Suppression of myocardial glucose metabolism in FDG PET/CT: impact of dose variation in heparin bolus pre-administration.

INTRODUCTION: Adequate suppression of physiologic myocardial glucose uptake is important to ensure the interpretability and diagnostic reliability of [18F]fluorodeoxyglucose (FDG) PET/CT studies performed in the context of cardiac inflammation and infection. This study describes our experience with 4 preparatory protocols used in our institution. METHODS: FDG PET/CT scans were performed according to 4 preparatory protocols (716 scans total), i.e. 6-h fast (group 1), low-carbohydrate diet plus 12-h fast (group 2), low-carbohydrate diet plus 12-h fast plus intravenous heparin pre-administration (15 IU/kg) (group 3), and low-carbohydrate diet plus 12-h fast plus intravenous heparin pre-administration (50 IU/kg) (group 4). Consecutive scans were retrospectively included from time frames during which the particular protocol was used. FDG uptake in normal myocardium was scored on a scale ranging from 0 (uptake less than that in the left ventricular blood pool) to 4 (diffuse uptake greater than that in the liver). Complete suppression was defined as uptake less than or equal to the blood pool (scores 0-1). RESULTS: Complete suppression was accomplished in 27% in group 1, 68% in group 2, 69% in group 3 and 81% in group 4. Complete suppression was significantly lower in group 1 compared with all other groups (P < 0.0001 for all comparisons) and significantly higher in group 4 compared with group 2 (P = 0.005) and group 3 (P = 0.007). Groups 2 and 3 did not differ significantly (P = 0.92). CONCLUSION: A total of 50 IU/kg single-dose heparin administration before FDG PET/CT in addition to a low-carbohydrate diet and prolonged fast significantly outperformed protocols with no or lower dose (15 IU/kg) heparin in completely suppressing myocardial glucose metabolism.

Dual-time-point FDG PET/CT imaging in prosthetic heart valve endocarditis.

PURPOSE: FDG PET/CT has been of increasing interest in the diagnostic workup of prosthetic heart valve endocarditis (PVE). Some reports advocate later imaging time points to improve the diagnostic accuracy for PVE. In this study, we compared standard and late FDG PET/CT images in patients with a clinical suspicion of PVE. MATERIALS AND METHODS: Fourteen scans in 13 patients referred for FDG PET/CT for suspicion of PVE performed at standard (60 min post injection) and late (150 min post injection) time points were scored based on visual interpretation and semi-quantitatively with SUVmax and target-to-background ratio (TBR, defined as [SUVmax valve/SUVmean blood pool]). Final diagnosis was based on surgical findings in all cases of infection (n = 6) and unremarkable follow-up in all others (n = 8). RESULTS: Late images were more prone to false positive interpretation for both visual and semi-quantitative analyses. Visual analysis of the standard images yielded 1 false negative and 1 false positive result. On the late images, no scans were false negative but 5 scans were false positive. CONCLUSION: Late FDG PET/CT imaging for PVE seems prone to false positive results. Therefore, late imaging should be interpreted with caution.

Novel imaging strategies for the detection of prosthetic heart valve obstruction and endocarditis.

Prosthetic heart valve (PHV) dysfunction remains difficult to recognise correctly by two-dimensional (2D) transthoracic and transoesophageal echocardiography (TTE/TEE). ECG-triggered multidetector-row computed tomography (MDCT), 18-fluorine-fluorodesoxyglucose positron emission tomography including low-dose CT (FDG-PET) and three-dimensional transoesophageal echocardiography (3D-TEE) may have additional value. This paper reviews the role of these novel imaging tools in the field of PHV obstruction and endocarditis.For acquired PHV obstruction, MDCT is of additional value in mechanical PHVs to differentiate pannus from thrombus as well as to dynamically study leaflet motion and opening/closing angles. For biological PHV obstruction, additional imaging is not beneficial as it does not change patient management. When performed on top of 2D-TTE/TEE, MDCT has additional value for the detection of both vegetations and pseudoaneurysms/abscesses in PHV endocarditis. FDG-PET has no complementary value for the detection of vegetations; however, it appears more sensitive in the early detection of pseudoaneurysms/abscesses. Furthermore, FDG-PET enables the detection of metastatic and primary extra-cardiac infections. Evidence for the additional value of 3D-TEE is scarce.As clinical implications are major, clinicians should have a low threshold to perform additional MDCT in acquired mechanical PHV obstruction. For suspected PHV endocarditis, both FDG-PET and MDCT have complementary value.

Differential FDG-PET Uptake Patterns in Uninfected and Infected Central Prosthetic Vascular Grafts.

OBJECTIVE: (18)F-fluorodeoxyglucose (FDG) positron emission tomography (PET) scanning has been suggested as a means to detect vascular graft infections. However, little is known about the typical FDG uptake patterns associated with synthetic vascular graft implantation. The aim of the present study was to compare uninfected and infected central vascular grafts in terms of various parameters used to interpret PET images. METHODS: From 2007 through 2013, patients in whom a FDG-PET scan was performed for any indication after open or endovascular central arterial prosthetic reconstruction were identified. Graft infection was defined as the presence of clinical or biochemical signs of graft infection with positive cultures or based on a combination of clinical, biochemical, and imaging parameters (other than PET scan data). All other grafts were deemed uninfected. PET images were analyzed using maximum systemic uptake value (SUVmax), tissue to background ratio (TBR), visual grading scale (VGS), and focality of FDG uptake (focal or homogenous). RESULTS: Twenty-seven uninfected and 32 infected grafts were identified. Median SUVmax was 3.3 (interquartile range [IQR] 2.0-4.2) for the uninfected grafts and 5.7 for the infected grafts (IQR 2.2-7.8). Mean TBR was 2.0 (IQR 1.4-2.5) and 3.2 (IQR 1.5-3.5), respectively. On VGS, 44% of the uninfected and 72% of the infected grafts were judged as a high probability for infection. Homogenous FDG uptake was noted in 74% of the uninfected and 31% of the infected grafts. Uptake patterns of uninfected and infected grafts showed a large overlap for all parameters. CONCLUSION: The patterns of FDG uptake for uninfected vascular grafts largely overlap with those of infected vascular grafts. This questions the value of these individual FDG-PET-CT parameters in identifying infected grafts.

Vemurafenib for BRAF V600 mutated advanced melanoma: results of treatment beyond progression.

BACKGROUND: Selective BRAF inhibition (BRAFi) by vemurafenib or dabrafenib has become approved standard treatment in BRAF V600 mutated advanced stage melanoma. While the response rate is high, the response duration is limited with a progression-free survival (PFS) of 5-6months. Our observation of accelerated disease progression within some patients after stopping vemurafenib treatment has fostered the idea of treatment beyond progression (BRAFi TBP). METHOD: In this retrospective study, we analysed 70 metastatic melanoma patients, treated at our institute, who experienced progression after prior objective response upon treatment with vemurafenib. Thirty-five patients that continued treatment beyond progression are compared with 35 patients who stopped BRAFi treatment at disease progression. RESULTS: Median overall survival beyond documented progression was found to be 5.2months versus 1.4months (95% confidence interval (CI): 3.8-7.4 versus 0.6-3.4; Log-Rank p=0.002) in favour of BRAFi TBP. In the multivariate survival analysis, stopping treatment at disease progression was significantly associated with shorter survival (hazard ratio: 1.92; 95% CI: 1.04-3.55; p=0.04). CONCLUSION: Our results suggest that continuing vemurafenib treatment beyond progression may be beneficial in advanced melanoma patients, who prior to progression responded to vemurafenib.

The role of prostatic arterial embolization in patients with benign prostatic hyperplasia: a systematic review.

PURPOSE: This study was designed to summarize the evidence on clinical outcomes and complications of prostatic arterial embolization (PAE) in patients with benign prostatic hyperplasia (BPH). METHODS: We searched Medline and Embase for PAE trials of patients with BPH upto November 2013. Two reviewers independently checked the inclusion and exclusion criteria and performed data extraction of study characteristics, quantitative and qualitative outcomes, and complications. RESULTS: The search yielded 562 studies, of which 9 articles with 706 patients were included. In these 9 articles, there was a possible overlap of data and the quality of 8 studies was assessed as poor. All patients had moderate-to-severe, lower urinary tract symptoms (LUTS). The mean age ranged from 63.4-74.1 years. After embolization, a decrease of the prostate volume (PV) and post void residual (PVR) was seen mainly in the first month with a further decrease up to 12 months, increasing afterwards. The prostate specific antigen (PSA) decreased up to 3 months after PAE, increasing afterwards. The peak urinary flow (Qmax) increased mainly the first month and decreased after 30 months. The international prostate symptom score (IPSS) and quality of life-related symptoms (QOL) improved mainly during the first month, with a further improvement up to 30 months. No deterioration of the international index of erectile function (IIEF) was seen after PAE. The PAE procedure seems safe. CONCLUSIONS: Although the number of studies was small, qualitatively poor, and with overlap of patients, the initial clinical outcomes as reported up to 12 months seem positive and the procedure seems safe.

Cardiac sympathetic innervation and cardiac resynchronization therapy.

Cardiac resynchronization therapy (CRT) is a disease modifying, device-driven treatment that can reduce morbidity and mortality in patients with heart failure. According to the current guidelines, the indication for CRT is only based on QRS duration and functional class of heart failure. However, a substantial amount of patients do not respond to therapy. In addition, CRT is accompanied by significant cost and potential morbidity. It is therefore vital to improve patient selection for CRT to improve patient outcome and minimize therapy-related complications. In this regard, cardiac sympathetic innervation may be of interest. This review addresses the currently available literature, 9 studies with a total number of 225 patients, on CRT and cardiac innervation scintigraphy with (123)I-metaiodobenzylguanidine.

Myocardial perfusion reserve compared with peripheral perfusion reserve: a [13N]ammonia PET study.

INTRODUCTION: [13N]ammonia PET allows quantification of myocardial perfusion. The similarity between peripheral flow and myocardial perfusion is unclear. We compared perfusion flow in the myocardium with the upper limb during rest and adenosine stress [13N]ammonia PET to establish whether peripheral perfusion reserve (PPR) correlates with MPR. METHODS: [13N]ammonia myocardial perfusion PET-scans of 58 patients were evaluated (27 men, 31 women, age 64 ± 13 years) and were divided in four subgroups: patients with coronary artery disease (CAD, n = 15), cardiac syndrome X (SX, n = 14), idiopathic dilating cardiomyopathy (DCM, n = 16), and normal controls (NC, n = 13). Peripheral limb perfusion was measured in the muscular tissue of the proximal upper limb and quantified through a 2-tissue-compartment model and the PPR was calculated (stress/rest ratio). MPR was also calculated by a 2-tissue-compartment model. The PPR results were compared with the MPR findings. RESULTS: Mean myocardial perfusion increased significantly in all groups as evidenced by the MPR (CAD 1.99 ± 0.47; SX 1.39 ± 0.31; DCM 1.72 ± 0.69; NC 2.91 ± 0.78). Mean peripheral perfusion also increased but not significantly and accompanied with great variations within and between groups (mean PPR: CAD 1.30 ± 0.79; SX 1.36 ± 0.71; DCM 1.60 ± 1.22; NC 1.27 ± 0.63). The mean difference between PPR and MPR for all subpopulations varied widely. No significant correlations in flow reserve were found between peripheral and myocardial microcirculatory beds in any of the groups (Total group: r = -0.07, SEE = 0.70, CAD: r = 0.14, SEE = 0.48, SX: r = 0.17, SEE = 0.30, DCM: r = -0.11, SEE = 0.71, NC: r = -0.19, SEE = 0.80). CONCLUSION: No correlations between myocardial and peripheral perfusion (reserve) were found in different patient populations in the same PET session. This suggests a functional difference between peripheral and myocardial flow in the response to intravenously administered adenosine stress.