Dosimetry during iodine-131 therapy - a technical point of view from a single centre's own experience.

BACKGROUND: Nuclear medicine uses radionuclides in medicine for diagnosis, staging, therapy, and monitoring the response to therapy. The application of radiopharmaceutical therapy for the treatment of certain diseases is well-established, and the field is expanding. Internal dosimetry is multifaceted and includes different workflows, as well as various calculations based on patient- specific dosimetry. AIM: The objective of this study was to introduce the technical issues which might occur during iodine-131 (¹³¹I) dosimetry performed in nuclear medicine departments. MATERIAL AND METHODS: Retrospective analysis was performed on a group of 44 patients with papillary thyroid cancer who between May 2021 and October 2021 underwent a 131I treatment: 80-100 mCi (2200-3700 MBq, based on the previous medical history and stage of the disease). Patients underwent a series of ¹³¹I therapy scans using gamma camera Discovery NM 670 CT. Whole body scan (WBS) was performed 2, 4, 24 and 48 hours after ¹³¹I administration. Additionally, after 24 hours of single photon emission computed tomography/ computed tomography, two fields of view (SPECT/CT 2-FOV) were performed from the mid-head to the bladder. RESULTS: During the dosimetry procedure, several issues arise. Firstly, after receiving therapeutic doses of ¹³¹I, patients should remain in their rooms until the appropriate activity is achieved before being transported to the diagnostic room. Secondly, the walls between examination rooms meet the requirements for accurate diagnosis but not for therapy, leading to the occurrence of artefacts in patients examined behind the wall, potentially influencing the examination results. Thirdly, personnel in the control room also experience additional exposure (10 times greater than in the case of standard diagnostic procedure). CONCLUSIONS: The dosimetry in patients in whom therapeutic procedures are performed with the use of isotopes is mandatory according to Polish and European law, technical issues which occur during the dosimetry procedures might influence the organization of the work in departments.

Comparison of diagnostic efficacy between 99mTc-methylene diphosphate SPECT/CT and MRI for bone and joint infections: a multicenter retrospective analysis.

Objective: There is currently no non-invasive examination that can fully determine the diagnosis of osteomyelitis. SPECT/CT tomographic fusion imaging can provide both local metabolic activity and anatomical information to determine the condition and location. This study evaluates the diagnostic efficacy of 99mTc-MDP SPECT/CT in bone infections, compared to MRI. Methods: In this multicenter retrospective study, 363 patients with suspected bone and joint infections or osteomyelitis were included. Participants underwent 99mTc-MDP SPECT/CT and/or MRI examinations, supplemented by pathogenic bacterial cultures and histopathological analysis. Results: Only SPECT/CT was tested in 169 patients, and only MRI was used in 116. 78 people have implemented both inspections and have detailed information. The diagnostic sensitivity and specificity of SPECT/CT for infection were 96% and 92% respectively, with an accuracy of 96%. For MRI, these figures were 88%, 84%, and 87% respectively. Conclusion: This represents the largest global study to date evaluating osteomyelitis and bone infection diagnosis using 99mTc-MDP SPECT/CT tomographic fusion imaging. The findings indicate that 99mTc-MDP SPECT/CT fusion imaging offers superior diagnostic accuracy compared to MRI. This is particularly evident in cases involving metallic implants and chronic infections. 99mTc-MDP SPECT/CT fusion imaging emerges as a highly suitable non-invasive diagnostic modality, facilitating enhanced clinical follow-up and treatment.

Deep learning approach for automated segmentation of myocardium using bone scintigraphy single-photon emission computed tomography/computed tomography in patients with suspected cardiac amyloidosis.

BACKGROUND: We employed deep learning to automatically detect myocardial bone-seeking uptake as a marker of transthyretin cardiac amyloid cardiomyopathy (ATTR-CM) in patients undergoing 99mTc-pyrophosphate (PYP) or hydroxydiphosphonate (HDP) single-photon emission computed tomography (SPECT)/computed tomography (CT). METHODS: We identified a primary cohort of 77 subjects at Brigham and Women's Hospital and a validation cohort of 93 consecutive patients imaged at the University of Pennsylvania who underwent SPECT/CT with PYP and HDP, respectively, for evaluation of ATTR-CM. Global heart regions of interest (ROIs) were traced on CT axial slices from the apex of the ventricle to the carina. Myocardial images were visually scored as grade 0 (no uptake), 1 (uptakeribs). A 2D U-net architecture was used to develop whole-heart segmentations for CT scans. Uptake was determined by calculating a heart-to-blood pool (HBP) ratio between the maximal counts value of the total heart region and the maximal counts value of the most superior ROI. RESULTS: Deep learning and ground truth segmentations were comparable (p=0.63). A total of 42 (55%) patients had abnormal myocardial uptake on visual assessment. Automated quantification of the mean HBP ratio in the primary cohort was 3.1±1.4 versus 1.4±0.2 (p<0.01) for patients with positive and negative cardiac uptake, respectively. The model had 100% accuracy in the primary cohort and 98% in the validation cohort. CONCLUSION: We have developed a highly accurate diagnostic tool for automatically segmenting and identifying myocardial uptake suggestive of ATTR-CM.

Deep transformer-based personalized dosimetry from SPECT/CT images: a hybrid approach for [177Lu]Lu-DOTATATE radiopharmaceutical therapy.

PURPOSE: Accurate dosimetry is critical for ensuring the safety and efficacy of radiopharmaceutical therapies. In current clinical dosimetry practice, MIRD formalisms are widely employed. However, with the rapid advancement of deep learning (DL) algorithms, there has been an increasing interest in leveraging the calculation speed and automation capabilities for different tasks. We aimed to develop a hybrid transformer-based deep learning (DL) model that incorporates a multiple voxel S-value (MSV) approach for voxel-level dosimetry in [177Lu]Lu-DOTATATE therapy. The goal was to enhance the performance of the model to achieve accuracy levels closely aligned with Monte Carlo (MC) simulations, considered as the standard of reference. We extended our analysis to include MIRD formalisms (SSV and MSV), thereby conducting a comprehensive dosimetry study. METHODS: We used a dataset consisting of 22 patients undergoing up to 4 cycles of [177Lu]Lu-DOTATATE therapy. MC simulations were used to generate reference absorbed dose maps. In addition, MIRD formalism approaches, namely, single S-value (SSV) and MSV techniques, were performed. A UNEt TRansformer (UNETR) DL architecture was trained using five-fold cross-validation to generate MC-based dose maps. Co-registered CT images were fed into the network as input, whereas the difference between MC and MSV (MC-MSV) was set as output. DL results are then integrated to MSV to revive the MC dose maps. Finally, the dose maps generated by MSV, SSV, and DL were quantitatively compared to the MC reference at both voxel level and organ level (organs at risk and lesions). RESULTS: The DL approach showed slightly better performance (voxel relative absolute error (RAE) = 5.28 ± 1.32) compared to MSV (voxel RAE = 5.54 ± 1.4) and outperformed SSV (voxel RAE = 7.8 ± 3.02). Gamma analysis pass rates were 99.0 ± 1.2%, 98.8 ± 1.3%, and 98.7 ± 1.52% for DL, MSV, and SSV approaches, respectively. The computational time for MC was the highest (~2 days for a single-bed SPECT study) compared to MSV, SSV, and DL, whereas the DL-based approach outperformed the other approaches in terms of time efficiency (3 s for a single-bed SPECT). Organ-wise analysis showed absolute percent errors of 1.44 ± 3.05%, 1.18 ± 2.65%, and 1.15 ± 2.5% for SSV, MSV, and DL approaches, respectively, in lesion-absorbed doses. CONCLUSION: A hybrid transformer-based deep learning model was developed for fast and accurate dose map generation, outperforming the MIRD approaches, specifically in heterogenous regions. The model achieved accuracy close to MC gold standard and has potential for clinical implementation for use on large-scale datasets.

SENTRI: Single-Particle Energy Transducer for Radionuclide Injections for Personalized Targeted Radionuclide Cancer Therapy.

PURPOSE: Targeted radionuclide therapy (TRT), whereby a tumor-targeted molecule is linked to a therapeutic beta- or alpha-emitting radioactive nuclide, is a promising treatment modality for patients with metastatic cancer, delivering radiation systemically. However, patients still progress due to suboptimal dosing, driven by the large patient-to-patient variability. Therefore, the ability to continuously monitor the real-time dose deposition in tumors and organs at risk provides an additional dimension of information during clinical trials that can enable insights into better strategies to personalize TRT. METHODS AND MATERIALS: Here, we present a single beta-particle sensitive dosimeter consisting of a 0.27-mm3 monolithic silicon chiplet directly implanted into the tumor. To maximize the sensitivity and have enough detection area, minimum-size diodes (1 µm2) are arrayed in 64 × 64. Signal amplifiers, buffers, and on-chip memories are all integrated in the chip. For verification, PC3-PIP (prostate-specific membrane antigen [PSMA]+) and PC3-flu (PSMA-) cell lines are injected into the left and right flanks of the mice, respectively. The devices are inserted into each tumor and measure activities at 5 different time points (0-2 hours, 7-9 hours, 12-14 hours, 24-26 hours, and 48-50 hours) after 177Lu-PSMA-617 injections. Single-photon emission computed tomography/computed tomography scans are used to verify measured data. RESULTS: With a wide detection range from 0.013 to 8.95 MBq/mL, the system is capable of detecting high tumor uptake as well as low doses delivered to organs at risk in real time. The measurement data are highly proportional (R2 > 0.99) to the 177Lu-PSMA-617 activity. The in vivo measurement data agree well with the single-photon emission computed tomography/computed tomography results within acceptable errors (±1.5%ID/mL). CONCLUSIONS: Given the recent advances in clinical use of TRT in prostate cancer, the proposed system is verified in a prostate cancer mouse model using 177Lu-PSMA-617.

SPECT/CT SUV-based metrics: A promising diagnostic tool in classifying patients with suspected transthyretin cardiac amyloidosis among the different Perugini grades?

OBJECTIVE: The purpose of this study was to evaluate the contribution of single photon emission computed tomography/computed tomography (SPECT/CT) standardized uptake value (SUV) metrics in classifying patients with suspected transthyretin cardiac amyloidosis (ATTR-CA) among the different Perugini grades. SUBJECTS AND METHODS: One hundred four patients suspected of ATTR-CA underwent planar scintigraphy with bone seeking tracer (99mTc pyrophosphate-PYP). Patients were classified according to the Perugini scale, the H/CL, H/Bone and H/Bkg ratios. A subset of 48 patients received additional SPECT/CT. Single photon emission computed tomography/CT SUV quantitative parameters, of the heart, myocardium, lungs, liver, soft tissues, bone, and SUV ratios (SUVmaxmyo, SUVmaxlungs, SUVmaxliver, SUVmaxbone and SUVmaxsoft tissue ratios), were evaluated in order to investigate potential metrics that could more clearly differentiate Perugini grades. RESULTS: A total of 33.7% of patients were considered grade 0, 34.6% grade 1 and 31.7% grade 2/3. A combination of H/CL >1.33 and H/Bone >0.85 showed the highest sensitivity 100%. Standardized uptake value-based metrics clearly differentiated grade 0 or 1 vs grades 2 or 3, whereas no significant difference was found between grades 0 and 1, or between grades 1 and 2. The combined cut-off values H/CL 1.33 and SUVmaxmyo 2.88 yielded 100% sensitivity and 84.6% specificity in differentiating ATTR-CA positives vs negatives. The metric SUVmaxmyo/SUVmaxliver was the best metric to classify patients with grade 1 as negative (grade 0) or positive (grade 2 or 3). CONCLUSION: Single photon emission computed tomography/CT SUV metrics could be complementary to planar scintigraphy in classifying patients among the different Perugini grades. The ratio SUVmaxmyo/SUVmaxliver was the only parameter with high affinity to differentiate patients with grade 1, as grade 0 or grade 2/3 for ATTR-CA.

3D-Quantitated Single Photon Emission Computed Tomography/Computed Tomography: Impact on intended Management Compared to Lung Perfusion Scan in Marginal Candidates for Pulmonary Resection.

OBJECTIVES: Based on previous studies, single-photon emission computed tomography/computed tomography (SPECT/CT) has been proven more accurate and reproducible than planar lung perfusion scintigraphy to assess lobar perfusion. However, the impact of 3D-quantitated SPECT/CT on intended management in functionally marginal candidates for pulmonary resection is unknown. The evaluation of this impact was the main aim of this study. METHODS: Consecutive candidates for lung resection underwent preoperative evaluation according to ERS/ESTS Algorithm and underwent preoperative lung perfusion imaging. The lobar contribution to the total lung perfusion was estimated using established planar scintigraphic methods and 3-dimensional quantitative SPECT/CT method (CT Pulmo3D and xSPECT-Quant, Siemens). The difference in estimated lobar perfusion with resulting changes in predicted postoperative (ppo) lung function and extent of lung resection were analyzed to reveal possible changes in operability. In-hospital outcome was assessed. RESULTS: One hundred twenty patients (46 females) were enrolled. The mean age (±SD) of patients was 68 ± 9 years, target lesions were in upper lobes in 57.7% and in lower lobes in 33.5%. The median FEV1 (forced expiratory volume in 1 second) was 70.5% (IQR 52-84) and median DLCO (diffusion capacity of lung for carbon monoxide) was 56.6% [47.1-67.4]. The planar posterior oblique method, compared to 3D-quantitated SPECT/CT, underestimated the perfusion of upper lobes by a median difference of 5% (right [2-9], left [2.5-8]; P = <.0001), while it overestimated the perfusion of lower lobes (left by 4% [2-7], right by 6% [2-9]; P = <.0001). In contrast to planar scintigraphy-based evaluation, 4 patients (3.3%), all with upper lobe lesions, were classified as inoperable when 3D-quantitated SPECT/CT was used for calculation of the ppo lung function. CONCLUSIONS: In selected patients with upper lobe lesions, 3D-quantitated SPECT/CT would have changed the treatment strategy from operable to inoperable. Importantly, postoperative mortality in this particular subgroup was disproportionally high. 3D-quantitated SPECT/CT shall be further evaluated as it might improve preoperative risk stratification in functionally marginal candidates.

[18F]MFBG PET/CT outperforming [123I]MIBG SPECT/CT in the evaluation of neuroblastoma.

PURPOSE: Iodine 123 labeled meta-iodobenzylguanidine ([123I]MIBG) scan with SPECT/CT imaging is one of the most commonly used imaging modalities in the evaluation of neuroblastoma. [18F]-meta-fluorobenzylguanidine ([18F]MFBG) is a novel positron emission tomography (PET) tracer which was reported to have a similar biodistribution to [123I]MIBG. However, the experience of using [18F]MFBG PET/CT in the evaluation of patients with neuroblastoma is limited. This preliminary investigation aims to assess the efficacy of [18F]MFBG PET/CT in the evaluation of neuroblastomas in comparison to [123I]MIBG scans with SPECT/CT. MATERIALS AND METHODS: In this prospective, single-center study, 40 participants (mean age 6.0 ± 3.7 years) with history of neuroblastoma were enrolled. All children underwent both [123I]MIBG SPECT/CT and [18F]MFBG PET/CT studies. The number of lesions and the Curie scores revealed by each imaging method were recorded. RESULTS: Six patients had negative findings on both [123I]MIBG and [18F]MFBG studies. Four of the 34 patients (11.8%) were negative on [123I]MIBG but positive on [18F]MFBG, while 30 patients were positive on both [123I]MIBG and [18F]MFBG studies. In these 34 patients, [18F]MFBG PET/CT identified 784 lesions while [123I]MIBG SPECT/CT detected 532 lesions (p < 0.001). The Curie scores obtained from [18F]MFBG PET/CT (11.32 ± 8.18, range 1-27) were statistically higher (p < 0.001) than those from [123I]MIBG SPECT/CT (7.74 ± 7.52, range 0-26). 30 of 34 patients (88.2%) with active disease on imaging had higher Curie scores based on the [18F]MFBG study than on the [123I]MIBG imaging. CONCLUSION: [18F]MFBG PET/CT shows higher lesion detection rate than [123I]MIBG SPECT/CT in the evaluation of pediatric patients with neuroblastoma. CLINICAL TRIAL REGISTRATION: Clinicaltrials.gov : NCT05069220 (Registered: 25 September 2021, retrospectively registered); Institute Review Board of Peking Union Medical College Hospital: ZS-2514.

Emerging role of bone scintigraphy single-photon emission computed tomography/computed tomography in foot pain management.

Foot and ankle joints being weight-bearing joints are commonly subjected to wear and tear and are prone to traumatic and other pathologies. Most of these foot and ankle pathologies present with pain. The diagnosis of pathology and localization of pain generators is difficult owing to the complex anatomy of the foot and similar clinical presentation. This makes the management of foot pain clinically challenging. Conventional anatomical imaging modalities are commonly employed for evaluation of any anatomical defect; however, these modalities often fail to describe the functional significance of the anatomical lesions, especially in presence of multiple lesions which is common in ankle and foot; however, hybrid single-photon emission computed tomography/computed tomography (SPECT/CT) by virtue of its dual modalities, that is, highly sensitive functional imaging and highly specific anatomical imaging can serve as a problem-solving tool in patient management. This review attempts to describe the role of hybrid SPECT/CT in overcoming the limitation of conventional imaging and describes its potential application in the management of foot and ankle pain.

Development of [177Lu]Lu-LNC1003 for radioligand therapy of prostate cancer with a moderate level of PSMA expression.

PURPOSE: Evans blue as an albumin binder has been widely used to improve pharmacokinetics and enhance tumor uptake of radioligands, including prostate-specific membrane antigen (PSMA) targeting agents. The goal of this study is to develop an optimal Evans blue-modified radiotherapeutic agent that could maximize the absolute tumor uptake and tumor absorbed dose thus the therapeutic efficacy to allow treatment of tumors even with moderate level of PSMA expression. METHODS: [177Lu]Lu-LNC1003 was synthesized based on PSMA-targeting agent and Evans blue. Binding affinity and PSMA targeting specificity were verified through cell uptake and competition binding assay in 22Rv1 tumor model that has moderate level of PSMA expression. SPECT/CT imaging and biodistribution studies in 22Rv1 tumor-bearing mice were performed to evaluate the preclinical pharmacokinetics. Radioligand therapy studies were conducted to systematically assess the therapeutic effect of [177Lu]Lu-LNC1003. RESULTS: LNC1003 showed high binding affinity (IC50 = 10.77 nM) to PSMA in vitro, which was comparable with that of PSMA-617 (IC50 = 27.49 nM) and EB-PSMA-617 (IC50 = 7.91 nM). SPECT imaging of [177Lu]Lu-LNC1003 demonstrated significantly improved tumor uptake and retention as compared with [177Lu]Lu-EB-PSMA and [177Lu]Lu-PSMA-617, making it suitable for prostate cancer therapy. Biodistribution studies further confirmed the remarkably higher tumor uptake of [177Lu]Lu-LNC1003 (138.87 ± 26.53%ID/g) over [177Lu]Lu-EB-PSMA-617 (29.89 ± 8.86%ID/g) and [177Lu]Lu-PSMA-617 (4.28 ± 0.25%ID/g) at 24 h post-injection. Targeted radioligand therapy results showed noteworthy inhibition of 22Rv1 tumor growth after administration of a single dose of 18.5 MBq [177Lu]Lu-LNC1003. There was no obvious antitumor effect after [177Lu]Lu-PSMA-617 treatment under the same condition. CONCLUSION: In this study, [177Lu]Lu-LNC1003 was successfully synthesized with high radiochemical purity and stability. High binding affinity and PSMA targeting specificity were identified in vitro and in vivo. With greatly enhanced tumor uptake and retention, [177Lu]Lu-LNC1003 has the potential to improve therapeutic efficacy using significantly lower dosages and less cycles of 177Lu that promises clinical translation to treat prostate cancer with various levels of PSMA expression.

The impact of sentinel lymph node mapping with hybrid single photon emission computed tomography/computed tomography in patients with melanoma. Comparison to planar radioisotopic lymphoscintigraphy.

We studied the diagnostic value of 16 slices of single photon emission computed tomography (SPECT)/computed tomography (CT) in the anatomical localization, image interpretation and extra-sentinel lymph nodes (SLNs) detection compared to dynamic and static planar radioisotopic lymphoscintigraphy (PLS) in patients with melanoma. Eighty-two patients with melanoma underwent dynamic PLS, static PLS and SPECT/CT. Data were obtained using a dual head SPECT/CT 16 slices γ-camera. We evaluated the number and localization of SLNs detected with each imaging method. SPECT/CT demonstrated 48 additional SLNs in comparison with PLS in 29 patients. In five truncal and seven head-neck lesions, dynamic and static PLS failed to detect the SLNs found on SPECT/CT (false negative). In one case of truncal and one case of lower limb melanoma, the foci of increased activity interpreted on PLS as possible SLNs were confirmed to be non-nodal sites of uptake on SPECT/CT (false positive). PLS underestimated the number of SLNs detected, whereas SPECT/CT revealed higher agreement compared to the respective number from histological reports. SPECT/CT showed a better prediction of the number of SLNs and higher diagnostic parameters in comparison to planar imaging. SPECT/CT is an important complementary diagnostic modality to PLS, that improves detection, preoperative evaluation, anatomical landmarks of SLNs and surgical management of patients with melanoma.

Sub 4 minute superfast single-photon emission computed tomography/computed tomography as an add-on for problem-solving in planar bone scintigraphy: a time-saving solution for departments without whole-body single-photon emission computed tomography/computed tomography.

Whole-body bone scintigraphy remains widely used in nuclear medicine as it is a relatively inexpensive and quick test in which the whole body can be imaged with good sensitivity. However, one downside of the technique is its lack of specificity. The difficulty comes when there is a single 'hot spot' which usually requires further anatomical imaging to identify the cause and differentiate malignant from benign lesions. In this situation, hybrid imaging with single-photon emission computed tomography/computed tomography (SPECT/CT) can be a useful problem solver. The addition of SPECT/CT can however, be time-consuming, adding up to 15-20 min for every bed position required, a process that can tax the compliance of the patient and reduce the scanning capacity of the department. We report the successful implementation of a new superfast SPECT/CT protocol comprising a 1 s per view over 24 views point and shoot approach, reducing the SPECT scan time to less than 2 min and the whole SPECT/CT to under 4 min while still producing images that allow diagnostic certainty in previously equivocal lesions. This is faster than previously reported ultrafast SPECT/CT protocols. The utility of the technique is demonstrated in a pictorial review of four disparate causes of solitary bone lesions: fracture, metastasis, degenerative arthropathy and Paget's disease. This technique may prove a cost-effective problem-solving adjunct in nuclear medicine departments unable to yet offer whole-body SPECT/CT to every patient, without adding much burden to the department's gamma camera usage and patient throughput.

Monitoring tafamidis treatment with quantitative SPECT/CT in transthyretin amyloid cardiomyopathy.

AIMS: Tafamidis treatment positively affects left ventricular (LV) structure and function and improves outcomes in patients with transthyretin amyloid cardiomyopathy (ATTR-CM). We aimed to investigate the relationship between treatment response and cardiac amyloid burden identified by serial quantitative 99mTc-DPD SPECT/CT. We furthermore aimed to identify nuclear imaging biomarkers that could be used to quantify and monitor response to tafamidis therapy. METHODS AND RESULTS: Forty wild-type ATTR-CM patients who underwent 99mTc-DPD scintigraphy and SPECT/CT imaging at baseline and after treatment with tafamidis 61 mg once daily [median, 9.0 months (interquartile range 7.0-10.0)] were divided into two cohorts based on the median (-32.3%) of the longitudinal percent change in standardized uptake value (SUV) retention index. ATTR-CM patients with a reduction greater than or equal to the median (n = 20) had a significant decrease in SUV retention index (P < 0.001) at follow-up, which translated into significant benefits in serum N-terminal prohormone of brain natriuretic peptide levels (P = 0.006), left atrial volume index (P = 0.038), as well as LV [LV global longitudinal strain: P = 0.028, LV ejection fraction (EF): P = 0.027, LV cardiac index (CI): P = 0.034] and right ventricular (RV) [RVEF: P = 0.025, RVCI: P = 0.048] functions compared with patients with a decrease less than the median (n = 20). CONCLUSION: Treatment with tafamidis in ATTR-CM patients results in a significant reduction in SUV retention index, associated with significant benefits for LV and RV function and cardiac biomarkers. Serial quantitative 99mTc-DPD SPECT/CT imaging with SUV may be a valid tool to quantify and monitor response to tafamidis treatment in affected patients. TRANSLATIONAL PERSPECTIVE: 99mTc-DPD SPECT/CT imaging with determination of SUV retention index as part of a routine annual examination can provide evidence of treatment response in ATTR-CM patients receiving disease-modifying therapy. Further long-term studies with 99mTc-DPD SPECT/CT imaging may help to evaluate the relationship between tafamidis-induced reduction in SUV retention index and outcome in patients with ATTR-CM and will demonstrate whether highly disease-specific 99mTc-DPD SPECT/CT imaging is more sensitive than routine diagnostic monitoring.

Description of a different quantification method for amyloid burden (DPDload) and validation of SPECT/CT in cardiac amyloidosis.

BACKGROUND: Bone tracers such as 99mTc-DPD have shown high sensitivity and specificity in the non-invasive diagnosis of transthyretin cardiac amyloidosis (ATTR-CA). This study aims to validate SPECT/CT and assess the usefulness of uptake quantification (DPDload) in the myocardial tissue as potential information on the amyloid burden. METHODS: In a retrospective analysis of 46 patients with suspected CA, 23 cases with ATTR-CA had two quantification methods conducted to estimate amyloid burden (DPDload) through planar scintigraphic scans and a SPECT/CT. RESULTS: SPECT/CT significantly provided an added value in the patient's diagnosis with CA (P<.05). The estimation of the amyloid burden substantiated that the most affected wall of the LV is the interventricular septum in most cases and the existence of a significant relationship between the Perugini score uptake and the DPDload. CONCLUSIONS: We validate the need for SPECT/CT to complement planar imaging in diagnosing ATTR-CA. For its part, quantifying the amyloid load continues to be a complex area of research. It requires further studies with a larger number of patients to validate a standardized method of amyloid load quantification, both for diagnosis and treatment monitoring.

Quantitative 99mTc-DPD-SPECT/CT assessment of cardiac amyloidosis.

INTRODUCTION: Transthyretin (ATTR) amyloidosis is responsible for the majority of cardiac amyloidosis (CA) cases and can be reliably diagnosed with bone scintigraphy and the visual Perugini score. We aimed to implement a quantification method of cardiac amyloid deposits in patients with suspected cardiac amyloidosis and to compare performance to visual scoring. METHODS AND MATERIALS: 136 patients received 99mTc-DPD-bone scintigraphy including SPECT/CT of the thorax in case of suspicion of cardiac amyloidosis. Imaging phantom studies were performed to determine the scaling factor for standardized uptake value (SUV) quantification from SPECT/CT. Myocardial tracer uptake was quantified in a whole heart volume of interest. RESULTS: Forty-five patients were diagnosed with CA. A strong relationship between cardiac SUVmax and Perugini score was found (Spearman r 0.75, p < 0.0001). Additionally, tracer uptake in bone decreased with increasing cardiac SUVmax and Perugini score (p < 0.0001). ROC analysis revealed good performance of the SUVmax for the detection of ATTR-CA with AUC of 0.96 ± 0.02 (p < 0.0001) with sensitivity 98.7% and specificity 87.2%. CONCLUSION: We demonstrate an accessible and accurate quantitative SPECT approach in CA. Quantitative assessment of the cardiac tracer uptake may improve diagnostic accuracy and risk classification. This method may enable monitoring and assessment of therapy response in patients with ATTR amyloidosis.

Cardiac DPD-uptake time dependency in ATTR patients verified by quantitative SPECT/CT and semiquantitative planar parameters.

BACKGROUND: Bone scintigraphy plays an important role in the diagnosis of cardiac Transthyretin-Related Amyloidosis (ATTR). The mechanism of myocardial tracer accumulation and its dependence over time are not fully understood. Recently, a scintigraphic quantification of the cardiac amyloid deposition has been discussed. Nevertheless, little is known regarding the right time of quantitative imaging. METHODS: The geometrical mean of decay corrected total counts over the heart and the heart/whole-body ratio (H/WB) were evaluated in 23 patients undergoing DPD-bone scan with planar whole-body images 1 and 3 hours post injection (p.i.). Myocardial standard uptake values (SUV)peak were assessed in another 15 patients with quantitative SPECT/CT imaging 1 hours and 3 hours p.i.. RESULTS: Total counts over the heart (1 hours p.i.: 81,676 cts, range 69,887 to 93,091 cts and 3 hours p.i.: 64,819 cts, range 52,048 to 86,123 cts, P = .0005) and H/WB ratio (1 hours p.i.:0.076 ± 0.020 and 3 hours p.i. 0.070 ± 0.022; P = .0003) were significantly increased 1 hours p.i.. Furthermore median myocardial SUVpeak (1 hours p.i.:12.2, range 9.6 to 18.9 and 3 hours p.i.: 9.6, range 8.2 to 15.0, P = 0.0012) was also significantly higher after 1 hours p.i. compared to 3 hours p.i.. CONCLUSION: Cardiac DPD activity and myocardial SUVpeak are time-dependent, which should be considered when using quantitative bone scintigraphy in ATTR patients.

Comparative Study of Initial Post-Therapeutic 131I Single-Photon Emission Computed Tomography/Computed Tomography and Reoperation for the Detection of Residual Lymph Node Metastasis in Patients With Papillary Thyroid Cancer.

OBJECTIVE: To assess the diagnostic performance of initial post-therapeutic 131I single-photon emission computed tomography/computed tomography (SPECT/CT) compared with that of reoperation in detecting residual lymph node metastasis (LNM). METHODS: Patients with iodine-avid LNM detected on the initial post-therapeutic 131I SPECT/CT and who underwent reoperative dissection within 6 months were included. LNMs (numbers and locations) detected via both methods were compared. The American Thyroid Association dynamic risk stratification was performed for patients receiving second radioactive iodine therapy after reoperation. RESULTS: Fifty-three patients with 95 iodine-avid LNMs detected by 131I SPECT/CT were enrolled. Fifty-one (96.2%) patients had 212 LNMs confirmed by reoperation (P = .004). The sensitivity and specificity of 131I SPECT/CT in detecting LNM were 44.8% (95/212) and 91.6% (87/95), respectively. The location frequency of residual LNMs found by 131I SPECT/CT was similar to that of reoperation (P = .057). Thirty-two patients received a second radioactive iodine treatment, and 6 (18.8%) patients still had residual iodine-avid LNM on SPECT/CT. Therapeutic response was evaluated by American Thyroid Association dynamic risk stratification in 16 patients. The number of patients with structural incomplete response, biochemical incomplete response, indeterminate response, and excellent response was 4 (23.5%), 4 (23.5%), 5 (29.4%), and 3 (17.6%), respectively. CONCLUSION: 131I SPECT/CT has high specificity but relatively low sensitivity in detecting all residual LNMs. Approximately 80% of patients were rendered structurally disease free after reoperation.