Effect of Point-Spread Function Reconstruction for Indeterminate PSMA-RADS-3A Lesions on PSMA-Targeted PET Imaging of Men with Prostate Cancer

Purpose: Prostate-specific membrane antigen (PSMA) positron emission tomography (PET) is emerging as an important modality for imaging patients with prostate cancer (PCa). As with any imaging modality, indeterminate findings will arise. The PSMA reporting and data system (PSMA-RADS) version 1.0 codifies indeterminate soft tissue findings with the PSMA-RADS-3A moniker. We investigated the role of point-spread function (PSF) reconstructions on categorization of PSMA-RADS-3A lesions. Methods: This was a post hoc analysis of an institutional review board approved prospective trial. Around 60 min after the administration of 333 MBq (9 mCi) of PSMA-targeted 18F-DCFPyL, patients underwent PET/computed tomography (CT) acquisitions from the mid-thighs to the skull vertex. The PET data were reconstructed with and without PSF. Scans were categorized according to PSMA-RADS version 1.0, and all PSMA-RADS-3A lesions on non-PSF images were re-evaluated to determine if any could be re-categorized as PSMA-RADS-4. The maximum standardized uptake values (SUVs) of the lesions, mean SUVs of blood pool, and the ratios of those values were determined. Results: A total of 171 PSMA-RADS-3A lesions were identified in 30 patients for whom both PSF reconstructions and cross-sectional imaging follow-up were available. A total of 13/171 (7.6%) were re-categorized as PSMA-RADS-4 lesions with PSF reconstructions. A total of 112/171 (65.5%) were found on follow-up to be true positive for PCa, with all 13 of the re-categorized lesions being true positive on follow-up. The lesions that were re-categorized trended towards having higher SUVmax-lesion and SUVmax-lesion/SUVmean-blood-pool metrics, although these relationships were not statistically significant. Conclusions: The use of PSF reconstructions for 18F-DCFPyL PET can allow the appropriate re-categorization of a small number of indeterminate PSMA-RADS-3A soft tissue lesions as more definitive PSMA-RADS-4 lesions. The routine use of PSF reconstructions for PSMA-targeted PET may be of value at those sites that utilize this technology.

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Ultrasonic B-Scan Imaging: Theory of Image Formation and a Technique for Restoration

Ultrasonic Imaging ◽

10.1177/016173468000200101 ◽

1980 ◽

Vol 2 (1) ◽

pp. 1-47 ◽

Cited By ~ 90

Author(s):

Mostafa Fatemi ◽

A. C. Kak

Keyword(s):

Soft Tissue ◽

Point Spread Function ◽

Image Formation ◽

Major Result ◽

Electromechanical Properties ◽

Point Spread ◽

Spread Function ◽

Imaging Theory ◽

B Scan Images ◽

Reflecting Surfaces

This paper presents a theory for ultrasonic B-scan image formation. Our theory is based on the assumption that imaging is done using broadband signals and that all the information in the returned echos is utilized for image formation, as opposed to only the “video” detected envelopes. We also assume that the image is formed from the backscattered returns caused by inhomogeneities within soft tissue structures. In other words, we do not take into account the contributions from the specularly reflecting surfaces that represent large impedance discontinuities. (Surfaces that only represent small impedance changes and are “visible” to the transducer are accounted for by our theory.) Our main reason for this omission is the fact that although the contributions of the surfaces with large impedance changes are important to the delineation of features in some 3-scan images, it is the presentation of the backscattered echos from small inhomogeneities within the tissues that is more severely distorted by the radiation and the electromechanical properties of the transducer. Also, it is currently believed that the backscattered echoes from the small inhomogeneities within the tissues carry important pathological information. Our theory is also limited to the case of Linearly scanned transducers with unfocused apertures. A major result of our theory is an analytical expression for the point spread function of the image degradation. As expected, this function is position variant. To simplify the computations required for image restoration, we have presented approximations that reduce the point spread function to the position-invariant form. We have shown experimentally that the resulting restoration filters retain their effectiveness over several centimeters of the object thickness. This has led us to conclude that the B-scan images of thick objects may be restored by using piecewise position-invariant techniques.

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