Characterisation of noise and sharpness of images from four digital breast tomosynthesis systems for simulation of images for virtual clinical trials

In-depth evaluation of the noise and sharpness characteristics of FujiFilm Innovality, GE SenoClaire, Hologic Selenia Dimensions and Siemens Inspiration digital breast tomosynthesis (DBT) systems was performed with the intention of improving image simulation for virtual clinical trials. Noise power spectra (NPS) and modulation transfer function curves (MTF) were measured for planar modes and for the first and central projections for DBT modes. In DBT mode, the x-ray beam was blocked for the projections before the central projection in order to remove the influence of lag and ghosting from the previous images. A quadratic fit between the NPS and linearised pixel value gave the noise coefficients for planar and DBT imaging modes. The spatial frequencies corresponding to an MTF of 0.5 (MTF0.5) were calculated from the MTF measurements made on the breast support and at 40 mm above the breast support. This was done for the first and the central projections. The percentage of signal carried over from the first projection to subsequent images (lag) was measured using a slit. The noise associated with lag was also evaluated. The DBT modes typically had lower electronic noise coefficients but higher structural noise coefficients compared to the respective planar mode MTF0.5 measured 40 mm above the table was between 6% and 47% lower for continuous scanning systems compared to 1% lower for step and shoot systems. For wide angle DBT, the MTF0.5 of the first projection was 18% (FujiFilm) and 28% (Siemens) lower than for the central projection. Lag in the second projection was 2.2%, 0.3%, 0.8% for the FujiFilm, GE and Hologic systems respectively. In all cases, the noise associated with lag was negligible. Current modelling frameworks for virtual clinical trials of breast DBT systems need to be adapted to account for signals from lag and variations in the MTF at wide angles.

[Comparison of a Radiation Dose During Standard Digital Radiography, Tomosynthesis, and Multislice Spiral Computed Tomography in an Experimental Study of Pediatric Anthropomorphic Phantom]

OBJECTIVE

To compare a radiation dose obtained during standard digital radiography, tomosynthesis, and multislice spiral computed tomography (MSCT).

MATERIAL AND METHODS

Life-size full body pediatric anthropomorphic mannequin phantom was examined with a Fujifilm FDR Ac Selerate 200 X-ray diagnostic apparatus and a Toshiba Aquilion Prime 64 computed scanner using the Piranha dosimetry equipment, as well as Gammex planar target, for comparison of the resolution of the apparatus. The effective radiation doses were calculated for different anatomical regions with the formulas specified in the methodical instructions, using the coefficients K and Kd.

RESULTS

The tables and graphs comparing the radiation dose when using different radiation diagnostic techniques were presented. The resolution of standard digital radiography versus that of tomosynthesis was analyzed. Fluctuations of the doses obtained were associated with the difference in the volume of irradiated tissue and in the presence of the doses in the irradiated volume of organs with high radiosensitivity. Optimal physical and technical parameters of photography were proposed, which could reduce a dose load on the patient, without significantly losing the quality of films.

CONCLUSION

The effective doses of tomosynthesis were significantly higher than those of standard digital radiography (p < 0.05) while those of (MSCT) were above those of both X-ray and tomosynthesis, and the resolution of the latter was slightly lower.

X-ray tomography system to investigate granular materials during mechanical loading

We integrate a small and portable medical x-ray device with mechanical testing equipment to enable in situ, non-invasive measurements of a granular material's response to mechanical loading. We employ an orthopedic C-arm as the x-ray source and detector to image samples mounted in the materials tester. We discuss the design of a custom rotation stage, which allows for sample rotation and tomographic reconstruction under applied compressive stress. We then discuss the calibration of the system for 3D computed tomography, as well as the subsequent image reconstruction process. Using this system to reconstruct packings of 3D-printed particles, we resolve packing features with 0.52 mm resolution in a (60 mm)(3) field of view. By analyzing the performance bounds of the system, we demonstrate that the reconstructions exhibit only moderate noise.

[Determination of total filtration and half attenuation layer in X-ray diagnostic units by relative radiation output]

Described is a relatively simple technique applicable to estimating the independent and additional filtration of X-ray images by the relative radiation output with a voltage generation range of 50 to 120 kB. It is shown as possible to determine the half-attenuation first layer in its aluminum equivalent and without using any aluminum filters. The suggested technique can be used in turn-over and regular tests of medical X-ray units as well as in their exploitation.

Accuracy of detection and measurement of renal calculi: in vitro comparison of three-dimensional spiral CT, radiography, and nephrotomography

PURPOSE

To compare accuracy of three-dimensional (3D) spiral computed tomography (CT) performed without administration of contrast material with that of radiography and linear nephrotomography in detection and measurement of renal calculi.

MATERIALS AND METHODS

Fifty renal calculi within an abdominal phantom were imaged with 3D spiral CT, radiography, and linear nephrotomography. Spiral CT data were analyzed with workstation-based 3D imaging software, with a thresholding procedure based on the maximally attenuating voxel within each calculus during measurement. Measurement accuracy and detection rates were compared according to modality. Conventional and magnification-corrected measurements from radiography and linear nephrotomography were included.

RESULTS

Spiral CT depicted calculi and allowed determination of the collective two-dimensional and 3D linear measurements statistically significantly more accurately than the other techniques; the mean linear measurement errors along individual axes did not exceed 3.6%. With 3D spiral CT, calculus volumes were determined with a mean error of -4.8%.

CONCLUSION

3D spiral CT enabled highly accurate determination of the volumes and all three linear dimensions of renal calculi. In addition, 3D spiral CT depicted calculi more sensitively than traditional techniques and provided new information and improved accuracy in the evaluation of nephrolithiasis.

Radiographic detectability of periodontal diseases. A comparison of perapical radiography with detailed zonography

OBJECTIVE

To compare the diagnostic accuracy of conventional periapical radiography with detailed zonography using the Scanora system for the detection of periodontal disease.

METHODS

We selected for comparison 311 periodontal sites in 165 patients. Five observers independently assessed the periapical radiographs and detailed zonograms for marginal widening of periodontal ligament space, crestal erosion, vertical bone loss, furcation involvement and calculus.

RESULTS

ROC analysis revealed no significant differences between the two imaging techniques for either overall or lesion-specific interpretation of periodontal pathology. The sensitivity of periapical radiography was 79%, and of detailed zonography 91% (multiview) and 89% (stereoscopic). Specificities were 82%, 77% and 83%, respectively.

CONCLUSION

Detailed zonography performs as well as periapical radiography in the detection of periodontal disease.

The role and limitations of computed tomographic scanning in the evaluation of cervical trauma

We retrospectively reviewed the medical records, plain films, CT scans and complex-motion tomographic studies (TOMOS) of 216 consecutive patients with cervical injuries to determine the uses and limitations of CT in the evaluation of cervical trauma and the indications, if any, for the continued use of TOMOS in evaluating cervical trauma. There were 453 fractures and 104 subluxations or dislocations of the cervical spine in the 216 patients. Plain films detected 58% (262 of 453) of the fractures and 93% (97 of 104) of the subluxations and dislocations; and 94% (202 of 216) of the patients with abnormalities were identified. Computed tomographic scans detected 90% (406 of 453) of the fractures and 54% (56 of 104) of the subluxations and dislocations; 92% (198 of 216) of the patients with abnormalities were identified. Most of the abnormalities missed on the CT scans involved the dens, C-6, and C-7, and were oriented in the axial plane. Although CT scanning was better than plain films in detecting most types of cervical fractures, plain films were better than CT for detecting fractures of the vertebral body, dens, and spinous processes, and significantly better than CT in detecting subluxation and dislocation. When plain films and CT scans were combined they identified 98% (443 of 453) of the fractures and 99% (103 of 104) of the subluxations and dislocations; 100% (216 of 216) of the patients with abnormalities were identified. In the 20 patients who underwent both CT scanning and TOMOS, TOMOS detected more fractures, subluxations, and dislocations than CT scanning. Complex-motion tomographic studies detected atlanto-occipital dislocation and subluxation of the vertebral bodies and fractures of the spinous processes, lateral masses, articular processes, vertebral bodies, and dens better than CT scanning. Although the more routine use of CT scanning in evaluating cervical trauma should increase the detection of cervical abnormalities to near 100%, TOMOS remain the gold standard of diagnosis for atlanto-occipital dislocation, subluxation of the vertebral bodies, and fractures of the lateral masses, articular processes, vertebral bodies, and dens.

Is the volume retained after defecation a valuable parameter at defecography?

The intention of this study was to correlate the retained volume at the end of defecography to certain defecographic findings and to the sense of incomplete emptying. In 170 defecographic series, the retained barium was estimated planimetrically. No particular defecographic finding determined a higher or lower amount of remaining volume, and the sense of incomplete evacuation did not depend on the amount of retained volume. Thresholds of urge and perception on anorectal manometry did not differ between patients with and without the feeling of incomplete evacuation. A rectocele, isolated or combined with an internal prolapse, caused the retained volume to be in the lowermost part of the rectum, whereas, in the case of an isolated intussusception, the remaining volume was located in the middle or higher part of the rectum. It is concluded that defecographic findings do not in general explain incomplete emptying or the sense of incomplete emptying, but they may determine the localization of the retained volume.

Radiologic evaluation of urolithiasis

Interobserver variations between three radiologists with different backgrounds (duration of practice, and departments) were studied in connection with the diagnosing of urolithiasis. Films from 152 consecutive patients (examined with conventional abdominal films, urography/tomography) were analyzed independently. With respect to the number of patients with or without calculi there was agreement between the three observers in 129 of the 152 cases, which was taken to represent very good agreement beyond chance. The total number of stones was interpreted as 832, 460 and 570 respectively, and the median stone size as 6, 9 and 11 mm2. There was a fair interobserver agreement rate regarding whether stones were localized to the renal parenchyma or calyces, and whether stenosis/stricture or hydronephrosis was present. Tomography appeared to reduce the interobserver variability significantly. Adequate bowel cleaning, oblique projections, and lack of clinical information apparently did not influence the agreement rate. It was concluded that such interobserver variations are factors of importance in the reliability of the radiologic evaluation of urolithiasis.

[Experimental dosimetric comparison between single tomography and multiple simultaneous tomography with Synchroplan in clinical practice]

Reference is made to a dosimetric comparison between single tomography and simultaneous multiple tomography with Synchroplan in 10 patients subjected to nefroangiotomography. Data from several thermoluminescence dosimeters placed on different parts of the body were used in a careful statistical analysis that showed the absence of significant differences in absorbed dose in function of constitutional habitus. It was also found that the dose absorbed for 6 tomograms of the renal cavities in single tomography was about 4 times higher than with the Synchroplan (using a previously experimented set of high-sensitivity intensifying screens), which provides 6 tomograms in the same dynamic phase at different levels for the same exposure.

[Quality assurance in roentgen tomography. Initial report on a sectional phantom assembly for all parameters]

A tomographie phantom developed by a new principle is presented for quality assurance and testing of the installation as well as for postgraduate teaching and lectures. It is composed likely to a set for construction-games consisting of fitting cubes and parts. The phantom-cubes include some test objects not yet published. The concerning parameters and conditions of tomographic technique are thus able to be demonstrated separately, in a selected combination or all together by one exposure. All parameters are to be read off the tomogram without calculations or further operations. Some examples are selected out of the group of the parameter- and teaching-cubes.

[Results of a program of quality control in radiodiagnosis]

The results of a program of quality control on about 30 tomographic and fluoroscopic radiological equipments in the Radiological Departments of Spedali Civili (Brescia, Italy), are reported; the physical performances of the beams (kVp, emission, linearity and reproducibility, HVL, focal spot size) and the geometrical conditions (alignment and beam size, thickness of cut for tomography, resolution and homogeneity) have been verified. During one month we have also verified the working conditions for two automatic film processing systems. Three commercial quality control equipments have been employed and tested. Our results recommend a periodic control of physical and geometrical performances (particularly kVp, emission and beam alignment) and a daily control of the working conditions for the film processing systems. The three quality control systems have given results each other comparable.

[Transversal blurring in tomography (author's transl)]

The article discusses the factors which govern blurring in transversal tomography. The amount of blurring is a multiple of the degree of blurring which occurs in normal horizontal tomography, assuming the usual conditions, ie small angle of incidence in case of fixed focus, and large diameter of rotation in case of a rotating arrangement. Hence, only large details will show up in transversal tomography, in contrast to the results obtained via comparable horizontal tomograms.

Quantity of tomographic blurring

A spiral tomographic movement gives rise to a lower quantity of blurring than does a circular movement with the same tomographic angle since in the former the focus comes nearer to the central point. It has been demonstrated that the transfer function may be used to express the quantity of blurring for different tomographic movements. For the sake of convenience the blurring quantity for every type of spiral movement may be expressed in terms of the tomographic angle of a circular movement giving rise to the same transfer function.

[Tomographic findings in C.S.F. fistulae (author's transl)]

The majority of C.S.F. fistulae are of traumatic origin and in order to avoid the threat of meningitis, they require operative closure. For the demonstration of the fronto-basal defects, multi-dimensional tomograms in various planes have proved very valuable. In 28 patients examined in the Radiological University Clinic (Münster), defects were most common in the cribriform plate. In addition to a break in its contour, one can find displacement of fragments, step formation, opacification of the adjacent nose or sinuses or intracranial air. 88% of defects could be localised in this way. The tomograms were not helpful in two very small fronto-basal fractures.

Evaluation of image quality in tomographic imaging

Modulation Transfer Functions (MTF) for tomographic imaging with linear, circular, hypocycloidal and spiral motion are given. They may be determined experimentally from tomographs of slits or line pair test patterns. In some cases calculation of the MTF from the blur pattern by Fourier transformation is possible. All tomographic MTFS show the same oscillatory behaviour as MTFS of focal spots, resulting in spurious structures and contours in the tomogram. A quantity named signal/spurios signal ratio (SSR) is introduced as a figure of merit. Effective exposure angles are determined from the MTF and compared with the commmonly used 'geometric' exposure angles which result from maximum tube elongations.

Quantitative evaluation of the depth effect in Muehllehner's tomographic camera

A set of computer programs written for Clincom allow the evaluation of the depth effect in Muehllehner's tomographic camera using MTFs and specificity as well as new quantites. The depth effect of the camera is compared with that of a rectilinear scanner.

[The image of the temporomandibular joint in the panoramic radiographs]

Of the general panoramic radiographs those with an intraoral focus (magnifying panoramic radiography) are not suitable to represent the temporo-mandibular joint. In contrast, panoramic tomograms represent the temporo-mandibular joint better, but they cannot be recommended unreservedly for the exact evaluation of this region. Presently there is no substitute for conventional radiographs.

[The effects of mechanical disturbances caused by additional body section roentgenographic equipment on the tomogram (author's transl)]

Attention was called to the false images which can appear if additional body section roentgenographic equipment is improperly operated. In practice, the alterations on the tomogram, however, are usually so slight that they are barely noticeable and, for this reason, the disturbances can be overlooked. Additional body section roentgenographic equipment should, therefore, be constructed in such a way that operational errors are basically impossible.

Performance evaluation and quality assurance of computed tomography scanners, with illustrations from the EMI, ACTA, and Delta scanners

Performance evaluation of equipment for computed tomography (CT) involves the integration of: (a) establishing performance criteria; (b) designing and implementing test procedures; and (c) reconciling test results in terms of desired performance. Precision (noise), contrast scale, linearity, accuracy, spatial independence, spatial resolution, artifacts, reproducible performance, and patient exposure are several parameters discussed, as are problems of measurement with regard to non-water bath scanners. Performance and quality control tests for the ACTA, Delta, and EMI scanners are outlined. Guidance for the prospective purchaser of CT equipment is presented as a summary of the ideas discussed.

Computed tomography standardization

Since the body of literature on computed tomography is growing rapidly, some universally acceptable expression for attenuation values should be adopted. In addition, there is controversy as to the manner of viewing CT scans of the torso: some prefer viewing from below, in the same orientation as conventional radiographs, while the authors prefer viewing from above, consistent with most cross-section anatomy texts and current cranial and body CT displays.

[Simple tests to control a tomographic device (author's transl)]

Simple tests to prove the resolution sharpness and blurring of a tomographic system are described.

Report of the Inter-Society Commission for Heart Disease Resources. Optimal resources for examination of the chest and cardiovascular system. A hospital planning and resource guideline. Radiologic facilities for conventional x-ray examination of the heart and lungs. Catheterization-angiographic Laboratories. Radiologic resources for cardiovascular surgical operating rooms and intensive care units

This is an updated and expanded planning and oprimal resource guideline for diagnostic examinations of the cardiovascular system. Catheterization-angiographic laboratories are described and detailed specifications given for radiologic and physiologic equipment. Case loads for maintaining safe and effective performance are recommended and complication rates discussed. An optimal location for the laboratory is defined and the status of affiliated laboratories reviewed. Professional staff qualifications, relationships and requirements are enumerated and recommendations are made for organization and administration of the services. There is a protocol for electrical safety and radiation protection and a data base for assessing case loads in hospitals within a community or region. This statement also defines optimal facility and equipment criteria for conventional chest x-rays and radiologic equipment requirements for cardiovascular surgical operating rooms and intensive care units.