[The future of bedside chest radiography: Comparative study of mobile flat-panels and needle-image plate storage phosphor systems]. / Die Zukunft der Thoraxbettaufnahme: Vergleichende Untersuchung von mobilen Flachdetektoren und Speicherfoliensystemen mit Nadelkristalldetektoren.

BACKGROUND: Chest radiography is the most common diagnostic modality in intensive care units with new mobile flat-panels gaining more attention and availability in addition to the already used storage phosphor plates. PURPOSE: Comparison of the image quality of mobile flat-panels and needle-image plate storage phosphor system in terms of bedside chest radiography. MATERIALS AND METHODS: Retrospective analysis of 84 bedside chest radiographs of 42 intensive care patients (20 women, 22 men, average age: 65 years). All images were acquired during daily routine. For each patient, two images were analyzed, one from each system mentioned above. Two blinded radiologists evaluated the image quality based on ten criteria (e.g., diaphragm, heart contour, tracheal bifurcation, thoracic spine, lung structure, consolidations, foreign material, and overall impression) using a 5-point visibility scale (1 = excellent, 5 = not usable). RESULTS: There was no significant difference between the image quality of the two systems (p < 0.05). Overall some anatomical structures such as the diaphragm, heart, pulmonary consolidations and foreign material were considered of higher diagnostic quality compared to others, e.g., tracheal bifurcation and thoracic spine. CONCLUSIONS: Mobile flat-panels achieve an image quality which is as good as those of needle-image plate storage phosphor systems. In addition, they allow immediate evaluation of the image quality but in return are much more expensive in terms of purchase and maintenance.

Quantitative image quality measurements of a digital breast tomosynthesis system.

PURPOSE: The aim of this study was to measure the image quality of a digital breast tomosynthesis (DBT) system quantitatively. MATERIALS AND METHODS: The signal transfer property (STP), modulation transfer function (MTF), noise power spectrum (NPS), and detective quantum efficiency (DQE) of the Hologic Selenia Dimensions breast tomosynthesis system were measured according to established methods. The NPS was calculated from two-dimensional (2 D) fast Fourier transform (FFT) of flat field images. The presampling MTF of the system was determined for 2 D standard projection mammography and 3 D breast tomosynthesis mode using the edge method. The DQE was derived for different detector air kerma (DAK) values from NPS and MTF measurements. RESULTS: The detector response function was linear for both two-dimensional (2 D) standard projection mammography and three-dimensional (3 D) breast tomosynthesis modes. The gradient of the detector response in the 3 D imaging mode was higher than the gradient in the 2 D imaging mode by a factor of 3.1. The MTF values measured at the Nyquist frequency were 32 % and 39 % in 2 D and 3 D imaging modes, respectively. The DQE was saturated at an air kerma value approximately 3.5 times lower in 3 D mode than in 2 D mode. The measured maximum DQE value was 54 %. CONCLUSION: The measured DQE values were comparable with breast tomosynthesis systems from other companies (Siemens, GE).

Performance of an automatic dose control system for CT: patient studies.

PURPOSE: To study the effect of an automatic dose control (ADC) system with adequate noise characteristic on the individual perception of image noise and diagnostic acceptance compared to objectively measured image noise and the dose reductions achieved in a representative group of patients. MATERIALS AND METHODS: In a retrospective study two matched cohorts of 20 patients each were identified: a manual cohort with exposure settings according to body size (small - regular - large) and an ADC cohort with exposure settings calculated by the ADC system (DoseRight 2.0™, Philips Healthcare). For each patient, 12 images from 6 defined anatomic levels from contrast-enhanced scans of chest and abdomen/pelvis were analyzed by 4 independent readers concerning image noise and diagnostic acceptance on a five-point Likert scale and evaluated for objectively measured image noise. Radiation exposure was calculated from recorded exposure data. RESULTS: Use of the ADC system reduced the average effective dose for patients by 36 % in chest scans (3.2 vs. 4.9 mSv) and by 17 % in abdomen/pelvis scans (7.6 vs. 8.3 mSv). Average objective noise was slightly lower in the manual cohort (11.1 vs. 12.8 HU), correlating with a slightly better rating in subjective noise score (4.4 vs. 4.2). However, diagnostic acceptance was rated almost equal in both cohorts with excellent image quality (4.6 vs. 4.5). CONCLUSION: Use of an ADC system with adequate noise characteristic leads to significant reductions in radiation exposure for patients while maintaining excellent image quality.

Average glandular dose in digital mammography and breast tomosynthesis.

PURPOSE: To determine the average glandular dose (AGD) in digital full-field mammography (2 D imaging mode) and in breast tomosynthesis (3 D imaging mode). MATERIALS AND METHODS: Using the method described by Boone, the AGD was calculated from the exposure parameters of 2247 conventional 2 D mammograms and 984 mammograms in 3 D imaging mode of 641 patients examined with the digital mammographic system Hologic Selenia Dimensions. The breast glandular tissue content was estimated by the Hologic R2 Quantra automated volumetric breast density measurement tool for each patient from right craniocaudal (RCC) and left craniocaudal (LCC) images in 2 D imaging mode. RESULTS: The mean compressed breast thickness (CBT) was 52.7 mm for craniocaudal (CC) and 56.0 mm for mediolateral oblique (MLO) views. The mean percentage of breast glandular tissue content was 18.0% and 17.4% for RCC and LCC projections, respectively. The mean AGD values in 2 D imaging mode per exposure for the standard breast were 1.57 mGy and 1.66 mGy, while the mean AGD values after correction for real breast composition were 1.82 mGy and 1.94 mGy for CC and MLO views, respectively. The mean AGD values in 3 D imaging mode per exposure for the standard breast were 2.19 mGy and 2.29 mGy, while the mean AGD values after correction for the real breast composition were 2.53 mGy and 2.63 mGy for CC and MLO views, respectively. No significant relationship was found between the AGD and CBT in 2 D imaging mode and a good correlation coefficient of 0.98 in 3 D imaging mode. CONCLUSION: In this study the mean calculated AGD per exposure in 3 D imaging mode was on average 34% higher than for 2 D imaging mode for patients examined with the same CBT.

Performance of an automatic dose control system for CT: specifications and basic phantom tests.

PURPOSE: To assess the performance and to provide more detailed insight into the characteristics and limitations of devices for automatic dose control (ADC) in CT. MATERIALS AND METHODS: A comprehensive study on DoseRight 2.0, the ADC system provided by Philips for its Brilliance CT scanners, was conducted. Phantom tests were carried out on a 64-slice scanner (Brilliance 64) using assorted quality control (QC) phantoms that allowed verification of the basic specifications. If feasible, the findings were verified by model calculations based on known specifications. RESULTS: For all tests, the dose reductions and modulation characteristics fully met the values expected from the specifications. Adverse effects due to increased image noise were only moderate as a result of the "adequate noise system" design that employs comparatively gentle modulation, and the additional use of adaptive filtration. CONCLUSION: Simple tests with QC phantoms allow evaluation of the most relevant characteristics of devices for ADC in CT.

Performance of an automatic dose control system for CT: anthropomorphic phantom studies.

PURPOSE: To assess the performance and to provide more detailed insight into characteristics and limitations of devices for automatic dose control (ADC) in CT. MATERIALS AND METHODS: A comprehensive study on DoseRight 2.0, the ADC system provided by Philips for its Brilliance CT scanners, was conducted with assorted tests using an anthropomorphic phantom that allowed simulation of the operation of the system under almost realistic conditions. The scan protocol settings for the neck, chest and abdomen with pelvis were identical to those applied in the clinical routine. RESULTS: Using the appropriate ADC functionalities, dose reductions equal 40% for the neck, 20% for the chest and 10% for the abdomen with pelvis. Larger dose reductions can be expected for average patients, since their attenuating properties differ significantly from the anthropomorphic phantom. Adverse effects due to increased image noise were only moderate as a consequence of the "adequate noise system" design and the complementary use of adaptive filtration. The results of specific tests also provided deeper insight into the operation of the ADC system that helps to identify the causes of suspected malfunctions and to prevent potential pitfalls. CONCLUSION: Tests with anthropomorphic phantoms allow verification of the characteristics of devices for ADC in CT under almost realistic conditions. However, differences in phantom shape and material composition require supplementary patient studies on representative patient groups.

[Assessment of clinical image quality in feline chest radiography with a needle-image plate (NIP) storage phosphor system--an approach to the evaluation of image quality in neonatal radiography]. / Untersuchungen zur Qualität von Thoraxaufnahmen bei Katzen mit einem auf einer Nadelstruktur basierenden Speicherfoliensystem - Modelluntersuchungen zur Bewertung der Bildqualität bei Neugeborenen.

PURPOSE: Is the image quality of thoracic radiographs of cats obtained with a needle-based storage phosphor (NIP) system superior to conventional (PIP) storage phosphor radiography? Is it possible to decrease the mAs by 50 % with the NIP system without significant loss of information? MATERIALS AND METHODS: From each of the 20 animals, three lateral radiographs were acquired. The assessment of the exposure level was based on the generated lgM-values. Images were acquired 1. with the NIP system and exposure settings equivalent to an lgM of 1.9, 2. with the PIP system and identical settings, and 3. with the NIP system and 50 % of the mAs. Six blinded readers used a 5-step scale to assess the reproducibility of five anatomical structures and image noise sensation. Data were analysed using Visual Grading Characteristics Analysis (VGC). RESULTS: While applying identical exposure values the NIP system for all features revealed superior ratings to those of the PIP system (AUC (VGC) values ranged from 0.81 for "cardiac silhouette" to 0.92 for "trachea"). Even when reducing mAs by 50 % in the NIP images all features were rated better compared with the PIP images and original settings (AUC (VGC) values ranged from 0.60 for "cardiac silhouette" to 0.74 for "trachea" and "caudal thoracic field"). CONCLUSION: The NIP system demonstrates clearly better image quality compared to the reference PIP system. A dose reduction of 50 % seems to be possible without relevant detraction from image quality. The results obtained in the animal model are valid for simulating conditions in neonatal radiological practise.

[Comparison of the image quality of a storage phospor system and a flat-panel detector in feline thoracic radiography]. / Vergleich der Bildqualität eines Speicherfoliensystems und eines Flachbilddetektors bei Thoraxröntgenaufnahmen von Katzen.

OBJECTIVE: The aim of the study was to compare the image quality of radiographs obtained with a storage phosphor (SP) system and a flat-panel detector (FD). Furthermore, the influence of different exposure settings was investigated. MATERIAL AND METHODS: In a prospective study a series of lateral thoracic radiographs of 45 normal cats were acquired by use of a standard SP-system and an opto-direct FD. From each animal four radiographs were taken with exposure settings adjusted to achieve sensitivity (S)-values of the system-specific dose indicator of S180 and S360. In a blind study, five observers rated the presentation of anatomical structures (trachea, cranial lung field, sternum, cardiac silhouette, caudal thoracic field) by use of a four-point scale (1 - excellent; 4 - insufficient). RESULTS: Independent of the detector-type and the exposure level applied the mean values of the ratings of the respective image criteria ranged from 1.14 to 1.67. In both systems higher doses related to better rating results. While comparing the detectors on the basis of identical exposure settings the FD demonstrated superior performance. CONCLUSION AND CLINICAL RELEVANCE: At the dose levels investigated both detectors reveal an image quality sufficient for the depiction of subtle, low-contrast thoracic structures in cats. Therefore, the detectors can be recommended for practical use in small animal radiology. In both systems a dose reduction of 50% in comparison to the original level (S180) is possible without a substantial loss of information. Because of the superior quantum efficiency the dose saving potential of the FD might be even higher. Alternatively, the higher dose efficiency can be utilised to improve image quality in comparison to the SP-system with identical exposure settings.

[Conversion coefficients for estimation of effective dose to patients from dose area product during fluoroscopy x-ray examinations]. / Konversionsfaktoren zur Ermittlung der effektiven Dosis für Patienten aus dem Dosisflächenprodukt bei Röntgendurchleuchtungsuntersuchungen.

PURPOSE: The effective dose, which is related to the stochastic radiation risk, cannot be measured directly. Therefore, conversion coefficients for estimating the effective dose for patients were calculated for fluoroscopy X-ray examinations from the dose area product which can be easily measured. MATERIALS AND METHODS: Conversion coefficients were calculated using the PC-based Monte Carlo program PCXMC in software version 1.5.1. Conversion coefficients were determined for tube voltages between 60 kV and 110 kV, for additional cupper filtration up to 0.9 mm, for different projections (a. p., p. a. and lateral) and X-ray field size (between 20 cm x 20 cm and 40 cm x 40 cm in image plane) and field position (from head to leg). RESULTS: Tube voltage, filtration and field position have a significant effect on conversion coefficients. Conversion coefficients increase as the tube voltage and filtration increase. Depending on the radiation spectrum used, the conversion coefficients may differ up to a factor of 4 for the same X-ray examination. The highest conversion coefficients were found for irradiation of the body region followed by the head and leg region. The effect of the field size and projection is moderate. Conversion coefficients for a. p. projection are higher than those for p. a. and lateral projections. CONCLUSION: Effective dose can be easily estimated by multiplying relevant conversion coefficients by the dose area product. Using conversion coefficients from the literature that do not take additional cupper filtration into consideration can underestimate the effective dose by a factor or up to 2 or more depending on the filtration used.

Influence of grid control and object detection on radiation exposure and image quality using mobile C-arms - first results.

PURPOSE: The objective of this study was to examine the extent to which the image quality on mobile C-arms can be improved by an innovative exposure rate control system (grid control). In addition, the possible dose reduction in the pulsed fluoroscopy mode using 25 pulses/sec produced by automatic adjustment of the pulse rate through motion detection was to be determined. MATERIALS AND METHODS: As opposed to conventional exposure rate control systems, which use a measuring circle in the center of the field of view, grid control is based on a fine mesh of square cells which are overlaid on the entire fluoroscopic image. The system uses only those cells for exposure control that are covered by the object to be visualized. This is intended to ensure optimally exposed images, regardless of the size, shape and position of the object to be visualized. The system also automatically detects any motion of the object. If a pulse rate of 25 pulses/sec is selected and no changes in the image are observed, the pulse rate used for pulsed fluoroscopy is gradually reduced. This may decrease the radiation exposure. The influence of grid control on image quality was examined using an anthropomorphic phantom. The dose reduction achieved with the help of object detection was determined by evaluating the examination data of 146 patients from 5 different countries. RESULTS: The image of the static phantom made with grid control was always optimally exposed, regardless of the position of the object to be visualized. The average dose reduction when using 25 pulses/sec resulting from object detection and automatic down-pulsing was 21 %, and the maximum dose reduction was 60 %. CONCLUSION: Grid control facilitates C-arm operation, since optimum image exposure can be obtained independently of object positioning. Object detection may lead to a reduction in radiation exposure for the patient and operating staff.

[Radiation exposure with 3D rotational angiography of the skull]. / Strahlenexposition bei der 3D-Rotationsangiographie des Schädels.

PURPOSE: Determination and comparison of radiation exposure for examinations of the skull with unsubtracted 3D Rotational Angiography (3D RA) and 2D Digital Subtraction Angiography (2D DSA). MATERIALS AND METHODS: Measurements were carried out with a skull of an Alderson phantom for 3D RA and for 2D DSA in p. a. and lateral projections using an Innova 4100 angiography system with a digital flat panel detector from GE Healthcare. 45 thermoluminescent dosimeters TLD 100H from Harshaw were placed inside the phantom to measure organ doses. In addition the dose area product was recorded and the effective dose was calculated using the Monte Carlo program PCXMC. RESULTS: For a biplanar DSA run (lateral and p. a. projection), the organ doses were 4 to 5 times higher and the effective dose was 4 times higher than for a 3D RA even though the number of images for the two DSA runs was only half of that for 3D RA. CONCLUSION: The radiation exposure for unsubtracted 3D RA using a flat panel detector is significantly lower than for biplanar DSA. Using 3D RA in place of 2D DSA can reduce the radiation exposure of patients in neuroradiology procedures.

[Radiation exposure in full-field digital mammography with a selenium flat-panel detector]. / Strahlenexposition bei der digitalen Vollfeldmammographie mit einem Selen-Flachdetektor.

PURPOSE: Calculation of the average glandular dose for mammography on a full-field digital mammography system using a selenium flat-panel detector. MATERIALS AND METHODS: Mammographic examinations were carried out using the Selenia digital mammographic system from Lorad/Hologic. 1992 mammographies of 500 patients in cranio-caudal and medio-lateral projections were evaluated. Based on the recorded exposure conditions (tube voltage, tube loading, filtration, compressed breast thickness), the entrance surface air kerma was calculated by multiplying the tube loading by the measured tube output and was corrected according to the inverse square law. The average glandular dose was determined for each exposure by multiplying the entrance surface air kerma value by the relevant conversion factor for a breast composition of 50 % adipose tissue and 50 % glandular tissue by weight. RESULTS: The mean values for patient age and compressed breast thickness were 61 years and 58 mm, respectively. The average glandular dose was 1.57 mGy for a single view (1.46 mGy for cranio-caudal view images and 1.68 mGy for medio-lateral view images). CONCLUSION: Full-field digital mammography with a selenium flat-panel detector requires a dose similar to that of units with a flat-panel detector based on amorphous silicon and a dose approximately 20 % lower than that of conventional screen/film mammography.

[Callus distraction of the midface. Requirements for diagnostic imaging]. / Kallusdistraktion des Mittelgesichts. Anforderungen an die bildgebende Diagnostik.

Callus distraction of the midface is a recently developed surgical method for treatment of atrophic or hypoplastic maxillae. The treatment planning is based on individual shaped models, being constructed with the help of computed tomographic data. Our experience is based on 10 patients (3 male/7 female; age: 11-55 years). The demands for imaging are reported. The following imaging procedure is recommended: 1. preoperative: lateral x-ray, orthopantomogram, spiral CT, 2. during the time of callus distraction with normaly takes 4 to 5 weeks: lateral x-ray (every 10 days), and 3. for follow up: lateral x-ray and spiral CT. The Radiation exposure caused by the repetitive images is calculated in detail.

[Reduction of radiation exposure for patient and investigator in interventional radiography]. / Reduktion der Strahlenexposition in der interventionellen Angiographie für Patient und Untersucher.

PURPOSE: In a retrospective analysis of vascular interventional procedures, relations between parameters of the examination and radiation exposure of patient and medical personnel are examined. MATERIAL AND METHOD: 1208 vascular interventional procedures are evaluated. Interventional procedures are divided into three groups: percutaneous transluminal angioplasty, implantation of a stent, thrombolysis. RESULTS: Mean values of the radiation dose of patient and radiology personnel are reported for these examinations. The mean value of the radiation dose of the physician was 7 microSv (maximum 24 microSv), that of the patient 1548 cGy.cm2 (maximum 8485 cGy.cm2). CONCLUSION: The quantity of X-rays to the patient may be lowered by using pulsed fluoroscopy and by reducing the number of radiographs. Reduction of the number of radiographs may be achieved by using the last-image hold and the road mapping mode. The operator's dose can be decreased by using additional radiation protection systems like a MAVIG-radiation protection wall. The radiation dose reduction was 61% for the physician and 17% for the patient.

[Detection of orbital foreign bodies by CT: are plain radiographs of foreign bodies still useful?]. / Darstellbarkeit von Orbita-Fremdkörpern in der CT. Ist die Fremdkörperübersicht noch sinnvoll?

PURPOSE: To prove the visualisation of orbital foreign bodies by CT. MATERIALS AND METHODS: In vitro we examined defined small objects of various materials (metal, wood, glass, stone) which are common as orbital foreign bodies, Density and minimum detectable size were studied. The findings of 27 patients with suspected orbital foreign bodies were compared with the results of plain radiographs, Comberg radiographs, sonography, and surgery. RESULTS: For iron, the minimum detectable size was 0.02 mm3. A differentiation of various materials by CT was not always possible, especially in small objects. There were wide differences in density of wood (-600 HU to +130 HU) according to hardness and water content. The CT scans correctly showed number and location of foreign bodies. Other methods were inferior in detection of foreign bodies. CONCLUSION: In diagnosis of foreign body injuries of the orbit, CT is the imaging method of choice.

[Determination of the radiation imparted to patients in x-ray diagnosis--methods and results]. / Ermittlung der Strahlenbelastung der Patienten in der Röntgendiagnostik--Methoden und Ergebnisse.

The amount of radiation committed to the patient is best described by appropriate organ doses. Methods for determining such dose values are described. For x-ray investigations of the chest, thoracic and lumbar spine, pelvis and kidney (excretion urography) our own organ-dose values are compared with those from the literature.

[Determination of global left ventricular functional parameters with intraventricular digital subtraction angiography in coronary disease]. / Die Bestimmung globaler linksventrikulärer Funktionsparameter mit intraventrikulärer digitaler Subtraktionsangiographie bei koronarer Herzkrankheit.

Left heart catheterisation, coronarography and conventional angiocardiography of the left ventricle (ACG) [30 degrees right anterior oblique; 45 ml contrast medium (Visotrast) with a flow of 12 ml per sec.] was performed in 86 patients with coronary heart disease. Additionally intraventricular digital subtraction angiography (DSA) was performed, using a Philips-device (DVI 2 CV). For DSA 15 ml contrast medium (Visotrast) was injected with a flow of 8 ml per sec. 73 examinations were selected for the study. The aim of the study was to compare the usefulness and applicability of ACG und DSA for ventriculography. There were no significant differences between enddiastolic (EDV) and endsystolic (ESV) volumes as well as ejection fractions (EF) determined by ACG and DSA. Results of the analysis of correlation were rEDV = 0.85;rESV = 0.93;rEF = 0.80. The increase of the end-diastolic pressure after ACG was determined with 7 Torr (mean), after DSA with less than 2 Torr (mean). According to these results we would prefer intraventricular DSA to conventional ACG, provided the technical equipment is available. This is concluded despite the fact that in single cases considerable differences were found between the volumes estimated by ACG and those determined by DSA. These differences were analysed in detail. The main advantages of the DSA are the by far smaller inconvenience for the patients, the rare occurrence of provoked extrasystoles and the fast and easy analysis of the ventriculographies by means of the implemented image processing programmes.