Virtual Monoenergetic Images from Spectral Detector CT Enable Radiation Dose Reduction in Unenhanced Cranial CT.

BACKGROUND AND PURPOSE: Our aim was to evaluate whether improved gray-white matter differentiation in cranial CT by means of 65- keV virtual monoenergetic images enables a radiation dose reduction compared to conventional images. MATERIALS AND METHODS: One hundred forty consecutive patients undergoing 171 spectral detector CTs of the head between February and November 2017 (56 ± 19 years of age; male/female ratio, 56%/44%) were retrospectively included. The tube current-time product was reduced during the study period, resulting in 61, 55, and 55 patients being examined with 320, 290, and 260 mAs, respectively. All other scanning parameters were kept identical. The volume CT dose index was recorded. ROIs were placed in gray and white matter on conventional images and copied to identical positions in 65- keV virtual monoenergetic images. The contrast-to-noise ratio was calculated. Two radiologists blinded to the reconstruction technique evaluated image quality on a 5-point Likert-scale. Statistical assessment was performed using ANOVA and Wilcoxon test adjusted for multiple comparisons. RESULTS: The mean volume CT dose index was 55, 49.8, and 44.7 mGy using 320, 290, and 260 mAs, respectively. Irrespective of the volume CT dose index, noise was significantly lower in 65- keV virtual monoenergetic images compared with conventional images (65- keV virtual monoenergetic images/conventional images: extraocular muscle with 49.8 mGy, 3.7 ± 1.3/5.6 ± 1.6 HU, P < .001). Noise slightly increased with a reduced radiation dose (eg, extraocular muscle in conventional images: 5.3 ± 1.4/5.6 ± 1.6/6.1 ± 2.1 HU). Overall, the contrast-to-noise ratio in 65- keV virtual monoenergetic images was superior to that in conventional images irrespective of the volume CT dose index (P < .001). Particularly, 65-keV virtual monoenergetic images with 44.7 mGy showed significantly lower noise and a higher contrast-to-noise ratio than conventional images with 55 mGy (P < .001). Subjective analysis confirmed better image quality in 65- keV virtual monoenergetic images, even using 44.7 mGy. CONCLUSIONS: The 65-keV virtual monoenergetic images from spectral detector CT allow radiation dose reduction in cranial CT. While this proof of concept included a radiation dose reduction of 19%, our data suggest that even greater reduction appears achievable.

Anisotropic 2D metallicity: plasmons in Ge(1 0 0)-Au.

The low-energy plasmonic excitations of the Ge(0 0 1)-Au close to one monolayer coverage of Au were investigated by momentum-resolved high resolution electron energy loss spectroscopy. A very weak plasmonic loss was identified dispersing along the chain direction of the [Formula: see text] formed at these Au coverages. The measured dispersion was compared with the Tomonaga-Luttinger-liquid (TLL) model and with a model for an anisotropic Fermi liquid. Using the TLL model both for single and arrays of wires, no consistent picture turned up that could describe all available data. On the contrary, a quasi-one-dimensional model of a confined 2D electron gas gave a satisfactorily consistent description of the data. From these results for the collective low-energy excitations we conclude that the Ge(0 0 1)-Au system is reasonably well described by a strongly anisotropic 2D Fermi liquid, but is incompatible with a TLL.

Lateral electronic screening in quasi-one-dimensional plasmons.

The properties of one-dimensional (1D) plasmons are rather unexplored. We investigated the plasmonic collective excitations, measured as one-dimensional plasmon dispersions with electron energy loss spectroscopy, highly resolved both in energy and lateral momentum, for both phases of Au induced chains on stepped Si(553) substrates. We observe 1D dispersions that are strongly influenced by the lateral chain width and by the interchain coupling. Indications for the existence of two different plasmons originating from two surface bands of the systems are given for the low coverage phase.

Endoscopic laser-assisted diverticulotomy without versus with wound closure in the treatment of Zenker's diverticulum.

The aim of the present study was to compare the modifications of endoscopic laser-assisted diverticulotomy regarding closure of mucosal wound at the cricopharyngeal bridge. The results of 62 cases after endoscopic laser-assisted diverticulotomy without and with wound closure were retrospectively compared. After laser-assisted transection of the cricopharyngeal bridge, the mucosa wound was left open (OW) in 35 cases (56%), whereas a closure of the mucosa wound (CW) with sutures and fibrin glue was performed in 27 patients (44%). Duration of hospitalization, residual diverticular sac rate and occurrence of complications did not differ significantly between the two groups. Mean surgical time was significantly less in the OW cases. According to these results, it can be assumed that readapting and sealing the wound after transecting the cricopharyngeal bridge does not significantly reduce the complication rate. It does, however, extend the length of surgery and increases the cost of the procedure.

[Computer-assisted joint replacement surgery. Financial and clinical impact for a specialised orthopaedic hospital]. / Navigation in der Endoprothetik. Die Kosten-Nutzen-Analyse einer orthopädischen Fachklinik.

AIM: Incorrect alignment is a known risk factor for early loosening of implants. Computer-assisted joint replacement surgery (CAS) improves the positioning of the used implants. So far there is no study comparing the improvement of radiological implant position and the extra costs for the CAS. METHOD: We therefore analysed 200 (100 navigated procedures versus 100 conventional operations) total knee replacements and 60 (30 navigated procedures versus 30 conventional operations) hip resurfacing procedures. Evaluation criteria were radiological alignment and costs produced by using computer-assisted navigation tools. RESULTS: In our series of total knee and hip resurfacing arthroplasties the number of outliers could be significantly reduced by using CAS. Patients receiving a navigated total knee replacement had a significantly lower blood loss and need for blood transfusion. The financial calculation for CAS for our specialised orthopaedic hospital showed that every CAS operation produced 442 euro extra costs per operation. So far these extra costs are not reimbursed. CONCLUSIONS: By using CAS the implant positioning is significantly improved. Total knee replacements have a lower blood loss. Due to the prolonged operation time, the leasing costs and the single use navigation tools of every navigated operation produced costs for our hospital of 442 euro. As there is so far no reimbursement of these costs, long-term survival studies are needed to reveal the superiority of the navigation method and to show an impact on the medical budget.

Comparison between the psychopathological profile of dental anxiety patients and an average dental population.

The psychological characteristics of 38 patients with extreme dental fear were compared with those of an age and sex matched control group chosen from the average population visiting the dental clinic. The results were assessed by means of the Kleinknecht Dental Anxiety test, the Brief Symptom Inventory and Spielberger Anxiety State questionnaires. The majority of the dental fear patients were women, the male/female ration being 0.29. In the sample group, the dental anxiety manifested as a state and not as a trait: the anxiety state mean score of the dental phobic group was significantly higher than that of the controls (p less than 0.05), while the mean score for anxiety trait did not differ. Profound psychopathological distress other than anxiety was present only among the phobic males.

Scandium oxide coatings for high-power UV laser applications.

Scandium oxide has proved to be a damage-resistant high-index material in laser coatings for use at 248 nm. The results of damage threshold measurements on laser reflectors and antireflection coatings of various designs, material combinations, and deposition temperatures are presented. The most significant effects are observed for overcoat layers on high reflectors and undercoat layers on antireflection coatings. Thresholds >6 J/cm(2) for 20 nsec pulses were observed in both cases.