Effective radiation doses associated with non-invasive versus invasive assessment of coronary anatomy and physiology.

OBJECTIVES: To compare the effective radiation dose (ERD) needed to obtain information on coronary anatomy and physiology by a non-invasive versus an invasive diagnostic strategy. BACKGROUND: Knowledge of anatomy and physiology is needed for management of patients with coronary artery disease (CAD). There is, however, a growing concern about detrimental long-term effects of radiation associated with diagnostic procedures. METHODS: In a total of 671 patients with suspected CAD, we compared the ERD needed to obtain anatomical and physiological information through a non-invasive strategy or an invasive strategy. The non-invasive strategy consisted of coronary computed tomography angiography (CCTA) and single photon emission computed tomography (SPECT). The invasive strategy included coronary angiography (CA) and fractional flow reserve (FFR) measurement. In 464 patients, the data were acquired in Period 2009 and in 207 the data were acquired in Period 2011 (after each period, the CCTA- and the CA-equipment had been upgraded). RESULTS: For the Period 2009 total ERD of the non-invasive approach was significantly larger compared to the invasive approach (28.45 ± 5.37 mSv versus 15.79 ± 7.95 mSv, respectively; P < 0.0001). For Period 2011, despite the significant decrease in ERD for both groups (P<0.0001 for both), the ERD remained higher for the non-invasive approach compared to the invasive approach (16.67 ± 10.45 mSv vs. 10.36 ± 5.87 mSv, respectively; P < 0.0001). Simulation of various diagnostic scenarios showed cumulative radiation dose is the lowest when a first positive test is followed by an invasive strategy. CONCLUSION: To obtain anatomic and physiologic information in patients with suspected CAD, the combination of CA and FFR is associated with lower ERD than the combination of CCTA and SPECT.

Gravitational perturbations correlated with the asteroid kinetic impact deflection technique.

This paper presents the use of the kinetic impact technique to deflect asteroids that may present some risk of collision with Earth. Within the work to be developed here, we intend to evaluate in more detail the possibility to deflect the orbit of the asteroid 101955 Bennu by applying variations in its velocity ([Formula: see text]v) at different positions along its orbital period and measuring effects of close encounters with planet Earth. We will see that, in a relatively long period of time, the asteroid has several close encounters with the planet, thus suffering a natural gravitational perturbation. With the application of the impulses, the relative distances change, causing variations in the energy of the asteroid and a large variation in the relative distance between the asteroid and Earth over a long period after the impulse. We present results related to the magnitude of the impulse applied, which is important because its defines the mass and velocity of the impactor to be considered. Then, we mapped the positions of the impulses along a period of the orbit of the asteroid. We finish by explaining what happens to the orbit of the asteroid during the periods of gravitational perturbation, since the close encounters amount to "Swing Bys" that intensify the variations of the relative distances between the bodies after the impulse is applied.

Validation of planar and tomographic radionuclide ventriculography by a dynamic ventricular phantom.

Although there is increasing interest in the automatic processing of tomographic radionuclide ventriculography (TRV) studies, validation is mainly limited to a comparison of TRV results with data from planar radionuclide ventriculography (PRV) or gated perfusion single photon emission computed tomography (SPECT). The aim of this study was to use a dynamic physical cardiac phantom to validate the ejection fraction (EF) and volumes from PRV and TRV studies. A new dynamic left ventricular phantom was constructed and used to obtain 21 acquisitions in the planar and tomographic mode. The directly measured volumes and EFs of the phantom during the acquisitions were considered as the gold standard for comparison with TRV and PRV. EFs were calculated from PRV by background-corrected end-diastolic and end-systolic frames. Volumes and EFs were calculated from TRV by region growing with different lower thresholds to search for the optimal threshold. EF from PRV correlated significantly with the real EF (r=0.94, P=0.00). The optimal threshold value for volume calculation from TRV in 336 cases was 50% (r=0.98, P=0.00) yielding the best slope after linear regression. When considering these calculated end-diastolic and end-systolic volumes, EF correlated well (r=0.99, P=0.00) with the real EF, and this correlation was significantly (P=0.04) higher than that of the EF from PRV. Our experiments prove that EF measured by TRV yields more accurate results compared with PRV in dynamic cardiac phantom studies.

Poststress left ventricular ejection fraction is an independent predictor of major cardiac events in patients with coronary artery disease and impaired left ventricular function.

AIM: The aim of this study was to investigate the prognostic value of myocardial perfusion and function SPECT imaging in patients with coronary artery disease (CAD) and poor left ventricular (LV) function. METHODS: We studied 261 patients (231 men, age 66+/-10 years) with CAD and a resting LV ejection fraction (LVEF)

Auditory event-related potentials to deviant stimuli during drowsiness and stage 2 sleep.

Twelve subjects were tested using a 3-tone auditory oddball paradigm consisting of a standard 1000 Hz tone (P = 80%) and two deviants, namely, a 1200 Hz tone and a 2000 Hz tone (both P = 10%). Testing took place in 3 conditions: (1) attend, in which the subject had to count one of the deviant tones; (2) ignore, in which the subject read a book; and (3) sleep, in which the subject was encouraged to go to sleep during presentation of the tones. In the awake conditions stimulus deviance elicited mismatch negativity (MMN) and P3. During drowsiness, no separate mismatch negativity (MMN) could be detected, but the 2000 Hz tone evoked a broad fronto-central early negative deflection, suggesting an overlap of N1 and MMN. In the same condition, P210, N330 and P430 appeared, all being sensitive to magnitude of deviance. During stage 2, the P210, N330 and P430 amplitudes increased, most notably to the large deviant. These data indicate that differential processing of auditory inputs is maintained during drowsiness and stage 2 sleep, but do not support the notion that MMN or P3 activity comparable to the waking state occurs to oddball stimuli during this stage. It is hypothesised that during light sleep, scanning of the environment is performed by a different system than in the awake state and that during drowsiness a gradual switch between these two systems takes place.

Event-related potentials to tones in the absence and presence of sleep spindles.

The present study focused on event-related potentials to tones in the presence and absence of sleep spindles. Six undergraduates were studied throughout an experimental night, following an adaptation session. The event-related potentials to tone stimuli were averaged for each subject. Separate averages were determined for trials on which no sleep spindle occurred 2 s before or after a tone and trials in which spindle activity was present. Both voltage distribution maps and multivariate analysis of the waveforms produced significant differences between these conditions, which could be seen as a higher initial positive component and sustained positively over the averaged epoch in the presence of spindles. Spectral analysis indicated that this result could not solely be ascribed to residual sigma activity in the spindle-present average. The results may provide insights into the functional role of sleep spindles in humans in addition to that suggested by a neurophysiological model of inhibition.

The clinical value of nuclear medicine in the assessment of irradiation-induced and anthracycline-associated cardiac damage.

Two groups of patients, those treated for Hodgkin's disease and breast cancer, are particularly at risk of developing late myocardial damage, since radiotherapy (RT) techniques for both patient groups may include (large) parts of the heart, and adjuvant systemic therapy is frequently administered to these patients, in particular anthracycline-containing chemotherapy. Available literature on the monitoring and prediction of RT-induced and anthracycline-associated cardiac damage using nuclear medicine techniques is presented. Based on relevant studies, the risk of overall cardiac disease post-RT and overt congestive heart failure during anthracycline-containing chemotherapy is probably low. Conventional nuclear medicine imaging, i.e. myocardial perfusion scintigraphy, may be of complementary use to echocardiographical evaluation for routine follow-up after RT with modern techniques, in a subgroup of patients with known cardiovascular risk factors. Left ventricle ejection fraction (LVEF) measurements, as assessed by radionuclide angiography for the monitoring of anthracycline-associated cardiac injury, are not very sensitive and early detection will probably be enhanced by combining LVEF measurements with other cardiac function parameters. Also, it may be expected that nuclear medicine techniques using molecular radioligands will constitute an essential future step in the evaluation of subclinical cardiac injury afforded by the combined effect of RT and cardiotoxic chemotherapy.

Recombinant humane thyrotropin (rhtSH) a new aid in the diagnosis and treatment of thyroid carcinoma with radio-iodine.

By example of two cases a newly available tool, the recombinant humane thyroid stimulating hormone (rhTSH) is discussed in its use as an adjunct in diagnosing and treating differentiated thyroid carcinoma with radio-iodine. This product is an easier and safe alternative to the necessary rise of TSH induced by thyroid hormone withdrawal and concurrent hypothyroidism. Although discrepancies in favour of the classical approach have been demonstrated in some patients, the clinical relevancy of these must be weighted against the advantage of avoiding undesirable symptoms and possible tumour growth by the use of rhTSH. The role of rhTSH in the follow-up diagnosis and radioiodine treatment of thyroid carcinoma will undoubtedly increase in importance.

Transfer of normal 99mTc-ECD brain SPET databases between different gamma cameras.

A stereotactic, normal perfusion database is imperative for optimal clinical brain single-photon emission tomography (SPET). However, interdepartmental use of normal data necessitates accurate transferability of these data sets. The aim of this study was to investigate transfer of three normal perfusion databases obtained in the same large population of healthy volunteers who underwent sequential scanning using multihead gamma cameras with different resolution. Eighty-nine healthy adults (46 females, 43 males; aged 20-81 years) were thoroughly screened by history, biochemistry, physical and full neurological examination, neuropsychological testing and magnetic resonance imaging. After injection of 925 MBq technetium-99m labelled ethyl cysteinate dimer (ECD) under standard conditions, 101 scans were acquired from all subjects (12 repeat studies) on a triple-head Toshiba GCA-9300A (measured average FWHM 8.1 mm). Ninety-one sequential scans were performed on a dual-head Elscint Helix camera (FWHM 9.6 mm) and 22 subjects also underwent imaging on a triple-head Prism 3000 (FWHM 9.6 mm). Images were transferred to the same processing platform and reconstructed by filtered back-projection with the same Butterworth filter (order 8, cut-off 0.9 cycles/cm) and uniform Sorensen attenuation correction (mu = 0.09). After automated rigid intrasubject registration, all subjects were automatically reoriented to a stereotactic template by a nine-parameter affine transformation. The databases were analysed using 35 predefined volumes of interest (VOIs) with normalisation on total VOI counts. For comparison, the high-resolution data were smoothed with a 3D Gaussian kernel to achieve more similar spatial resolution. Hoffman phantom measurements were conducted on all cameras. Partial volume effects after smoothing varied between -6.5% and 10%, depending on VOI size. Between-camera reproducibility was 2.5% and 2.7% for the Toshiba camera versus the Helix and the Prism database, respectively. The highest reduction in between-camera variability was achieved by resolution adjustment in combination with linear washout correction and a Hoffman phantom-based correction. In conclusion, transfer of normal perfusion data between multihead gamma cameras can be accurately achieved, thereby enabling widespread interdepartmental use, which is likely to have a positive impact on the diagnostic capabilities of clinical brain perfusion SPET.

Modulation of liver canalicular transport processes by the tyrosine-kinase inhibitor genistein: implications of genistein metabolism in the rat.

Rat liver cells express the multispecific organic anion transporter (cmoat, cmrp, mrp2) and P-glycoprotein (Pgp) in their canalicular membranes, proteins that are homologous to the multidrug-resistance related protein (MRP) and multidrug resistance (MDR) gene products in multidrug resistant tumor cells. We tested whether genistein, a modulator of drug resistance in tumor cells, affects biliary secretion of substrates of canalicular multispecific organic anion transporter (cmoat) (glucuronides of bilirubin and rhodamine, glutathione conjugate of bromsulphthalein) and of P-glycoprotein (Pgp) (rhodamine), respectively. Using the isolated perfused rat liver of control Wistar rats (TR+) and of a mutant strain (TR-) that expresses Pgp but not cmoat, we show that genistein effectively inhibits the secretion of anionic substrates of cmoat in Wistar rats but stimulates secretion of cationic rhodamine in TR- rats. Genistein is subject to glucuronidation and sulfatation and secretion of genistein and its metabolites stimulates bile flow in Wistar rats, but secretion is nearly absent in TR- rats. Because genistein and its metabolites are substrates for cmoat, inhibition of anion secretion by genistein is partially explained by competition for this transporter. Genistein is also a substrate of uridindiphosphate (UDP)-glucuronyltransferase isoenzyme(s). Inhibition of glucuronidation reduces the availability of bilirubin and rhodamine glucuronates for transport via cmoat, but unconjugated cationic rhodamine becomes available for transport via Pgp at an increased cellular concentration. Daidzein, a genistein analogue with no effect on protein tyrosine kinase (PTK) shows Similar effects on secretion of organic anions and cations supporting the conclusion that genistein affects transport in liver mainly through competition with other substrates at the sites of glucuronidation and transport via cmoat.