Correction of head movement on PET studies: comparison of methods.

Head movement presents a continuing problem in PET studies. Head restraint minimizes movement but is unreliable, resulting in the need to develop alternative strategies. These include frame-by-frame (FBF) realignment or use of motion tracking (MT) during the scan to realign PET acquisition data. Here we present a comparative analysis of these 2 methods of motion correction. METHODS: Eight volunteers were examined at rest using (11)C-raclopride PET with the radioligand administered as a bolus followed by constant infusion to achieve steady state. Binding potential (BP) was estimated using the ratio method during 2 periods of the scan at steady state. Head movement was compensated by using coregistration between frames (FBF) and 3 methods using MT measurements of head position acquired with a commercially available optical tracking system. RESULTS: All methods of realignment improved test-retest reliability and noise characteristics of the raw data, with important consequences for the power to detect small changes in radiotracer binding, and the potential to reduce false-positive and false-negative results. MT methods were superior to FBF realignment using coregistration on some indices. CONCLUSION: Such methods have considerable potential to improve the reliability of PET data with important implications for the numbers of volunteers required to test hypotheses.     

Vaginal tape erosion following transobturator tape (TOT) operation for stress urinary incontinence.

Inorganic sling materials when used for treatment of urinary stress incontinence have a high success rate of achieving continence. They unfortunately attract the complication of vaginal tape erosion. When used for Transobturator tape procedure (TOT) we found the Obtape sling (Mentor-Porges, Le Plessis-Robinson, France) attracted a high rate of erosion, likely due to the tape properties. We describe a series of tape erosions with the Obtape sling, the presentation, conservative and surgical management with favourable rates of maintenance of continence. We suggest the use of larger pore sized tapes to decrease the occurrence of vaginal tape erosion.     

Repeated measurements of mite and pet allergen levels in house dust over a time period of 8 years

BACKGROUND: Studies of the association between indoor allergen exposure and the development of allergic diseases have often measured allergen exposure at one point in time. OBJECTIVE: We investigated the variability of house dust mite (Der p 1, Der f 1) and cat (Fel d 1) allergen in Dutch homes over a period of 8 years. METHODS: Data were obtained in the Dutch PIAMA birth cohort study. Dust from the child's mattress, the parents' mattress and the living room floor was collected at four points in time, when the child was 3 months, 4, 6 and 8 years old. Dust samples were analysed for Der p 1, Der f 1 and Fel d 1 by sandwich enzyme immuno assay. RESULTS: Mite allergen concentrations for the child's mattress, the parents' mattress and the living room floor were moderately correlated between time-points. Agreement was better for cat allergen. For Der p 1 and Der f 1 on the child's mattress, the within-home variance was close to or smaller than the between-home variance in most cases. For Fel d 1, the within-home variance was almost always smaller than the between-home variance. Results were similar for allergen levels expressed per gram of dust and allergen levels expressed per square metre of the sampled surface. Variance ratios were smaller when samples were taken at shorter time intervals than at longer time intervals. CONCLUSION: Over a period of 4 years, mite and cat allergens measured in house dust are sufficiently stable to use single measurements with confidence in epidemiological studies. The within-home variance was larger when samples were taken 8 years apart so that over such long periods, repetition of sampling is recommended.     

Changes in immune regulation in response to examination stress in atopic and healthy individuals

BACKGROUND: Stress can aggravate the allergic inflammation, but determinants of disturbed immune regulation are largely unknown. OBJECTIVE: To determine systemic immunological, local inflammatory and functional airway responses to stress in healthy and atopic individuals. METHODS: Forty-one undergraduate students, 22 with allergy of whom 16 had asthma, and 19 healthy controls, were studied in a low-stress period and in association with a large exam. Subjects completed questionnaires on stress and health behaviours, underwent lung function tests, bronchial methacholine challenge, measurements of exhaled nitric oxide and urine cortisol. Blood cells were phenotyped, and cytokines from mononuclear blood cells were analysed. RESULTS: Perceived stress and anxiety increased in both groups during the exam period while cortisol increased only in the atopy group. Cytokine production decreased broadly in response to stress in both groups, which was paralleled by an increase in the proportion of regulatory T cells (CD4(+)CD45RO(+)CD25(bright)). Interestingly, atopic individuals, but not controls, reacted with a decreased T-helper type 1/T-helper type 2 (Th1/Th2) ratio and a decrease in natural killer (NK) cell numbers in response to stress. In control subjects only, exhaled nitric oxide decreased and forced expiratory volume in one second increased during stress. CONCLUSION: Atopic and non-atopic subjects shared some immune changes in response to stress, such as a dramatic decline in cytokines and an increase in the number of regulatory T cells in peripheral blood. However, other stress-induced immune changes were unique to atopic individuals, such as a skewed Th1/Th2 ratio and reduced NK cell numbers, indicating that some pathogenic mechanisms in atopics may be more strongly affected by stress than others.     

In vivo PET imaging of cardiac presynaptic sympathoneuronal mechanisms in the rat.

The sympathetic nervous system of the heart plays a key role in the pathophysiology of various cardiac diseases. Small-animal models are valuable for obtaining further insight into mechanisms of cardiac disease and therapy. To determine the translational potential of cardiac neuronal imaging from rodents to humans, we characterized the rat sympathetic nervous system using 3 radiotracers that reflect different subcellular mechanisms: (11)C-meta-hydroxyephedrine (HED), a tracer of neuronal transport showing stable uptake and no washout in healthy humans; (11)C-phenylephrine (PHEN), a tracer of vesicular leakage and intraneuronal metabolic degradation with initial uptake and subsequent washout in humans; and (11)C-epinephrine (EPI), a tracer of vesicular storage with stable uptake and no washout in humans. METHODS: We used a small-animal PET system to study healthy male Wistar rats at baseline, after desipramine (DMI) pretreatment (DMI block), and with DMI injection 15 min after tracer delivery (DMI chase). The rats were kept under general isoflurane anesthesia while dynamic emission scans of the heart were recorded for 60 min after radiotracer injection. A myocardial retention index was determined by normalizing uptake at 40 min to the integral under the arterial input curve. Washout rates were determined by monoexponential fitting of myocardial time-activity curves. RESULTS: At baseline, HED showed high myocardial uptake and sustained retention, EPI showed moderate uptake and significant biphasic washout, and PHEN showed moderate uptake and monoexponential washout. The average (+/- SD) left ventricular retention index for HED, PHEN, and EPI was 7.38% +/- 0.82%/min, 3.43% +/- 0.45%/min, and 4.24% +/- 0.59%/min, respectively; the washout rate for HED, PHEN, and EPI was 0.13% +/- 0.23%/min, 1.13% +/- 0.35%/min, and 0.50% +/- 0.24%/min, respectively. The DMI chase resulted in increased washout only for HED. DMI block decreased myocardial uptake of all tracers by less than 90%. CONCLUSION: Kinetic profiles of HED in the rat myocardium were similar to those of HED in humans, suggesting comparable neuronal transport density. Unlike in humans, however, significant washout of EPI and faster washout of PHEN were encountered, consistent with high intraneuronal metabolic activity, high catecholamine turnover, and reduced vesicular storage. This evidence of increased neuronal activity in rodents has implications for translational studies of cardiac neuronal biology in humans.     

203Pb-labeled alpha-melanocyte-stimulating hormone peptide as an imaging probe for melanoma detection.

Peptide-targeted alpha-therapy with 7.4 MBq of (212)Pb-[1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid]-ReO-[Cys(3,4,10),d-Phe(7),Arg(11)]alpha-MSH(3-13) ((212)Pb-DOTA-Re(Arg(11))CCMSH) cured 45% of B16/F1 murine melanoma-bearing C57 mice in a 120-d study, highlighting its melanoma treatment potential. However, there is a need to develop an imaging surrogate for patient-specific dosimetry and to monitor the tumor response to (212)Pb-DOTA-Re(Arg(11))CCMSH therapy. The purpose of this study was to evaluate the potential of (203)Pb-DOTA-Re(Arg(11))CCMSH as a matched-pair SPECT agent for (212)Pb-DOTA-Re(Arg(11))CCMSH. METHODS: DOTA-Re(Arg(11))CCMSH was labeled with (203)Pb in 0.5 M NH(4)OAc buffer at pH 5.4. The internalization and efflux of (203)Pb-DOTA-Re(Arg(11))CCMSH were determined in B16/F1 melanoma cells. The pharmacokinetics of (203)Pb-DOTA-Re(Arg(11))CCMSH was examined in B16/F1 melanoma-bearing C57 mice. A micro-SPECT/CT study was performed with (203)Pb-DOTA-Re(Arg(11))CCMSH in a B16/F1 melanoma-bearing C57 mouse at 2 h after injection. RESULTS: (203)Pb-DOTA-Re(Arg(11))CCMSH was easily prepared in NH(4)OAc buffer and completely separated from the excess nonradiolabeled peptide by reversed-phase high-performance liquid chromatography (RP-HPLC). (203)Pb-DOTA-Re(Arg(11))CCMSH displayed fast internalization and extended retention in B16/F1 cells. Approximately 73% of (203)Pb-DOTA-Re(Arg(11))CCMSH activity internalized after a 20-min incubation at 25 degrees C. After incubation of the cells in culture medium for 20 min, 78% of internalized activity remained in the cells. (203)Pb-DOTA-Re(Arg(11))CCMSH exhibited a biodistribution pattern similar to that of (212)Pb-DOTA-Re(Arg(11))CCMSH in B16/F1 melanoma-bearing mice. (203)Pb-DOTA-Re(Arg(11))CCMSH exhibited a peak tumor uptake of 12.00+/-3.20 percentage injected dose per gram (%ID/g) at 1 h after injection. The tumor uptake gradually decreased to 3.43+/-1.12 %ID/g at 48 h after injection. (203)Pb-DOTA-Re(Arg(11))CCMSH exhibited a peak tumor-to-kidney uptake ratio of 1.53 at 2 h after injection. The absorbed doses to the tumor and kidneys were 4.32 and 4.35 Gy, respectively, per 37 MBq. Whole-body clearance of (203)Pb-DOTA-Re(Arg(11))CCMSH was fast, with approximately 89% of the injected activity cleared through the urinary system by 2 h after injection. (203)Pb showed 1.6-mm SPECT resolution, which was comparable to (99m)Tc. Melanoma lesions were visualized through SPECT/CT images of (203)Pb-DOTA-Re(Arg(11))CCMSH at 2 h after injection. CONCLUSION: (203)Pb-DOTA-Re(Arg(11))CCMSH exhibited favorable pharmacokinetic and tumor imaging properties, highlighting its potential as a matched-pair SPECT agent for (212)Pb-DOTA-Re(Arg(11))CCMSH melanoma treatment.