Annals of Nuclear Medicine最新文献

Aim: Conventional imaging techniques and prostate-specific antigen (PSA) values are not useful to follow-up patients during Radium-223 treatment. The study aimed to evaluate the predictive value of prostate-specific membrane antigen PSMA PET/CT-based response in patients with metastatic castration-resistant prostate cancer (mCRPC) receiving Radium-223 dichloride treatment.

Materials and methods: Patients treated with radium-223, having performed two ⁶⁸Ga-PSMA-11 PET/CT scans (baseline 1 month before treatment initiation and follow-up 2 weeks after the third cycle), were retrospectively evaluated. Visual and quantitative PET image analyses were performed, and patients were dichotomized into progressive (PD) and non-PD according to Response Evaluation Criteria in PSMA‑imaging (RECIP1.0) and PSMA-PET Progression criteria (PPP). The primary endpoint was overall survival (OS). Cohen's Kappa (κ) was used to test the agreement between the two criteria. The Cox regression hazard model and Kaplan-Meier method were used for survival analyses.

Results: Twenty-eight mCRPC patients were evaluated. Sixteen (43%) and 18 (64%) patients had PD according to RECIP1.0 and PPP, respectively; κ = 0.85 (95% CI 0.65-1.00). After a median follow-up of 16 months (interquartile IQR 9-33), 20 (71%) patients died. Patients with PSMA PD showed a higher risk of death than non-PD according to RECIP1.0 (HR = 2.9; 95% CI 1.14-7.46; p = 0.029) and PPP (HR = 2.8; 95% CI 1.04-7.64; p = 0.042). For both criteria, the median OS was shorter for PD than non-PD (37 vs. 12 months, Log-rank; p < 0.05). The C-index for RECIP1.0 and PPP were almost equal (0.66 and 0.63; respectively).

Conclusion: This study demonstrated that PSMA-PET/CT imaging is valuable for monitoring radium-223 treatment. Both PSMA PET/CT response criteria (RECIP1.0 and PPP) perform similarly predicting OS at follow-up after three cycles of radium-223. These findings urge further validation in prospective trials.

Objective: Dead-time loss is reported to be non-negligible for some patients with a high tumor burden in Lu-177 radionuclide therapy, even if the administered activity is 7.4 GBq. Hence, we proposed a simple method to shorten the apparent dead time and reduce dead-time loss using a thin lead sheet in previous work. The collimator surface of the gamma camera was covered with a lead sheet in our proposed method. While allowing the detection of 208-keV gamma photons of Lu-177 that penetrate the sheet, photons with energies lower than 208 keV, which cause dead-time loss, were shielded. In this study, we evaluated the usefulness of tungsten functional paper (TFP) for the proposed method using Monte Carlo simulation.

Methods: The count rates in imaging of Lu-177 administered to patients were simulated with the International Commission on Radiological Protection (ICRP) 110 phantom using the GATE Monte Carlo simulation toolkit. The simulated gamma cameras with a 0.5-mm lead sheet, 1.2-mm TFP, or no filter were positioned closely on the anterior and posterior sides of the phantom. The apparent dead times and dead-time losses at 24 h after administration were calculated for an energy window of 208 keV ± 10%. Moreover, the dead-time losses at 24-120 h were analytically assessed using activity excretion data of Lu-177-DOTATATE.

Results: The dead-time loss without a filter was 5% even 120 h after administration in patients with a high tumor burden and slow excretion, while those with a lead sheet and TFP were 0.22 and 0.58 times less than those with no filter, respectively. The count rates with the TFP were 1.3 times higher than those with the lead sheet, and the TFP could maintain primary count rates at 91-94% of those without a filter.

Conclusions: Although the apparent dead time and dead-time loss with the lead sheet were shorter and less than those with TFP, those with TFP were superior to those without a filter. The advantage of TFP over the lead sheet is that the decrease in primary count rates was less.

Background: Brain-dedicated positron emission tomography (PET) systems offer high spatial resolution and sensitivity for accurate clinical assessments. Attenuation correction (AC) is important in PET imaging, particularly in brain studies. This study assessed the reproducibility of attenuation maps (µ-maps) generated by a specialized time-of-flight (TOF) brain-dedicated PET system for imaging using different PET tracers.

Methods: Twelve subjects underwent both ¹⁸F-fluorodeoxyglucose (FDG)-PET and ¹⁸F-flutemetamol (FMM) amyloid-PET scans. Images were reconstructed with µ-maps obtained by a maximum likelihood-based AC method. Voxel-based and region-based analyses were used to compare µ-maps obtained with FDG-PET versus FMM-PET; FDG-PET images reconstructed using an FDG-PET µ-map (FDG × FDG) versus those reconstructed with an FMM-PET µ-map (FDG × FMM); and FMM-PET images reconstructed using an FDG-PET µ-map (FMM × FDG) versus those reconstructed with an FMM-PET µ-map (FMM × FMM).

Results: Small but significant differences in µ-maps were observed between tracers, primarily in bone regions. In the comparison between the µ-maps obtained with FDG-PET and FMM-PET, the µ-maps obtained with FDG-PET had higher µ-values than those obtained with FMM-PET in the parietal regions of the head and skull, in a portion of the cerebellar dentate nucleus and on the surface of the frontal lobe. The comparison between FDG and FDG × FMM values in different regions yielded findings similar to those of the µ-maps comparison. FDG × FMM values were significantly higher than FDG values in the bilateral temporal bones and a small part of the temporal lobe. Similarly, FMM values were significantly higher than FMM × FDG values in the bilateral temporal bones. FMM × FDG values were significantly higher than FMM values in a small area of the right cerebellar hemisphere. However, the relative errors in these µ-maps were within ± 4%, suggesting that they are clinically insignificant. In PET images reconstructed with the original and swapped µ-maps, the relative errors were within ± 7% and the quality was nearly equivalent.

Conclusion: These findings suggest the clinical reliability of the AC method without an external radiation source in TOF brain-dedicated PET systems.

Introduction: Stereotactic ablative body radiotherapy (SABR) is a standard treatment option for patients with malignant pulmonary masses (including primary and metastatic lesions) who are unfit for surgery or who are medically operable but refuse surgery. Flourine-18 flurodeoxyglucose positron emission tomography (¹⁸F-FDG PET) volumetric metabolic parameters, i.e., metabolic tumour volume (MTV) and total lesion glycolysis (TLG) play an important role in assessing the biological characteristics of some tumours and its role as potential prognostic factors has also been introduced.

Objectives: The aim of this retrospective study is to assess the value of baseline metabolic volumetric parameters as prognostic imaging biomarkers in patients with pulmonary masses/nodules treated with SABR.

Methods: 70 patients were included in this retrospective study (39 male and 31 female, age range 47-91 years, mean 76 years). Standardized uptake value (SUVmax), SUVmean, MTV and TLG for all the patients were calculated on baseline ¹⁸F-FDG PET/CT. Patient outcome was divided into 3 categories free of disease, stable disease and disease progression.

Results: There was no significant statistical difference in the SUVmax and SUVmean in all the three categories. Mean SUVmax ranges from 7.13 to 8.08 with its highest value in the stable disease and lowest value in the progressive disease categories. Similarly, the average SUVmean was 4.9 in the free of disease category and 4.68 in the progressive disease category. MTV and TLG were low in the free of disease and the highest in progressive disease. MTV increased from 2.25 cm³ in free of disease category to 3.23 cm³ and 7.29 cm³ in stable disease and progressive disease, respectively. TLG has increased from 11.7 in the disease-free survival category to 18.77 and 40.39 in the stable and progressive disease, respectively. Patients with low MTV had longer overall survival (OS) than patients with high MTV (37 months versus 27 months, p value = 0. 0018). In addition, OS was longer in patients with low TLG (36 months versus 24 months, p value = 0.016).

Conclusions: TLG and MTV are more useful than SUVmax and SUVmean for predicting outcome, OS and progression-free survival (PFS) in patients receiving SABR. The TLG and MTV measurement on ¹⁸F-FDG PET imaging may be routinely recommended in baseline ¹⁸F-FDG PET/CT prior to SABR.

Objective: The purpose of this study was to validate the concordance of visual ratings of [18F] flutemetamol amyloid positron emission tomography (PET) images and to investigate the correlation between the agreement of each rater and the Centiloid (CL) scale.

Methods: A total of 192 participants, clinically classified as cognitively normal (CN) (n = 59), mild cognitive impairment (MCI) (n = 65), Alzheimer's disease (AD) (n = 55), or non-AD dementia (n = 13), participated in this study. Three experts conducted visual ratings of the amyloid PET images for all 192 patients, assigning a confidence level to each rating on a three-point scale (certain, probable, or neither). The positive or negative determination of amyloid PET results was made by majority vote. The CL value was calculated using the CapAIBL pipeline.

Results: Overall, 101 images were determined to be positive, and 91 images were negative. Of the 101 positive images, the three raters were in complete agreement for 92 images and in disagreement for 9 images. Of the 91 negative images, the three raters were in complete agreement for 75 images and in disagreement for 16 images. Interrater reliability among the three experts was particularly high, with both Fleiss' kappa and Conger's kappa measuring 0.83 (0.76-0.89). The CL values of the unanimous positive group were significantly greater than those of the other groups, whereas the CL values of the unanimous negative group were significantly lower than those of the other groups. Images with rater disagreement had intermediate CLs. In cases with a high confidence level, the positive or negative visual ratings were in almost complete agreement. However, as confidence levels decreased, experts' visual ratings became more variable. The lower the confidence level was, the greater the number of cases with disagreement in the visual ratings.

Conclusion: Three experts independently rated 192 amyloid PET images, achieving a high level of interrater agreement. However, in patients with intermediate amyloid accumulation, visual ratings varied. Therefore, determining positive and negative decisions in these patients should be performed with caution.

Objectives: The use of ¹⁸F-Sodium fluoride (NaF) PET/CT is established in the detection of metastatic bone disease, yet its utility in osteoporosis remains underexplored. This research aims to assess the variations in ¹⁸F-NaF uptake among individuals with differing bone mineral density (BMD) and to examine the relationship between ¹⁸F-NaF uptake and BMD.

Methods: In this retrospective study, 199 patients (average age 56 ± 6, comprising 52 males and 147 females) with a history of cancer were analyzed. Each participant underwent both ¹⁸F-NaF PET/CT and lumbar dual-energy X-ray absorptiometry (DXA) scans within a span of 7 days. Based on DXA outcomes, patients and their lumbar vertebrae were categorized into normal BMD, osteopenia, and osteoporosis groups. The lumbar ¹⁸F-NaF uptake across these groups were compared, and to explore the association between lumbar standardized uptake values (SUV) values and BMD. The efficacy of ¹⁸F-NaF uptake in diagnosing osteoporosis or osteopenia was also evaluated. Analysis was conducted using Mann-Whitney U tests, Spearman regression, and receiver operating characteristic (ROC) curve analysis through GraphPad Prism 10.0.

Results: A total of 796 lumbar vertebrae from 199 patients were measured. It was observed that osteoporotic patients had significantly lower ¹⁸F-NaF uptake than those with osteopenia and normal BMD across the L1-L4 lumbar vertebrae (P < 0.0001). In a vertebra-based analysis, normal BMD vertebrae exhibited the highest maximum SUV(SUV_max) compared to osteopenic (8.13 ± 1.28 vs. 6.61 ± 1.01, P < 0.0001) and osteoporotic vertebrae (8.13 ± 1.28 vs. 4.82 ± 1.01, P < 0.0001). There was a positive correlation between lumbar ¹⁸F-NaF uptake and BMD across all vertebrae, with correlation coefficients exceeding 0.5 (range: 0.57-0.8). The area under the ROC curve values were notably high, at 0.96 for osteoporosis and 0.83 for osteopenia diagnosis.

Conclusion: This study demonstrates distinct ¹⁸F-NaF uptake patterns among individuals with varying BMD levels, with a positive correlation between ¹⁸F-NaF uptake and BMD. These findings highlight the potential of ¹⁸F-NaF PET/CT as a supportive diagnostic method in the management of osteoporosis.

Background: The efficacy of a second radioactive iodine-131 (¹³¹I) treatment in patients with differentiated thyroid cancer (DTC) who did not achieve an excellent response (ER) following initial ¹³¹I therapy remains controversy and the population that would derive limited benefit from it is currently unclear.

Objectives: The aim of this retrospective study was to assess the efficacy of the second ¹³¹I treatment in DTC patients with non-ER after the initial ¹³¹I therapy, and to identify potential risk factors associated with non-benefit of the second ¹³¹I treatment.

Methods: 127 DTC patients who underwent two ¹³¹I treatments following thyroidectomy were included in this study, and the therapeutic response was evaluated after each ¹³¹I treatment. Beneficial treatment was defined as an improvement in therapy response grade (e.g. from indeterminate response to ER) after the second ¹³¹I treatment, while unbeneficial treatment was defined as no change or a downgrade in therapy response grade. The potential risk factors associated with the non-benefit of the second ¹³¹I treatment were identified using univariate and multivariate logistic regression models.

Results: Following the second ¹³¹I treatment, therapy responses of 55.12% (70/127) of patients were reclassified to a better grade indicating treatment benefit, while 44.88% (57/127) showed no change or were reclassified to a worse grade suggesting no benefit from treatment. The non-benefit of the second ¹³¹I treatment was significantly associated with potential risk factors including stimulated thyroglobulin (sTg) level ≥ 11.46 ng/mL before the second ¹³¹I treatment, primary tumor size > 2 cm, status T2 or higher, N1b status and ATA high risk.

Conclusions: The study results demonstrated that more than half of DTC patients could potentially benefit from a second ¹³¹I therapy. However, over 40% of patients exhibited no benefit in response to the second ¹³¹I treatment, suggesting potential overtreatment for this subgroup. Therefore, clinicians should exercise meticulous and precise decision-making based on identified risk factors when considering the necessity of a second ¹³¹I treatment.