Faculty Bibliography

Fahr disease is a rare neurodegenerative syndrome characterized by abnormal symmetric calcium deposition in the white matter, cerebral cortex, deep gray, and cerebellar nuclei. The characteristic CT pattern is well known, but descriptions of molecular imaging in Fahr disease remain sparse. We present the characteristic imaging patterns of Fahr disease by CT, I-123-Ioflupane SPECT, and integrated FDG PET/MRI in a single patient.

PURPOSE/OBJECTIVE:To explore pragmatic approaches integrating MRI and PSMA-PET/CT for evaluating extraprostatic extension (EPE) of prostate cancer (PCa). METHODS:>12). Diagnostic performance was tested with receiver operating characteristic (ROC) curves and compared using DeLong and McNemar tests. RESULTS:>12 among which 87.5% (7/8) were corrected upgraded and had pathological EPE. CONCLUSION/CONCLUSIONS:Several pragmatic approaches were explored for integrating MRI and PSMA-PET/CT to assess EPE in PCa. Combining morphological information from MRI and PSMA expression on PET/CT demonstrated good diagnostic performance and may be a simple pragmatic integrated method that can be used.

OBJECTIVES/OBJECTIVE:Prostate-specific membrane antigen (PSMA)-PET/CT has become integral to management of prostate cancer; however, PSMA-avid rib lesions pose a diagnostic challenge. This study investigated clinicopathological and imaging findings that predict metastatic etiology of PSMA-avid rib lesions. MATERIALS AND METHODS/METHODS:), miPSMA score), CT features (sclerotic, lucent, fracture, no correlate), other sites of metastases, and primary tumor findings. A composite reference standard for rib lesion etiology (metastatic vs non-metastatic) based on histopathology, serial imaging, and clinical assessment was used. RESULTS:, miPSMA), more commonly involved multiple ribs, and were more often sclerotic (p < 0.01); lucency/fractures were only seen in benign lesions. CONCLUSION/CONCLUSIONS:Several imaging and clinicopathological factors differed between PSMA-avid metastatic and benign lesions. Isolated rib lesions without other sites of metastasis are almost always benign. Careful assessment of CT features can help diagnose benign lesions. KEY POINTS/CONCLUSIONS:Question While prostate-specific membrane antigen (PSMA)-PET/CT has become integral to the management of prostate cancer, PSMA-avid rib lesions pose a diagnostic challenge. Findings Approximately a quarter of patients who had PSMA-avid rib lesions were metastatic. However, only 2.1% of them had isolated rib metastasis (without PSMA-avid metastases elsewhere). Clinical relevance Isolated PSMA-avid rib lesions are almost always benign when there is no evidence of metastatic disease elsewhere. Scrutinizing CT features can help diagnose benign PSMA-avid lesions with greater certainty.

OBJECTIVES/OBJECTIVE:An increasing number of patients with prostate cancer (PCa) undergo assessment with magnetic resonance imaging (MRI) and prostate-specific membrane antigen positron emission tomography/computed tomography (PSMA-PET/CT). This offers comprehensive multimodality staging but can lead to discrepancies. The objective was to assess the rates and types of discordance between MRI and PSMA-PET/CT for primary PCa assessment. MATERIALS AND METHODS/METHODS:Consecutive men diagnosed with intermediate and high-risk PCa who underwent MRI and PSMA-PET/CT in 2021-2023 were retrospectively included. MRI and PSMA-PET/CT were interpreted using PI-RADS v2.1 and PRIMARY scores. Discordances between the two imaging modalities were categorized as "minor" (larger or additional lesion seen on one modality) or "major" (positive on only one modality or different index lesions between MRI and PSMA-PET/CT) and reconciled using radical prostatectomy or biopsy specimens. RESULTS:Three hundred and nine men (median age 69 years, interquartile range (IQR) 64-75) were included. Most had Gleason Grade Group ≥ 3 PCa (70.9% (219/309)). Median PSA was 9.0 ng/mL (IQR 5.6-13.6). MRI and PSMA-PET/CT were concordant in 157/309 (50.8%) and discordant in 152/309 (49.1%) patients; with 39/152 (25.7%) major and 113/152 (74.3%) minor discordances. Of 27 patients with lesions only seen on MRI, 85.2% (23/27) were clinically significant PCa (csPCa). Of 23 patients with lesions only seen on PSMA-PET/CT, 78.3% (18/23) were csPCa. Altogether, lesions seen on only one modality were csPCa in 80.0% (36/45). CONCLUSION/CONCLUSIONS:MRI and PSMA-PET/CT were discordant in half of patients for primary PCa evaluation, with major discrepancies seen in roughly one out of eight patients. KEY POINTS/CONCLUSIONS:Question While both MRI and PSMA-PET/CT can be used for primary tumor assessment, the discordances between them are not well established. Findings MRI and PSMA-PET/CT were discordant in about half of the patients. Most prostate lesions seen on only one modality were significant cancer. Clinical relevance MRI and PSMA-PET/CT are often discordant for assessing the primary prostate tumor. Using both modalities for primary prostate tumor evaluation can provide complementary information that may substantially impact treatment planning.

Purpose/UNASSIGNED:The goal of partial gland ablation (PGA) is to eradicate focal lesions of clinically significant prostate cancer (csPCa) with minimal adverse impact on functional outcomes. The primary objective of this study is to characterize the performance of 18F-Fluciclovine PET imaging for detection of prostate cancer following PGA. Materials and Methods/UNASSIGNED:Subjects 2 years following primary partial gland cryoablation (PPGCA) were invited to participate in an IRB-approved study providing they met the following inclusion criteria: a single reported mpMRI region of interest (ROI) concordant with biopsy Gleason Grade Group (GGG) < 4, no gross extra-prostatic extension on mpMRI, and no GGG > 1 or GGG 1 with a core length > 6 mm on contralateral systematic biopsy. 18F-Fluciclovine PET MRI imaging of the prostate was performed followed by in and out-of-field biopsies. Results/UNASSIGNED:Twenty-seven men who met eligibility criteria participated in the prospective study. In-field and out-of-field csPCa recurrence rate was 7.4% and 22.2%, respectively. The sensitivity and positive predictive value of mpMRI and PET imaging did not reach performance to reliably inform who should undergo prostate biopsy. Conclusion/UNASSIGNED:At 2 years following PPGCA, the rate of in-field csPCa was exceedingly low indicating a limited role for imaging to inform in-field biopsy decisions. The csPCa detection rate of out-of-field recurrence was 22% which provides an opportunity for imaging to inform out-of-field biopsy decisions. Based on our findings, 18F-Fluciclovine PET MRI cannot be used to inform who should undergo out-of-field prostate biopsy at 2 years following PPGCA.

Prostate specific membrane antigen (PSMA) is a transmembrane protein that is highly expressed on prostate epithelial cells and is strongly upregulated in prostate cancer. Radioligand therapy using beta-emitting Lutetium-177 (¹⁷⁷Lu)-labeled-PSMA-617, a radiolabeled small molecule, has gained attention as a novel targeted therapy for metastatic prostate cancer, given its high affinity and long tumor retention, and rapid blood pool clearance. In March 2022, the United States Food and Drug administration has granted approval to the targeted ¹⁷⁷Lu-PSMA-617 therapy for treatment of patients with PSMA-positive metastatic castration resistant prostate cancer, who have been previously treated with an androgen-receptor pathway inhibitor and taxane-based chemotherapy. Studies have demonstrated the adverse effects of this treatment, mainly encountered due to radiation exposure to non-target tissues. Salivary glands show high PSMA-ligand uptake and receive increased radiation dose secondary to accumulation of ¹⁷⁷Lu-PSMA-617. This predisposes the glands to radiation-mediated toxicity. The exact mechanism, scope and severity of radiation-mediated salivary gland toxicity are not well understood, however, the strategies for its prevention and treatment are under evaluation. This review will focus on the current knowledge about salivary gland impairment post ¹⁷⁷Lu labeled PSMA-based radioligand therapies, diagnostic methodologies, and imaging with emphasis on salivary gland scintigraphy. The preventive strategies and known treatment options would also be briefly highlighted.

A 68-year-old man with a history of prostate cancer post-primary treatment presented with rising prostate-specific antigen levels and was referred for F-fluciclovine PET/MRI to localize recurrent disease. PET/MRI revealed a solitary focus of uptake in a soft tissue nodule in the anterior mediastinum, which was resected and found to be a type B2 thymoma. F-fluciclovine uptake is mediated by amino acid transporters, primarily alanine-serine-cysteine transporter 2 and L-type amino acid transporter 1, previously demonstrated to be expressed on thymic carcinomas. This case highlights the possibility of overexpression of amino acid transporters in thymomas as well, rarely described before.

Beta amyloid (Aβ) accumulation is the earliest pathological marker of Alzheimer's disease (AD), but early AD pathology also affects white matter (WM) integrity. We performed a cross-sectional study including 44 subjects (23 healthy controls and 21 mild cognitive impairment or early AD patients) who underwent simultaneous PET-MR using 18F-Florbetapir, and were categorized into 3 groups based on Aβ burden: Aβ- [mean mSUVr ≤1.00], Aβi [1.00 < mSUVr <1.17], Aβ+ [mSUVr ≥1.17]. Intergroup comparisons of diffusion MRI metrics revealed significant differences across multiple WM tracts. Aβi group displayed more restricted diffusion (higher fractional anisotropy, radial kurtosis, axonal water fraction, and lower radial diffusivity) than both Aβ- and Aβ+ groups. This nonmonotonic trend was confirmed by significant continuous correlations between mSUVr and diffusion metrics going in opposite direction for 2 cohorts: pooled Aβ-/Aβi and pooled Aβi/Aβ+. The transient period of increased diffusion restriction may be due to inflammation that accompanies rising Aβ burden. In the later stages of Aβ accumulation, neurodegeneration is the predominant factor affecting diffusion.

BACKGROUND:The authors reviewed the two most common current uses of brain 18F-labeled fluoro-2-deoxyglucose positron emission tomography (FDG-PET) at a large academic medical center. For epilepsy patients considering surgical management, FDG-PET can help localize epileptogenic lesions, discriminate between multiple or discordant EEG or MRI findings, and predict prognosis for post-surgical seizure control. In elderly patients with cognitive impairment, FDG-PET often demonstrates lobar-specific patterns of hypometabolism that suggest particular underlying neurodegenerative pathologies, such as Alzheimer's disease. FDG-PET of the brain can be a key diagnostic modality and contribute to improved patient care.

Aim: Determine if MR-guided FDG-PET reconstruction improves diagnostic accuracy and epileptogenic lesion localization for patients with focal epilepsy. Introduction: Abnormalities detected on MRI or FDG PET alter clinical management and prognosis in patients with focal epilepsy considering surgery (1). Concordant MRI findings are not always present, whereas -80% of adult patients with chronic seizures have FDG PET abnormalities. State-of-art FDG PET, however, remains limited by partial volume effects (PVEs) that reduce sensitivity particularly for extra-temporal epilepsy (2). MR-guided (MRG) PET reconstruction reduces PVEs (3). We tested the hypothesis that MRG PET reconstruction increases correct localization of epileptogenic lesions across readers with different levels of clinical experience.
Method(s): After IRB approval, a neuroradiologist with 1000+ brain PET interpretations identified 26 epilepsy subjects that underwent simultaneous FDG PET-MRI (Siemens Biograph mMR, Siemens Healthcare, Erlangen, Germany) with final adjudicated diagnosis either as normal (N=10) or cortical dysplasia (N=16). PET emission images were reconstructed using conventional OSEM and MRG PET reconstructions (asymmetric Bowsher prior with 3D MPRAGE as anatomical prior image). Then, 3 blinded readers (with 12, 6 & 18 years of experience; respectively) evaluated cases containing either OSEM or MRG PET in the sagittal, axial and coronal planes for each case (MRI data was not provided). Readers determined if there were focal FDG abnormalities consistent with an epileptogenic zone, then assigned ordinal values to image quality (0-3; where 3 was "excellent") and diagnostic confidence (1-3; where 3 = "definite" abnormality or normal study).
Result(s): The figure below shows coronal OSEM and MRG PET reconstructions (A & B respectively) with co-registered MRI (C) - MRG PET better demonstrated the focal FDG abnormality associated with right frontal cortical dysplasia. All 3 readers rated MRG PET images higher in overall quality (2.6 +/- 0.7 vs 2.0 +/- 0.5, Mann-Whitney test, P<0.00001). Reconstruction method did not affect diagnostic confidence (2.6 +/- 0.7 vs 2.9 +/- 0.4, Mann-Whitney test, P=0.555). Readers 2 & 3 (with less experience reading brain FDG PET), improved their localization of the seizure focus using MRG PET images from 42.9 to 75%, and 50 to 75% correct respectively. Reader 1, with the most experience, demonstrated no change in correct localization (85.7 vs 83.3%), but reported more confidence in the diagnosis (P=0.033). Global percentage correct for all 3 raters increased from 59.5% to 77.8% (chi-squared test, P=0.086). MRG PET images increased interpretation sensitivity from 69% to 75%, specificity from 70% to 83% and accuracy from 70% to 78%, but these changes did not reach statistical significance.
Conclusion(s): These initial results demonstrate that MRG PET reconstruction of FDG data can increase correct seizure localization for PET readers with less experience. Study limitations include that clinical history, anatomical correlation and non-attenuation corrected FDG PET images were not available to blinded readers. Future work will increase the number of subjects evaluated by the 3 readers to increase statistical power