Biomedical subjects

K P Hermann

Publications and source records attributed to K P Hermann.

At least 19 recordsLinked to original sources

PubMed2005

Digital mammography: current state and future aspects.

The introduction of digital technique in mammography has been the last step in completing the process of digitalization in diagnostic imaging. Meanwhile, some different digital techniques as well as a couple of different digital mammography systems were developed and have already been available for some years. In this review article, the relevant data of key studies are reported, the current status is defined, and perspectives of digital mammography are described.

Breast Neoplasms↗

PubMed2005

Applications and literature review of the BI-RADS classification.

The Breast Imaging Reporting and Data System (BI-RADS) of the American College of Radiology (ACR) is a tool created to reduce variability in the terminology used in mammographic reports. An illustration of mammographic examples from our institution interpreted according to the BI-RADS lexicon of the American College of Radiology (ACR) is presented. A literature review concerning the usefulness and limitations of the BI-RADS lexicon is given.

Breast Diseases↗

PubMed2002

[Soft copy versus hard copy findings in digital mammography].

The advantages of full field digital mammography are the excellent and reliable image quality and the reduction of radiation exposure. Image acquisition and display are decoupled in digital mammography allowing for optimization of both independently. Image displays are currently either hardcopy produced with a laser printer or softcopy using a computer monitor. Since the amount of data is high the hardware and software must meet specific technical specifications. The diagnostic accuracy of softcopy and hardcopy interpretation is comparable if a high resolution laser printer and a high quality workstation with high spatial and contrast resolution monitors are used. However, using film display the potential benefits of digital mammography in terms of manipulation of the data is lost. Additional diagnostic benefits might be gained by the combination of softcopy display and computer assisted diagnosis (CAD) and telemammography.

Breast Neoplasms↗

PubMed2002

[Digital full field mammography: comparison between radiographic direct magnification and digital monitor zooming].

PURPOSE: Our goal was to compare digital magnification mammograms with images zoomed from the digital contact mammogram in patients with microcalcifications. PATIENTS AND METHODS: Fifty-five patients with 57 microcalcification clusters were evaluated with a FFDM system (Senographe 2000D, GE). In addition to a digital contact mammogram, a digital direct magnification mammogram (factor 1.8 [MAG1.8]) and an image zoomed from the contact mammogram with a magnification factor of 1.8 [ZOOM1.8] were obtained in each patient. The image quality (perfect = 5 points to inadequate = 1 point) and the characterization of microcalcifications (BI-RADS 2-5) were evaluated by 4 readers. The results were compared to histopathologic findings in 35 patients (37 lesions) and follow-up in 20 patients. RESULTS: Histopathology revealed 16 benign and 21 malignant lesions. 20 patients had benign changes verified by long-term follow-up. Image quality of direct magnification FFDM was assessed superior (4.44 points) to zoomed images (4.14 points). Sensitivity was superior for direct magnification (97.5%) in comparison to the zoomed images (96.3%). However, specificity (MAG1.8: 34.3%, ZOOM1.8: 40%), PPV (MAG1.8: 47.5%, ZOOM1.8: 49.8%) and accuracy (MAG1.8: 58.1%, ZOOM1.8: 61.2%) were better with zooming technique. Deviation steps from best BI-RADS assessment were 0.45 for MAG1.8 and 0.44 for ZOOM1.8. CONCLUSIONS: In patients with mammographic microcalcifications, monitor zooming of the digital contact mammogram is equivalent to direct magnification FFDM. Therefore, monitor zooming allows a reduction of the radiation exposure and an optimization of the work-flow.

Breast Diseases↗

PubMed2002

[Physical and technical aspects of digital mammography].

The establishment of digital mammography systems constitutes a slow process, the reason for this being the general need of particular image quality in mammography. This article provides an overview of the physical basis of digital mammography with high image quality and dose as low as reasonably achievable. The trade-off of high contrast resolution and effective quantum efficiency of the imaging system on the one hand, and the demand of high spatial resolution or very small pixel size on the other hand is discussed. The actual status of the available digital detector technology for mammography is described. The digital systems presently available are superior to conventional screen-film mammographic systems with respect to contrast resolution. An outlook on possible further developments in the field of digital mammography is presented.

Equipment Design↗

PubMed2002

Average glandular dose with amorphous silicon full-field digital mammography - Clinical results.

PURPOSE: Determination of average glandular dose with a full-field digital mammography system using a flat-panel X-ray detector based on amorphous silicon technology for a large group of patients. MATERIAL AND METHODS: The patient group includes women who were examined in a 4-month period with the digital mammographic system Senographe 2000D. The number of women was 591 and the number of exposures was 1116; only cranio-caudal projections were considered. Various quantities, including entrance surface air kerma, tube loading, and compressed breast thickness, were determined during actual mammography. Average glandular dose was determined using conversion factors g for standard breast composition. RESULTS: The mean average glandular dose was 1.51 mGy (0.66 - 4.05 mGy) for a single view. The mean compressed breast thickness was 55.7 mm. The mean age of patients was 55 years (34 - 81 years). CONCLUSION: The results demonstrate that full-field digital mammography with a flat-panel detector based on amorphous silicon needs about 25 % less dose in comparison with conventional screen-film mammography.

Adult↗

PubMed2001

[Value and significance of digital full-field mammography within the scope of mammography screening].

To evaluate the digital technique for screening mammography various experimental studies and clinical examinations were performed by using direct full-field digital mammography (FFDM). The findings concerning the detectability and characterization of microcalcifications and soft tissue masses as well as the radiation exposure were compared to the state-of-the-art conventional screen-film mammography (SFM). The results of these studies revealed a high performance of the digital images, which are at least equivalent to the conventional images, whereas digital spot views were significantly superior to conventional ones particularly in the detection of microcalcifications. This was especially true, when the potential of post-processing was used. In addition, the sensitivity of FFDM should be increased, if computer-aided-diagnosis (CAD) is available. Furthermore, the patient radiation dose can be significantly reduced. Additional advantages are quick and easy handling, efficient data transfer and digital archiving. Thus, FFDM will become an important tool in screening mammography.

Breast Neoplasms↗

PubMed2001

Dose reduction by direct-digital cephalometric radiography.

Patient radiation exposure was determined for conventional and direct-digital cephalometric radiography. An anthropomorphic phantom was positioned to expose lateral cephalographs from the patient's left side. The conventional radiographs were exposed with a Siemens Orthophos C unit (77 kV, 14 mA, 0.5 s) and a film-screen system of a relative speed of 400. The direct-digital radiographs were exposed with a Siemens Orthophos DS Ceph (73 kV, 15 mA, 15.8 s). A set of 108 thermoluminescence detectors (TLDs; Bicron STI/Harshaw, Solon, Ohio) was used for dose measurements. For each measurement, 84 TLDs were placed at the surface of the head and neck, as well as inside the phantom, at anatomically relevant positions. The remaining detectors were employed for calibration purposes and quality control. The highest absorbed doses were recorded for the conventional technique at the skin of the left parotid region (132 microGy), in the left parotid gland (103 microGy), and in the ocular lens of the left eye (81 microGy). Digital cephalometry resulted in an absorbed dose about 2 times lower than the dose received by the conventional technique. The effective doses had the same relation (conventional 2.3 microSv; digital 1.1 microSv). The results demonstrate that direct-digital cephalometric radiography cuts the patient's dose in half compared with the conventional screen-film technique. Direct-digital cephalometry is more advantageous than the conventional technique from the perspective of radiation protection.

Cephalometry↗

PubMed2000

[Dose measurements comparing conventional and digital panoramic radiography].

OBJECTIVE: The purpose of our study was to measure and compare patient exposure by direct digital and conventional panoramic radiography. MATERIAL AND METHODS: Dose measurements were carried out on an anthropomorphic phantom, which was specially developed for dental radiography. Panoramic radiographs were taken with three different conventional devices (Orthopantomograph 10E, Orth Oralix FD, Siemens Orthophos) and two direct digital devices (Orthopantomograph 100 Digipan, Siemens Orthophos DS Ceph). The exposure conditions were according to clinical routine. The energy dose was measured at 28 places inside and on the surface of the phantom by using a set of 108 thermoluminescence detectors. Additionally, exposure time, tube voltage, central-beam dose, and dose-area products were measured. The effective doses were calculated on the basis of the absorbed doses. RESULTS: In each case, the highest energy doses were recorded at the parotid gland, the mandibular angle, the submandibular gland, and the skin in the neck. Panoramic radiographs taken with the conventional units yielded in effective doses in the range of 16-21 microSv, the digital units caused 5 or 14 microSv. CONCLUSION: In comparison with conventional techniques, patient exposure can be reduced by direct digital panoramic radiography. The extent of dose reduction depends on the device employed and is generally smaller than the dose reduction that can be achieved by digital imaging devices in intraoral radiography.

Humans↗

PubMed2000

[Full-field digital mammography: a phantom study for detection of microcalcification].

OBJECTIVES: The study compares direct full-field digital mammography (FFDM) to the state-of-the-art conventional screen-film mammography (SFM) concerning the detectability of simulated microcalcifications. MATERIALS AND METHODS: The investigations were performed with a FFDM system (Senographe 2000D, GEMS) and a SFM system (Senographe DMR, GEMS, Fuji UM MA film with Fuji UM MAMMO FINE screen). An anthropomorphic breast phantom with superimposed microcalcifications (50-200 microns) was used to evaluate the detectability of microcalcifications with a confidence level ranging from 1 to 5. Contact mammograms and magnification spot views (m = 1.8) of the FFDM and SFM systems were compared. A receiver operating characteristic (ROC) analysis was performed by three well-experienced readers. RESULTS: The ROC analysis revealed a higher performance of the digital images compared to the conventional screen-film mammograms. The area under the ROC-curve (Az) in the digital contact mammograms was 0.68 versus 0.63 in the conventional technique. The results were not significantly different. In digital spot views, Az was 0.79 versus 0.70 in the conventional spot views. CONCLUSIONS: The results suggest that FFDM is at least equivalent or--as far as spot views are concerned--may be superior to conventional SFM in the detection of microcalcifications.

Breast Diseases↗

PubMed2000

[Radiation exposure in full-field digital mammography with a flat-panel x-ray detector based on amorphous silicon in comparison with conventional screen-film mammography].

PURPOSE: Comparison of radiation exposure between a digital amorphous silicon and a screen-film based mammography system. Evaluation of a possible potential of full-field digital mammography in order to decrease the radiation dose. METHODS: The average glandular dose for phantom thicknesses from 30 to 60 mm was calculated from experimentally determined entrance surface air kerma for a digital and a conventional mammography system. The effect of reducing the detector dose and of changing the radiation quality on radiation exposure and on image quality were investigated. RESULTS: By using the delivered settings of the automatic exposure control (AEC) devices, both mammographic systems needed nearly the same doses. Regulations and guidelines on radiation doses were complied. With the digital system, a reduction of radiation exposure of up to 40% by using a higher radiation quality and decreasing slightly the detector dose without loss of diagnostic image quality, might be possible. CONCLUSION: The potential of full-field digital mammography for radiation dose reduction, as shown in the present phantom study, needs however, a careful examination under clinical conditions.

Female↗

PubMed2000

[Full-field digital mammography: dose-dependent detectability of breast lesions and microcalcinosis].

OBJECTIVES: The study compares contrast-detail and microcalcification detectability of a full-field digital mammography (FFDM) to a state-of-the-art conventional screen-film mammography (SFM) by using different doses in the digital system. MATERIALS AND METHODS: The investigations were performed with an FFDM (Senographe 2000 D, GEMS) and an SFM system (Senographe DMR, GEMS) using a contrast-detail mammography phantom (CDMAM) and an anthropomorphic breast phantom with superimposed microcalcifications. The digital detector was exposed with standard dose of SFM and with a dose reduction of up to 75%. Contrast-detail curves and correct observation ratio (COR) were performed for the CDMAM phantom. ROC analysis with a confidence level ranging from 1 to 5 was done with the results of the anthropomorphic phantom. RESULTS: Digital mammography with the same dose revealed at least an equivalent or even higher detectability rate than conventional mammography, COR could be increased at about 10-25%. The ROC analysis yielded better results for the FFDM system. The same lesion detectability in digital mammography as in the conventional method was reached at a dose reduction of about 25%, concerning spot views even at higher reduction. Dose reduction in the anthropomorphic phantom resulted in a linear loss of detectability. The same detectability as in conventional mammography was reached, however, by a dose reduction of about 50%. CONCLUSION: The results suggest that FFDM is at least equivalent to or--as far as spot views are concerned--superior to conventional SFM concerning the detectability of simulated lesions. Thus, a potential of dose reduction is suggested.

Breast Diseases↗

PubMed1999

[Slice sensitivity profile and image pixel noise of multi-slice spiral CT in comparison with single slice spiral CT].

PURPOSE: Presentation and evaluation of slice sensitivity profile and pixel noise of multi-slice CT in comparison to single-slice CT. METHODS: Slice sensitivity profiles and pixel noise of a multi-slice CT equipped with a 2D matrix detector array and of a single-slice CT were evaluated in phantom studies. RESULTS: For the single-slice CT the width of the slice sensitivity profiles increased with increasing pitch. In spite of a much higher table speed the slice sensitivity profiles of multi-slice CT were narrower and did not increase with higher pitch. Noise in single-slice CT was independent of pitch. For multi-slice CT noise increased with higher pitch and for the higher pitch decreased slightly with higher detector row collimation. CONCLUSIONS: Multi-slice CT provides superior z-resolution and higher volume coverage speed. These qualities fulfill one of the prerequisites for improvement of 3D postprocessing.

Artifacts↗

PubMed1999

[Dental CT: image quality and radiation exposure in relation to scan parameters].

PURPOSE: To develop a scan protocol for dental-CT which guarantees good image quality at the lowest possible radiation dose. METHODS: In an experimental investigation Dental-CT (HSA, GE, Milwaukee, USA) of the mandible of two human skeletons positioned in a water tank were performed in order to define the most advantageous scan protocol. Tube currents ranged from 40 to 200 mA and the scan technique was modified (axial mode or helical mode with pitches of 1 to 3 and corresponding increments of 0.4 to 1.0 mm). 39 patients underwent a dental-CT with decreased current (80 mA) in the helical scan mode (pitch 2, slice thickness 1 mm). Dose measurements were performed for two different scan protocols (A: axial, 130 mAs, B: helical, 80 mA, pitch 2). RESULTS: The preliminary investigations of image quality showed only a minor effect of the applied current. For the helical scan mode, pitches of more than 2 impaired image quality. A low increment had no advantages. There were no disadvantages in clinical practice using protocol B with decreased tube current. Absorbed radiation dose of dental CT performed with protocol B was decreased to one third in comparison to protocol A. CONCLUSIONS: A scan protocol with a low tube current (e.g., 80 mA, for a rotation time of 1 s) and a helical scan mode (e.g., for a slice thickness of 1 mm with a pitch of 2 and an increment of 1 mm) is recommended for performing dental-CT.

Adult↗

PubMed1999

[Direct digital magnification mammography with a large-surface detector made of amorphous silicon].

PURPOSE: To investigate the image quality of a new direct digital mammography system using a large-area amorphous silicon X-ray detector in a phantom study. MATERIALS AND METHODS: The contrast-detail resolution as a function of the tube voltages, the magnification factors and the mean glandular doses were investigated using dedicated test objects. RESULTS: The contrast-detail resolution was significantly improved in comparison with conventional screen-film mammography. Usually, the doses necessary to obtain these high-quality survey mammograms were smaller. CONCLUSIONS: By combining the direct magnification technique and a digital flat panel detector the limited spatial resolution of such image receptors can be overcome. With this direct digital mammography technique, a digital image was directly captured without an intermediate step of optical or mechanical scan.

Equipment Design↗

PubMed1998

Storage phosphor direct magnification mammography in comparison with conventional screen-film mammography--a phantom study.

Contact mammography with current photostimulable storage phosphors is hampered by its low spatial resolution. Detail visualization can be improved by geometric magnification radiography which enlarges small details to exceed inherent image noise. This study compares storage phosphor mammography using a dedicated direct magnification system with state-of-the-art conventional screen-film mammography. Storage phosphor direct magnification survey views (1.7x) and spot views (4x) were obtained with a prototype mammography unit providing focal spot sizes of 120-40 microns. Conventional technique screen-film survey views (1.1x) and spot views (1.8x) served as comparison. A contrast detail study and a receiver operating characteristic (ROC) analysis using an anthropomorphic breast phantom with superimposed microcalcifications was performed. Contrast detail resolution in the digital and conventional survey views were equivalent. For the spot views, contrast detail resolution was significantly higher with the digital technique (p < 0.001). ROC analysis of 400 observations demonstrated a significantly higher performance (p < 0.001) with digital images versus conventional screen-film mammograms. The area under the ROC curve (Az) in the digital survey views was 0.76 +/- 0.07 versus 0.59 +/- 0.02 in the conventional technique. In digital spot views, Az was 0.82 +/- 0.07 as compared with 0.66 +/- 0.04 in the conventional spot views. These results suggest that storage phosphor digital mammography in conjunction with direct geometric magnification technique may be superior to conventional screen-film mammography in the detection of microcalcifications.

Breast Diseases↗

PubMed1997

[Digital magnification mammography in computed radiography. Initial clinical results].

INTRODUCTION: The combination of direct magnification mammography and computed radiography provides an improvement in spatial resolution of storage phosphor-based digital systems. A clinical study comparing conventional and digital direct magnification mammograms was performed. METHODS: 100 survey mammograms in 1.5-or 1.7-fold magnification and 50 4-fold spot magnification views were obtained with a prototype direct magnification mammography system and a storage phosphor-based digital system. An intraindividual comparison of these with previous conventional radiograms of the same patients was carried out. RESULTS: The diagnostic value of digital survey mammograms using the direct magnification technique is comparable to that of conventional radiograms of the breast, especially with regard to the identification of microcalcifications and lesions and the clinical consequences. Spot magnification views performed with this combination of techniques allowed improvement in the evaluation of microcalcifications. In 15% of cases, diagnostic procedures were adjusted accordingly. CONCLUSION: The combination of the direct magnification technique with digital storage phosphor radiography systems allows the performance of digital mammography by improving the overall spatial resolution. The diagnostic value of digital direct magnification survey mammograms was comparable to that of conventional mammograms. Digital 4-fold spot magnification views improved visualisation of the morphologic aspects of microcalcifications.

Breast Neoplasms↗

PubMed1997

[Direct radiographic magnification mammography with a new microfocus tube. Experimental studies of resolution and radiation exposure].

A recently developed X-ray unit for mammography using microfocal (spot size 0.12-0.05 mm) direct magnification radiography will soon be introduced into clinical practice. Unit arrangement and tube construction have been demonstrated. Mean surface dose was measured using PMMA-phantoms. A dose reduction of up to 50% was obtained in 1.7-fold magnification mammography (full sized views) compared with conventional techniques. The image quality was almost equivalent. However, in comparison with 1.7-fold magnification mammography, a comparable dose range for 4-fold magnifications with the microfocus system was measured with a substantial gain in spatial resolution. These findings satisfy the demands of a modern mammographic unit.

Equipment Design↗