Search Results (7)

Background/Objectives: Artificial intelligence (AI) is a promising tool for the enhancement of physician workflow and serves to further improve the efficiency of their diagnostic evaluations. This study aimed to assess the performance of an AI-based bone scan noise-reduction filter on noisy, low-count images in a routine clinical environment. Methods: The performance of the AI bone-scan filter (BS-AI filter) in question was retrospectively evaluated on 47 different patients’ ^99mTc-MDP bone scintigraphy image pairs (anterior- and posterior-view images), which were obtained in such a manner as to represent the diverse characteristics of the general patient population. The BS-AI filter was tested on artificially degraded noisy images—75, 50, and 25% of total counts—which were generated by binominal sampling. The AI-filtered and unfiltered images were concurrently appraised for image quality and contrast by three nuclear medicine physicians. It was also determined whether there was any difference between the lesions seen on the unfiltered and filtered images. For quantitative analysis, an automatic lesion detector (BS-AI annotator) was utilized as a segmentation algorithm. The total number of lesions and their locations as detected by the BS-AI annotator in the BS-AI-filtered low-count images was compared to the total-count filtered images. The total number of pixels labeled as lesions in the filtered low-count images in relation to the number of pixels in the total-count filtered images was also compared to ensure the filtering process did not change lesion sizes significantly. The comparison of pixel numbers was performed using the reduced-count filtered images that contained only those lesions that were detected in the total-count images. Results: Based on visual assessment, observers agreed that image contrast and quality were better in the BS-AI-filtered images, increasing their diagnostic confidence. Similarities in lesion numbers and sites detected by the BS-AI annotator compared to filtered total-count images were 89%, 83%, and 75% for images degraded to counts of 75%, 50%, and 25%, respectively. No significant difference was found in the number of annotated pixels between filtered images with different counts (p > 0.05). Conclusions: Our findings indicate that the BS-AI noise-reduction filter enhances image quality and contrast without loss of vital information. The implementation of this filter in routine diagnostic procedures reliably improves diagnostic confidence in low-count images and elicits a reduction in the administered dose or acquisition time by a minimum of 50% relative to the original dose or acquisition time. Full article

Radionuclide bone scintigraphy is the cornerstone of an imaging-based algorithm for accurate non-invasive diagnosis of transthyretin cardiac amyloidosis (ATTR-CA). In patients with heart failure and suggestive echocardiographic and/or cardiac magnetic resonance imaging findings, the positive predictive value of Perugini grade 2 or 3 myocardial uptake on a radionuclide bone scan approaches 100% for the diagnosis of ATTR-CA as long as there is no biochemical evidence of a clonal dyscrasia. The technetium-labelled tracers that are currently validated for non-invasive diagnosis of ATTR-CA include pyrophosphate (^99mTc-PYP); hydroxymethylene diphosphonate (^99mTc-HMDP); and 3,3-diphosphono-1,2-propanodicarboxylate (^99mTc-DPD). Although nuclear scintigraphy has transformed the contemporary diagnostic approach to ATTR-CA, a number of grey areas remains, including the mechanism for binding tracers to the infiltrated heart, differences in the kinetics and distribution of these radiotracers, differences in protocols of image acquisition worldwide, the clinical significance of extra-cardiac uptake, and the use of this technique for prognostic stratification, monitoring disease progression and assessing the response to disease-modifying treatments. This review will deal with the most relevant unmet needs and clinical questions concerning scintigraphy with bone tracers in ATTR-CA, providing expert opinions on possible future developments in the clinical application of these radiotracers in order to offer practical information for the interpretation of nuclear images by physicians involved in the care of patients with this ATTR-CA. Full article

Transthyretin cardiac amyloidosis (ATTR-CA) is characterized by high ^99mTc-labeled bone tracer uptake in the heart. However, the mechanism of bone tracer uptake into the heart remains controversial. Since bone tracer uptake into metastatic bone tumors is thought to be associated with increased bone metabolism, we examined ^99mTc-pyrophosphate (PYP) scintigraphy findings, endomyocardial biopsy (EMB) tissue findings, and the expression of bone metabolism-related genes in the EMB tissues in patients with ATTR-CA, amyloid light-chain cardiac amyloidosis (AL-CA), and noncardiac amyloidosis (non-CA) in this study. The uptake of ^99mTc-PYP in the heart was significantly higher in the ATTR-CA patients than in the AL-CA and non-CA patients. A higher percentage of ATTR-CA EMB tissue showed von Kossa-positive microparticles: ATTR-CA, 62%; AL-CA, 33%; and non-CA, 0%. Calcified microparticles were identified using transmission electron microscopy. However, none of the osteogenic marker genes, osteoclastic marker genes, or phosphate/pyrophosphate-related genes were upregulated in the EMB samples from ATTR-CA patients compared to those from AL-CA and non-CA patients. These results suggest that active calcification-promoting mechanisms are not involved in the microcalcification observed in the heart in ATTR-CA. The mechanisms explaining bone tracer uptake in the heart, which is stronger than that in the ribs, require further investigation. Full article

99-Metastabil Technetium (^99mTc) is a radiopharmaceutical widely used in skeletal scintigraphy. Recent publications show it can also be used to determine the osteogenic potential of human mesenchymal stem cells (hMSCs) by binding to hydroxyapatite formed during bone tissue engineering. This field lacks non-destructive methods to track live osteogenic differentiation of hMSCs. However, no data about the uptake kinetics of ^99mTc and its effect on osteogenesis of hMSCs have been published yet. We therefore evaluated the saturation time of ^99mTc by incubating hMSC cultures for different periods, and the saturation concentration by using different amounts of ^99mTc activity for incubation. The influence of ^99mTc on osteogenic potential of hMSCs was then evaluated by labeling a continuous hMSC culture three times over the course of 3 weeks, and comparing the findings to cultures labeled once. Our findings show that ^99mTc saturation time is less than 0.25 h, and saturation concentration is between 750 and 1000 MBq. Repeated exposure to γ-radiation emitted by ^99mTc had no negative effects on hMSC cultures. These new insights can be used to make this highly promising method broadly available to support researchers in the field of bone tissue engineering using this method to track and evaluate, in real-time, the osteogenic differentiation of hMSC, without any negative influence on the cell viability, or their osteogenic differentiation potential. Full article

Amyloidosis is a heterogeneous group of diseases caused by the extracellular deposition of amyloid insoluble fibrils in multiple organs, resulting in various clinical manifestations. Cardiac amyloidosis (CA) occurs mainly in primary light-chain (AL) amyloidosis, hereditary transthyretin (ATTRv) amyloidosis and senile or wild-type transthyretin (ATTRwt) amyloidosis. Knowing that myocardial uptake at bone scintigraphy is an essential step in the ATTR-CA diagnostic algorithm, the level of awareness among nuclear medicine physicians (NMPs) using bone tracer scintigraphy is of great importance. The objective of the study was to evaluate NMPs’ awareness of scintigraphy with bisphosphonates for the detection of CA. We conducted an online survey among NMPs from Romania to assess their current awareness and state of knowledge of nuclear techniques used in CA. Among the total 65 Romanian NMPs, 35 (53%) responded to this questionnaire. Approximately three-quarters of participants (74%) found a diffuse accumulation of bisphosphonates in the heart on scintigraphy performed for bone pathology as an incidental discovery. Detection of myocardial uptake of 99mTc-labeled bisphosphonates on scintigraphy suggests CA-AL for 3% of participants and for 9% of respondents, the appearance is of uncertain cardiac amyloidosis, while 5% of participants observed cardiac uptake but did not report it as CA. Even if more than half of those who responded to this survey (54%) found abnormal cardiac uptake and interpreted it as CA-ATTR, only 14% contacted the referring physician to draw attention to the incidental discovery to refer the patient to a specialist in rare genetic cardiomyopathy. Regarding the knowledge about the categories of bisphosphonates recommended in the diagnosis of CA-ATTR, 54% answered inadequately that methylene diphosphonate (MDP) could be used. Romanian nuclear physicians are partially familiar with CA diagnosis by scintigraphy, but its diagnostic potential and standardization, recommended radiotracers and acquisition times and interpretation algorithms are known in varying proportions. Therefore, there is a need to enhance knowledge through continuing medical education programs in order to standardize the protocols for the acquisition, processing and interpretation of bisphosphonate scintigraphy for the detection of cardiac ATTR amyloidosis. Full article

Background: Red blood cells (RBC) scintigraphy can be used not only for detection of bleeding sites, but also of spleen tissue. However, there is no established quantitative readout. Therefore, we investigated uptake in suspected splenic lesions in direct quantitative correlation to sites of physiologic uptake in order to objectify the readout. Methods: 20 patients with Tc-99m-labelled RBC scintigraphy and SPECT/low-dose CT for assessment of suspected splenic tissue were included. Lesions were rated as vital splenic or non-splenic tissue, and uptake and physiologic uptake of bone marrow, pancreas, and spleen were then quantified using a volume-of-interest based approach. Hepatic uptake served as a reference. Results: The median uptake ratio was significantly higher in splenic (2.82 (range, 0.58–24.10), n = 47) compared to other lesions (0.49 (0.01–0.83), n = 7), p < 0.001, and 5 lesions were newly discovered. The median pancreatic uptake was 0.09 (range 0.03–0.67), bone marrow 0.17 (0.03–0.45), and orthotopic spleen 14.45 (3.04–29.82). Compared to orthotopic spleens, the pancreas showed lowest uptake (0.09 vs. 14.45, p = 0.004). Based on pancreatic uptake we defined a cutoff (0.75) to distinguish splenic from other tissues. Conclusion: As the uptake in extra-splenic regions is invariably low compared to splenules, it can be used as comparator for evaluating suspected splenic tissues. Full article

Background and objectives: The objective of this study was to assess the value of a whole-body bone scintigraphy using 99m technetium labelled-methyl diphosphonate (99mTc-MDP) for the diagnosis and the assessment of grades of muscle damage after prolonged acute or chronic obstruction of the main arteries in lower extremities. Material and Methods: Fifty consecutive patients were selected for the study. The patients’ condition had not improved after primary peripheral arterial reconstruction operation or limb amputation and after conservative treatment. The clinical suspicion was of arterial obstruction and muscle necrosis. All the patients underwent whole-body scintigraphy with 99mTc-MDP. Muscle necrosis was identified as an increased soft tissue uptake of 99mTc-MDP. Results: Forty-five patients had gross muscle necrosis detected on whole-body scintigraphy with 99mTc-MDP and were histologically confirmed after repeated surgery (necrectomy or amputation) or by muscle biopsy, if only fasciotomy was performed. The location and extent of muscle injury were assessed preoperatively and the findings were confirmed in all 45 patients. Twelve patients with clinically suspected minor muscle damage, which was confirmed as relatively minor muscle necrosis on 99mTc-MDP scintigraphy, were treated conservatively. The clinical outcome of all 50 patients was favorable. The 99mTc-MDP scintigraphy, in detection of muscular necrosis, demonstrated sensitivity, specificity, and accuracy of 97.3% (95% confidence interval (CI) 85.4 to 99.3%), 30.77% (95% confidence interval (CI) 9.09 to 61.43%), and 80% (95% confidence interval (CI) 66.28 to 89.97%), respectively. Conclusion: The 99mTc-MDP scintigraphy is a valuable tool in the detection of muscular necrosis. It is able to define location, extent, and grade of involvement. Therefore, it has a clinical impact in patient management, allowing clinicians to select adequate treatment policy and specify the scope of necrectomy. Full article