Commensurate germanium light emitters in silicon-on-insulator photonic crystal slabs.

We report on the fabrication and characterization of silicon-on-insulator (SOI) photonic crystal slabs (PCS) with commensurately embedded germanium quantum dot (QD) emitters for near-infrared light emission. Substrate pre-patterning defines preferential nucleation sites for the self-assembly of Ge QDs during epitaxial growth. Aligned two-dimensional photonic crystal slabs are then etched into the SOI layer. QD ordering enhances the photoluminescence output as compared to PCSs with randomly embedded QDs. Rigorously coupled wave analysis shows that coupling of the QD emitters to leaky modes of the PCS can be tuned via their location within the unit cell of the PCS.

[Comments on the standards for acceptance and consistency testing of systems for digital radiography]. / Kommentierungen zu den Normen zu Abnahme- und Konstanzprüfungen bei digitalen Radiographiesystemen (Projektionsradiographie).

Due to German regulations, acceptance and consistency tests have to be obtained by 12.31.2005 for all equipment used for computed radiography according to special standards published in DIN 6868. This article familiarizes all users with the most important aspects of these standards. In addition, explanatory and background information for establishing these regulations are provided.

[Radiation exposure and image sharpness of mammographic units in bavaria with respect to the European guidelines]. / Strahlenexposition und Abbildungsschärfe an bayerischen Mammographie--Einrichtungen im Hinblick auf die Europäischen Leitlinien.

In a survey including all mammography units in Bavaria, entrance doses in air and other quality-relevant parameters were measured with standard settings and under comparable conditions. The study was aimed to discover discrepancies between practical mammographic imaging techniques and the demands established in the European Guidelines. Test images were made by the operators themselves with phantoms used for constancy checks. Entrance dose values were measured with official film dosimeters. The survey showed that more than 95 % of all mammographic units in Bavaria comply with the European guidelines with respect to radiation exposure and imaging sharpness.

Chest imaging with flat-panel detector at low and standard doses: comparison with storage phosphor technology in normal patients.

The purpose of this study was to evaluate the performance of standard-dose and low-dose cesium iodide (CsI)-doted amorphous silicon (a-Si) flat-panel detector technology (FDT) as compared with storage-phosphor technology (SPT) in the depiction of relevant anatomical structures in chest radiography. In 75 patients referred for thoracic CT, digital chest radiographs were randomly obtained with either SPT at a standard dose (speed class S400, n=25), standard-dose FDT (S400, n=25) or FDT at a low dose (S800, n=25). Five radiologists evaluated the visibility of eight pulmonary and mediastinal anatomical structures using a five-point rating scale. To determine statistically significant differences between the three groups, the Mann-Whitney U-test was employed. No statistically significant differences were found in the depiction of eight criteria between SPT and standard-dose or low-dose FDT chest radiographs. The performance of FDT S400 was equal to SPT for most criteria and better for retrocardiac structures and soft tissue. FDT S800 was inferior to both SPT and FDT S400. Standard-dose FDT is equivalent to SPT in the depiction of relevant anatomical structures of the chest. Our results also indicate that a dose reduction of 50% with FDT may result in small but not significant decrease of image quality.

[Assessment of the effective dose for routine protocols in conventional CT, electron beam CT and coronary angiography]. / Abschätzung der effektiven Dosis für Routineprotokolle beim konventionellen CT, Elektronenstrahl-CT und bei der Koronarangiographie.

PURPOSE: To compare the effective dose applied by sequential CT (SEQ), spiral CT (SCT), electron beam CT (EBT) and coronary angiography for investigations of the chest, abdomen and the heart. METHODS: The Alderson Phantom was used to compare the effective dose for all modalities. In addition, the effective dose for conventional CT (SEQ and SCT) was estimated with a mathematical phantom. RESULTS: For CT investigation of the chest and abdomen the dose was highest for the EBT (11 mSv and 25 mSv, respectively) and slightly lower for the SEQ (7.8 mSv and 21.5 mSv, respectively), whereas spiral CT required the least dose (5.3 mSv and 8.8 mSv, respectively). For coronary calcium screening (0.8 mSv) and EBT coronary angiography (1.7 mSv) the dose was lower than for coronary catheter angiography (3.3 mSv). For conventional CT the difference between the effective dose derived by the mathematical phantom and by the Alderson phantom was 2% to 20%. CONCLUSIONS: For investigations of the chest and abdomen the effective dose applied by SCT is significantly lower than that with EBT and SEQ. For investigation of the coronary arteries the effective dose applied by EBT is lower than that for coronary catheter angiography.

[Virtual colonoscopy using CT and MRI]. / Virtuelle CT- und MRT-Koloskopie.

PURPOSE: To evaluate experimentally and in patients the sensitivity and effective dose of virtual electron-beam tomography (EBT) colonoscopy for detecting small colon tumors and to compare the methods and results with virtual colonoscopy using spiral CT and MR imaging in a review of the literature. MATERIALS AND METHODS: Six polyps with diameters between 3 and 12 mm were created and randomly placed in resected pig colon. After distension with air, the pig colon was scanned with continuous volume scanning (CVS, 3 mm collimation) and a pitch of 0.4, 0.8 and 1.5. Twenty patients positive for the fecal blood test were examined after rectal CO2 insufflation and i.v. administration of 1 mg glucagon. A 13 s CVS scan was used to cover the entire colon within one breath-hold. 3D volume-rendered fly-throughs were evaluated by two independent radiologists. Effective dose equivalent was estimated using an Alderson phantom equipped with thermoluminescence dosimeters. RESULTS: In the tumor model, all polyps were detectable at a pitch of 1.5. A further reduction of the pitch ratio did not improve the conspicuity of the polyps. In patient studies, all tumors (n = 4) and polyps (n = 3) were correctly identified on 3D fly-throughs. Two false positive results were obtained. Effective dose equivalent was calculated at 3.2 mSv per scan. CONCLUSIONS: Our preliminary results indicate that virtual EBT colonoscopy holds promise for fast screening for colon polyps. The best technique for virtual colonoscopy (Spiral CT, EBT, MRI) has not yet been determined and the future role of virtual colonoscopy must still be defined.

[Radiation exposure during CT examination of thorax and abdomen. Comparison of sequential, spiral and electron beam computed tomography]. / Strahlenexposition bei der CT-Untersuchung des Thorax und Abdomens. Vergleich von Einzelschicht-, Spiral- und Elektronenstrahlcomputertomographie.

Comparison of radiation exposure applied by different types of CT scanners for the investigation of the chest and abdomen. Determination of radiation exposure applied by multi-phase spiral CT. Estimation of the dose in air in the system axis of the scanner, the CT dose index (CTDI) and the effective dose for electron beam tomography (EBT) and two conventional CT scanners (sequence, SEQ; spiral, SCT). For EBT, dose in system axis for investigation of the abdomen was above 50 mGy. Effective dose for investigation of the chest and abdomen was higher with EBT (11 and 26 mSv, respectively) than with conventional CT (SEQ, 4 and 20 mSv; SCT, 2 and 7 mSv). The effective dose for a biphasic investigation (liver 5 mSv, kidney 4 mSv) was below, for a triphasic investigation (liver 7 mSv) above the effective dose of the investigation of the abdomen (6 mSv). Investigation of the abdomen with the EBT should only be performed for certain indications. With spiral CT, effective dose is much lower than with EBT.

[A comparison of the monitor and alternator findings of digital thoracic images with the aid of a computer-supported procedure]. / Vergleich der Monitor- und Alternatorbefundung von digitalen Thoraxaufnahmen mittels eines computergestützen Verfahrens.

PURPOSE: To compare softcopy and hardcopy reading of chest radiographs a software tool was designed for creating lesions with clearly defined size, location and contrast. METHOD: An ROC study was performed using a set of chest radiographs with 300 simulated small nodules and linear details displayed on film and on a 1 K monitor. Six observers participated in the study. ROC curves were generated on the basis of 7200 decisions. RESULTS: There was no significant difference in observer performance overall (AUC = Area under curve). Monitor: 0.84 +/- 0.08 vs. AUC, Film: 0.84 +/- 0.08). Slight, but not statistical significant differences were found in the detection of low-contrast lung nodules and of linear lung details. CONCLUSION: Soft-copy reading using a high quality 1 K CRT display provides the same accuracy for the detection of subtle computer-simulated lesions as hardcopy reading. A software tool could be used for assigning optimal characteristics of CRT- and hardcopy displays using clearly defined lesions as a gold standard.

[Technical bases and acquisition conditions of electron-beam computed tomography]. / Technische Grundlagen und Akquisitionsbedingungen der Elektronenstrahl-Computertomographie.

PURPOSE: In this review the technical principle and scanner characteristics of electron beam computer tomography (EBCT) are discussed. METHODS: In contrast to conventional CT, image acquisition in EBCT is achieved without mechanically moving parts. This construction allows for short acquisition times in investigating given anatomical regions (100 ms per slice) or up to 8 levels without table movement and short interscan delays (50 ms per slice). RESULTS: Depending on the nature of the investigation, the scanner can be used in the single slice, continuous volume scanning and multi slice mode. The single slice mode is used for detection and quantification of coronary calcifications and for CT angiography of the coronary vessels. Equivalent to the spiral mode in conventional CT, continuous volume scanning may be used for routine investigation of the chest and abdomen. Functional investigations of the heart and perfusion measurement of different organs can be performed in multi slice mode. Because of the geometry of the electron beam scanner, radiation exposure for certain investigations is above the exposure with conventional CT. CONCLUSION: Future developments will focus on dose efficient radiation collimation, high resolution detector systems and artefact reducing reconstruction kernels.

[Initial experiences with pulsed fluoroscopy on a multifunctional fluoroscopic unit]. / Erste Erfahrungen mit gepulster Durchleuchtung an einer multifunktionellen Durchleuchtungsanlage.

PURPOSE: Comparison of radiation doses in pulsed and continuous fluoroscopy to quantify the dose reduction by pulsed fluoroscopy. Further, the applicability of pulsed fluoroscopy in clinical routine has been evaluated. MATERIALS AND METHODS: In a human pelvic phantom, the radiation dose (skin entry dose in cGycm2) was measured at two pulses per second (pps), 3 pps, 6 pps, 12 pps and continuous fluoroscopy mode, respectively, using image-intensifier entries of 38 cm, 25 cm, and 17 cm. 300 examinations were carried out, and the results of the different fluoroscopy modes were registered. RESULTS: Dose reduction depends on the image-intensifier entry. Compared to the radiation dose in continuous fluoroscopy, with 12 pps fluoroscopy the radiation dose can be reduced at a minimum of 51%, with 6 pps fluoroscopy to 40%, with 3 pps fluoroscopy to 20%, and with 2 pps fluoroscopy to a minimum of 14.5%. Clinical routine has shown that 78% of all examinations can be performed with 2 or 3 pps fluoroscopy mode. In 12.7% of the cases pulsed fluoroscopy of diverse frequencies was used, in an additional 2% combined with continuous fluoroscopy. Exclusively, continuous fluoroscopy has been employed in 2% of the cases. CONCLUSIONS: Using pulsed fluoroscopy, an 80% reduction of the radiation dose compared to continuous fluoroscopy is possible. About 96% of all examinations can be performed with pulsed fluoroscopy of different pulse rate and without using continuous fluoroscopy.

[Digital luminescence radiography in comparison with the conventional film-screen technique in diagnosis of fractures]. / Digitale Lumineszenzradiographie im Vergleich zur konventionellen Film-Folien-Technik bei der Diagnostik von Frakturen.

PURPOSE: The accuracy of digital luminescence radiography was compared with that of conventional film/screen techniques, using animal preparations and clinical examinations. MATERIAL AND METHOD: Fine fissures were made in 8 animal bones and these were examined radiologically. The digital examinations were carried out with and without edge enhancement. 208 patients were examined in a similar way. Film quality and assessment of the fractures were evaluated quantitatively. RESULTS: In no instance did either of the digital methods provide inferior quality when compared with conventional films. ROC analysis for evaluation of fractures in patients, using an experienced radiologist, showed no significant difference between the various methods (ROC areas: conventional 0.947, digital 0.958, digital with edge enhancement 0.943). With a less experienced observer there were significant advantages for both digital methods (ROC areas: 0.851, 0.886, 0.908). CONCLUSION: Our investigation has proved that fractures which are difficult to see can be reliably demonstrated by digital luminescence radiography.

[The diagnostic value of digital and conventional imaging in intravenous urography]. / Diagnostische Wertigkeit digitaler und konventioneller Bildgebung bei intravenöser Urographie.

PURPOSE: To compare image quality of digital luminescence radiography with conventional film-screen techniques during excretion urography. Four field tests and ROC analysis for determining diagnostic value. MATERIAL AND METHOD: 135 patients were included in a prospective study. Three independent observers judged the five minute (59 cases) or ten minute (76 cases) films after contrast injection using digital images as well as corresponding conventional images (five minutes-76 cases, ten minutes-59 cases). RESULTS: The digital technique provided better information concerning the renal parenchyma, the soft tissues and bone structures. Contrast enhanced detail was demonstrated equally well by both systems. The two systems had similar sensitivity but digital radiography showed higher specificity.

Muscarinic receptors in gastric mucosa are increased in peptic ulcer disease.

Muscarinic receptors stimulate the secretion of acid pepsinogen and mucous in gastric mucosa. Whether muscarinic receptors are involved in the pathogenesis of benign gastric disease is unknown. Receptor changes in these conditions were therefore sought. An autoradiographic technique was developed to determine quantitatively muscarinic receptors in microtome sections of biopsy specimens obtained during gastroscopy. Muscarinic receptor density was mean (SEM) 18.4 (1.2) fmol/mg protein in the corpus and 8.9 (0.7) fmol/mg protein in the antrum (n = 53). Neither chronic nor active gastritis was associated with receptor changes in the antrum but chronic gastritis was associated with a receptor loss in the corpus. Patients with acute or recent duodenal or antral ulcers (n = 23) had significantly higher levels of muscarinic receptors in the corpus than controls (n = 25) (22.2 (1.5) v 16.9 (1.7) fmol/mg protein respectively (p < 0.025). These results suggest that muscarinic M3 receptor is overexpressed in duodenal ulcer disease and may play a part in its pathogenesis.

[Reducing radiation dosage with modern DSA equipment]. / Einsparungen bei der Durchleuchtungsdosis durch moderne DSA-Anlagen.

PURPOSE: In angiographic and interventional procedures the often long fluoroscopy times add a great deal to the total patient dose. The new Multistar T.O.P. (Siemens) is equipped with various features for dose reduction. In this study pulsed fluoroscopy was tested versus standard continuous fluoroscopy and supervisions. MATERIALS AND METHODS: Fluoroscopy with 3, 7.5, and 15 pulses/s in the Multistar T.O.P. were compared to standard fluoroscopy and to reduced-dose supervision in a human pelvic phantom. The skin entry dose and pelvic dose were continuously registered. RESULTS: The supervision mode used 58% of the dose used in continuous fluoroscopy. Pulsed fluoroscopy with 15 pulses/s required 54%, 7.5 pulses/s 27% and 3 pulses/s. These provide adequate image quality with only 10% of the standard dose. CONCLUSIONS: It was possible to save up to 90% of the fluoroscopy dose in interventions and angiographies when using the new pulsed fluoromodes available in the Multistar T.O.P.

[Comparison of input grey values and contrast profiles: a contribution to the discussion on optimization of evaluation parameters in storage phosphorus radiography]. / Vergleich von Eingangsgrauwerten mit Kontrastprofilen--ein Beitrag zur Diskussion um die Optimierung der Auswerteparameter bei der Speicherfolienradiographie.

On comparing the individual imaging stages in conventional and digital image radiography it becomes evident that a significant advantage of the digital method is the possibility to adapt the image character and exposure dose individually to various problems requiring an answer. To take advantage of this it is imperative to optimise image processing with care, especially contrast processing. No systematic procedure based on objective criteria had existed to date. This paper describes a method of taking into account both the diagnostic significance of the structures to be imaged and their distribution within the relevant density range, in order to arrive at the best possible contrast conversion. A prerequisite is to know for every kind of imaging which distribution of grey values pertaining to the relevant structures can be expected before digital image processing (initial grey values). This distribution determines the most favourable contrast conversion. The processing parameters for several types of imaging were optimised by this method. The method is demonstrated via thoracic images of newborn and children.

[A comparison of digital radiography and conventional x-ray diagnosis for shoulder arthrography]. / Vergleich der digitalen Radiographie (DLR) und der konventionellen Röntgendiagnostik bei der Schulterarthrographie.

Fifty double-contrast arthrographies of the shoulder were obtained using conventional film-screen methods as well as by digital luminescence radiography (DLR). The supplied picture-evaluation programs had to be modified and improved prior to this study. In DLR two different post-processed images were obtained, one resembling a conventional film-screen, the other with an intensified edge-enhancement. Some of the digital luminescence radiographs were exposed with only 50% of the conventional doses. A comparison showed the equivalent diagnostic values of both the improved DLR and the conventional film screen. Even a reduction of the exposure dosage did not lead to a loss of information.

Standardized quantitative high resolution CT in lung diseases.

Twenty-seven patients with diffuse fibrosing alveolitis (DFA), 27 patients with granulomatous lung disease (GLD), 3 patients with homozygous alpha 1-proteinase inhibitor deficiency (alpha 1-PID), and 6 healthy volunteers (C) were studied using thin section high resolution CT (HRCT) at 50% of actual vital capacity (VC), determined and controlled spirometrically during each exposure. A fast contour tracing algorithm was used to isolate the lung parenchyma followed by a quantitative histogram analysis of the frequencies of CT values. Mean CT values enabled us to discriminate significantly between the groups of C and alpha 1-PID. Significant differences were found between the groups of GLD and DFA versus C by applying suitably selected intervals of CT values. Moreover, if the patients were assigned to four different groups according to their lung function results (normal, restrictive, obstructive, restrictive and obstructive), again significant differences existed with respect to defined intervals of CT values. Mean CT values showed a significant negative correlation with lung function tests representative of lung parenchymal disease, i.e., VC, diffusing capacity, and exercise PaO2. Moreover, CT values ranging from -899 to -800 HU correlated positively, whereas CT value frequencies above -699 HU correlated inversely with these same lung function parameters. These results indicated that certain intervals of CT values do reflect functionally different abnormalities of lung parenchyma. It is concluded that an analysis of frequencies of CT values determined by spirometrically standardized HRCT provides objective quantitative data that reflect changes of pulmonary structure corresponding to lung function impairments. Thus, spirometrically standardized HRCT may be helpful for evaluating and staging patients with diffuse pulmonary disease.

[Results of interstitial radiotherapy using I-125 seeds in the treatment of prostatic cancer]. / Ergebnisse nach interstitieller Strahlentherapie mit J-125-Seeds bei der Behandlung des Prostatakarzinoms.

30 patients with localized adenocarcinoma of the prostate were treated with pelvic lymphadenectomy and I-125 interstitial implantation from 1980 to 1985 (21/30 T3-tumors and 14/30 with poor differentiation). The mean follow-up is 59.5 months (range 18 to 88 months). The crude, progression-free and local progression-free survival rates (Kaplan-Meier) for all patients are 68%, 61% and 71% respectively. But, the progression-free survival is 39% in patients with G3-tumors after five years and only 25% in patients with T3 G3-tumors after four years. The local progression rate was 33% in patients with T3-tumors. We did not observe any late intestinal side-effects, but 11/30 (37%) patients suffered from later urinary flow problems caused mainly by local tumor progression. Therefore, we regard interstitial implantation with I-125-seeds as an alternative treatment to radical prostatectomy in patients with T1, 2 G1, 2-tumors but as insufficient in patients with T3 G3-tumors.