Frontiers in nuclear medicine (Lausanne, Switzerland)最新文献

Background: Calcinosis is a morbid complication of dermatomyositis (DM) and systemic sclerosis (SSc) with no effective pharmacologic treatment or validated whole-body assessment modality. ¹⁸F-NaF PET/CT may help to quantify and characterize calcinosis.

Methods: In this pilot study, we enrolled three adults with DM and three with SSc, all with new calcinosis deposits. Each underwent ¹⁸F-NaF PET/CT and clinical examination with semi-quantitative scoring of calcinosis. We described the ¹⁸F-NaF PET/CT findings and compared these to CT imaging alone as well as to clinical examination.

Results: Calcinosis was noted on ¹⁸F-NaF PET/CT in the subcutaneous tissue in all patients and the muscle in three patients, including two with SSc. The average semi-quantitative score was 23.5 by ¹⁸F-NaF PET/CT and 20 by clinical exam. Wilcoxon signed rank test indicated greater scores by ¹⁸F-NaF PET/CT than by clinical exam (p = 0.0264). ¹⁸F-NaF uptake varied among calcinosis deposits and occurred without corresponding calcifications on CT.

Conclusions: ¹⁸F-NaF PET/CT appears to be a sensitive method of detecting and characterizing calcinosis that provides both quantitative and qualitative data beyond what can be obtained by physical examination or CT alone. ¹⁸F-NaF uptake occurs in muscle in both SSc and DM, suggesting the possibility that myositis may be driving calcinosis in a subset of patients with SSc.

[This corrects the article DOI: 10.3389/fnume.2024.1469487.].

Introduction: Fluorodeoxyglucose (FDG) PET/CT is typically the reference imaging method for assessing and tracking lymphomas. However, fibroblast activation protein inhibitor (FAPI) PET is being explored as a potentially useful option, especially when Fluorodeoxyglucose (FDG) scans do not show clear results.

Methods: For this systematic review, two researchers searched PubMed/MEDLINE and Cochrane CENTRAL for studies on FAPI PET/CT in lymphoma patients.

Results: The literature search initially retrieved 249 articles. After removing duplicates and screening titles and abstracts, and full text, there was a final selection of 15 articles (3 original studies and 12 case reports), encompassing a total of 270 patients. The three original studies were judged to have a low risk of bias according to the QUADAS-2 criteria. The systematic review reveals that FAPI PET/CT exhibits lower diagnostic sensitivity than [¹⁸F]FDG PET/CT in lymphomas characterized by low FAP expression. Nevertheless, FAPI PET/CT retains potential as a complementary imaging modality.

Discussion: [¹⁸F]FDG PET/CT remains the gold standard in lymphoma imaging, but FAPI PET/CT can potentially provide supplementary information regarding the molecular characteristics of lymphomas. FAPI PET/CT may have prognostic and therapeutic implications. In particular, it could help identify lymphoma subgroups with distinct stromal environments, potentially serving as a prognostic biomarker. Further large-scale prospective studies are warranted to validate its role in lymphoma management.

Background: Carbonic anhydrase-IX (CA-IX) is overexpressed in tumors due to hypoxic conditions and considered an attractive biomarker for tumor-targeting radioligands. The introduction of an albumin binder (ALB) to radioligands can delay their renal clearance, resulting in increased radioactivity delivered to tumors and decreased renal uptake of radioligands. In this study, we designed novel CA-IX-targeted trifunctional radioligands consisting of imidazothiadiazole sulfonamide (IS) as a CA-IX-targeted ligand, DOTA as a chelator with four free carboxylic groups, and lysine-conjugated 4-(p-iodophenyl)butyric acid (Lys-IPBA) as ALB, with IS-[¹¹¹In]In-DOTADG-ALB in a linear-chain arrangement and [¹¹¹In]In-DOTAGA-ALB-IS in a branched-chain arrangement. Fundamental properties of IS-[¹¹¹In]In-DOTADG-ALB and [¹¹¹In]In-DOTAGA-ALB-IS were evaluated by in vitro and in vivo assays.

Methods: IS-DOTADG-ALB and DOTAGA-ALB-IS were synthesized and radiolabeled with [¹¹¹In]InCl₃. The stability of IS-[¹¹¹In]In-DOTADG-ALB and [¹¹¹In]In-DOTAGA-ALB-IS was evaluated by HPLC analysis after incubation in murine plasma. A cell saturation binding assay using CA-IX-positive HT-29 cells and albumin-binding assay were performed for IS-[¹¹¹In]In-DOTADG-ALB and [¹¹¹In]In-DOTAGA-ALB-IS to evaluate their capacity to bind CA-IX and albumin. Biodistribution assays of IS-[¹¹¹In]In-DOTADG-ALB and [¹¹¹In]In-DOTAGA-ALB-IS were performed using HT-29 tumor-bearing mice to evaluate their pharmacokinetics.

Results: IS-[¹¹¹In]In-DOTADG-ALB and [¹¹¹In]In-DOTAGA-ALB-IS were successfully synthesized by ligand substitution reaction from their corresponding precursors. IS-[¹¹¹In]In-DOTADG-ALB and [¹¹¹In]In-DOTAGA-ALB-IS exhibited similar stabilities in murine plasma and affinities to CA-IX, although the affinities to albumin were higher for [¹¹¹In]In-DOTAGA-ALB-IS compared with IS-[¹¹¹In]In-DOTADG-ALB. In the biodistribution assays, [¹¹¹In]In-DOTAGA-ALB-IS showed higher blood retention and tumor accumulation and lower renal uptake than IS-[¹¹¹In]In-DOTADG-ALB, reflecting their albumin-binding affinities.

Conclusion: These data suggest that the branched-chain arrangement of DOTAGA-ALB-IS may be useful for the design of CA-IX-targeted radioligands consisting of an IS ligand, DOTA, and Lys-IPBA.

Hyperparathyroidism disrupts the balance of physiological bone formation and resorption by upregulating osteoclast activity. This leads to hypercalcemia, resulting in osteoporosis and eventually the formation of "brown tumors." Currently used radiological and nuclear medicine imaging for primary hyperparathyroidism face challenges in accurately diagnosing bone-related complications. Molecular bone imaging techniques routinely consist of bone scintigraphy, with possible addition of bone-SPECT/CT. Recently, renewed interest has emerged in the use of Na[¹⁸F]F-PET/CT. Both applications are highly sensitive to in vivo osteoblast activity. However, the latter technique offers improved spatial resolution and sensitivity, as well as shorter incubation and faster scanning. This article summarizes current limitations and potential improvements in bone-SPECT/CT and Na[¹⁸F]F-PET/CT imaging in selected patients with hyperparathyroidism, compared to other relevant techniques and clinical parameters.

In this case, we report the usefulness of bone scintigraphy in evaluating osteoarticular pain when the diagnosis is unclear after standard morphological imaging. A 24-year-old male patient exhibited mild left tibial pain that had been intensifying over a period of 2 years. The initial radiological evaluation suggested a diagnosis of pediatric tibial bone marrow osteosclerosis associated with periostitis, based on standard radiographs and MRI. However, a complementary bone scan was required for confirmation and showed moderate hyperemia and severe hyperfixation of the tibial lesion along with similar lesions on the left femur, both humeri, and the right ulna. These new findings led to a diagnosis of Ribbing disease, a rare sclerosing bone dysplasia.

Background: ¹⁸F-FDG-PET/CT may reveal widespread inflammation of musculoskeletal structures in polymyalgia rheumatica (PMR). Currently, scans are subjectively analysed based on the overall gestalt of the scan. Standardized PET scores may potentially aid the interpretation of the scans for suspected PMR. Here, we compared the agreement and diagnostic accuracy of routine PET scan reports vs. the most validated PET scores for PMR.

Methods: 68 consecutive patients with suspected PMR (treatment-naïve, n = 29; already treated, n = 39) undergoing ¹⁸F-FDG-PET/CT were included. In glucocorticoid-treated patients, complete tapering was pursued prior to the scan. Conclusions of routine PET scan reports were interpretated by three independent readers as "PMR", "not PMR" or "unclear". The Leuven and Leuven/Groningen scores were determined. Agreement of scan report interpretation, and agreement of routine scan reports and PET scores were determined. Sensitivity and specificity were determined for the routine scan report and the two scores, with the clinical diagnosis established after 6 months follow-up as the reference standard.

Results: A diagnosis of PMR was made in 45/68 patients. Routine scan reports were uniformly rated by all three readers in 54 (78%) cases. Following a consensus meeting, scans were rated as "PMR" in 43 cases, "unclear" in 10 cases and "not PMR" in 15 cases. The routine scan report showed a sensitivity of 82% and specificity of 74%, if "unclear" cases were considered negative for PMR. The Leuven and Leuven/Groningen Scores showed similar diagnostic accuracy. Agreement between the routine scan report and PET scores was good (Cohen's kappa 0.60-0.64), if "unclear" cases were excluded from the analysis. Among 8/10 "unclear" cases, the PMR PET Scores accurately distinguished between PMR/PMR-mimicking inflammatory conditions and non-inflammatory conditions. Agreement and diagnostic accuracy of routine scan reports and PET scores were better among treatment-naïve patients than those that had been treated previously.

Conclusion: Our study reveals that routine PET scan reports for suspected PMR can be interpreted differently between readers. Although the routine PET scan reports and PMR PET scores did not always agree, they demonstrated similar diagnostic accuracy, with the highest accuracy observed in treatment-naive patients. The Leuven and Leuven/Groningen score could especially be helpful for cases in which the nuclear medicine physician is uncertain.

Medical images are hampered by noise and relatively low resolution, which create a bottleneck in obtaining accurate and precise measurements of living organisms. Noise suppression and resolution enhancement are two examples of inverse problems. The aim of this study is to develop novel and robust estimation approaches rooted in fundamental statistical concepts that could be utilized in solving several inverse problems in image processing and potentially in image reconstruction. In this study, we have implemented Bayesian methods that have been identified to be particularly useful when there is only limited data but a large number of unknowns. Specifically, we implemented a locally adaptive Markov chain Monte Carlo algorithm and analyzed its robustness by varying its parameters and exposing it to different experimental setups. As an application area, we selected radionuclide imaging using a prototype gamma camera. The results using simulated data compare estimates using the proposed method over the current non-locally adaptive approach in terms of edge recovery, uncertainty, and bias. The locally adaptive Markov chain Monte Carlo algorithm is more flexible, which allows better edge recovery while reducing estimation uncertainty and bias. This results in more robust and reliable outputs for medical imaging applications, leading to improved interpretation and quantification. We have shown that the use of locally adaptive smoothing improves estimation accuracy compared to the homogeneous Bayesian model.

Aim/background: Dynamic PET imaging requires an input function typically obtained through blood sampling. Image-derived input functions (IDIFs) of the ascending aorta (AA), aortic arch, descending aorta (DA), or left ventricle (LV) offer non-invasive alternatives, especially with long-axial field-of-view (LAFOV) PET/CT systems enabling whole-body dynamic ¹⁸F-FDG imaging. This study aimed to validate uncorrected IDIFs derived from the AA, DA, aortic arch, and LV by comparing them to (late) venous whole-blood in patients undergoing LAFOV PET/CT.

Methods: Eleven oncology patients who underwent 70-min dynamic ¹⁸F-FDG PET/CT scans on a LAFOV PET/CT system after receiving an intravenous bolus injection of 3.0 MBq/kg were included. Seven venous blood samples were collected manually at approximately 5, 10, 15, 25, 35, 45, and 60 min post-injection (pi) and compared to IDIFs derived from the AA, aortic arch, DA, and LV. Bias between IDIFs and venous blood samples was assessed at each time point.

Results: IDIF accuracy relative to venous blood samples improved over time, with a median percentage bias <10% after 25 min pi. At 60 min pi, the aortic arch showed the smallest bias (median -1.1%, IQR 5.9%), followed by the AA (2.5%, IQR 7.0%), DA (5.1%, IQR 8.6%), and LV (7.4%, IQR 7.6%).

Conclusion: The high precision of aorta-derived IDIFs suggests that IDIFs are a reliable alternative to manual blood sampling for dynamic ¹⁸F-FDG PET imaging on a LAFOV PET/CT system. Using IDIFs reduces variability, simplifies protocols, minimizes radiation exposure, and enhances patient safety with a non-invasive approach.

Background and objective: This study aimed to assess the impact of upsampling and downsampling techniques on the noise characteristics and similarity metrics of scintigraphic images in nuclear medical imaging.

Methods: A physical phantom study using dynamic imaging was used to generate reproducible static images of varying count statistics. Naïve upsampling and downsampling with linear interpolation were compared against alternative methods based on the preservation of Poisson count statistics and principles of nuclear scintigraphic imaging; namely, linear interpolation with a Poisson resampling correction (upsampling) and a sliding window summation method (downsampling). For each resizing method, we computed the similarity of resized images to count-matched images acquired at the target grid size with the structural similarity index measure and the logarithm of the mean squared error. These image quality metrics were subsequently compared to those of two independent count-matched images at the target grid size (representing variance due to natural noise permutations) as a reference to establish an optimal resizing method.

Results: Only upsampled images with the Poisson resampling correction after linear interpolation produced images that were similar to those acquired at the target grid size. For downsampling, both linear interpolation and sliding window summation yielded similar outcomes for a reduction factor of 2. However, for a reduction factor of 4, only sliding window summation resulted in image similarity metrics in agreement with those at the target grid size.

Conclusions: The study underlines the importance of applying appropriate resizing techniques in nuclear medical imaging to produce realistic images at the target grid size.