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This article discusses a case study of a 35-year-old man with a history of uraemia who presented with increased tumor marker levels. The patient underwent both [18F]F-FDG PET/CT and [68 Ga]Ga-FAPI-04 total-body PET/CT scans. The [18F]F-FDG PET/CT showed increased FDG uptake in osteogenic destructive bones and extensive calcification, while the [68 Ga]Ga-FAPI-04 PET/CT revealed FAPI uptake in the same lesions as well as additional abnormal foci. The study suggests that FAPI PET/CT may be superior to FDG PET/CT in diagnosing and assessing kidney fibrosis and related calcium phosphorus metabolism disorders in chronic kidney disease. [Extracted from the article]

Background: [68Ga]Ga-FAPI-04 (gallium-68-labeled fibroblast activation protein inhibitor-04) PET/CT has been widely used in diagnosing malignant tumors. Total-body PET/CT has a long axial field of view and provides higher sensitivity compared to traditional PET/CT. However, whether the reduced injected dose of [68Ga]Ga-FAPI-04 could obtain qualified imaging has not been evaluated. Purpose: To explore the effect of half-dose [68Ga]Ga-FAPI-04 on image quality and tumor detectability in oncology patients. Methods: A total of twenty-seven patients with tumors or clinically suspected tumors were included, and all patients were scanned with total-body PET/CT after an injected dose of 0.84–1.14 MBq/kg [68Ga]Ga-FAPI-04. All patients obtained superior image quality with 300 s original acquisition time. Images were reconstructed using 180 s, 120 s, 60 s, 40 s, 30 s, 20 s scanning duration by ordered subset expectation maximization algorithm. The subjective image quality of all patients in each time group was scored using 5-point Likert scale. Mediastinal blood pool, liver, spleen, and muscle were analyzed as background using semi-quantitative parameters maximum standardized uptake values (SUVmax), mean standardized uptake values (SUVmean), standard deviation (SD), and signal to noise ratio (SNR). The lesion detection rate, SUVmax, and tumor-to-background ratio (TBR) were calculated for tumors confirmed by pathology. Results: The subjective image quality score decreased with the shortening of scanning time; however, both 180 s and 120 s images met the diagnostic requirements in terms of overall quality, lesion conspicuity, and image noise. The SUVmax of background increased with the reduction of scanning time, while the SUVmean was relatively stable. With the shortening of scanning time, the SD gradually increased, and the SNR gradually decreased, which was consistent with subjective image quality scores. In 180 s and 120 s images, all 11 primary lesions and 79 metastatic lesions were detected. The SUVmax of tumor focus showed an increasing trend as same as the background. Compared with 300 s, the TBR muscle had no statistical difference in 180 s and 120 s. Conclusions: Half-dose [68Ga]Ga-FAPI-04 in total-body PET/CT imaging can shorten the acquisition time to 120 s with acceptable subjective image quality and 100% tumor detection rate. Total-body PET/CT imaging with a half-dose [68Ga]Ga-FAPI-04 and reduced acquisition time can be used in radiation-sensitive and poor tolerant to prolong horizontal positioning and waiting time populations such as children and gravidas. [ABSTRACT FROM AUTHOR]

Purpose: Multiple myeloma (MM) is a malignant disease characterized by the secretion of monoclonal immunoglobulins and has a high demand for amino acids. [11C]methionine total-body PET is capable of noninvasive dynamic monitoring of radiotracer in vivo, thus providing a way to reveal the dynamic changes of myeloma metabolism. This study aims to analyze the metabolic process of [11C]methionine based on kinetic modeling, and to preliminary reveal its application value in MM. Methods: Dynamic total-body [11C]methionine PET/CT was conducted with uEXPLORER in 12 subjects (9 MM patients and 3 controls). The tissue time activity curves (TACs) of organs and bone marrows were extracted. Model fitting of TACs was operated using PMOD Kinetic Modeling. After validation by Goodness of fit (GOF), the reversible two-tissue compartment model (2T4k) was used to further analysis. R software was used to analyze the correlation between kinetic parameters and clinical indicators. Results: The 2T4k has passed the criterion of GOF and was used to fit the data of 0-20 minutes. The [11C]methionine net uptake rate (Ki) was significantly higher in the MM lesions than in the non-myeloma controls (control: 0.040±0.007 mL/g/min, MM: 0.171±0.108 mL/g/min, p=0.009). The Ki values were found to be correlated with M protein levels in MM patients. MM patients with t(4;14) translocations had an elevated k4 value compared with t(4;14) negative patients. Conclusion: MM lesions have a propensity for uptake of [11C]methionine. The serum levels of M protein are correlated with [11C]methionine uptake rate in myeloma. Metabolic classification based on the k4 value may be a promising strategy for risk stratification in MM. [ABSTRACT FROM AUTHOR]

Purpose: [68 Ga]Ga-FAPI-04 PET/CT has been widely used in oncology patients. The patients need to lie still for 20–30 min during scan after waiting for 60 min post-tracer injection in traditional [68 Ga]Ga-FAPI-04 PET/CT scan. This is difficult for some patients who are intolerant to prolonged horizontal positioning and waiting time. Therefore, we evaluated the diagnostic value of the images obtained in ultra-early and fast scan (5-min p.i., 30-s acquisition time) by the total-body [68 Ga]Ga-FAPI-04 PET/CT and to investigate whether they could meet the requirements of clinical diagnosis. Methods: Total-body [68 Ga]Ga-FAPI-04 PET/CT was conducted in 12 patients at the Renji Hospital. Patients underwent PET with two acquisitions: 5-min p.i. and 30-s acquisition time (ultra-early and fast imaging) and 60-min p.i. and 300-s acquisition time (traditional imaging). Mean [68 Ga]Ga-FAPI-04 injection dose was 1.85 MBq/kg. Results: Forty-four lesions were detected in 12 patients on traditional imaging. All the 44 lesions on conventional imaging could also detected by ultra-early and fast imaging. For all the 12 patients, the tumor stage did not change, as same lesions were visible for every case in both images. There was no statistically significant difference in SUVmax of lesions between ultra-early and fast imaging and traditional imaging (12.5 ± 8.7 vs 13.7 ± 8.5, P = 0.528). Background bloodpool (4.0 ± 0.6 vs 0.9 ± 0.2, P < 0.001)and liver (2.5 ± 0.7 vs 1.0 ± 0.5, P < 0.001)at traditional imaging showed a significant decrease in SUVmean compared to ultra-early and fast imaging. Conclusions: Ultra-early and fast imaging versus traditional [68 Ga]Ga-FAPI-04 imaging resulted in equivalent tumor detection and lesion uptake. Ultra-early and fast total-body [68 Ga]Ga-FAPI-04 PET/CT scan could meet clinical diagnostic requirements for patients with poor tolerant to prolonged horizontal positioning and waiting time. [ABSTRACT FROM AUTHOR]

Background: 68 Ga-PSMA PET/CT has been widely used in patients with prostate cancer. Due to the limited axial field of view of conventional PET scanners, whole-body dynamic 68 Ga-PSMA PET/CT has not been performed. We investigated the time-activity curves (TACs) of prostate cancer pathological lesions and physiologic bladder activity to determine the optimal 68 Ga-PSMA PET/CT imaging time by total-body (TB) PET/CT. Methods: Dynamic TB-PET performed on 11 patients with prostate cancer was analyzed. TACs were obtained by drawing regions of interest in normal organs and pathological lesions (primary prostate lesions and lymph nodes and bone metastases). We evaluated the 68 Ga-PSMA uptake pattern of normal organs, urinary bladder, and pathological lesions. Results: The urinary bladder TAC increased slowly between 180 and 330 s post-injection and then rapidly between 5.5 and 60.0 min post-injection. The pathological lesion uptake increased rapidly during the first 5 min post-injection and then slowly through the remaining 55 min. Six minutes post-injection was the optimal time with the highest pathological lesion SUVmean values still higher than the urinary bladder activity value. However, these prostate lesion, lymph node metastasis, and bone metastasis SUVmean values were one-third, one-half, and one-half the corresponding values 60 min post-injection, suggesting that early imaging might miss low PSMA uptake lesions. A minimum of 35 min post-injection was required for the pathological lesions to have SUVmean values similar to the corresponding values at 60 min post-injection (all P > 0.05), even though the pathological lesion SUVmean values showed a continuous upward trend through the 60 min. Conclusions: Combining early dynamic 68 Ga-PSMA PET (75–360 s) and conventional static imaging 60 min post-injection could avoid the urinary bladder activity interference to better detect pathological lesions and lesions with relatively low PSMA uptake. The pathological lesion SUVmean values at 35–59 min and 60 min post-injection were similar, so 68 Ga-PSMA PET imaging could also be made at 35–59 min post-injection. [ABSTRACT FROM AUTHOR]

Purpose: Multiple myeloma (MM) remains incurable and its diagnosis relies heavily on bone marrow aspiration and biopsy. CD38 is a glycoprotein highly specific for MM. Antibody therapeutics (e.g., daratumumab) targeting CD38 have shown encouraging efficacy in treating MM, either as a monotherapy agent or in combination with other regimens. However, efficient stratification of patients who might benefit from daratumumab therapy and timely monitoring of the therapeutic responses are still clinical challenges. This work aims to devise a CD38-targeted imaging strategy and assess its value in diagnosing MMs. Methods: By labeling a CD38-specific single domain antibody (Nb1053) with 68Ga (t1/2 = 1.1 h), we developed a CD38-targeted immuno-positron emission tomography (immunoPET) imaging probe [68Ga]Ga-NOTA-Nb1053. The probe was developed with good radiochemical yield (> 50%), excellent radiochemical purity (> 99%), and immunoreactivity (> 95%). The diagnostic accuracy of the probe was thoroughly investigated in preclinical MM models. Results: ImmunoPET imaging with [68Ga]Ga-NOTA-Nb1053 specifically depicted all the subcutaneous and orthotopic MM lesions, outperforming the traditional 18F-fluorodeoxyglucose PET and the nonspecific [68Ga]Ga-NOTA-NbGFP immunoPET. More importantly, daratumumab preloading significantly reduced [68Ga]Ga-NOTA-Nb1053 uptake in the disseminated bone lesions, indicating the overlapping targeting epitopes of [68Ga]Ga-NOTA-Nb1053 with that of daratumumab. Furthermore, premedication with sodium maleate or fructose significantly decreased kidney retention of [68Ga]Ga-NOTA-Nb1053 and improved the diagnostic value of the probe in lymphoma models. Conclusion: This work successfully developed a novel CD38-targeted immunoPET imaging approach that enabled precise visualization of CD38 and diagnosis of MMs. Upon clinical translation, [68Ga]Ga-NOTA-Nb1053 immunoPET may serve as a valuable CD38-targeted molecular imaging toolbox, facilitating early diagnosis of MM and precise assessment of the therapeutic responses. [ABSTRACT FROM AUTHOR]