Dosimetric implications of kidney anatomical volume changes in 177Lu-DOTATATE therapy.

INTRODUCTION: This study aims to evaluate the use of CT-based whole kidney parenchyma (WKP) segmentation in 177Lu-DOTATATE dosimetry. Specifically, it investigates whether WKP volumes change during treatment and evaluates the accuracy of applying a single delineated WKP volume for dosimetry. Furthermore, it aims to determine the cause of WKP volume changes-whether caused by radiation or amino acid infusion-by comparing them with spleen volume changes as a marker for radiation-induced alterations. METHODS: SPECT/CT images of 18 patients were acquired over the abdomen approximately 4 h (h) (D0), 24 h (D1), 48 h (D2) and 168 h (D7) post-administration of 177Lu-DOTATATE. CT guided WKP volumes were measured before (baseline) and during treatment. Kidney activity concentrations at each time point were derived from CT-segmented WKP overlaid on SPECT scans. The accuracy of using WKP segmentation from a single CT for all time points was assessed against the gold standard of segmenting each WKP individually. Time-integrated activity calculations were based on a tri-exponential curve fit of the kidney activity concentration over time. Kidney absorbed doses were estimated under the assumption of local energy deposition. Additionally, the impact of various partial volume correction methods on dosimetry was evaluated. RESULTS: Whole-kidney parenchyma (WKP) volumes, ranging from 31 to 243 mL, showed a gradual increase from baseline (mean ± SD = 130.6 ± 46.1 mL) at the initial time points D0 (138.5 ± 44.7 mL) and D1 (139.4 ± 41.6 mL), followed by a slight decrease at D2 (132.8 ± 44.5 mL) and a further decrease at D7 (129.2 ± 42.7 mL). The volume increase at D0 and D1 was statistically significant. Spleen volume did not change during treatment, suggesting that amino acid infusion rather than irradiation effects caused WKP volume changes. Bland-Altman analysis revealed WKP volume biases of 8.77% (D0 vs. BL), 10.77% (D1 vs. BL), 1.10% (D2 vs. BL), and 1.10% (D7 vs. BL), with corresponding uncertainties of 24.4%, 23.6%, 25.4%, and 25.4%, respectively. When WKP segmentation from a single CT is applied across all SPECTs, these WKP volume changes could overestimate the activity concentration and mean absorbed doses up to 4.3% and 2.5%, respectively. The absorbed dose uncertainties using a recovery coefficient (RC) of 0.85 for single-time-point WKP delineation increase the absorbed dose uncertainty by 4% compared to the use of patient-specific RCs and time specific segmentation of WKP volumes. CONCLUSIONS: Kidney volume exhibited significant variation form D0 to D7, affecting the precision of dosimetry calculation, primarily due to errors in whole-kidney parenchyma (WKP) delineation. Notably, using WKP segmentation from a single CT scan applied to sequential SPECT images introduce further uncertainty and may lead to an overestimation of the absorbed dose. The fluctuations in kidney volume are most likely attributable to amino acid infusion.

Clinical value of Tc-99m MDP SPECT/CT bone imaging for early diagnosis of Relapsing Polychondritis: a report of 5 cases.

BACKGROUND: Relapsing Polychondritis(RP) is a rare rheumatic immune disease. As with most diseases, if intervention is delayed, the patient's prognosis is worse. Currently, the diagnostic criteria used in clinical practice do not include CT, PET/CT, SPECT/CT and other new imaging examinations that have developed rapidly in recent years. However, these examinations have some special manifestations for RP, which can help clinicians diagnose RP earlier and distinguish it from other diseases. CASE PRESENTATION: These five RP patients all had respiratory symptoms such as cough and wheezing as the first symptom, which could not be diagnosed in time according to the previous diagnostic criteria. The clinical data of the five patients are listed in Table 1. The relatively specific manifestations of SPECT/CT examination provided clinicians with very valuable clues to help them advance the diagnosis time. CONCLUSIONS: The application of SPECT/CT bone imaging in early diagnosing RP proves to be effective, enabling clinicians to intervene promptly and enhance the overall well-being and quality of life for individuals affected by this condition.

SPECT/CT with 99mTc-DTPA in a Patient with Persistent Complex Pneumothorax after Endobronchial Valve Placement.

Ventilation-perfusion SPECT with or without CT using technetium 99m (99mTc)-diethylenetriaminepentaacetic acid (DTPA) has been used to identify patterns typical of cardiopulmonary diseases, such as pulmonary embolism, pneumonia, heart failure, and obstructive lung disease. This case demonstrates the utility of a ventilation scan with SPECT/CT using 99mTc-DTPA for investigating the cause of a persistent complex pneumothorax in a patient with severe chronic obstructive pulmonary disease who recently underwent endobronchial valve placement. Keywords: CT-Spectral Imaging (Multienergy), SPECT/CT, Thorax, Lung Supplemental material is available for this article. © RSNA, 2024.

Impact of postoperative cerebral hyperperfusion on 2-year cognitive outcomes of patients undergoing carotid endarterectomy.

OBJECTIVE: In 10% of patients undergoing carotid endarterectomy (CEA), the cognitive function declines postoperatively, primarily in association with postoperative cerebral hyperperfusion. In contrast, in the majority of patients undergoing CEA, long-term cognitive outcomes remain unclear. Furthermore, it is not known whether the decline in cognition due to cerebral hyperperfusion recovers on a long-term basis. This study aimed to understand how postoperative cerebral hyperperfusion affects the cognitive outcomes of patients who undergo CEA. METHODS: The participants in this prospective observational study were patients with internal carotid artery stenosis who underwent CEA. Cerebral hyperperfusion syndrome or asymptomatic cerebral hyperperfusion following CEA was determined based on brain perfusion SPECT scans and symptomatology before and after surgery. Neuropsychological testing was performed preoperatively, at 1-2 months postoperatively, and at 2 years postoperatively to investigate cognitive decline. RESULTS: A logistic regression analysis revealed that asymptomatic cerebral hyperperfusion (95% CI 13.0-84.5, p < 0.0001) and cerebral hyperperfusion syndrome (95% CI 449.7-14,237.4, p < 0.0001) were significantly associated with cognitive decline at 1-2 months postoperatively. The incidence of cognitive decline was significantly decreased at 2 years postoperatively (7%) in comparison to 1-2 months postoperatively (11%) (p = 0.0461). A logistic regression analysis also revealed that asymptomatic cerebral hyperperfusion (95% CI 3.7-36.7, p < 0.0001), cerebral hyperperfusion syndrome (95% CI 128.0-6183.6, p < 0.0001), and further strokes during the 2-year follow-up period (95% CI 1.5-78.7, p = 0.0167) were significantly associated with cognitive decline at 2 years postoperatively. The incidence of cognitive decline at 1-2 months postoperatively was significantly higher in patients with cerebral hyperperfusion syndrome (100%) than in those with asymptomatic cerebral hyperperfusion (44%) (p < 0.0001). No significant difference in incidence was observed in the former patients at 2 years postoperatively (88%), but significant reduction was found in patients with asymptomatic cerebral hyperperfusion and cognitive decline between the timepoints of 1-2 months postoperatively (100%) and 2 years postoperatively (39%) (p = 0.0001). CONCLUSIONS: Postoperative cerebral hyperperfusion causes prolonged cognitive decline at 2 years postoperatively in patients undergoing CEA.

Impact of Posttreatment SPECT/CT on Patient Management During 177Lu-PSMA-617 Radiopharmaceutical Therapy.

177Lu can be imaged after administration using SPECT/CT. Most work to date has focused on using posttreatment imaging to measure normal organ and tumor dose. We aimed to assess the impact of posttreatment SPECT/CT on the management of patients undergoing 177Lu-prostate-specific membrane antigen (PSMA) radiopharmaceutical therapy (RPT). Methods: In this retrospective study, 122 patients underwent PSMA RPT with subsequent SPECT/CT 24 h after treatment. We determined a qualitative response at each cycle and reviewed patient charts to assess the impact that posttreatment SPECT/CT had on patient management. Changes in patient management were classified as changes on the basis of progression and response, and specific cycles when they occurred were noted. Miscellaneous changes in patient management were also evaluated. Results: Among the 122 consecutive patients examined, 42%-56% exhibited stable disease, whereas 19%-39% of patients exhibited response on visual assessment across treatment cycles. In total, 49% (n = 60) of patients experienced changes in management, of which 57% (n = 34) were due to progression, 40% (n = 24) were due to response, and 3% (n = 2) were due to miscellaneous changes. Changes due to disease progression were observed mostly after cycles 2 and 4. Changes due to response to RPT occurred mostly after cycles 3 and 4. Conclusion: At our center, 49% of patients experienced changes in management based on posttreatment SPECT/CT, and most of these changes occurred at cycles 2 and 4. Integrating posttreatment SPECT/CT into routine PSMA RPT protocols can aid in patient management.

Refining Cardiovascular Calcification in the Appraisal of Ischemic Heart.

BACKGROUND: Even in asymptomatic patients, there is a high association of ischemia on myocardial perfusion scans in those with coronary artery calcification or valvular calcifications. Patients without coronary artery calcifications have exceeding-low rates of cardiovascular events. The absence of cardiovascular calcification, including coronary artery, valvular, and thoracic aorta is a strong negative predictor of myocardial ischemia. In individuals with suspected ischemia who had chest computed tomography imaging, evaluation for cardiovascular calcification (coronary artery, valves, and thoracic aorta) is an invaluable tool to guide management for further diagnostic imaging. We hypothesize that the complete absence of cardiovascular calcification has a high negative predictive value for defects in myocardial perfusion imaging such as single-photon emission computed tomography (SPECT) or positron emission tomography (PET). METHODS: Non-contrast computed tomography performed for SPECT/PET CT attenuation correction from March 1, 2017, to September 30, 2017, were retrospectively reviewed for the absence of cardiovascular calcification by a cardiologist and radiologist who were blinded to patients' medical history. Medical records were reviewed to include patient demographics and medical history. A total of 132 patients were analyzed. RESULTS: Of the 132 patients without calcifications, seven patients had small myocardial perfusion defects suggestive of ischemia or infarct, but none were considered significant defects. Of these seven patients, six were managed medically and one was from an outside institution with no follow-up data. Two of the seven patients had follow-up invasive angiography or coronary CTA that did not show significant atherosclerotic coronary artery disease. CONCLUSION: A complete absence of cardiovascular calcification indicates a 100% negative predictive value for a significant perfusion defect on same-day confirmatory nuclear stress testing. Patients with suspected ischemia but absent cardiovascular calcifications can be safely managed medically without further testing for ischemia.

Effect of Beta-Blocker Consumption on the Severity and Extension of Perfusion Defects in Dipyridamole Myocardial Perfusion Single-Photon Emission Computed Tomography.

Background Regarding the less-known effects of beta-blocker consumption on the diagnostic value of the myocardial perfusion scan with dipyridamole stress in coronary artery disease (CAD), we aimed to compare the findings of the scans done on the beta-blocker consumption course and after discontinuation of this medications. Materials and Methods Thirty patients with probably CAD and abnormal myocardial perfusion scans (presence of reversible defect), who had been treated with beta-blockers for at least 3 months, were studied. Dipyridamole stress phase of myocardial perfusion single-photon emission computed tomography (SPECT) was performed two times with an interval of about 1 week, once after discontinuation of all antianginal and anti-ischemic medications, statins, and beta-blockers for 72 hours prior to the study, and again after discontinuation of all these medications except for beta-blockers. Imaging was done with the same protocol, radiopharmaceutical dose, and imaging parameters. Summed stress score (SSS), summed stress rest, and summed difference scores (SDS), total perfusion deficit (TPD), severity, and extension of myocardial perfusion defects in three coronary artery territories were analyzed, using quantitative perfusion SPECT software. Results Most variables such as SSS, SDS, TPD, severity, and extension of defects showed a significant difference between the two conditions including beta-blocker consumption and after discontinuing beta-blocker consumption before stress imaging ( p < 0.05). Moreover, in patients on treatment with metoprolol, all studied factors including SSS, SDS, TPD, severity, and extension of perfusion defects were significantly reduced when patients consumed beta-blockers before SPECT evaluation ( p < 0.05). Conclusion Beta-blocker consumption can lead to a decrease in the severity and extent of myocardial perfusion defects and therefore probably a decrease in the sensitivity of myocardial scans. Discontinuation of beta-blocker prior to the dipyridamole myocardial perfusion scan can improve diagnostic accuracy.

SPECT/CT in the Diagnosis of Ectopic Gastric Mucosa-Meckel's Diverticulum.

Aim The imaging of Meckel's diverticulum (MD) is based of accumulation of Tc-99m pertechnetate in the ectopic gastric mucosa (EGM) content. Although the diagnostic accuracy of this imaging modality is high, there are some overlap patients with coexisting gastrointestinal bleeding and false positive causes hampering diagnostic power. The aim of this study was to evaluate the possible contribution of single-photon emission computed tomography/computed tomography (SPECT/CT) in EGM-MD diagnosis and to determine the indication of this additional imaging modality. Materials and Methods Fifty-two pediatric patients (24 girls, 28 boys; mean age: 8.06 ± 5.22 years old) who have suspicion of MD and referred for scintigraphy were evaluated retrospectively. Additional SPECT/CT were performed to selected five cases among the group. The results of the scintigraphy as well as SPECT/CT were compared with endoscopy, pathology, and/or follow-up results. Results There were 9 patients with equivocal study results, 12 positive results, and the others were considered negative MD scintigraphy. One patient was out of follow-up and 10 patients underwent surgery. Only one single patient was negative during surgery but scintigraphy was also negative. The diagnostic sensitivity, specificity, and accuracy were 100, 95, and 96%, respectively. Among five patients with SPECT/CT results one patient was diagnosed by only SPECT/CT who had EGM in duplication cyst, one equivocal patient was diagnosed as descending colon bleeding, and one patient's lesion was clearly delineated by SPECT/CT. Conclusion SPECT/CT has clear advantage over standard planar scintigraphy imaging in EGM-MD determination. This modality might decrease equivocal and false positive results but this issue has to be addressed with further studies.

From SPECT/CT towards absolute quantification? - the case of unilateral condylar hyperplasia of the mandible.

BACKGROUND: Unilateral condylar hyperplasia (UCH) of the mandible is a rare condition characterized by asymmetric growth of the mandibular condyles. Bone scintigraphy with SPECT(/CT) is commonly used to diagnose UCH and guide treatment. Still, varying results have been reported using the traditional threshold of 55%:45% in relative tracer uptake. While absolute quantification of uptake on SPECT/CT could improve results, optimal correction and reconstruction settings are currently unknown. METHODS: Three anthropomorphic phantoms representing UCH were developed from patient CT volumes and produced using 3D printing technology. Fillable spherical inserts of different sizes (Ø: 8-15 mm) were placed in the condylar positions representing symmetrical and asymmetrical distributions. Recovery coefficients were determined for SPECT/CT using various reconstruction corrections, including attenuation and scatter correction (ACSC), resolution modeling (RM), and partial volume correction (PVC) using phantom measurements. Uptake ratios between condyles and condyle to clivus were evaluated. Finally, the impact of these correction techniques on absolute activity and diagnostic accuracy was assessed in a retrospective patient cohort for the diagnostic threshold of 55%:45%. RESULTS: The activity was only partially recovered in all spherical inserts (range: 22.5-64.9%). However, RM improved relative recovery by 20.2-62.3% compared to ACSC. In the symmetric phantoms, the 95% confidence interval (CI) of condyle ratios included the diagnostic threshold (57.6%:42.4%) for UCH when using ACSC potentially leading to false positives, but not for ACSCRM datasets. Partial volume corrections coefficients from the NEMA IQ phantom was positionally dependent, with improvements seen performing PVC using coefficients derived from anthropomorphic phantoms. Retrospective application in a patient cohort showed only a weak linear correlation (R²: 0.25-0.67) and large limits of agreement (9.6-12.5%) between different reconstructions. Up to 44% of patients were reclassified using the 55%:45% threshold. Using clinical outcome data, ACSCRM had highest sensitivity (91%; 95% CI 59-100%) and specificity (66%; 95% CI 47-81%), significantly improving specificity (P = 0.038). CONCLUSIONS: Anthropomorphic phantoms were shown to be essential in determining optimal settings for acquisition, reconstruction, and analysis. SPECT/CT reconstructions with attenuation and scatter correction and resolution modeling are recommended and could improve specificity when using the 55%:45% threshold to assess condylar growth.

How anatomical impairments found on CT affect perfusion percentage assessed by SPECT/CT scan?

AIM: CT images can identify structural and opacity alterations of the lungs while nuclear medicine's lung perfusion studies show the homogeneity (or lack of) of blood perfusion on the organ. Therefore, the use of SPECT/CT in lung perfusion scintigraphies can help physicians to assess anatomical and functional alterations of the lungs and to differentiate between acute and chronic disease. OBJECTIVE: To develop a computer-aided methodology to quantify the total global perfusion of the lungs via SPECT/CT images and to compare these results with parenchymal alterations obtained in CT images. METHODS: 39 perfusion SPECT/CT images collected retrospectively from the Nuclear Medicine Facility of Botucatu Medical School's Clinics Hospital in São Paulo, Brazil, were analyzed. Anatomical lung impairments (emphysema, collapsed and infiltrated tissue) and the functional percentage of the lungs (blood perfusion) were quantified from CT and SPECT images, with the aid of the free, open-source software 3D Slicer. The results obtained with 3D Slicer (3D-TGP) were also compared to the total global perfusion of each patient's found on their medical report, obtained from visual inspection of planar images (2D-TGP). RESULTS: This research developed a novel and practical methodology for obtaining lungs' total global perfusion from SPECT/CT images in a semiautomatic manner. 3D-TGP versus 2D-TGP showed a bias of 7% with a variation up to 67% between the two methods. Perfusion percentage showed a weak positive correlation with infiltration (p = 0.0070 and ρ = 0.43) and collapsed parenchyma (p = 0.040 and ρ = 0.33). CONCLUSIONS: This research brings meaningful contributions to the scientific community because it used a free open-source software to quantify the lungs blood perfusion via SPECT/CT images and pointed that the relationship between parenchyma alterations and the organ's perfusion capability might not be so direct, given compensatory mechanisms.

Serum phosphorus levels associated with nigrostriatal dopaminergic deficits in drug-naïve Parkinson's disease.

INTRODUCTION: A major component of Lewy bodies is phosphorylated α-synuclein. This post-translational modification of α-synuclein, phosphorylation, may consume a great amount of serum phosphorus. We aimed to investigate serum phosphorus levels and their associations with clinical phenotype and the degeneration of cardiac sympathetic and nigrostriatal dopaminergic neurons in patients with Parkinson's disease (PD). MATERIALS AND METHODS: We examined serum phosphorus levels in 127 participants (drug-naïve PD, 97; age- and sex-matched controls, 30). Associations of serum phosphorus levels with clinical features, heart-to-mediastinum (H/M) ratio on cardiac 123I-metaiodobenzylguanidine scintigraphy and striatal specific binding ratio of 123I-2-carbomethoxy-3-(4-iodophenyl)-N-(3-fluoropropyl) nortropane (123I-FP-CIT) were examined. RESULTS: Serum phosphorus levels were 3.4 ± 0.5 mg/dL in patients with PD and were not different from those in controls after controlling for age and sex (p = 0.850). Serum phosphorus levels were significantly lower in patients with PD and decreased H/M ratio than in those with PD and normal H/M ratio (3.3 ± 0.4 mg/dL vs. 3.6 ± 0.5 mg/dL, p = 0.003). Lower serum phosphorus levels were significantly associated with more severe degeneration of nigrostriatal dopaminergic neurons in patients with PD and decreased H/M ratio. However, this association was not observed in patients with PD and normal H/M ratio. CONCLUSIONS: Serum phosphorus levels and their association with nigrostriatal dopaminergic degeneration are different between patients with decreased H/M ratio and those with normal H/M ratio. Serum phosphorus levels may reflect the degree of nigrostriatal dopaminergic degeneration in patients with decreased H/M ratio, namely, Body-First PD.

Comparison of diagnostic value of technetium 99m-labeled red blood cell computed single photon emission computed tomography/computed tomography (99mTc-RBC SPECT/CT) and contrast-enhanced multidetector computed tomography (MDCT) for small bowel bleeding: a retrospective study.

Background: Although small bowel bleeding is relatively rare, it is a potentially fatal disease, and its diagnosis still faces challenges. Technetium 99m-labeled red blood cell computed single photon emission computed tomography/computed tomography (99mTc-RBC SPECT/CT) and contrast-enhanced multidetector computed tomography (MDCT) are common imaging methods for diagnosing small bowel bleeding, but there have been no studies comparing their diagnostic efficacy for this purpose. This study aims to compare the diagnostic value of 99mTc-RBC SPECT/CT and contrast-enhanced MDCT for small bowel bleeding. Methods: A total of 44 patients (30 males and 14 females, median age of 64 years) definitively diagnosed with small bowel bleeding and 15 non-small bowel bleeding patients (8 males and 7 females, median age of 66 years) were consecutively included in this study. All patients underwent 99mTc-RBC SPECT/CT and contrast-enhanced MDCT examinations at Beijing Friendship Hospital of Capital Medical University between January 2020 to September 2023. The definitive diagnosis had been made through surgery or colonoscopy, or through patient history, patient management, and clinical follow-up. We collected clinical data of the participants. 99mTc-RBC SPECT/CT and contrast-enhanced MDCT were reviewed in a blinded fashion for accuracy of detection of active bleeding as well as the active small bowel bleeding location. Results: Among the 59 patients, the accuracy, sensitivity, and specificity of 99mTc-RBC SPECT were 27.3%, 93.3%, and 92.3%; for 99mTc-RBC SPECT/CT they were 76.3%, 40.5%, and 93.3%; whereas for contrast-enhanced MDCT they were 45.8%, 27.3%, and 100%, respectively. The diagnostic accuracy of 99mTc-RBC SPECT/CT for jejunal and ileal bleeding was high, at 100% and 86.4%, respectively. Meanwhile, 99mTc-RBC SPECT/CT had a higher accuracy in diagnosing more causes of small bowel bleeding. In 59 patients, the combination of 99mTc-RBC SPECT/CT and contrast-enhanced MDCT accurately diagnosed small bowel bleeding and provided precise localization in 50 patients, resulting in the accuracy, sensitivity, and specificity of 84.7%, 79.5%, and 100.0%, respectively. Conclusions: 99mTc-RBC SPECT/CT has high diagnostic value in diagnosing small bowel bleeding and is superior to 99mTc-RBC SPECT and contrast-enhanced MDCT. The combination of 99mTc-RBC SPECT/CT and contrast-enhanced MDCT can further improve the diagnostic accuracy of diagnosis, and can accurately guide the diagnosis and treatment of small bowel bleeding.

Solitary Osseous Metastasis of Hepatocellular Carcinoma on SPECT/CT.

Hepatocellular carcinoma (HCC), sixth most common cancer world-over, commonly metastasizes to lung, lymph nodes and adrenal glands. Incidence of osseous metastases in HCC has been reported to be 3-20 % which occurs predominantly in the axial skeleton. It only rarely occurs in the appendicular skeleton and that too as the solitary focus of metastatic deposit.3,4 We present a case of HCC with solitary osseous metastases to the proximal tibia.

Review of the Clinical and Technical Aspects of 99mTc-Dimercaptosuccinic Acid Renal Imaging: The Comeback "Kit".

99mTc-labeled dimercaptosuccinic acid (99mTc-DMSA) imaging is a well-established and highly sensitive method for the diagnosis of several renal cortical disorders affecting children and adults. Beginning in 2014, 99mTc-DMSA availability was severely impaired when it was added to the Drug Shortages List of the U.S. Food and Drug Administration and was commercially unavailable thereafter. The agent shortage negatively impacted practitioners' ability to evaluate renal cortical defects in children and adults and changed renal imaging practice. A survey among pediatric nuclear medicine clinicians confirmed the clinical need for 99mTc-DMSA. Finally, in early 2023 the Food and Drug Administration again approved 99mTc-DMSA in the United States. During the 99mTc-DMSA shortage, established practitioners may not have had the opportunity of using 99mTc-DMSA as they were accustomed in their experience. Also, newer imaging specialists and referring physicians and technologists may not have benefited from having 99mTc-DMSA in their training. Therefore, it is time to bring back 99mTc-DMSA into the armamentarium of imaging methods available to evaluate regional cortical renal function.

Can a Carbonated Lemon Drink Reduce Extracardiac Activity in Myocardial Perfusion Imaging?

Myocardial perfusion imaging (MPI) provides physiologic and functional information about the heart muscle and its blood flow. Extracardiac radioactivity can interfere with visualization of the inferior wall of the myocardium, leading to poor-quality images, difficulties in interpretation, and delays in routine practice. This study aimed to identify the efficiency of having the patient consume a carbonated lemon drink to minimize the extracardiac radioactivity of 99mTc-sestamibi in comparison to 99mTc-tetrofosmin during MPI. Methods: This was a retrospective study that recruited 158 patients with known or suspected coronary artery disease referred to undergo 99mTc-sestamibi or 99mTc-tetrofosmin rest/stress single-day MPI. The patients were divided into 2 groups of mixed sexes and different ages. The first group comprised 78 patients injected with 99mTc-sestamibi, and the second group comprised 80 patients injected with 99mTc-tetrofosmin. For both groups, the patients drank 30 mL of fresh lemon juice diluted with 150 mL of soda water, and then we gave the patients about 100 mL of straight soda water, before imaging for both the rest and the stress phases. Results: Generally, in both groups, the 99mTc-tetrofosmin produced a good-quality image in comparison with the 99mTc-sestamibi. The mean rank of the total score for 99mTc-tetrofosmin (62.75) was less than that for 99mTc-sestamibi (96.68), and this difference was highly statistically significant (P = 0.000). There were statistically significant differences in the ratios and mean ranks for both groups in favor of 99mTc-tetrofosmin in patients having coronary artery disease. Conclusion: The use of a carbonated lemon drink minimizes extracardiac activity from both 99mTc-labeled MPI radiopharmaceuticals. This finding was more statistically significant for 99mTc-tetrofosmin MPI, providing better image quality and earlier imaging in both the rest and the stress phases because of faster hepatobiliary clearance.

Prospective study of 99mTc-3PRGD2 SPECT/CT diagnosing metastatic lymph nodes in esophageal squamous cell carcinoma.

BACKGROUND: Lymph node (LN) metastasis is a significant prognostic factor for esophageal squamous cell carcinoma (ESCC), and there are no satisfactory methods for accurately predicting metastatic LNs. The present study aimed to assess the efficacy of 99mTc-3PRGD2 single-photon emission computed tomography (SPECT)/computed tomography (CT) for diagnosing metastatic LNs in ESCC. METHODS: A total of 15 enrolled patients with ESCC underwent 99mTc-3PRGD2 SPECT/CT and 18F-fluorodeoxyglucose positron emission tomography-computed tomography (18F-FDG PET/CT) examinations preoperatively. High-definition bone carving reconstruction technology (HD-xSPECT Bone) was applied to quantitatively assess the LN's SUVmax via SPECT/CT. The two methods were compared for diagnosing metastatic LNs with pathology as the gold standard. RESULTS: Among 15 patients, 23 metastatic lymph node stations (mLNSs) were predicted by SPECT/CT, with a mean SUVmax of 2.71 ± 1.34, of which 15 were pathologically confirmed; 32 mLNSs were predicted by PET/CT with a mean SUVmax of 4.41 ± 4.02, of which 17 were pathologically confirmed. The sensitivity, specificity, accuracy, positive predictive value and negative predictive value of SPECT/CT for diagnosing metastatic LNs were 62.50%, 91.30%, 85.34%, 65.22%, and 90.32%, respectively, and those of PET/CT were 70.83%, 83.70%, 81.03%, 53.13%, and 91.67%, respectively. There was no significant difference in sensitivity (p = 0.061) or specificity (p = 0.058) between the two methods. The AUCSPECT/CT was 0.816 and the SUVmax threshold was 2.5. CONCLUSION: 99mTc-3PRGD2 SPECT/CT might be an effective method for diagnosing metastatic LNs in ESCC, especially in combination with HD-xSPECT Bone. The diagnostic efficiency of this method was noninferior to that of 18F-FDG PET/CT. The SUVmax threshold of 2.5 showed the highest agreement with the pathology findings.

Short- and long-term prognostic performance of exercise ECG and myocardial perfusion SPECT.

BACKGROUND: Myocardial perfusion SPECT (MPS) and exercise electrocardiography (Ex-ECG) results are of prognostic importance for short-term follow up duration. However, the value of MPS or Ex-ECG findings for long-term risk assessment is less evident as underlying risk factors for ischemic heart disease (IHD) gain in importance. OBJECTIVES: To assess the short- and long-term prognostic value of MPS and Ex-ECG in relation to known risk factors. METHODS AND MATERIALS: An observational study of 908 patients (age 63 years, 49% male, 45% prior IHD) referred for MPS and Ex-ECG. Follow-up was divided into two periods (short-term: <5 years and long-term: >5 years). Cardiac events were defined as a composite of acute myocardial infarction, unstable angina, unplanned revascularization and cardiovascular death. RESULTS: The composite endpoint occurred in 95 patients (short-term follow up) and in 94 patients (long-term follow up). In multivariable models stress testing had a strong predictive value for short-term follow up (HR for MPS = 2.9, CI = 1.9-4.5, p < 0.001 and HR for Ex-ECG = 2.1, CI 1.3-3.3, p = 0.002), but no predictive value for long-term follow up (HR for MPS = 0.9, CI = 0.5-1.5, p = 0.70 and HR for Ex-ECG = 1.0, CI = 0.6-1.6, p = 0.92). Male sex and prior IHD were significant predictors regardless of follow up duration. Age, diabetes and decreased exercise capacity were risk factors for long-term follow up. CONCLUSIONS: The prognostic value of MPS and Ex-ECG results are strong for short-term follow up but diminish over time and do not contribute significantly in multivariable models after 5 years. Long-term prognosis is primarily governed by underlying risk factors and exercise capacity.

SPECT/CT imaging: quantifying 99mTc-MDP concentration in the spine and pelvis.

OBJECTIVE: This study aimed to identify a relatively robust SUV for guiding clinical practice through quantitative measurement and comparison of various normalization methods based on the SUV of 99mTc-MDP in the normal spine and pelvis using an integrated SPECT/CT scanner. METHODS: Between June 2017 and September 2019, a total of 500 oncology patients (mean age, 60.9; men, 66.0%) who underwent bone SPECT/CT scans with 99mTc-MDP were enrolled in this retrospective study. The mean SUV (SUVmean) of 4962 spinal and pelvic bones was calculated based on the patients' body weight (BW), lean body mass (LBM), bone mineral content (BMC), body surface area (BSA), and body mass index (BMI), defined as SUVbw, SUVlbm, SUVbmc, SUVbsa, and SUVbmi, respectively. The coefficients of variation (CoVs) of the aforementioned parameters were compared, and the correlation and multiple linear regression analyses were used to compare the extent to which these parameters were affected by sex, age, height, weight, BMI, and CT values. RESULTS: The average SUVs in the normal spine and pelvis displayed a relatively wide variability: 4.573 ± 1.972 for SUVbw, 3.555 ± 1.517 for SUVlbm, 0.163 ± 0.071 for SUVbmc, 0.124 ± 0.052 for SUVbsa, and 1.668 ± 0.732 for SUVbmi. In general, SUVbsa had relatively lowest CoV (42.1%) in all vertebrae and pelvis compared with other SUVs. For correlation analyses, all SUVs displayed weak but significant correlations with age and CT values. For regression analyses, SUVbsa was influenced only by age, BMI, and CT values independently. The effects of these variables on SUVbsa were all smaller than those on conventional SUVbw. CONCLUSIONS: The SUVs of 99mTc-MDP in normal bone derived from quantitative bone SPECT/CT could serve as a reference for evaluating tumor bone metastasis, but it should be assessed on a site-specific basis. SUVbsa exhibited superior robustness among all the SUV normalization variations, indicating potential clinical applications.

Subtraction of single-photon emission computed tomography (SPECT) in radioembolization: a comparison of four methods.

BACKGROUND: Subtraction of single-photon emission computed tomography (SPECT) images has a number of clinical applications in e.g. foci localization in ictal/inter-ictal SPECT and defect detection in rest/stress cardiac SPECT. In this work, we investigated the technical performance of SPECT subtraction for the purpose of quantifying the effect of a vasoconstricting drug (angiotensin-II, or AT2) on the Tc-99m-MAA liver distribution in hepatic radioembolization using an innovative interventional hybrid C-arm scanner. Given that subtraction of SPECT images is challenging due to high noise levels and poor resolution, we compared four methods to obtain a difference image in terms of image quality and quantitative accuracy. These methods included (i) image subtraction: subtraction of independently reconstructed SPECT images, (ii) projection subtraction: reconstruction of a SPECT image from subtracted projections, (iii) projection addition: reconstruction by addition of projections as a background term during the iterative reconstruction, and (iv) image addition: simultaneous reconstruction of the difference image and the subtracted image. RESULTS: Digital simulations (XCAT) and phantom studies (NEMA-IQ and anthropomorphic torso) showed that all four methods were able to generate difference images but their performance on specific metrics varied substantially. Image subtraction had the best quantitative performance (activity recovery coefficient) but had the worst visual quality (contrast-to-noise ratio) due to high noise levels. Projection subtraction showed a slightly better visual quality than image subtraction, but also a slightly worse quantitative accuracy. Projection addition had a substantial bias in its quantitative accuracy which increased with less counts in the projections. Image addition resulted in the best visual image quality but had a quantitative bias when the two images to subtract contained opposing features. CONCLUSION: All four investigated methods of SPECT subtraction demonstrated the capacity to generate a feasible difference image from two SPECT images. Image subtraction is recommended when the user is only interested in quantitative values, whereas image addition is recommended when the user requires the best visual image quality. Since quantitative accuracy is most important for the dosimetric investigation of AT2 in radioembolization, we recommend using the image subtraction method for this purpose.

From neurons to brain networks, pharmacodynamics of stimulant medication for ADHD.

Stimulants represent the first line pharmacological treatment for attention-deficit/hyperactivity disorder (ADHD) and are among the most prescribed psychopharmacological treatments. Their mechanism of action at synaptic level has been extensively studied. However, it is less clear how their mechanism of action determines clinically observed benefits. To help bridge this gap, we provide a comprehensive review of stimulant effects, with an emphasis on nuclear medicine and magnetic resonance imaging (MRI) findings. There is evidence that stimulant-induced modulation of dopamine and norepinephrine neurotransmission optimizes engagement of task-related brain networks, increases perceived saliency, and reduces interference from the default mode network. An acute administration of stimulants may reduce brain alterations observed in untreated individuals in fronto-striato-parieto-cerebellar networks during tasks or at rest. Potential effects of prolonged treatment remain controversial. Overall, neuroimaging has fostered understanding on stimulant mechanism of action. However, studies are often limited by small samples, short or no follow-up, and methodological heterogeneity. Future studies should address age-related and longer-term effects, potential differences among stimulants, and predictors of treatment response.