Reliability of standardized uptake value normalized to lean body mass using the liver as a reference organ, in contrast-enhanced 18F-FDG PET/CT imaging

Use of PET/CT to detect myocardial inflammation and the risk of malignant arrhythmia in chronic Chagas disease

BACKGROUND

Chagas heart disease (CHD) is characterized by progressive myocardial inflammation associated with myocardial fibrosis and segmental abnormalities that may lead to malignant ventricular arrhythmia and sudden cardiac death. This arrhythmia might be related to the persistence of parasitemia or inflammation in the myocardium in late-stage CHD. Positron emission tomography/computed tomography (PET/CT) has been used to detect myocardial inflammation in non-ischemic cardiomyopathies, such as sarcoidosis, and might be useful for risk prediction in patients with CHD.

METHODS AND RESULTS

Twenty-four outpatients with chronic CHD were enrolled in this prospective cross-sectional study between May 2019 and March 2022. The patients were divided into two groups: those with sustained ventricular tachycardia and/or aborted sudden cardiac death who required implantable cardioverter-defibrillators, and those with the same stages of CHD and no complex ventricular arrhythmia. Patients underwent 18F-fluorodeoxyglucose (18F-FDG) and 68Ga-DOTATOC PET/CT, and blood samples were collected for qualitative parasite assessment by polymerase chain reaction. Although similar proportions of patients with and without complex ventricular arrhythmia showed 18F-FDG and 68Ga-DOTATOC uptake, 68Ga-DOTATOC corrected SUVmax was higher in patients with complex arrhythmia (3.4 vs 1.7; P = .046), suggesting that inflammation could be associated with the presence of malignant arrhythmia in the late stages of CHD. We also detected Trypanosoma cruzi in both groups, with a nonsignificant trend of increased parasitemia in the group with malignant arrhythmia (66.7% vs 33.3%).

CONCLUSION

18F-FDG and 68Ga-DOTATOC uptake on PET/CT may be useful for the detection of myocardial inflammation in patients with Chagas cardiomyopathy, and 68Ga-DOTATOC uptake may be associated with the presence of malignant arrhythmia, with potential therapeutic implications.

Variations induced by body weight and background lesion normalization in standardized uptake value estimated by F18-FDG PET/CT

AIM

This work aims to study the impact of different SUV variants in terms of mean and maximum measures as well as various normalization methods with respect to body weight, body mass index, body surface area, and lean body mass in patients with lymphoma.

METHODS

Sixty-nine patients (34 male-35 female) were retrospectively selected. All patients had undergone F18-FDG PET/CT using the standard imaging protocol. In the first part of this study, SUVmean and SUVmax of patients' lesions and three background sites including liver, aorta, and muscle were determined. Then, the normalization of lesion SUV to body weight and body background sites was performed. The ratio of lesion SUVmax to body background sites (muscle, aorta, and liver) SUVmax was determined in addition to the ratio of lesion SUVmean to body background sites SUVmean. The second part of the study included the calculations of the body mass index (BMI), body surface area (BSA), and lean body mass (LBM). The normalization of lesion, liver, aorta, and muscle SUV to BMI, BSA, and LBM was calculated and compared to each other.

RESULTS

After performing the appropriate statistical calculations, the results showed that there is a significant difference in SUV measurements between the three background sites. Lesions normalized to the liver were significantly lower than those normalized to aorta and muscle and the results also showed a higher magnitude of lesions normalized to muscle in comparison to the aorta. The SUVmax and SUVmean normalized to different body weight indices showed the lowest variation with BSA and BMI while being increasingly higher with lean body mass using the two methods James and Janmahasatian, respectively, and then highest with body weight.

CONCLUSION

The SUVmax and SUVmean showed lower variance in comparison to other background regions. Less variation was also remarkable in SUVmean normalized to BSA and Janma lean mass and also when SUVmax is normalized to James lean body mass. The SUVmax normalized to lean (i.e., James) as well as SUVmean normalized to lean (i.e., Janma) and BSA showed a significant independence with body weight.

The utility of the standardized uptake value, metabolic tumor volume and total lesion glycolysis as predictive markers of recurrent breast cancer

Background

Breast cancer is the second leading cancer killer of women globally. An early measure utilizing a noninvasive molecular marker for predicting cancer aggressiveness is important to better manage the patient and to avert early disease progression. We aimed to determine whether metabolic tumor volume (MTV) and total lesion glycolysis (TLG) are able to predict risk in high TNM tumor staging and the need for the appropriate treatment in breast cancer patients. This is a retrospective study of confirmed breast cancer patients who underwent neoadjuvant, local and adjuvant treatment and follow-up. The 18F-FDG PET/CT study for initial staging was performed, and metabolic parameters (MTV, TLG, SUVmax mean) were analyzed. Spearman correlation was used to assess correlations between metabolic parameters and clinicopathological factors with TNM staging and treatment intention. SUVmean, wbMTV and wbTLG were analyzed to predict the dichotomization of patient endpoint for low (stage I and II) and high (stage III and IV) TNM stage.

Results

Twenty-six patients (4 low stage, 22 high stage) with a mean age of 51.8 ± 11.8 years with confirmed breast cancer underwent 18FFDG PET/CT. The MTV and TLG parameters in the tumor (T) were significantly correlated with the TNM stage (P < 0.050); the SUVmax mean (4.18 ± 1.68 g/dl), wbMTV mean (404.68 ± 558.02 cm3) and wbTLG (1756.55 ± 2432.11 g) differed significantly in the high versus low TNM staging with the best predictive cut-off value of SUVmax mean (3.55 g/ml, p < 0.05), wbMTV (20 cm3, p < 0.05) and wbTLG (130 g, p < 0.05) when these values were exceeded. Only wbTLG (130 g, p < 0.05) showed significance difference in treatment intention.

Conclusions

In this study, the metabolic parameters SUVmax mean, MTV and TLG showed potential good relationships with TNM staging. TLG was the only marker that influenced the treatment intention in predicting breast cancer aggressiveness.

2-[18F]FDG PET/CT as a Predictor of Microvascular Invasion and High Histological Grade in Patients with Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) generally presents a low avidity for 2-deoxy-2-[18F]fluoro-d-glucose (FDG) in PET/CT although an increased FDG uptake seems to relate to more aggressive biological factors. To define the prognostic value of PET/CT with FDG in patients with an HCC scheduled for a tumor resection, forty-one patients were prospectively studied. The histological factors of a poor prognosis were determined and FDG uptake in the HCC lesions was analyzed semi-quantitatively (lean body mass-corrected standardized uptake value (SUL) and tumor-to-liver ratio (TLR) at different time points). The PET metabolic parameters were related to the histological characteristics of the resected tumors and to the evolution of patients. Microvascular invasion (MVI) and a poor grade of differentiation were significantly related to a worse prognosis. The SULpeak of the lesion 60 min post-FDG injection was the best parameter to predict MVI while the SULpeak of the TLR at 60 min was better for a poor differentiation. Moreover, the latter parameter was also the best preoperative variable available to predict any of these two histological factors. Patients with an increased TLRpeak60 presented a significantly higher incidence of poor prognostic factors than the rest (75% vs. 28.6%, p = 0.005) and a significantly higher incidence of recurrence at 12 months (38% vs. 0%, p = 0.014). Therefore, a semi-quantitative analysis of certain metabolic parameters on PET/CT can help identify, preoperatively, patients with histological factors of a poor prognosis, allowing an adjustment of the therapeutic strategy for those patients with a higher risk of an early recurrence.

Assessment of Brain Glucose Metabolism Following Cardiac Arrest by [18F]FDG Positron Emission Tomography

BACKGROUND

Cardiac arrest (CA) patients who survived by cardiopulmonary resuscitation (CPR) can present different levels of neurological deficits ranging from minor cognitive impairments to persistent vegetative state and brain death. The pathophysiology of the resulting brain injury is poorly understood, and whether changes in post-CA brain metabolism contribute to the injury are unknown. Here we utilized [¹⁸F]fluorodeoxyglucose (FDG)-Positron emission tomography (PET) to study in vivo cerebral glucose metabolism 72 h following CA in a murine CA model.

METHODS

Anesthetized and ventilated adult C57BL/6 mice underwent 12-min KCl-induced CA followed by CPR. Seventy-two hours following CA, surviving mice were intraperitoneally injected with [¹⁸F]FDG (~ 186 µCi/200 µL) and imaged on Molecubes preclinical micro-PET/computed tomography (CT) imaging systems after a 30-min awake uptake period. Brain [¹⁸F]FDG uptake was determined by the VivoQuant software on fused PET/CT images with the 3D brain atlas. Upon completion of Positron emission tomography (PET) imaging, remaining [¹⁸F]FDG radioactivity in the brain, heart, and liver was determined using a gamma counter.

RESULTS

Global increases in brain [¹⁸F]FDG uptake in post-CA mice were observed compared to shams and controls. The median standardized uptake value of [¹⁸F]FDG for CA animals was 1.79 versus sham 1.25 (p < 0.05) and control animals 0.78 (p < 0.01). This increased uptake was consistent throughout the 60-min imaging period and across all brain regions reaching statistical significance in the midbrain, pons, and medulla. Biodistribution analyses of various key organs yielded similar observations that the median [¹⁸F]FDG uptake for brain was 7.04%ID/g tissue for CA mice versus 5.537%ID/g tissue for sham animals, p < 0.05).

CONCLUSIONS

This study has successfully applied [¹⁸F]FDG-PET/CT to measure changes in brain metabolism in a murine model of asystolic CA. Our results demonstrate increased [¹⁸F]FDG uptake in the brain 72 h following CA, suggesting increased metabolic demand in the case of severe neurological injury. Further study is warranted to determine the etiology of these changes.

Revalidation of PET/computed tomography criteria (Hopkins criteria) for the assessment of therapeutic response in lung cancer patients: inter-reader reliability, accuracy and survival outcomes

BACKGROUND/AIM

Systematic reporting using qualitative evaluation of PET/computed tomography (CT) results has been demonstrated to be very accurate and reproducible in posttherapy assessment of lung cancer (so-called Hopkins criteria). Our aim was to test, in a different cohort of patients, the Hopkins criteria for assessment of therapeutic response in lung cancer and to compare the results with those obtained using a semi-quantitative evaluation of uptake.

METHODS

This is a retrospective study. A total of 85 patients with known lung cancer who underwent fluorine-18 fluorodeoxyglucose PET/CT assessment within 24 weeks (mean 7.9 weeks) of completion of treatment were included. Treatments included surgical resection, chemotherapy, radiation therapy, immunotherapy or combinations thereof. PET/CT interpretation was done by two nuclear medicine physicians, and discrepancies were resolved by a third interpreter. Studies were scored both according to the Hopkins criteria using qualitative assessment of tracer uptake for the primary tumour, locoregional disease in the mediastinum and distant metastatic sites and by applying the same five-point score using a semi-quantitative measure, maximum standardized uptake value. Overall scores of 1, 2 and 3 were considered negative for residual disease, while scores of 4 and 5 were considered positive. Patients were followed up for a median of 18.5 months (range 2-139 months). Kaplan-Meier plots with a Mantel-Cox log-rank test were performed, considering death as the endpoint. Inter-reader variability was assessed using percent agreement and kappa statistics.

RESULTS

The Cohen κ coefficient analysis showed substantial agreement between the two interpreters on the five-point Hopkins criteria scoring, with a κ of 0.73. There was almost perfect agreement between the interpreters with respect to classification as positive or negative according to the Hopkins criteria, with a κ of 0.89. The sensitivity, specificity, positive predictive value, negative predictive value and accuracy of the Hopkins criteria were 88.5% [95% confidence interval (CI) 80.6-96.5%), 79.2% (95% CI 63.2-95.1%), 91.5% (95% CI 84.4-98.6%), 73.1% (95% CI 61.8-84.4%) and 85.9% (95% CI 78.5-93.3%), respectively. There was almost perfect agreement between the qualitative and semi-quantitative scoring with a κ of 0.87, with sensitivity, specificity, positive predictive value, negative predictive value and accuracy of the semi-quantitative Hopkin's criteria of 86.9% (95% CI 78.4-95.4%), 79.2% (95% CI 62.9-95.4%), 91.4% (95% CI 84.2-98.6%), 70.4% (95% CI 58.6-82.1%) and 84.7% (95% CI 80.8-92.4%), respectively.

CONCLUSION

The use of Hopkins criteria for posttherapy assessment in patients with lung cancer represents an easy and reproducible method with substantial to almost perfect interobserver agreement and high positive predictive value and accuracy; moreover, it is easily understood by referring physicians. Additionally, there was no significant difference when applying a semi-quantitative measure to the same five-point score.

Voxel-wise analysis of 18F-fluorodeoxyglucose metabolism in correlation with variations in the presentation of Alzheimer’s disease: a clinician’s guide

BACKGROUND Diagnostic imaging can be applied in the management of Alzheimer’s disease as it provides structural and functional information to exclude possible secondary causes and offers additional information, especially in atypical cases of Alzheimer’s disease. The utility of positron emission tomography/computed tomography (PET/CT) can help in the noninvasive diagnosis of Alzheimer’s disease by voxel-wise quantification of cerebral 18F-fluorodeoxyglucose (FDG) metabolism.  METHODS This prospective study was conducted among 10 subjects with Alzheimer’s disease and 10 healthy control subjects who underwent neuropsychological testing and 18F-FDG PET/CT scans. Images of the brain were postprocessed using voxel-wise analysis and segmented into 20 regions of interest. The standardized uptake value (SUV)max/SUVmean/standard deviation of SUVmean results were analyzed accordingly and correlated with the subjects’ Montreal cognitive assessment (MoCA) results that were adjusted for age and education level.  RESULTS Hypometabolism at the right parietal lobe significantly correlated with increasing age and lower MoCA scores. Global hypometabolism was observed in subjects who had advanced Alzheimer’s disease but preserved primary somatosensory cortices (S1) region metabolism. Predominance of frontal lobe hypometabolism was a feature of subjects with Alzheimer’s disease having associated depressive symptoms.  CONCLUSIONS 18F-FDG PET/CT voxel-wise analysis can be used for quantitative assessment and can assist clinicians in the diagnosis of Alzheimer’s disease and other variations of the disease spectrum.

The Who, When, Why, and How of PET Amyloid Imaging in Management of Alzheimer's Disease-Review of Literature and Interesting Images

Amyloid imaging using positron emission tomography (PET) has an emerging role in the management of Alzheimer’s disease (AD). The basis of this imaging is grounded on the fact that the hallmark of AD is the histological detection of beta amyloid plaques (Aβ) at post mortem autopsy. Currently, there are three FDA approved amyloid radiotracers used in clinical practice. This review aims to take the readers through the array of various indications for performing amyloid PET imaging in the management of AD, particularly using 18F-labelled radiopharmaceuticals. We elaborate on PET amyloid scan interpretation techniques, their limitations and potential improved specificity provided by interpretation done in tandem with genetic data such as apolipiprotein E (APO) 4 carrier status in sporadic cases and molecular information (e.g., cerebral spinal fluid (CSF) amyloid levels). We also describe the quantification methods such as the standard uptake value ratio (SUVr) method that utilizes various cutoff points for improved accuracy of diagnosing AD, such as a threshold of 1.122 (area under the curve 0.894), which has a sensitivity of 92.3% and specificity of 90.5%, whereas the cutoff points may be higher in APOE ε4 carriers (1.489) compared to non-carriers (1.313). Additionally, recommendations for future developments in this field are also provided.