Ultra-low-dose dual-source CT coronary angiography with high pitch: diagnostic yield of a volumetric planning scan and effects on dose reduction and imaging strategy

OBJECTIVE To evaluate the role of an ultra-low-dose dual-source CT coronary angiography (CTCA) scan with high pitch for delimiting the range of the subsequent standard CTCA scan. METHODS 30 patients with an indication for CTCA were prospectively examined using a two-scan dual-source CTCA protocol (2.0 × 64.0 × 0.6 mm; pitch, 3.4; rotation time of 280 ms; 100 kV): Scan 1 was acquired with one-fifth of the tube current suggested by the automatic exposure control software [CareDose 4D™ (Siemens Healthcare, Erlangen, Germany) using 100 kV and 370 mAs as a reference] with the scan length from the tracheal bifurcation to the diaphragmatic border. Scan 2 was acquired with standard tube current extending with reduced scan length based on Scan 1. Nine central coronary artery segments were analysed qualitatively on both scans. RESULTS Scan 2 (105.1 ± 10.1 mm) was significantly shorter than Scan 1 (127.0 ± 8.7 mm). Image quality scores were significantly better for Scan 2. However, in 5 of 6 (83%) patients with stenotic coronary artery disease, a stenosis was already detected in Scan 1 and in 13 of 24 (54%) patients with non-stenotic coronary arteries, a stenosis was already excluded by Scan 1. Using Scan 2 as reference, the positive- and negative-predictive value of Scan 1 was 83% (5 of 6 patients) and 100% (13 of 13 patients), respectively. CONCLUSION An ultra-low-dose CTCA planning scan enables a reliable scan length reduction of the following standard CTCA scan and allows for correct diagnosis in a substantial proportion of patients. ADVANCES IN KNOWLEDGE Further dose reductions are possible owing to a change in the individual patient's imaging strategy as a prior ultra-low-dose CTCA scan may already rule out the presence of a stenosis or may lead to a direct transferal to an invasive catheter procedure.

[Strategies for reducing the CT radiation dose]

The rapid technical advances in computed tomography have led to an increased number of clinical indications. Unfortunately, at the same time the radiation exposure to the population has also increased due to the increased total number of CT examinations. In the last few years various publications have demonstrated the feasibility of radiation dose reduction for CT examinations with no compromise in image quality and loss in interpretation accuracy. The majority of the proposed methods for dose optimization are easy to apply and are independent of the detector array configuration. This article reviews indication-dependent principles (e.g. application of reduced tube voltage for CT angiography, selection of the collimation and the pitch, reducing the total number of imaging series, lowering the tube voltage and tube current for non-contrast CT scans), manufacturer-dependent principles (e.g. accurate application of automatic modulation of tube current, use of adaptive image noise filter and use of iterative image reconstruction) and general principles (e.g. appropriate patient-centering in the gantry, avoiding over-ranging of the CT scan, lowering the tube voltage and tube current for survey CT scans) which lead to radiation dose reduction.

Trunk sway in mildly disabled multiple sclerosis patients with and without balance impairment

Multiple sclerosis (MS) causes a broad range of neurological symptoms. Most common is poor balance control. However, knowledge of deficient balance control in mildly affected MS patients who are complaining of balance impairment but have normal clinical balance tests (CBT) is limited. This knowledge might provide insights into the normal and pathophysiological mechanisms underlying stance and gait. We analysed differences in trunk sway between mildly disabled MS patients with and without subjective balance impairment (SBI), all with normal CBT. The sway was measured for a battery of stance and gait balance tests (static and dynamic posturography) and compared to that of age- and sex-matched healthy subjects. Eight of 21 patients (38%) with an Expanded Disability Status Scale of 1.0-3.0 complained of SBI during daily activities. For standing on both legs with eyes closed on a normal and on a foam surface, patients in the no SBI group showed significant differences in the range of trunk roll (lateral) sway angle and velocity, compared to normal persons. Patients in the SBI group had significantly greater lateral sway than the no SBI group, and sway was also greater than normal in the pitch (anterior-posterior) direction. Sway for one-legged stance on foam was also greater in the SBI group compared to the no SBI and normal groups. We found a specific laterally directed impairment of balance in all patients, consistent with a deficit in proprioceptive processing, which was greater in the SBI group than in the no SBI group. This finding most likely explains the subjective symptoms of imbalance in patients with MS with normal CBT.

Evidence for impaired sound intensity processing in schizophrenia

Patients with schizophrenia are impaired in many aspects of auditory processing, but indirect evidence suggests that intensity perception is intact. However, because the extraction of meaning from dynamic intensity relies on structures that appear to be altered in schizophrenia, we hypothesized that the perception of auditory looming is impaired as well. Twenty inpatients with schizophrenia and 20 control participants, matched for age, gender, and education, gave intensity ratings of rising (looming) and falling intensity sounds with different mean intensities. Intensity change was overestimated in looming as compared with receding sounds in both groups. However, healthy individuals showed a stronger effect at higher mean intensity, in keeping with previous findings, while patients with schizophrenia lacked this modulation. We discuss how this might support the notion of a more general deficit in extracting emotional meaning from different sensory cues, including intensity and pitch.

Affective and linguistic processing of speech prosody: DC potential studies

Speech melody or prosody subserves linguistic, emotional, and pragmatic functions in speech communication. Prosodic perception is based on the decoding of acoustic cues with a predominant function of frequency-related information perceived as speaker's pitch. Evaluation of prosodic meaning is a cognitive function implemented in cortical and subcortical networks that generate continuously updated affective or linguistic speaker impressions. Various brain-imaging methods allow delineation of neural structures involved in prosody processing. In contrast to functional magnetic resonance imaging techniques, DC (direct current, slow) components of the EEG directly measure cortical activation without temporal delay. Activation patterns obtained with this method are highly task specific and intraindividually reproducible. Studies presented here investigated the topography of prosodic stimulus processing in dependence on acoustic stimulus structure and linguistic or affective task demands, respectively. Data obtained from measuring DC potentials demonstrated that the right hemisphere has a predominant role in processing emotions from the tone of voice, irrespective of emotional valence. However, right hemisphere involvement is modulated by diverse speech and language-related conditions that are associated with a left hemisphere participation in prosody processing. The degree of left hemisphere involvement depends on several factors such as (i) articulatory demands on the perceiver of prosody (possibly, also the poser), (ii) a relative left hemisphere specialization in processing temporal cues mediating prosodic meaning, and (iii) the propensity of prosody to act on the segment level in order to modulate word or sentence meaning. The specific role of top-down effects in terms of either linguistically or affectively oriented attention on lateralization of stimulus processing is not clear and requires further investigations.

Unattended emotional intonations modulate linguistic prosody processing

Prosody or speech melody subserves linguistic (e.g., question intonation) and emotional functions in speech communication. Findings from lesion studies and imaging experiments suggest that, depending on function or acoustic stimulus structure, prosodic speech components are differentially processed in the right and left hemispheres. This direct current (DC) potential study investigated the linguistic processing of digitally manipulated pitch contours of sentences that carried an emotional or neutral intonation. Discrimination of linguistic prosody was better for neutral stimuli as compared to happily as well as fearfully spoken sentences. Brain activation was increased during the processing of happy sentences as compared to neutral utterances. Neither neutral nor emotional stimuli evoked lateralized processing in the left or right hemisphere, indicating bilateral mechanisms of linguistic processing for pitch direction. Acoustic stimulus analysis suggested that prosodic components related to emotional intonation, such as pitch variability, interfered with linguistic processing of pitch course direction.

Abdominal multislice CT for obese patients: effect on image quality and radiation dose in a phantom study

RATIONALE AND OBJECTIVES: To evaluate the effect of a modified abdominal multislice computed tomography (CT) protocol for obese patients on image quality and radiation dose. MATERIALS AND METHODS: An adult female anthropomorphic phantom was used to simulate obese patients by adding one or two 4-cm circumferential layers of fat-equivalent material to the abdominal portion. The phantom was scanned with a subcutaneous fat thickness of 0, 4, and 8 cm using the following parameters (detector configuration/beam pitch/table feed per rotation/gantry rotation time/kV/mA): standard protocol A: 16 x 0.625 mm/1.75/17.5 mm/0.5 seconds/140/380, and modified protocol B: 16 x 1.25 mm/1.375/27.5 mm/1.0 seconds/140/380. Radiation doses to six abdominal organs and the skin, image noise values, and contrast-to-noise ratios (CNRs) were analyzed. Statistical analysis included analysis of variance, Wilcoxon rank sum, and Student's t-test (P < .05). RESULTS: Applying the modified protocol B with one or two fat rings, the image noise decreased significantly (P < .05), and simultaneously, the CNR increased significantly compared with protocol A (P < .05). Organ doses significantly increased, up to 54.7%, comparing modified protocol B with one fat ring to the routine protocol A with no fat rings (P < .05). However, no significant change in organ dose was seen for protocol B with two fat rings compared with protocol A without fat rings (range -2.1% to 8.1%) (P > .05). CONCLUSIONS: Using a modified abdominal multislice CT protocol for obese patients with 8 cm or more of subcutaneous fat, image quality can be substantially improved without a significant increase in radiation dose to the abdominal organs.

Comparison of music perception in bilateral and unilateral cochlear implant users and normal-hearing subjects

Music plays an important role in the daily life of cochlear implant (CI) users, but electrical hearing and speech processing pose challenges for enjoying music. Studies of unilateral CI (UCI) users' music perception have found that these subjects have little difficulty recognizing tempo and rhythm but great difficulty with pitch, interval and melody. The present study is an initial step towards understanding music perception in bilateral CI (BCI) users. The Munich Music Questionnaire was used to investigate music listening habits and enjoyment in 23 BCI users compared to 2 control groups: 23 UCI users and 23 normal-hearing (NH) listeners. Bilateral users appeared to have a number of advantages over unilateral users, though their enjoyment of music did not reach the level of NH listeners.

Dual energy versus single energy MDCT: measurement of radiation dose using adult abdominal imaging protocols

RATIONALE AND OBJECTIVES: The aim of this study was to measure the radiation dose of dual-energy and single-energy multidetector computed tomographic (CT) imaging using adult liver, renal, and aortic imaging protocols. MATERIALS AND METHODS: Dual-energy CT (DECT) imaging was performed on a conventional 64-detector CT scanner using a software upgrade (Volume Dual Energy) at tube voltages of 140 and 80 kVp (with tube currents of 385 and 675 mA, respectively), with a 0.8-second gantry revolution time in axial mode. Parameters for single-energy CT (SECT) imaging were a tube voltage of 140 kVp, a tube current of 385 mA, a 0.5-second gantry revolution time, helical mode, and pitch of 1.375:1. The volume CT dose index (CTDI(vol)) value displayed on the console for each scan was recorded. Organ doses were measured using metal oxide semiconductor field-effect transistor technology. Effective dose was calculated as the sum of 20 organ doses multiplied by a weighting factor found in International Commission on Radiological Protection Publication 60. Radiation dose saving with virtual noncontrast imaging reconstruction was also determined. RESULTS: The CTDI(vol) values were 49.4 mGy for DECT imaging and 16.2 mGy for SECT imaging. Effective dose ranged from 22.5 to 36.4 mSv for DECT imaging and from 9.4 to 13.8 mSv for SECT imaging. Virtual noncontrast imaging reconstruction reduced the total effective dose of multiphase DECT imaging by 19% to 28%. CONCLUSION: Using the current Volume Dual Energy software, radiation doses with DECT imaging were higher than those with SECT imaging. Substantial radiation dose savings are possible with DECT imaging if virtual noncontrast imaging reconstruction replaces precontrast imaging.

Direction detection thresholds of passive self-motion in artistic gymnasts

In this study, we compared direction detection thresholds of passive self-motion in the dark between artistic gymnasts and controls. Twenty-four professional female artistic gymnasts (ranging from 7 to 20 years) and age-matched controls were seated on a motion platform and asked to discriminate the direction of angular (yaw, pitch, roll) and linear (leftward–rightward) motion. Gymnasts showed lower thresholds for the linear leftward–rightward motion. Interestingly, there was no difference for the angular motions. These results show that the outstanding self-motion abilities in artistic gymnasts are not related to an overall higher sensitivity in self-motion perception. With respect to vestibular processing, our results suggest that gymnastic expertise is exclusively linked to superior interpretation of otolith signals when no change in canal signals is present. In addition, thresholds were overall lower for the older (14–20 years) than for the younger (7–13 years) participants, indicating the maturation of vestibular sensitivity from childhood to adolescence.

Evaluation of a new six degrees of freedom couch for radiation therapy

Purpose: The aim of this work is to evaluate the geometric accuracy of a prerelease version of a new six degrees of freedom (6DoF) couch. Additionally, a quality assurance method for 6DoF couches is proposed. Methods: The main principle of the performance tests was to request a known shift for the 6DoF couch and to compare this requested shift with the actually applied shift by independently measuring the applied shift using different methods (graph paper, laser, inclinometer, and imaging system). The performance of each of the six axes was tested separately as well as in combination with the other axes. Functional cases as well as realistic clinical cases were analyzed. The tests were performed without a couch load and with a couch load of up to 200 kg and shifts in the range between −4 and +4 cm for the translational axes and between −3° and +3° for the rotational axes were applied. The quality assurance method of the new 6DoF couch was performed using a simple cube phantom and the imaging system. Results: The deviations (mean ± one standard deviation) accumulated over all performance tests between the requested shifts and the measurements of the applied shifts were −0.01 ± 0.02, 0.01 ± 0.02, and 0.01 ± 0.02 cm for the longitudinal, lateral, and vertical axes, respectively. The corresponding values for the three rotational axes couch rotation, pitch, and roll were 0.03° ± 0.06°, −0.04° ± 0.12°, and −0.01° ± 0.08°, respectively. There was no difference found between the tests with and without a couch load of up to 200 kg. Conclusions: The new 6DoF couch is able to apply requested shifts with high accuracy. It has the potential to be used for treatment techniques with the highest demands in patient setup accuracy such as those needed in stereotactic treatments. Shifts can be applied efficiently and automatically. Daily quality assurance of the 6DoF couch can be performed in an easy and efficient way. Long-term stability has to be evaluated in further tests.

Apatani phonology and lexicon, with a special focus on tone

Despite being one of the most extensively researched of Eastern Himalayan languages, the basic morphological and phonological-prosodic properties of Apatani (Tibeto-Burman > Tani > Western) have not yet been adequately described. This article attempts such a description, focusing especially on interactions between segmental-syllabic phonology and tone in Apatani. We highlight three features in particular – vowel length, nasality and a glottal stop – which contribute to contrastively-weighted syllables in Apatani, which are consistently under-represented in previous descriptions of Apatani, and in absence of which tone in Apatani cannot be effectively analysed. We conclude that Apatani has two “underlying”, lexically-specified tone categories H and L, whose interaction with word structure and syllable weight produce a maximum of three “surface” pitch contours – level, falling and rising – on disyllabic phonological words. Two appendices provide a set of diagnostic procedures for the discovery and description of Apatani tone categories, as well as an Apatani lexicon of approximately one thousand entries.

High-density large-scale field emitter arrays for x-ray free electron laser cathodes

High brightness electron sources are of great importance for the operation of the hard X-ray free electron lasers. Field emission cathodes based on the double-gate metallic field emitter arrays (FEAs) can potentially offer higher brightness than the currently used ones. We report on the successful application of electron beam lithography for fabrication of the large-scale single-gate as well as double-gate FEAs. We demonstrate operational high-density single-gate FEAs with sub-micron pitch and total number of tips up to 106 as well as large-scale double-gate FEAs with large collimation gate apertures. The details of design, fabrication procedure and successful measurements of the emission current from the single- and double-gate cathodes are presented.

On sex-related differences in auditory and visual sensory functioning

The present study was designed to elucidate sex-related differences in two basic auditory and one basic visual aspect of sensory functioning, namely sensory discrimination of pitch, loudness, and brightness. Although these three aspects of sensory functioning are of vital importance in everyday life, little is known about whether men and women differ from each other in these sensory functions. Participants were 100 male and 100 female volunteers ranging in age from 18 to 30 years. Since sensory sensitivity may be positively related to individual levels of intelligence and musical experience, measures of psychometric intelligence and musical background were also obtained. Reliably better performance for men compared to women was found for pitch and loudness, but not for brightness discrimination. Furthermore, performance on loudness discrimination was positively related to psychometric intelligence, while pitch discrimination was positively related to both psychometric intelligence and levels of musical training. Additional regression analyses revealed that each of three predictor variables (sex, psychometric intelligence, and musical training) accounted for a statistically significant portion of unique variance in pitch discrimination. With regard to loudness discrimination, regression analysis yielded a statistically significant portion of unique variance for sex as a predictor variable, whereas psychometric intelligence just failed to reach statistical significance. The potential influence of sex hormones on sex-related differences in sensory functions is discussed.

Assessment of patient setup errors in IGRT in combination with a six degrees of freedom couch

PURPOSE The range of patient setup errors in six dimensions detected in clinical routine for cranial as well as for extracranial treatments, were analyzed while performing linear accelerator based stereotactic treatments with frameless patient setup systems. Additionally, the need for re-verification of the patient setup for situations where couch rotations are involved was analyzed for patients treated in the cranial region. METHODS AND MATERIALS A total of 2185 initial (i.e. after pre-positioning the patient with the infrared system but before image guidance) patient setup errors (1705 in the cranial and 480 in the extracranial region) obtained by using ExacTrac (BrainLAB AG, Feldkirchen, Germany) were analyzed. Additionally, the patient setup errors as a function of the couch rotation angle were obtained by analyzing 242 setup errors in the cranial region. Before the couch was rotated, the patient setup error was corrected at couch rotation angle 0° with the aid of image guidance and the six degrees of freedom (6DoF) couch. For both situations attainment rates for two different tolerances (tolerance A: ± 0.5mm, ± 0.5°; tolerance B: ± 1.0 mm, ± 1.0°) were calculated. RESULTS The mean (± one standard deviation) initial patient setup errors for the cranial cases were -0.24 ± 1.21°, -0.23 ± 0.91° and -0.03 ± 1.07° for the pitch, roll and couch rotation axes and 0.10 ± 1.17 mm, 0.10 ± 1.62 mm and 0.11 ± 1.29 mm for the lateral, longitudinal and vertical axes, respectively. Attainment rate (all six axes simultaneously) for tolerance A was 0.6% and 13.1% for tolerance B, respectively. For the extracranial cases the corresponding values were -0.21 ± 0.95°, -0.05 ± 1.08° and -0.14 ± 1.02° for the pitch, roll and couch rotation axes and 0.15 ± 1.77 mm, 0.62 ± 1.94 mm and -0.40 ± 2.15 mm for the lateral, longitudinal and vertical axes. Attainment rate (all six axes simultaneously) for tolerance A was 0.0% and 3.1% for tolerance B, respectively. After initial setup correction and rotation of the couch to treatment position a re-correction has to be performed in 77.4% of all cases to fulfill tolerance A and in 15.6% of all cases to fulfill tolerance B. CONCLUSION The analysis of the data shows that all six axes of a 6DoF couch are used extensively for patient setup in clinical routine. In order to fulfill high patient setup accuracies (e.g. for stereotactic treatments), a 6DoF couch is recommended. Moreover, re-verification of the patient setup after rotating the couch is required in clinical routine.