European Journal of Nuclear Medicine and Molecular Imaging最新文献

Hidradenocarcinoma is a rare and aggressive malignant cutaneous adnexal tumor that originates from the intradermal ducts of eccrine sweat glands. Herein, we report a case of hidradenocarcinoma that had transformed from a previously excised benign hidradenoma. [¹⁸F] FDG PET/CT revealed an FDG-avid mass in the left calf, and extensive metastatic disease, including soft tissue, pulmonary, osseous, and extensive nodal metastases. This case underscores the potential for malignant transformation of hidradenoma and highlights the utility of [¹⁸F] FDG PET/CT in staging hidradenocarcinoma.

Purpose

Off-target binding remains a significant challenge in tau-PET neuroimaging. While off-targets including monoamine oxidase enzymes and neuromelanin-containing cells have been identified, recent studies indicated a relevant binding of novel tau tracers to melanin-containing structures. To date, little is known about the effect of melanocytes in the meninges on tracer signals in brain PET data. Thus, we aimed to identify the target structure causal for the frequently observed [¹⁸F]PI-2620 PET signal in the vermis and adjacent cerebellar regions.

Methods

274 participants underwent dynamic [¹⁸F]PI-2620 tau-PET: 3/4R-tauopathies (n = 85), 4R-tauopathies (n = 147), tau-negative disease controls (n = 24), and healthy controls (n = 18). Standardized uptake value ratio (SUVR) and kinetic parameters including the distribution volume ratio (DVR), tracer clearance (k2) and relative perfusion (R1), were compared among the cohorts and sexes using the Automated Anatomical Labelling (AAL) atlas. Age and p-Tau levels in cerebrospinal fluid (CSF) were assessed for their relationship with vermal tau-PET signal. Furthermore, we combined autoradiographic and histochemical experiments on post-mortem brain tissue of deceased patients (n = 9).

Results

Male participants revealed higher mean vermal [¹⁸F]PI-2620 DVR (0.95 ± 0.13; vs. females 0.88 ± 0.10, p < 0.0001). Sex-related differences were most pronounced in the 3/4R-tauopathy cohort (p < 0.0001). Mean SUVR_Ver/Cbl, k2 and correlation analyses of kinetic parameters did not differ among groups. Histological assessments revealed co-localization of leptomeningeal pigmented cells with strong autoradiography signal spots within the vermal fissures. Tau-related autoradiography signals, age or p-Tau levels did not correlate significantly with tau-PET signals. Iron deposits did not cause relevant autoradiography signals in the vermis.

Conclusion

Leptomeningeal melanocytes are the primary target structure for [¹⁸F]PI-2620 PET binding in anterior vermis, whereas iron and tau deposits do not contribute significantly.

Purpose

The aim of this study is to investigate the impact of lymph node metastases (LNM) detected on cervical ¹³¹I single photon emission computed tomography/computed tomography (SPECT/CT) after the first radioiodine therapy (RAI) on complete response (CR) and progression-free survival (PFS) in patients with differentiated thyroid cancer (DTC).

Methods

This retrospective study included 942 DTC patients who underwent cervical ¹³¹I SPECT/CT after their first RAI. LNM were categorized based on CT (enlarged ≥ 1 cm, small < 1 cm) and ¹³¹I uptake. CR and PFS were analysed using Kaplan–Meier curves and Cox regression.

Results

Patients with no LNM had a shorter median time to CR (9.4 months) than those with LNM (44 months, HR 2.2; p < 0.01) and a lower risk of progression (median PFS not reached, HR 0.46; p < 0.01). Among patients with LNM, those with enlarged ¹³¹I negative LNM had the longest time to CR (24 months, HR 0.36; p < 0.01). Patients with small LNM had a PFS similar to patients without LNM (median PFS not reached, HR 1.22; p = 0.54). Reoperation after first RAI (13.5 months) led to earlier CR than second RAI (median not reached) in patients with enlarged LNM. For small LNM, second RAI was associated with longer PFS than reoperation (38.4 months vs. not reached, HR 4.0; p = 0.02).

Conclusion

Patients without LNM on post-therapy ¹³¹I SPECT/CT have better chances for early CR and longer PFS. Patients with LNM benefit from early reoperations but treatment strategies should be tailored based on LNM characteristics.

Purpose

To determine the most important patient factors influencing quantitative MBF and to report the lower (LRL) and upper (URL) reference limits for 13N-ammonia positron emission tomography (PET) myocardial perfusion imaging (MPI).

Methods

Patients who underwent 13N-ammonia PET-MPI were screened, and those with evidence of myocardial ischemia or scar, known cardiomyopathy, impaired left ventricular function, non-response to vasodilators, and those who underwent a stress-rest protocol were excluded. Multiple linear regression analyses were performed to identify independent predictors of rest MBF (rMBF), stress MBF (sMBF), and myocardial flow reserve (MFR), and predictor importance was calculated. Finally, median, LRL, and URL for rMBF, sMBF, and MFR were calculated based on the presence of predictors.

Results

Among 784 patients with a median coronary artery calcium score (CACS) of 69, median rMBF was 0.75mL∙min^− 1∙g^− 1 (LRL = 0.49 mL∙min^− 1∙g^− 1; URL = 1.33 mL∙min^− 1∙g^− 1), median sMBF was 2.41mL∙min^− 1∙g^− 1 (LRL = 1.42 mL∙min^− 1∙g^− 1; URL = 3.73 mL∙min^− 1∙g^− 1), and median MFR was 3.09 (LRL = 2.11; URL = 4.65). The body mass index (BMI) was the single most important independent predictor of rMBF, sMBF, and MFR (predictor importance of 72%, 87%, and 41%, respectively; standardized β=-0.434, -0.566 and − 0.174, respectively). Additional predictors were sex and hypertension for rMBF, sex for sMBF, and hypertension and CACS for MFR.

Conclusion

In patients without flow-limiting CAD, MBF is strongly influenced by the patient’s habitus, whereby median and reference limits for sMBF and rMBF decrease with increasing BMI. Consequently, MFR exhibits stable lower reference limits across a wide range of BMI and may be considered the most robust quantitative parameter derived from 13N-ammonia PET-MPI.

Background

This work aimed to develop deep learning (DL) models for CT-free attenuation and Monte Carlo-based scatter correction (AC, SC) in quantitative ⁹⁰Y SPECT imaging for improved dose calculation.

Methods

Data of 190 patients who underwent ⁹⁰Y selective internal radiation therapy (SIRT) with glass microspheres was studied. Voxel-level dosimetry was performed on uncorrected and corrected SPECT images using the local energy deposition method. Three deep learning models were trained individually for AC, SC, and joint ASC using a modified 3D shifted-window UNet Transformer (Swin UNETR) architecture. Corrected and unorrected dose maps served as reference and as inputs, respectively. The data was split into train set (~ 80%) and unseen test set (~ 20%). Training was conducted in a five-fold cross-validation scheme. The trained models were tested on the unseen test set. The model’s performance was thoroughly evaluated by comparing organ- and voxel-level dosimetry results between the reference and DL-generated dose maps on the unseen test dataset. The voxel and organ-level evaluations also included Gamma analysis with three different distances to agreement (DTA (mm)) and dose difference (DD (%)) criteria to explore suitable criteria in SIRT dosimetry using SPECT.

Results

The average ± SD of the voxel-level quantitative metrics for AC task, are mean error (ME (Gy)): -0.026 ± 0.06, structural similarity index (SSIM (%)): 99.5 ± 0.25, and peak signal to noise ratio (PSNR (dB)): 47.28 ± 3.31. These values for SC task are − 0.014 ± 0.05, 99.88 ± 0.099, 55.9 ± 4, respectively. For ASC task, these values are as follows: -0.04 ± 0.06, 99.57 ± 0.33, 47.97 ± 3.6, respectively. The results of voxel level gamma evaluations with three different criteria, namely “DTA: 4.79, DD: 1%”, “DTA:10 mm, DD: 5%”, and “DTA: 15 mm, DD:10%” were around 98%. The mean absolute error (MAE (Gy)) for tumor and whole normal liver across tasks are as follows: 7.22 ± 5.9 and 1.09 ± 0.86 for AC, 8 ± 9.3 and 0.9 ± 0.8 for SC, and 11.8 ± 12.02 and 1.3 ± 0.98 for ASC, respectively.

Conclusion

We developed multiple models for three different clinically scenarios, namely AC, SC, and ASC using the patient-specific Monte Carlo scatter corrected and CT-based attenuation corrected images. These task-specific models could be beneficial to perform the essential corrections where the CT images are either not available or not reliable due to misalignment, after training with a larger dataset.

Purpose

Long-axial field-of-view PET scanners capture multi-organ tracer distribution with high sensitivity, enabling lower dose dynamic protocols and dual-tracer imaging for comprehensive disease characterization. However, reducing dose may compromise data quality and time-activity curve (TAC) fitting, leading to higher bias in kinetic parameters. Parametric imaging poses further challenges due to noise amplification in voxel-based modelling. We explore the potential of deep learning denoising (DL-DN) to improve quantification for low-dose dynamic PET.

Methods

Using 16 [¹⁸F]FDG PET studies from the PennPET Explorer, we trained a DL framework on 10-min images from late-phase uptake (static data) that were sub-sampled from 1/2 to 1/300 of the counts. This model was used to denoise early-to-late dynamic frame images. Its impact on quantification was evaluated using compartmental modelling and voxel-based graphical analysis for parametric imaging for single- and dual-tracer dynamic studies with [¹⁸F]FDG and [¹⁸F]FGln at original (injected) and reduced (sub-sampled) doses. Quantification differences were evaluated for the area under the curve of TACs, K_i for [¹⁸F]FDG and V_T for [¹⁸F]FGln, and parametric images.

Results

DL-DN consistently improved image quality across all dynamic frames, systematically enhancing TAC consistency and reducing tissue-dependent bias and variability in K_i and V_T down to 40 MBq doses. DL-DN preserved tumor heterogeneity in Logan V_T images and delineation of high-flux regions in Patlak K_i maps. In a /[¹⁸F]FDG dual-tracer study, bias trends aligned with single-tracer results but showed reduced accuracy for [¹⁸F]FGln in breast lesions at very low doses (4 MBq).

Conclusion

This study demonstrates that applying DL-DN trained on static [¹⁸F]FDG PET images to dynamic [¹⁸F]FDG and [¹⁸F]FGln PET can permit significantly reduced doses, preserving accurate FDG K_i and FGln V_T measurements, and enhancing parametric image quality. DL-DN shows promise for improving dynamic PET quantification at reduced doses, including novel dual-tracer studies.

Background

Prostate-specific membrane antigen (PSMA) positron emission tomography/computed tomography (PET/CT) is currently under evaluation for detecting clinically significant prostate cancer. The PSMA-PET/CT may complement the current standard diagnostic pathway for prostate cancer, which includes prostate-specific antigen (PSA) testing and multiparametric magnetic resonance imaging (mpMRI). This study evaluated the cost-effectiveness and quality of life impact of incorporating PSMA-PET/CT into this diagnostic algorithm.

Methods

A life-time decision model compared the current standard of care of a MRI driven diagnostic pathway, where men undergo prostate biopsy in case of a Prostate Imaging Reporting and Data System (PI-RADS) scores 3–5, to a strategy incorporating PSMA-PET/CT to potentially avoid unnecessary biopsies. Long-term quality-adjusted life years (QALY) and healthcare costs were calculated for each approach.

Results

In PI-RADS 3 lesions, PSMA-PET/CT improved the per-patient QALY by 0.002 and was borderline cost-effective, with an increased cost of €170-€186 per patient and an incremental cost-effectiveness ratio (ICER) of €56,700-€93,212 per QALY. In PI-RADS 1–2, additional biopsies and over-detection of low-risk prostate cancers led to a per-patient QALY decrease of 0.001 points, a cost increase of €416-€429 per patient and was thus not cost-effective.

Conclusion

The addition of PSMA-PET/CT to MRI in patients with equivocal MRI findings appears to be borderline cost-effective due to biopsy avoidance and a reduced detection of indolent, low-risk tumors. In men with a negative MRI, adding a PSMA-PET/CT does not seem to be cost-effective due to a higher number of unnecessary biopsies and only minor improvement in the detection of clinically significant prostate cancer.