Blood perfusion and bone formation before and after minimally invasive periacetabular osteotomy analysed by Positron Emission Tomography combined with Computed Tomography.

PURPOSE: Sufficient blood perfusion is essential for successful bone healing after periacetabular osteotomy (PAO). The purpose of this study was to quantify blood perfusion and bone formation before and after PAO analysed by positron emission tomography (PET) combined with computed tomography (CT). METHODS: Twelve dysplastic patients (nine women) were included consecutively in the study and all were operated upon by the senior author (KS). Median age was 33 (23-55) years. Initially, two patients were PET scanned in a pilot study to test our models for calculation of the physiological parameters. The following ten patients had their hip joints PET/CT scanned immediately before PAO and three to four weeks after. Oxygen-15-water was used to quantify blood perfusion and Flourine-18-fluoride was used to produce quantitative images interpreted as new bone formation in the acetabular fragment. RESULTS: The blood perfusion of the operated acetabulum before surgery was 0.07 ± 0.02 ml/min/ml, and after surgery 0.19 ± 0.03 ml/min/ml (p = 0.0003). Blood perfusion of the non-operated acetabulum was 0.07 ± 0.02 ml/min/ml before PAO and 0.07 ± 0.02 ml/min/ml after surgery (p = 0.47). The fluoride-clearance per volume bone of the operated acetabulum was 0.02 ± 0.01 ml/min/ml preoperatively, and 0.06 ± 0.01 ml/min/ml postoperatively (p = 0.0005). Fluoride-clearance of the non-operated acetabulum was 0.01 ± 0.01 ml/min/ml before PAO and 0.02 ± 0.01 ml/min/ml after PAO (p = 0.49). CONCLUSION: Blood perfusion and new bone formation increased significantly in the acetabular fragment. Thus, the results of this study do not support the concern about surgically damaged vascularity after PAO.

Serotonin modulation of cerebral blood flow measured with positron emission tomography (PET) in humans.

To develop a method to measure the dynamic response of the serotonin system in vivo, the effects of intravenously administered citalopram (the most selective of the serotonin reuptake inhibitors) or clomipramine on cerebral blood flow (CBF) were evaluated. CBF was measured with positron emission tomography (PET) in 27 normal subjects scanned under baseline conditions and, on the same day, after an intravenous (IV) infusion of placebo, citalopram, or clomipramine using a randomized, double-blind design. The main effects of the drugs on blood flow occurred in the thalamus, hypothalamus, and cingulate cortex. Compared to placebo, clomipramine reduced blood flow in the mediodorsal and ventral lateral nuclei of the thalamus, whereas citalopram reduced blood flow in the pulvinar nucleus and the hypothalamus. Compared to clomipramine, citalopram decreased blood flow in the cingulate cortex. The findings support previous reports showing acute central effects of citalopram and clomipramine on regional serotonergic functions measured by PET. Acute side effects may, however, require that care is taken in the selection of experimental designs for future PET studies using IV administration of these antidepressants.

[N-methyl-11C]Mirtazapine for positron emission tomography neuroimaging of antidepressant actions in humans.

RATIONALE: Many actions of antidepressant drugs cannot yet be studied using positron emission tomography (PET) neuroimaging due to lack of suitable radioligands. We believe that mirtazapine, radiolabeled with C-11, might be suitable for PET neuroimaging of alpha2-adrenoceptors in selected regions of the living human brain. OBJECTIVE: To determine the regional central biodistribution and pharmacokinetics of [N-methyl-11C]mirtazapine in humans. METHODS: Five healthy volunteers received an intravenous injection of [N-methyl-11C]mirtazapine for evaluating its metabolism, biodistribution and pharmacokinetics. RESULTS: [N-methyl-11C]Mirtazapine entered the brain readily, with initial clearance from blood to tissue (K1) ranging from 0.31 ml/ml/min in amygdala to 0.54 ml/ml/min in thalamus. The rate of metabolism of [N-methyl-11C]mirtazapine in the bloodstream was relatively slow, with 20-40% of [11C]-derived radioactivity still present as parent compound at 60 min post-injection. The clearance of [N-methyl-11C]mirtazapine from the tissue compartment (k2') ranged from a low of 0.03 min(-1) in amygdala to a high of 0.06-0.07 min(-1) in thalamus and cerebellum. The volume of distribution (Ve') of [N-methyl-11C]mirtazapine was markedly greater in hippocampus and amygdala (11.3-12.0) than in cerebellum (6.7), with intermediate levels in the thalamus (9.4). CONCLUSIONS: [N-methyl-11C]Mirtazapine has suitable properties for PET neuroimaging. We envision [N-methyl-11C]mirtazapine as a molecular probe for PET imaging of antidepressant actions at sites such as alpha2-adrenoceptors in the living human brain.

Electromechanical mapping versus positron emission tomography and single photon emission computed tomography for the detection of myocardial viability in patients with ischemic cardiomyopathy.

OBJECTIVES: We compared catheter-based electromechanical mapping (NOGA system, Biosense-Webster, Haifa, Israel) with positron emission tomography (PET) and single photon emission computed tomography (SPECT) for prediction of reversibly dysfunctional myocardium (RDM) and irreversibly dysfunctional myocardium (IDM) in patients with severe left ventricular dysfunction. Furthermore, we established the optimal discriminatory value of NOGA measurements for distinction between RDM and IDM. BACKGROUND: The NOGA system can detect viable myocardium but has not been used for prediction of post-revascularization contractile function in patients with ischemic cardiomyopathy. METHODS: Twenty patients (19 males, age [mean +/- SD] 60 +/- 16 years, ejection fraction [EF] 29 +/- 6%) underwent viability testing with NOGA and PET or SPECT before revascularization. Left ventricular function was studied at baseline and six months after revascularization. RESULTS: The EF increased to 34 +/- 13% at six months (p < 0.05 vs. baseline). The 58 RDM and 57 IDM regions differed with regard to unipolar voltage amplitude (UVA) (9.2 +/- 3.9 mV vs. 7.6 +/- 4.0 mV, p < 0.05), normalized UVA (106 +/- 54% vs. 75 +/- 39%, p < 0.05), and tracer uptake (76 +/- 17% vs. 60 +/- 20%, p < 0.05). The NOGA local shortening did not distinguish between RDM and IDM (6.4 +/- 5.8% vs. 5.4 +/- 6.6%). By receiver operating characteristic curve analysis, myocardial tracer uptake had better diagnostic performance than UVA (area under curve [AUC] +/- SE: 0.82 +/- 0.04 vs. 0.63 +/- 0.05, p < 0.05) and normalized UVA (AUC +/- SE: 0.70 +/- 0.05, p < 0.05). Optimal threshold was defined as the value yielding sensitivity = specificity for prediction of RDM. Sensitivity and specificity were 59% at a UVA of 8.4 mV, 65% at a normalized UVA of 83%, and 78% at a tracer uptake of 69%. CONCLUSIONS: The NOGA system may discriminate RDM from IDM with optimal discriminatory values for UVA and normalized UVA of 8.4 mV and 83%, respectively. However, the diagnostic performance does not reach the level obtained by PET and SPECT in patients with severe heart failure.