b>Introduction:</b> Prostate specific membrane antigen (PSMA) has become an attractive diagnostic and therapeutic target for small molecule ligands. Radionuclide-chelating ligands can be labeled with either ⁶⁸Ga for positron-emission-tomography (PET) or ¹⁷⁷Lu for radionuclide therapy.</p> <p><b>Areas covered:</b> In this literature review we evaluate the diagnostic value of ⁶⁸Ga PSMA PET/CT and the therapeutic potential of ¹⁷⁷Lu PSMA radioligand therapy (RLT) in patients with prostate cancer. ⁶⁸Ga PSMA PET/CT is more accurate than CT for nodal staging and superior to conventional imaging in patients with biochemical recurrence, translating into major changes in clinical management. The preliminary data for ¹⁷⁷Lu PSMA indicates >50% reduction of PSA levels in up to 59% of patients. Severe adverse events occurred <10% of patients after RLT.</p> <p><b>Expert commentary:</b> PSMA ligands for diagnostic and therapeutic purpose will significantly impact the management of patients with prostate cancer.</p

Revolver insert placed in the NEMA IQ Phantom.

<p>Illustrative schematic layout, (A) and a representative slice of the attenuation corrected PET image (B).</p

A Study on the Basic Criteria for Selecting Heterogeneity Parameters of F18-FDG PET Images

<div><p>Textural analysis might give new insights into the quantitative characterization of metabolically active tumors. More than thirty textural parameters have been investigated in former F18-FDG studies already. The purpose of the paper is to declare basic requirements as a selection strategy to identify the most appropriate heterogeneity parameters to measure textural features. Our predefined requirements were: a reliable heterogeneity parameter has to be volume independent, reproducible, and suitable for expressing quantitatively the degree of heterogeneity. Based on this criteria, we compared various suggested measures of homogeneity. A homogeneous cylindrical phantom was measured on three different PET/CT scanners using the commonly used protocol. In addition, a custom-made inhomogeneous tumor insert placed into the NEMA image quality phantom was imaged with a set of acquisition times and several different reconstruction protocols. PET data of 65 patients with proven lung lesions were retrospectively analyzed as well. Four heterogeneity parameters out of 27 were found as the most attractive ones to characterize the textural properties of metabolically active tumors in FDG PET images. These four parameters included Entropy, Contrast, Correlation, and Coefficient of Variation. These parameters were independent of delineated tumor volume (bigger than 25–30 ml), provided reproducible values (relative standard deviation< 10%), and showed high sensitivity to changes in heterogeneity. Phantom measurements are a viable way to test the reliability of heterogeneity parameters that would be of interest to nuclear imaging clinicians.</p></div

Representative volume dependence of four different HePs.

<p>Phantom data points (“Ph.Data”) measured on three different scanners are differentiated by continuous color lines. Individual data points calculated from human lung lesions are displayed as the individual purple dots (“Hu.Data”). The volume dependence of the all investigated parameters can be found in the Supplemental Material.</p

List of Indices Calculated from Texture Matrices, followed by the short name.

<p>List of Indices Calculated from Texture Matrices, followed by the short name.</p

The geometry (A) and the activity distribution within the Revolver insert at (B) t = 0min, (C) t = 45 min, and (D) t = 80 min.

<p>The geometry (A) and the activity distribution within the Revolver insert at (B) t = 0min, (C) t = 45 min, and (D) t = 80 min.</p

Revolver heterogeneous phantom insert.

<p>Revolver heterogeneous phantom insert.</p

Volume dependence (A) and reproducibility (B) of the Coefficient of Variation parameter.

<p>Volume dependence (A) and reproducibility (B) of the Coefficient of Variation parameter.</p

Reproducibility of the 8 remaining HePs (see Table 3, type A), as the function of reconstruction settings (see in Table 1) and acquisition time.

<p>Reproducibility of the 8 remaining HePs (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0164113#pone.0164113.t003" target="_blank">Table 3</a>, type A), as the function of reconstruction settings (see in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0164113#pone.0164113.t001" target="_blank">Table 1</a>) and acquisition time.</p

The Classification of 26 Textural Indices According to the Kind of Dependency of Parameter vs. Volume.

<p>The Classification of 26 Textural Indices According to the Kind of Dependency of Parameter vs. Volume.</p