All You Need to Know as an Authorized User.

OBJECTIVE: The purpose of this article is to review the training requirements for practicing nuclear radiology, the scope of licensing, how to start a new practice, and the key concepts an authorized user needs to know for responsible use of radiopharmaceuticals. CONCLUSION: Physicians responsible for the daily operations of nuclear medicine clinics often find the regulations concerning the safe handling and administration of radiopharmaceuticals daunting. Even experienced authorized users have concerns about handling many new therapeutic agents. Those studying for certifying and subspecialty examinations or for maintenance of certification for the American Board of Nuclear Medicine and the American Board of Radiology must clearly understand the overall process for becoming an authorized user.

Essentials and guidelines for clinical medical physics residency training programs: executive summary of AAPM Report Number 249.

There is a clear need for established standards for medical physics residency training. The complexity of techniques in imaging, nuclear medicine, and radiation oncology continues to increase with each passing year. It is therefore imperative that training requirements and competencies are routinely reviewed and updated to reflect the changing environment in hospitals and clinics across the country. In 2010, the AAPM Work Group on Periodic Review of Medical Physics Residency Training was formed and charged with updating AAPM Report Number 90. This work group includes AAPM members with extensive experience in clinical, professional, and educational aspects of medical physics. The resulting report, AAPM Report Number 249, concentrates on the clinical and professional knowledge needed to function independently as a practicing medical physicist in the areas of radiation oncology, imaging, and nuclear medicine, and constitutes a revision to AAPM Report Number 90. This manuscript presents an executive summary of AAPM Report Number 249.

[89Zr]-Atezolizumab-PET Imaging Reveals Longitudinal Alterations in PDL1 during Therapy in TNBC Preclinical Models.

Triple-negative breast cancers (TNBCs) currently have limited treatment options; however, PD-L1 is an indicator of susceptibility to immunotherapy. Currently, assessment of PD-L1 is limited to biopsy samples. These limitations may be overcome with molecular imaging. In this work, we describe chemistry development and optimization, in vitro, in vivo, and dosimetry of [89Zr]-Atezolizumab for PD-L1 imaging. Atezolizumab was conjugated to DFO and radiolabeled with 89Zr. Tumor uptake and heterogeneity in TNBC xenograft and patient-derived xenograft (PDX) mouse models were quantified following [89Zr]-Atezolizumab-PET imaging. PD-L1 expression in TNBC PDX models undergoing therapy and immunohistochemistry (IHC) was used to validate imaging. SUV from PET imaging was quantified and used to identify heterogeneity. PET/CT imaging using [89Zr]-Atezolizumab identified a significant increase in tumor:muscle SUVmean 1 and 4 days after niraparib therapy and revealed an increased trend in PD-L1 expression following other cytotoxic therapies. A preliminary dosimetry study indicated the organs that will receive a higher dose are the spleen, adrenals, kidneys, and liver. [89Zr]-Atezolizumab PET/CT imaging reveals potential for the noninvasive detection of PD-L1-positive TNBC tumors and allows for quantitative and longitudinal assessment. This has potential significance for understanding tumor heterogeneity and monitoring early expression changes in PD-L1 induced by therapy.

Real-Time Gain Control of PET Detectors and Evaluation With Challenging Radionuclides.

Accurate gain control of PET detectors is a prerequisite for quantitative accuracy. A shift in the 511 keV peak position can lead to errors in scatter correction, degrading quantitation. The PET detectors in a PET/MR scanner are subject to thermal transients due to eddy currents induced during gradient-intensive MRI sequences. Since the gain of silicon photomultiplier-based detectors changes with temperature, good gain control is particularly challenging. In this paper we describe a method that utilizes information from the entire singles spectrum to create a real-time gain control method that maintains gain of PET detectors stable within approximately ±0.5% (±2.5 keV) with varying levels of scatter and in the presence of significant thermal transients. We describe the methods used to combine information about multiple peaks and how this algorithm is implemented in a way that permits real-time processing on a field-programmable gate array. Simulations demonstrate rapid response time and stability. A method ("virtual scatter filter") is also described that extracts unscattered photopeak events from phantom data and demonstrates the accuracy of the photopeak for various radionuclides that emit energies in addition to the pure 511 keV annihilation peak. Radionuclides 52 Mn, 55 Co, 64 Cu, 89 Zr, 90 Y, and 124 I are included in the study for their various forms of spectral contamination.

Density measurements of dentin by dual-energy radiography.

OBJECTIVES: The aim of this study was to apply the dual-energy radiographic technique to teeth and to soft tissue simulated with Lucite and report the visual and quantitative results. STUDY DESIGN: High- and low-energy image pairs were exposed of aluminum and Lucite calibration wedges and human teeth sections. Reconstructed images of the calibration wedges and teeth sections were viewed and measured. RESULTS: The aluminum reconstruction images accentuated the aluminum wedge and the teeth, whereas the Lucite reconstruction images minimized them. Correlations between the nominal direct and dual-energy measurements of the wedges and teeth thicknesses were found to be very good. The root-mean-square deviation of the dual-energy reconstructions from the measured nominal thicknesses was found to be no greater than 0.6 mm. CONCLUSION: These results demonstrate the feasibility of using dual energy as a means of selective cancellation of unwanted tissues and the measurement of posterior tooth density.