A randomised controlled trial assessing the effect of oral diazepam on 18F-FDG uptake in the neck and upper chest region

Effect of Propranolol on 18F-Fluorodeoxyglucose Uptake in Brown Adipose Tissue in Children and Young Adults with Neoplastic Diseases

PURPOSE

To evaluate the effectiveness of propranolol at mitigating FDG uptake in brown adipose tissue (BAT) of pediatric patients with known or suspected malignancies.

METHODS

PET/CT scans of 3 cohorts of patients treated from 2005 to 2017 were scored for the presence of FDG uptake by BAT at 7 sites: right or left neck/supraclavicular area, right or left axilla, mediastinum, posterior thorax, and abdomen/pelvis. Uptake was scored as follows: 0, none; 1, mild uptake < liver; 2, moderate uptake = liver; and 3, intense uptake > liver. Group 1 consisted of 323 patients (630 scans) who had no specific preparation to mitigate FDG uptake by BAT. Group 2 consisted of 345 patients (705 scans) who underwent only warming in an uptake room with a fixed temperature at 24 °C. Group 3 consisted of 622 patients (1457 scans) who underwent warming. In group 3, patients 8 years and older, 471 patients (1114 scans), were also pre-medicated with oral propranolol 60 min before injection of FDG. Generalized estimation equation, using the logit link method, was used to model the relationship between the incidence of BAT score > 0, in any site, as a function of age, sex, seasonal effect, and body surface area (BSA).

RESULTS

In patients aged 8 years or older, the incidence of BAT uptake was 35-44 % and declined to 15 % with propranolol. BAT was most frequent in the neck (26 %), axilla (18 %), posterior thorax (18 %), mediastinum (14 %), and abdomen/pelvis (8 %); BAT was less common in warm months (p = 0.001). No substantial benefit was shown with pre-injection warming alone. No significant effect was found for age, sex, or BSA separately. When BAT uptake was present, it was usually intense.

CONCLUSION

Propranolol preparation minimizes FDG uptake by BAT and should be considered routine for pediatric FDG PET/CT cancer-related protocols in children, adolescents, and young adults.

Factors influencing brown fat activation in FDG PET/CT: a retrospective analysis of 15,000+ cases

OBJECTIVE

Brown fat can exhibit high uptake of fluorine-18 fludeoxyglucose (¹⁸F-FDG) on positron emission tomography (PET) and interferes with interpretation of the scan. The goal of this study was to identify factors that may influence brown adipose tissue (BAT) activation.

METHODS

A retrospective study of ¹⁸F-FDG PET scans was performed using a database of 15,109 PET/CT reports. BAT activation reported by nuclear medicine physicians and factors influencing BAT activation were gathered. The data were analyzed using in-house software.

RESULTS

The total reported BAT activation was 3.6%. BAT activation was reported significantly more often in patients who were female (p < 0.0001), younger (p < 0.0001), with lower body mass index (p < 0.0001), with lower blood glucose levels (p = 0.01), indicated for breast cancer (p = 0.004), not administered chemotherapy recently before the scan (p < 0.0001) and shown to have BAT activation in a previous scan (p < 0.0001). BAT activation was also reported significantly more for lower outdoor temperatures (p < 0.0001) and for late morning scans than for afternoon (p = 0.005) and early morning (p = 0.001) scans.

CONCLUSION

This retrospective study of 15,109 scans highlights multiple factors contributing to BAT activation on ¹⁸F-FDG PET. The identification of new factors influencing BAT and confirmation of previously identified factors with a larger data set can be used to more accurately identify patients at risk for BAT activation so that prevention strategies can be implemented. Advances in knowledge: This study presents new factors associated with higher incidence of BAT activation, such as time of day, previous BAT activation and breast cancer. Conversely, recent chemotherapy was associated with reduced incidence of BAT activation.

Meditative music listening to reduce state anxiety in patients during the uptake phase before positron emission tomography (PET) scans

OBJECTIVE

This study examines the effects of listening to meditative music on state anxiety and heart rate variability (HRV) of patients during the uptake phase before positron emission tomography (PET) scans.

METHODS

A two-group randomized experimental design was used. Eligible patients were randomly assigned to either the experimental or control group. All patients received baseline assessments of state anxiety using Spielberger State-Trait Anxiety Inventory (STAI-S) and HRV before receiving an intravenous injection of radiopharmaceutical fluorine-18 fludeoxyglucose in the uptake room. The experimental group (n = 35) listened individually to 30 min of meditative music, integrating Chinese "Chi" and western frequency resonation in the uptake room. The control group (n = 37) lay on bed quietly for 40 min in the uptake room without music. All patients were assessed for their anxiety level and HRV again, before receiving PET scanning as post-test.

RESULTS

The results indicated that patients in the experimental group showed a significant reduction in state anxiety and heart rate, and increase on high frequency norm of HRV (p < 0.001). There was a statistically significant reduction on anxiety level (p < 0.001), heart rate (p < 0.001) and high frequency norm (p = 0.001) in the experimental group compared with those of the control group.

CONCLUSION

Listening to meditative music as a non-invasive and cost-effective strategy can help maximize efforts to promote comfort and relaxation for patients awaiting stressful procedures, such as PET scans. Meditative music can be effective in alleviating state anxiety of patients during the uptake phase before PET scans. Advances in knowledge: The study provides scientific evidence of the effects of listening to meditative music for reducing state anxiety in patients during the uptake phase before PET scans. It may have the potential to lower the risk of unwanted false-positive fluorine-18 fludeoxyglucose uptake in normal organs and to further improve image quality and image interpretation. Listening to meditative music is a safe and inexpensive intervention which can be incorporated into routine procedures to reduce anxiety of patients undergoing PET scans.

Multiple symmetric lipomatosis: a rare disease and its possible links to brown adipose tissue

AIM

Aim of this study is an updated review of our case series (72 patients) as well as available literature on the Multiple Symmetric Lipomatosis (MSL), a rare disease primarily involving adipose tissue, characterized by the presence of not encapsulated fat masses, symmetrically disposed at characteristic body sites (neck, trunk, proximal parts of upper and lower limbs).

DATA SYNTHESIS

The disease is more frequent in males, associated to an elevated chronic alcohol consumption, mainly in form of red wine. Familiarity has been reported and MSL is considered an autosomic dominant inherited disease. MSL is associated to severe clinical complications, represented by occupation of the mediastinum by lipomatous tissue with a mediastinal syndrome and by the presence of a somatic and autonomic neuropathies. Hyper-alphalipoproteinemia with an increased adipose tissue lipoprotein-lipase activity, a defect of adrenergic stimulated lipolysis and a reduction of mitochondrial enzymes have been described. The localization of lipomatous masses suggests that MSL lipomas could originate from brown adipose tissue (BAT). Moreover, studies on cultured pre-adipocytes demonstrate that these cells synthetize the mitochondrial inner membrane protein UCP-1, the selective marker of BAT. Surgical removal of lipomatous tissue is to date the only validated therapeutic approach.

CONCLUSIONS

MSL is supposed to be the result of a disorder of the proliferation and differentiation of human BAT cells.

Head and neck: normal variations and benign findings in FDG positron emission tomography/computed tomography imaging

Positron emission tomography (PET)/computed tomography with FDG of the head and neck region is mainly used for the diagnosis of head and neck cancer, for staging, treatment evaluation, relapse, and planning of surgery and radio therapy. This article is a practical guide of imaging techniques, including a detailed protocol for FDG PET in head and neck imaging, physiologic findings, and pitfalls in selected case stories.

FDG PET/CT: EANM procedure guidelines for tumour imaging: version 2.0

The purpose of these guidelines is to assist physicians in recommending, performing, interpreting and reporting the results of FDG PET/CT for oncological imaging of adult patients. PET is a quantitative imaging technique and therefore requires a common quality control (QC)/quality assurance (QA) procedure to maintain the accuracy and precision of quantitation. Repeatability and reproducibility are two essential requirements for any quantitative measurement and/or imaging biomarker. Repeatability relates to the uncertainty in obtaining the same result in the same patient when he or she is examined more than once on the same system. However, imaging biomarkers should also have adequate reproducibility, i.e. the ability to yield the same result in the same patient when that patient is examined on different systems and at different imaging sites. Adequate repeatability and reproducibility are essential for the clinical management of patients and the use of FDG PET/CT within multicentre trials. A common standardised imaging procedure will help promote the appropriate use of FDG PET/CT imaging and increase the value of publications and, therefore, their contribution to evidence-based medicine. Moreover, consistency in numerical values between platforms and institutes that acquire the data will potentially enhance the role of semiquantitative and quantitative image interpretation. Precision and accuracy are additionally important as FDG PET/CT is used to evaluate tumour response as well as for diagnosis, prognosis and staging. Therefore both the previous and these new guidelines specifically aim to achieve standardised uptake value harmonisation in multicentre settings.

An ¹⁸F-FDG PET study of cervical muscle in parkinsonian anterocollis

The underlying etiology of parkinsonian anterocollis has been the subject of recent debate. The purpose of this study is to test the hypothesis that anterocollis in parkinsonian syndromes is associated with dystonia of the deep cervical flexors (longus colli and capitis). Eight patients with anterocollis, six in the setting of parkinsonism and two primary cervical dystonia control subjects with anterocollis underwent prospective structured clinical evaluations (interview, examination and rating scales), systematic electromyography of the cervical extensor musculature and (18)F-FDG PET/CT studies of cervical muscles to examine evidence of hypermetabolism or overactivity of deep cervical flexors. Subjects with parkinsonian anterocollis were found to have hypermetabolism of the extensor and sub-occipital muscles but not in the cervical flexors (superficial or deep). EMG abnormalities were observed in all evaluated patients, but only one patient was definitely myopathic. Meanwhile, both dystonia controls exhibited hypermetabolism of cervical flexors (including the longus colli). In conclusion, we were able to demonstrate hypermetabolism of superficial and deep cervical flexors with muscle (18)F-FDG PET/CT in dystonic anterocollis patients, but not in parkinsonian anterocollis patients. The hypermetabolic changes seen in parkinsonian anterocollis patients in posterior muscles may be compensatory. Alternative explanations for anterocollis include myopathy of the cervical extensors, or unbalanced rigidity of the cervical flexors, but this remains to be proven.

Determinants of physiologic 18F-FDG uptake in brown adipose tissue in sequential PET/CT examinations

PURPOSE

The aim of this study was to assess independent predictors of 2-deoxy-2-[(18)F]fluoro-D-glucose ((18)F-FDG) uptake in brown adipose tissue (BAT) in patients undergoing repeated positron emission tomography (PET)/computed tomography (CT) scans.

PROCEDURES

Eight hundred forty-eight (mean age 50.9 ± 16 years) patients in whom PET/CT scan was repeated (mean interval 5 ± 1.5 months) constituted the study group. (18)F-FDG uptake in characteristic areas of BAT, with CT density of adipose tissue, greater than background soft-tissue activity was considered as evidence of BAT uptake. Both distribution and maximum standardized uptake values (SUVmax) were registered. Clinical and anamnestic data were collected for each patient.

RESULTS

(18)F-FDG uptake in BAT was present in 8.6% patients at first scan. Independent predictors of presence of uptake were age (younger), gender (female), body mass index (lower), and maximum outdoor temperature (lower). Age was the only independent predictor of BAT (18)F-FDG uptake distribution, while SUVmax was related to both age and outdoor temperature. Independent determinants of persistence of BAT (18)F-FDG uptake at second PET/CT were outdoor temperature at time of second scan and extension of metabolically active BAT at first scan.

CONCLUSIONS

Age, body mass index, and outdoor temperature are significant determinants of BAT evidence at (18)F-FDG PET/CT. Moreover, extension of BAT and outdoor temperature are the strongest determinants of persistence of BAT evidence on (18)F-FDG PET/CT in repeated scan.

Intravenous administration of diazepam significantly reduces brown fat activity on 18F-FDG PET/CT

BACKGROUND

Brown adipose tissue (BAT) activity on (18)F-fluorodeoxyglucose (FDG) PET/CT can introduce an undesirable element of complexity when attempting to discern physiologic activity from more ominous entities. Recent studies have demonstrated several methods to reduce BAT FDG uptake. Benzodiazepines, however, have yet to been proven effective against BAT.

METHODS

Twenty-five patients with increased BAT FDG uptake were selected retrospectively from our PET/CT database between November 2004 and January 2011. These patients had been asked to return on a different day for repeat scanning with 5mg of intravenous diazepam, administered ten minutes prior to FDG. Two patients underwent this procedure on a second occasion (for a follow-up scan at a later date), thus resulting in a total of twenty-seven scans from twenty five patients. FDG uptake in BAT was recorded using the maximum standardized uptake value (SUVmax).

RESULTS

The mean basal BAT SUVmax was 10.1 ± 4.6 compared to a mean SUVmax of 2.8 ± 3.3 post IV diazepam (p < 0.0001). Approximately 89% (24 of 27) of scans had no significant residual BAT activity. The three remaining scans had a reduction in SUVmax ranging from 23-64% following diazepam administration. No adverse effects were noted.

CONCLUSION

We observed a significant reduction in brown fat activity in para-spinal, cervical, mediastinal, para-adrenal, and supra- and infra-clavicular regions on PET/CT following premedication with intravenous diazepam. We feel that IV benzodiazepines should be considered a pharmacologic option for reducing BAT FDG uptake, which in turn, will aid in distinguishing physiologic metabolic activity from pathology.

Brown adipose tissue 18F-FDG uptake in pediatric PET/CT imaging

Positron emission tomography (PET) using [F-18]2-fluoro-2-deoxyglucose (FDG) fused with CT ((18)F-FDG PET/CT) has been widely adopted in oncological imaging. However, it is known that benign lesions and other metabolically active tissues, such as brown adipose tissue (BAT), can accumulate (18)F-FDG, potentially resulting in false-positive interpretation. Previous studies have reported that (18)F-FDG uptake in BAT is more common in children than in adults. We illustrate BAT FDG uptake in various anatomical locations in children and adolescents. We also review what is known about the effects of patient-related physical attributes and environmental temperatures on BAT FDG uptake, and discuss methods used to reduce BAT FDG uptake on (18)F-FDG PET.

Therapeutic prospects of metabolically active brown adipose tissue in humans

The world-wide obesity epidemic constitutes a severe threat to human health and wellbeing and poses a major challenge to health-care systems. Current therapeutic approaches, relying mainly on reduced energy intake and/or increased exercise energy expenditure, are generally of limited effectiveness. Previously believed to be present only in children, the existence of metabolically active brown adipose tissue (BAT) was recently demonstrated also in healthy human adults. The physiological role of BAT is to dissipate chemical energy, mainly from fatty acids, as heat to maintain body temperature in cold environments. Recent studies indicate that the activity of BAT is negatively correlated with overweight and obesity, findings that raise the exciting possibility of new and effective weight reduction therapies based on increased BAT energy expenditure, a process likely to be amenable to pharmacological intervention.

Altered biodistribution on FDG-PET with emphasis on brown fat and insulin effect

(18)F-fluorodeoxyglucose (FDG) is the radiotracer used in the vast majority of positron emission tomography (PET) cancer studies. FDG is a powerful radiotracer that provides valuable data in many cancer types. Normal FDG biodistribution is easily identified. In the PET-only era, physiological uptake provided important anatomical landmarks. However, the normal biodistribution of FDG is often variable and can be altered by intrinsic or iatrogenic factors. Recognizing these patterns of altered biodistribution is important for optimal FDG-PET interpretation. Altered FDG uptake in muscles, brown adipose tissue, bone marrow, the urinary tract, and the bowel is demonstrated in a significant proportion of patients, which can hide underlying malignant foci or mimic malignant lesions. The introduction of PET/computed tomography revolutionized PET imaging, bringing much-needed anatomical information. This modality allowed better characterization of some types of uptake, particularly brown adipose tissue FDG uptake. Different approaches to minimize interference from altered FDG biodistribution should be considered when performing PET scans. Otherwise, careful review and correlation of metabolic (FDG-PET) and anatomical (computed tomography) data should be performed to accurately characterize the foci of increased FDG uptake.

Seasonal variation in the effect of constant ambient temperature of 24 degrees C in reducing FDG uptake by brown adipose tissue in children

PURPOSE

It has been shown that warming patients prior to and during (18)F-FDG uptake by controlling the room temperature can decrease uptake by brown adipose tissue (BAT). The aim of this study is to determine if this effect is subject to seasonal variation.

METHODS

A retrospective review was conducted of all patients referred for whole-body (18)F-FDG PET between December 2006 and December 2008. After December 2007, all patients were kept in the PET injection room at a constant 24 degrees C for 30 min before and until 1 h following FDG administration. Patients over 22 years of age and those who received pre-medication known to reduce FDG uptake by BAT were excluded. One hundred and three patients were warmed to 24 degrees C prior to scanning. The number of patients showing uptake by BAT in this group was compared to a control group of 99 patients who underwent PET prior to December 2007 when the injection room temperature was 21 degrees C.

RESULTS

Uptake by BAT occurred in 9% of studies performed after patient warming (24 degrees C), compared to 27% of studies performed on the control group (21 degrees C) (p < 0.00001). The effect of warming on decreasing FDG accumulation in BAT was statistically significant in the winter (p < 0.005) and summer (p < 0.001). However, in the spring and autumn, though the effect of warming on decreasing FDG accumulation in BAT was evident, it was not statistically significant (p > 0.05).

CONCLUSION

Maintaining room temperature at a constant 24 degrees C for 30 min prior to and 1 h after IV tracer administration significantly decreases FDG uptake by BAT in children. This effect is greatest in the summer and winter.

Methodological considerations in quantification of oncological FDG PET studies

Purpose

This review aims to provide insight into the factors that influence quantification of glucose metabolism by FDG PET images in oncology as well as their influence on repeated measures studies (i.e. treatment response assessment), offering improved understanding both for clinical practice and research.

Methods

Structural PubMed searches have been performed for the many factors affecting quantification of glucose metabolism by FDG PET. Review articles and references lists have been used to supplement the search findings.

Results

Biological factors such as fasting blood glucose level, FDG uptake period, FDG distribution and clearance, patient motion (breathing) and patient discomfort (stress) all influence quantification. Acquisition parameters should be adjusted to maximize the signal to noise ratio without exposing the patient to a higher than strictly necessary radiation dose. This is especially challenging in pharmacokinetic analysis, where the temporal resolution is of significant importance. The literature is reviewed on the influence of attenuation correction on parameters for glucose metabolism, the effect of motion, metal artefacts and contrast agents on quantification of CT attenuation-corrected images. Reconstruction settings (analytical versus iterative reconstruction, post-reconstruction filtering and image matrix size) all potentially influence quantification due to artefacts, noise levels and lesion size dependency. Many region of interest definitions are available, but increased complexity does not necessarily result in improved performance. Different methods for the quantification of the tissue of interest can introduce systematic and random inaccuracy.

Conclusions

This review provides an up-to-date overview of the many factors that influence quantification of glucose metabolism by FDG PET.