Unbound states in quantum heterostructures

We report in this review on the electronic continuum states of semiconductor Quantum Wells and Quantum Dots and highlight the decisive part played by the virtual bound states in the optical properties of these structures. The two particles continuum states of Quantum Dots control the decoherence of the excited electron – hole states. The part played by Auger scattering in Quantum Dots is also discussed

Diaphragm pacing system implanted in a patient with ALS

PMID = 2644432

Assessment of image quality of a standard and three dose-reducing protocols in adult cranial CT

The purpose of this study was to analyze the effect of various tube current settings (mAs) and optimize the image quality and dose for adult cranial CT protocol. Sixty adult patients who underwent a cranial CT scanning for different indications were subdivided into three subgroups. Subjective image and noise quality scores and quantitative noise measurements were selectively studied on three reference levels (cerebellar, basal ganglia and centrum semiovale levels). For each subgroup, only one level was studied. Head circumference (HC) and the maximum anteroposterior diameter (MAPD) of each patient were measured. At 50% decreased dose protocol, there was no poor quality score at any level. At nearly 60% decreased dose protocol, the incidence of poor quality scores was much higher at the cerebellar level than at the other two levels. For the same protocol number, quantitative noise measurements were higher at the cerebellar level than the other two supratentorial levels. The correlation was found to be significant between HC, MAPD and quantitative noise measurements, and there was a non-significant correlation between HC and subjective noise scores. In adult cranial CT, depending on the level, a dose reduction of up to 60% may be possible while maintaining image quality. © Springer-Verlag 2004

The visual scoring of emphysema with high-resolution computed tomography examination: Intraobserver and interobserver correlations [Amfizemin yüksek rezolüsyonlu bilgisayarlı tomografi i·ncelemesinde görsel skorlama: Gözlemci i·çi ve gözlemciler arasında korelasyon]

Purpose: The subjective visual assessment is usually used on the hard-copy film or CT monitor for assessment of emphysema. This method has a higher interobserver and intraobserver discrepancy than quantitative analyzes. In this study, the effect of interobserver and intraobserver discrepancy was investigated on subjective visual scoring of conventional images and emphysematous parenchyma images which is gained with the density mask method. Material and Methods: In this study, ten emphysematous patient and seven healthy subjects were examined. HRCT images were scored on the standard hard-copy film and emphysematous parenchymal window settings as the distribution and severity of emphysema by two observers. Total emphysema score was calculated for each patient and the interobserver and intraobserver correlations were evaluated. Results: An increase was observed in 19 scores of distribution and 30 scores of severity. The interobserver correlation was observed in both conventional images and emphysematous parenchyma images. In addition, an intraobserver correlation was also observed similar to interobserver correlation. Conclusion: The visual scoring methodology of patients with emphysema can be easily applicable in HRCT examination of emphysematous parenchymal window. Intraobserver correlation was increased, and the concordance was reduced in repeated assessments of physicians with this method. © 2012 Düzce Medical Journal

Venous reflux: Measurement variability due to positional differences [Venöz reflü: hasta pozisyonuna bagli ölçüm farkliliklari.]

PURPOSE: The purpose of this study was to evaluate the role of the subject's position and two different maneuvers in the reflux measurements in femoral veins. MATERIALS AND METHODS: Venous reflux times in the common femoral vein (CFV) and superficial femoral vein (SFV) were studied in 50 healthy subjects (25 women, 25 male) aged between 22-57 years-old while the subjects were in supine and standing positions. Reflux was provocated only by Valsalva maneuver (VM) when the subject was lying down, whereas it was provocated by (1) Valsalva maneuver and (2) compression and release maneuver, respectively, when the subject was standing. Reflux times were recorded with each of the three methods. RESULTS: Regarding CFV, a reflux time of 1 second or more was recorded in 29 limbs (29%) only in the supine position. Of these 29 measurements, 19 were between 1 and 1.9 sec and 8 between 2 and 2.9 sec. When the subjects were examined in the standing position, the prevalence of reflux lasting more than 1 sec substantially decreased (5%). The prevalence of reflux lasting less than 0.5 sec was 97% with standing compression maneuver, 84% with standing VM and 27% with supine VM. Similarly, prevalence of reflux of longer than 0.5 sec or 1 sec was lower in the standing position than in the supine position in SFV. In CFV, mean reflux time was 1.3 sec in the supine position, whereas it was 0.7 sec and 0.4 sec with standing compression and standing Valsalva maneuvers, respectively. Corresponding values in SFV were 0.5 sec, 0.3 sec and 0.2 sec, respectively. CONCLUSION: The probability of making a false positive diagnosis of pathological reflux is high with supine examinations. When an examination in the supine position reveals a reflux time of longer than 1 second, making the patient stand up is expected to yield more reliable results. Compression and release maneuver, with its lowest false positive reflux prevalence, is the most reliable method in the evaluation of venous insufficiency

The benefit of expiratory-phase quantitative CT densitometry in the early diagnosis of chronic obstructive pulmonary disease

PURPOSE We aimed to compare the inspiratory and expiratory quantitative computed tomography (CT) densitometric data of healthy volunteers, individuals with chronic obstructive pulmonary disease (COPD) risk, and COPD patients to aid in the early diagnosis of COPD. MATERIALS AND METHODS Of the study patients, 14 were healthy volunteers (Group I), 12 were patients at risk for COPD (Group II), and 13 were COPD patients (Group III). The high-resolution CT was performed at three levels (the upper, middle, and lower parts of the lungs). All images were evaluated with a specific program for the segmentation of pulmonary parenchyma. The mean lung density (MLD) was measured, and the emphysema index (EI) was calculated using this program. RESULTS Both MLD values and calculated EI ratios showed significant differences between Groups I and III, and Groups II and III in both expiratory and inspiratory phases (P < 0.05). However, in the comparison of healthy volunteers and patients at risk for COPD (Group I and II), only expiratory-phase MLD values showed statistically significant difference (P < 0.001). CONCLUSION In patients at risk for COPD, expiratory-phase MLD measurements can be used as an early diagnostic method. © Turkish Society of Radiology 2012

Migration of an Intrauterine Contraceptive Device to the Ovary

We present the case of a 37-year-old woman with a history of 2 consecutive insertions of intrauterine contraceptive devices (IUDs) 3 years before she was referred to us for sonographic evaluation of lower abdominal pain. The first of the IUDs was presumed to have been expulsed spontaneously, and 3 months after insertion of the second device, the patient had begun experiencing lower abdominal pain. Medical treatment with antibiotics and spasmolytics had been unsuccessful. We performed transvaginal sonography, which revealed the presence of an IUD in the uterus and a 2-cm linear metallic echogenic area in the left ovary, believed to represent another IUD. Anteroposterior radiography confirmed that there were 2 IUDs in the pelvis, and CT demonstrated 1 IUD in the uterus and another in the left ovary. The patient underwent laparoscopic removal of the ovarian IUD and was discharged in good condition. To our knowledge, this is the first report of migration of an IUD to the ovary detected on transvaginal sonography. We recommend consideration of this possibility during evaluation of women with unexplained chronic pelvic pain. © 2004 Wiley Periodicals, Inc

Transabdominal pulse inversion harmonic imaging improves assesment of ovarian morphology in virgin patients with PCOS: Comparison with conventional B-mode sonography

Objective: In virgin policystic ovary syndrome (PCOS) patients transabdominal sonography is the preferential method of the pelvic examination. The purpose of this study was to determine ovarian morphology by the transabdominal route by pulse inversion harmonic imaging (PIHI) in virgin PCOS patients and to compare the diagnostic image quality with conventional B-mode ultrasonography (CBU). Methods: Fifty-two ovaries in 26 virgin patients were evaluated by the transabdominal approach. Each ovary was examined using both PIHI and CBU. The sharpness of the follicular cysts walls, degree of internal echo definitions of the follicle cysts and overall ovarian conspicuity was assessed subjectively, using 4 point scoring (0, being worst; 3, being best score). The number of countable follicles, the size of largest and smallest ovarian follicle and ovarian volumes were assessed quantitively by both techniques. The effect of body mass index (BMI) on qualitative and quantitative scoring was evaluated. Results: The sharpness of the cyst wall and internal echo structure was significantly better with PIHI than with CBU (P < 0.001 P < 0.001 and P < 0.001, respectively). PIHI improved overall ovarian conspicuity in 41 (78.8%) of 52 examination. The number of countable follicles was significantly lower with CBU (P < 0.001). The maximum diameter of the largest follicle was larger with PIHI sonography to compared CBU (P < 0.001). Mean ovarian volume was significantly larger with CBU (P < 0.001). When data were analyzed separately according to BMI, number of non-diagnostic overall ovarian conspicuity scores with CBU was markedly high in obese patients (88% with CBU versus 3.8% with PIHI). On the other hand, mean number of countable follicles with CBU became much more lower in the obese group (P < 0.001). Conclusion: In virgin PCOS patients, when compared to transabdominal CBU, PIHI significantly improved the detection of ovarian follicles, especially in high BMI obese subjects, through increased contrast sensitivity for cystic structures and decreased intrafollicular artifactual echoes. Transabdominal ultrasonographic examination by PIHI mode can contribute to the evaluation of ovaries. © 2004 Elsevier Ireland Ltd. All rights reserved

Fast MRI evaluation of pulmonary progressive massive fibrosis with VIBE and HASTE sequences: Comparison with CT

PURPOSE: The aim of this prospective study was to evaluate the diagnostic utility of volumetric interpolated breath-hold examination (VIBE) and half-Fourier-acquisition single-shot turbo spin-echo (HASTE) fast magnetic resonance imaging (MRI) sequences in the evaluation of pulmonary progressive massive fibrosis (PMF) in comparison with computed tomography (CT) imaging. If fast MRI is proven to be diagnostically significant, this modality can be used for diagnosis and follow-up studies of PMF patients. MATERIALS AND METHODS: Twenty-two PMF lesions from 20 coal workers were evaluated. After CT imaging, patients underwent pre-contrast VIBE, contrast-enhanced VIBE, and HASTE MRI studies for detection and evaluation of the PMF lesions. Measurements of the three groups were evaluated with intra-class coefficients. Correlation levels between sizes, image quality, and artifact were evaluated with linear Pearson correlation analysis. RESULTS: There was almost perfect agreement among radiologists for lesion detection with kappa analysis. There was significant agreement between three MRI study groups and gold standard CT images. We found the best agreement values with contrast-enhanced VIBE images for lesion detection and image quality in comparison with CT imaging. Presence of artifact was also lowest with this protocol. CONCLUSION: With fast MRI sequences in pulmonary imaging, image quality has significantly improved being very close to that of CT studies. In this study, contrast-enhanced VIBE protocol provided the best depiction of PMF lesions. This protocol may be an alternative choice for CT, avoiding the use of iodinated contrast material and minimizing exposure to ionizing radiation for follow-up studies. © Turkish Society of Radiology 2010