Conventional X-ray Radiography Research Articles

Diagnostic performance of an AI algorithm for the detection of appendicular bone fractures in pediatric patients

PurposeTo evaluate the diagnostic performance of an Artificial Intelligence (AI), previously trained using both adult and pediatric patients, for the detection of acute appendicular fractures in the pediatric population on conventional X-ray radiography (CXR). Materials and methodsIn this retrospective study, anonymized extremities CXRs of pediatric patients (age <17 years), with or without fractures, were included. Six hundred CXRs (maintaining the positive-for-fracture and negative-for-fracture balance) were included, grouping them per body part (shoulder/clavicle, elbow/upper arm, hand/wrist, leg/knee, foot/ankle). Follow-up CXRs and/or second-level imaging were considered as reference standard. A deep learning algorithm interpreted CXRs for fracture detection on a per-patient, per-radiograph, and per-location level, and its diagnostic performance values were compared with the reference standard. AI diagnostic performance was computed by using cross-tables, and 95 % confidence intervals [CIs] were obtained by bootstrapping. ResultsThe final cohort included 312 male and 288 female with a mean age of 8.9±4.5 years. One-hundred-fifty CXRs (50 %) were positive for fractures, according to the reference standard. For all fractures, the AI tool showed a per-patient 91.3 % [95 %CIs = 87.6–94.3] sensitivity, 76.7 % [71.5, 81.3] specificity, and 84 % [82.1–86.0] accuracy. In the per-radiograph analysis the AI tool showed 85 % [81.9–87.8] sensitivity, 88.5 % [86.3–90.4] specificity, and 87.2 % [85.7–89.6] accuracy. In the per-location analysis, the AI tool identified 606 bounding boxes: 472 (77.9 %) were correct, 110 (18.1 %) incorrect, and 24 (4.0 %) were not-overlapping. ConclusionThe AI algorithm provides good overall diagnostic performance for detecting appendicular fractures in pediatric patients.

Programming for exposure chart modelling in conventional X-ray radiography

In radiography, an exposure chart is needed to determine the correct exposure. The creation of exposure chart so far requires a lot of film. To reduce the use of film, a program was created that utilizes the principles of radiographic exposure in the form of the relationship between tube current, tube voltage, exposure time, and geometry principles. The program was validated through curve fitting and Mean Absolute Percentage Error (MAPE) by comparing the density of the specimen radiograph image with the exposure chart generated by the program. The generated exposure chart is the exposure chart for steel with voltages of 120 kV, 130 kV, 140 kV, 150 kV, and 160 kV. The resulting exposure chart has a coefficient of determination of 0.97 and has high accuracy.

Experimental Investigation of Lung Toxicity after Radiation Therapy Combined with Immune Checkpoint Inhibitors

The combination of radiation therapy (RT) with immune checkpoint inhibitors (ICIs) has resulted in prolonged survival in patients with locally advanced lung cancer (NSCLC). However, RT and ICIs carry the risk of inflammatory and irreversible lung damage and might have synergistic effects on these adverse events. Importantly, only little is known about the risk of enhanced side effects of the lung and which factors modulate such toxicity. In addition, there is a need for sensitive diagnostics for the early detection of lung injury after combined radioimmunotherapy. Recently, experimental x-ray dark-field radiography was able to detect radiation-induced lung injury earlier than conventional radiography in mice. The right thorax of mice was irradiated with unfractionated RT (1x15 Gy or 1x30 Gy) or fractionated RT (5x9 Gy). In addition, indicated experimental groups received ICIs (a-PD1, a-CTLA4 or combination) for one month. After four months, the mice were analyzed using different methods to quantify lung damage: lung coefficient as surrogate marker for lung fibrosis, histopathological staining of fibrosis, conventional x-ray, and dark-field radiography. We found enhanced signs of lung fibrosis (lung coefficient and histopathological score) after unfractionated RT in combination with ICIs. Surprisingly, combination of ICIs with RT resulted in opposite effects. Specifically, concomitant combination of ICIs with fractionated RT resulted in reduced lung coefficients and lower histopathological signs of lung fibrosis in mice treated in this way. Importantly, in vivo x-ray dark-field radiographs showed the same trend as the ex vivo assessment of the lungs. To the best of our knowledge, this is the first experimental study to find that the combination of RT with ICIs has an impact on the risk of pulmonary fibrosis. Strikingly, ICIs (a-PD1 + a-CTLA4) combined with unfractionated RT resulted in increased lung damage, while concomitant use of ICIs (a-PD1 + a-CTLA4) with fractionated RT resulted in reduced lung toxicity. In the field of radioimmunotherapy, such studies are of great value for the interpretation of clinical studies and of importance for the design of further clinical trials.

Fast implicit diffusive dark-field retrieval for single-exposure, single-mask x-ray imaging

Complementary to conventional and phase x-ray radiography, dark-field imaging has become central in visualizing diffusive scattering signals that come from spatially unresolved texture within an object. To date, most diffusive dark-field retrieval methods require either the acquisition of multiple images at the cost of higher radiation dose or significant amounts of computational memory and time. In this work, a simple method of x-ray diffusive dark-field retrieval is presented, applicable to any single-mask imaging setup, with only one exposure of the sample. The approach, which is based on a model of geometric and diffusive reverse-flow conservation, is implicit and noniterative. This numerically fast methodology is applied to experimental x-ray images acquired using both a random mask and a grid mask, giving high-quality reconstructions that are very stable in the presence of noise. The method should be useful for high-speed imaging and/or imaging with low-flux sources.

A Non-Invasive Method for Monitoring Osteogenesis and Osseointegration Using Near-Infrared Fluorescent Imaging: A Model of Maxilla Implantation in Rats.

Currently, computed tomography and conventional X-ray radiography usually generate a micro-artifact around metal implants. This metal artifact frequently causes false positive or negative diagnoses of bone maturation or pathological peri-implantitis around implants. In an attempt to repair the artifacts, a highly specific nanoprobe, an osteogenic biomarker, and nano-Au-Pamidronate were designed to monitor the osteogenesis. In total, 12 Sprague Dawley rats were included in the study and could be chategorized in 3 groups: 4 rats in the X-ray and CT group, 4 rats in the NIRF group, and 4 rats in the sham group. A titanium alloy screw was implanted in the anterior hard palate. The X-ray, CT, and NIRF images were taken 28 days after implantation. The X-ray showed that the tissue surrounded the implant tightly; however, a gap of metal artifacts was noted around the interface between dental implants and palatal bone. Compared to the CT image, a fluorescence image was noted around the implant site in the NIRF group. Furthermore, the histological implant-bone tissue also exhibited a significant NIRF signal. In conclusion, this novel NIRF molecular imaging system precisely identifies the image loss caused by metal artifacts and can be applied to monitoring bone maturation around orthopedic implants. In addition, by observing the new bone formation, a new principle and timetable for an implant osseointegrated with bone can be established and a new type of implant fixture or surface treatment can be evaluated using this system.

X-ray phase imaging reaching clinical uses.

X-ray phase imaging that uses the phenomena of X-ray refraction and scattering to generate image contrast has the potential to overcome the drawback of conventional X-ray radiography in observing biological soft tissues. After its dawn at synchrotron radiation facilities 30years ago, the development of X-ray phase imaging is expanding to hospitals by grating-based phase-imaging approaches available with a conventional X-ray tube. In this review, after introducing the physical advantages and methodological details of X-ray phase imaging, recent trials of instrumentation in hospitals for diagnoses of rheumatoid arthritis and chronic obstructive pulmonary disease are introduced.

Photon-counting spectral basis component material decomposition for musculoskeletal radiographs

As a very fast and non-invasive examination, conventional X-ray radiography is well established as the first line diagnostic imaging method of the human bone system. While major bone injuries such as fractures and dislocations are usually easily detectable on conventional X-ray images, more subtle injuries such as microfractures are often missed, leading to mistreatment and potential long-term consequences. The technology of Photon-Counting Dual-Energy Radiography (PCDER) yields the possibility to decompose conventional X-ray images into basis material images such as bone- and soft-tissue-equivalence images. The obtained basis material images offer significant advantages in terms of image contrast and image details over the raw attenuation image which shows an overlap of bone and soft tissue. Whereas the advantages of bone- and soft-tissue-equivalence images have been broadly discussed referring to bone subtraction images in the detection of pulmonary diseases, this method has not been considered for the analysis of musculoskeletal images until present. In this study we show that basis component equivalence images have high potential to improve the diagnostic accuracy of the detection of minor bone lesions during clinical trauma imaging. A reader study performed by three experienced radiologists compares the image quality of basis material images to a standard radiograph image of a non-fractured cadaveric hand.

Dynamic K-edge Subtraction Fluoroscopy at a Compact Inverse-Compton Synchrotron X-ray Source

X-ray fluoroscopy is a commonly applied diagnostic tool for morphological and functional evaluation of the intestine in clinical routine. Acquisition of repetitive X-ray images following oral or rectal application of iodine contrast agent visualizes the time dependent distribution of the contrast medium, and helps to detect for example leakages, tumors or functional disorders. However, movements of the intestine and air trapped inside usually prevent temporal subtraction imaging to be applied to fluoroscopy of the gastrointestinal tract. K-edge subtraction (KES) imaging would enable subtraction fluoroscopy because it allows for imaging of moving organs with little artefacts. Although KES imaging is a well established technique at synchrotron sources, this imaging method is not applied in clinical routine as it relies on brilliant synchrotron radiation. Recently emerging compact synchrotron X-ray sources could provide a quasi-monochromatic, high-flux X-ray beam and allow for the application of KES in a laboratory environment. Here, we present a filter-based dynamic KES approach at the Munich Compact Light Source (MuCLS), the first user-dedicated installation of a compact synchrotron X-ray source worldwide. Compared to conventional temporal subtraction X-ray radiography, our approach increases the contrast while reducing the generated image artefacts.

Design of Reference Phantom for Quality Control of Conventional X-ray Radiography Units in Port Sudan

The Quality Control (QC) system, based on simple, cheap equipment and minimum personnel time, enables a resource-limited facility and staff to control the fundamental components of the imaging process on a low cost basis. Quality Assurance (QA) is a product or service quality management program. Customer reviews, capacity building and quality control can also be included. Quality control requires specific measures for ensuring measurable process-related aspects of product output or for the delivery of services within a given limit. Research was conducted at the Medical Physics Department of Red Sea University. The main objective of this work was to boost quality assurance rays. The imagination is more user-friendly and produces better results than a person or object. Phantoms, including fluoroscopy or x-rays, and certain image quality measurements have been used in x-rays imaging. The manufactured phantom in this study showed high precision in different QC tests.

Multiple Pulmonary Calssified Nodules and Cavitation Filled With the Dense Body on Chest X-Ray: A Case Report

Imaging in the clinical study has a significant value in medical diagnosing and the following diseases. The characteristic signs of imaging are a clue in approach to differential diagnosis. A conventional chest x-ray radiography is a more prevalent image used in the initial clinical assessment of pulmonary diseases. Iran is one of the 9 countries with a 95% burden of tuberculosis in the Eastern Mediterranian region. Chest radiography is the initial imaging for the evaluation of pulmonary tuberculosis.

Research at Tsinghua University on electrical explosions of wires

Electrical explosion of a wire (EEW) has been investigated for more than ten years at Tsinghua University, and the main results are reviewed in this paper. Based on EEW in vacuum, an X-pinch was used as an x-ray source for phase-contrast imaging of small insects such as mosquitoes and ants in which it was possible to observe clearly their detailed internal structures, which can never be seen with conventional x-ray radiography. Electrical explosion of a wire array (EEWA) in vacuum is the initial stage in the formation of a wire-array Z-pinch. The evolution of EEWA was observed with x-ray backlighting using two X-pinches as x-ray sources. It was found that each wire in an EEWA exhibits a core–corona structure instead of forming a fully vaporized metallic vapor. This structure is detrimental to the plasma implosion of a Z-pinch. By inserting an insulator as a flashover switch into the cathode, formation of a core–corona structure was suppressed and core-free EEWA was realized. EEW in gases was used for nanopowder production. Three parameters (vaporization rate, gas pressure, and energy deposited in the exploding plasma) were found to influence the nanoparticle size. EEW in water was used for shock-wave generation. The shock wave generated by melting could be recorded with a piezoelectric gauge only in underheat EEW. For EEW with a given stored energy but different energy-storage capacitor banks, the small capacitor bank produced a rapidly rising current that deposited more energy into the wire and generated a stronger shock wave.

Few-photon computed x-ray imaging

X-rays are a ubiquitous imaging modality in clinical diagnostics and industrial inspections, thanks to their high penetration power. Conventional transmission-based x-ray radiography or computed tomography systems collect approximately 103–104 counts per pixel to ensure sufficient signal to noise ratio. The recent development of energy sensitive photon counting detectors has made x-ray imaging at low photon fluxes possible. In this paper, we report a photon-counting scheme that records the time stamp of individual photons, which follows a negative binomial distribution, and demonstrate the reconstruction based on the few-photon statistics. The x-ray projection and tomography reconstruction from measurements of ∼16 photons per beam show potential for using photon counting detectors for dose-efficient x-ray imaging applications.

Magnetic resonance imaging of the Lisfranc ligament

BackgroundThe Lisfranc joint has complex structures, and articular surfaces overlap on conventional X-ray radiographs. Hence, there is no available auxiliary examination for diagnosing related injuries. At present, few studies on the imaging of Lisfranc ligaments have been reported, and related imaging data are rare. Therefore, no imaging reference can be used for related diagnosis and repair operations. This study aims to observe and describe the morphology and structure of Lisfranc ligaments using magnetic resonance imaging (MRI), in order to provide imaging reference for the diagnosis and repair of Lisfranc joint injuries.MethodsMRI scanning was performed on 60 sides of normal feet of 30 healthy adult volunteers. In the MRI scanning on the Lisfranc joint, sagittal scanning was focused on the area between the lateral margin and medial margin of the Lisfranc joint, while oblique coronal scanning was focused on the area parallel to the Lisfranc joint clearance. After acquisition of MRI images, data were burned into a CD, and the morphology and structure of the Lisfranc ligament on the MRI image were observed and described. Hence, the imaging parameters of the Lisfranc ligament were acquired, providing an imaging reference for the diagnosis and repair of Lisfranc joint injuries.ResultsBy observing the obtained images of the Lisfranc ligament through appropriate MRI scanning, it was found that the Lisfranc ligament originates at the site 12.63 ± 1.20 mm from the lateral side of the base of the medial cuneiform bone, with a length of 8.02 ± 1.5 mm, a width of 2.53 ± 0.61 mm, a height of 6.96 ± 1.01 mm, forms an included angle of 46.79 ± 3.47° with the long axis of the first metatarsal bone, and finally ends at the base of the second phalanx. Detailed imaging parameters of the Lisfranc joint and ligament were obtained from the present imaging experiment, providing an imaging reference for the diagnosis and repair of Lisfranc joint injuries.ConclusionsOn the MRI images, the sagittal section can clearly display the corresponding situation of the Lisfranc joint bone and longitudinal arch of the foot, tolerably display the Lisfranc joint dorsal ligaments and metatarsal ligaments, and poorly display the Lisfranc ligament. The oblique coronal section can clearly display the transverse arch of the foot and clearly display the cross-section of the Lisfranc ligament. The oblique crosssection can clearly display the horizontal arch of the Lisfranc joint and more clearly display its surrounding ligaments and tendons, especially the entire Lisfranc ligament and its attachment points. This is an important section for the diagnosis of Lisfranc ligament injuries. This study provides a certain imaging reference for the MRI scanning, diagnosis, and repair of Lisfranc joint injuries. Further research with large sample size is still needed to confirm the conclusions.

Difference assessment of composite resins and sound tooth applicable in the resin-imbedded tooth for resin repair using fluorescence, microhardness, DIAGNOdent, and X-ray image.

Visual differentiation of resin and tooth in a tooth cavity is not simple due to their highly similar shade. The purpose of the present study was to find any noninvasive method which can effectively differentiate resin from sound tooth in a resin-imbedded tooth for resin repair. For the study, various resin products were imbedded into the cavity of sound tooth. By applying laser of different wavelengths, autofluorescence (AF) of sound tooth and resin products were obtained. Microhardness, X-ray radiograph, and DIAGNOdent were tested for each tooth, resin product, and resin-imbedded tooth. For the AF spectra obtained using the 405-nm wavelength, sound tooth has emission peak at 440-470nm and near 490nm. Sound tooth has several times higher microhardness than resin products regardless of position in tooth subsurface. Due to the difference of radiopaque fillers' composition and concentration, resin products have different brightness in the X-ray radiograph. DIAGNOdent readings for tooth and resin products were inconsistently different, and the difference of obtained values was slightly not to be applicable for the differentiation. Among the tested methods, with noninvasive treatment, AF spectrum by the 405-nm wavelength showed the apparent difference between resin and tooth. For the resin repair in a resin-imbedded tooth cavity, AF spectrum produced by 405-nm wavelength could be a useful method in tracing the resin-tooth boundary if combined with conventional X-ray radiography.

Trabecular bone anisotropy imaging with a compact laser-undulator synchrotron x-ray source

Conventional x-ray radiography is a well-established standard in diagnostic imaging of human bones. It reveals typical bony anatomy with a strong surrounding cortical bone and trabecular structure of the inner part. However, due to limited spatial resolution, x-ray radiography cannot provide information on the microstructure of the trabecular bone. Thus, microfractures without dislocation are often missed in initial radiographs, resulting in a lack or delay of adequate therapy. Here we show that x-ray vector radiography (XVR) can overcome this limitation and allows for a deeper insight into the microstructure with a radiation exposure comparable to standard radiography. XVR senses x-ray ultrasmall-angle scattering in addition to the attenuation contrast and thereby reveals the mean scattering strength, its degree of anisotropy and the orientation of scattering structures. Corresponding to the structural characteristics of bones, there is a homogenous mean scattering signal of the trabecular bone but the degree of anisotropy is strongly affected by variations in the trabecular structure providing more detailed information on the bone microstructure. The measurements were performed at the Munich Compact Light Source, a novel type of x-ray source based on inverse Compton scattering. This laboratory-sized source produces highly brilliant quasi-monochromatic x-rays with a tunable energy.

MA-XRF imaging on Ren\xe9 Magritte\u2019s La condition humaine: insights into the artist\u2019s palette and technique and the discovery of a third quarter of La pose enchant\xe9e

Magritte’s composition La condition humaine, 1935 was found to conceal under its paint layers an entire quarter of a lost composition by the artist, until recently only known from a small black/white catalogue illustration—La pose enchantée, 1927. This study is the latest contribution to the discovery of the artist’s missing painting, now known to have been cut into four parts and re-used by Magritte as the support for new compositions. Non-destructive analytical and examination methods and specifically macroscopic X-ray fluorescence (MAXRF) scanning and conventional X-ray radiography (XRR) were the two non-destructive analytical and examination methods used to study both compositions and add to the existing knowledge on the artist’s palette during both periods. The first method is capable of identifying the presence and the distribution of key chemical elements present in artists’ materials. In some instances elemental mapping provided useful information on the hidden painting, but conventional X-ray radiography (XRR) enabled a better visualisation of the form and paint application of the underlying composition. Furthermore, the turnover edges of the canvas reveal after over 80 years the artist’s palette directly to the viewer. Additional XRF scanning of this exposed paint has confirmed and added to the existing research published to date of this lost painting, including a proposed colour reconstruction, but at the same time highlighting the need for further analytical research involving both non-destructive point analysis and the use of paint samples.

Investigating Early/Middle Bronze Age copper and bronze axes by micro X-ray fluorescence spectrometry and neutron imaging techniques

Micro X-ray fluorescence (micro-XRF) analysis and neutron imaging techniques, namely 2D radiography and 3D tomography, have been applied for the study of four metal axes from the Early/Middle Bronze Age in Western Iberia, a period characterized by a metallurgical change in the use of copper to bronze. Micro-XRF analysis has shown that one of the axes was produced in copper with some arsenic while the other three were produced in a copper-tin alloy (bronze) with variable tin contents and some arsenic and lead. Neutron radiography and tomography were applied to study internal heterogeneities of the axes in a non-invasive way since the specificities of neutron interaction with matter allow a suitable penetration of these relatively thick copper-based objects when compared to the use of a conventional X-ray radiography. Neutron imaging allowed the visualization of internal fissures and pores and the evaluation of their distribution, size and shape. Relevant information for the reconstruction of ancient manufacturing techniques was gathered, revealing that one ax was produced with the mold in an angle of ≈25°, probably to facilitate gas escape during metal pouring. Also, information regarding physical weaknesses of the axes was collected, providing relevant data for their conservation. Novelty statementThe present paper combines the use of micro-XRF and neutron imaging techniques, namely (2D) radiography and (3D) tomography for the study of prehistoric metal axes. The XRF spectra allowed identifying major and minor elements present in the alloys, inferring on the absence of elements that could become radioactive for a long period of time after irradiation with neutrons. The specificities of neutron interaction with matter allowed a suitable penetration of these relatively thick copper-based objects when compared to the use of a conventional X-ray radiography.The combination of these non-destructive techniques allowed the evaluation of the metal composition and the internal structure of the axes. Micro-XRF allowed the distinction among copper and bronze axes, and provided data about the composition of early bronzes for which data is scarce. The neutron imaging study allowed for the first time the visualization of internal heterogeneities in early bronze axes, namely pores and large voids, providing relevant information for the reconstruction of ancient manufacturing techniques and raising pertinent information regarding physical weaknesses of these types of objects.

Non-destructive investigation of thermoplastic reinforced composites

This paper studies various manufacturing defects in glass fiber/Polypropylene (PP) composite parts and their methods of detection. Foreign Object Inclusion (FOI) of different shapes, sizes, and materials were placed in a glass fiber/PP panel made by compression molding. The paper aims to characterize the fiber orientation and fiber related defects such as fiber waviness in the composite specimen. Comprehensive investigation for different Non Destructive Evaluation (NDE) techniques, namely X-ray radiography and Ultrasonic Testing (UT) techniques to trace and characterize the embedded defects and the composite texture are presented. Conventional X-ray radiography successfully identified the fiber orientation in two dimension (2-D) plane; however, information for the sample depth was not captured. The radiography techniques showed low relative errors for the defect size measurements (maximum error was below 9.5%) when compared to the ultrasonic techniques. Ultrasonic techniques were able to map all the embedded artificial defects. Phase Array (PA) ultrasonic technique was able to precisely locate the FOI in the glass fiber/PP specimen. Nerveless, the shape and size of the defects were not accurately determined due to the high signal attenuation and distortion characteristics of the E-glass fiber.

Equally sloped X-ray microtomography of living insects with low radiation dose and improved resolution capability

Three-dimensional X-ray imaging of living specimens is challenging due to the limited resolution of conventional absorption contrast X-ray imaging and potential irradiation damage of biological specimens. In this letter, we present microtomography of a living specimen combining phase-contrast imaging and a Fourier-based iterative algorithm termed equally sloped tomography. Non-destructive 3D imaging of an anesthetized living yellow mealworm Tenebrio molitor was demonstrated with a relatively low dose using synchrotron generated X-rays. Based on the high-quality 3D images, branching tracheoles and different tissues of the insect in a natural state were identified and analyzed, demonstrating a significant advantage of the technique over conventional X-ray radiography or histotomy. Additionally, the insect survived without problem after a 1.92-s X-ray exposure and subsequent absorbed radiation dose of ∼1.2 Gy. No notable physiological effects were observed after reviving the insect from anesthesia. The improved static tomographic method demonstrated in this letter shows advantage in the non-destructive structural investigation of living insects in three dimensions due to the low radiation dose and high resolution capability, and offers many potential applications in biological science.

Preliminary study on a chest digital tomosynthesis: development and evaluation

Chest digital tomosynthesis (chest DTS) has been recently introduced to overcome the limitations for high patient dose of conventional X-ray radiography and of a cone-beam computed tomography (CBCT) in studies of overlap of anatomical structures. In the present study, we constructed chest DTS system with amorphous-silicon (a-Si) digital flat-panel detector with pixel pitch of 143 × 143 μ m2 based upon filtered backprojection (FBP) reconstruction methods We performed both experiments and systematic simulations using our chest DTS system. The image performances were evaluated by means of root-mean-square error (RMSE) and signal difference-to-noise ratio (SDNR) with respect to scan angles such as ± 5̂, ± 10̂, ± 15̂, and ± 20̂. We also performed experiments using our chest DTS system. According to the results, the image performances obtained from chest DTS are improved by using our wide scan angle approach The chest DTS slices showed an improvement in the depth resolution with increasing scan angle. It was found that the optimized filter with a Hanning window to limit the high-frequency components improves image performance because of noise reduction. The chest DTS slices showed an improvement in the depth resolution with increasing scan angle. Both simulation and experimental results showed the same tendency when image performances quantitatively compared. Based on our results, we successfully obtained chest DTS reconstruction images by using a FBP method and promising to application to field of medical imaging.