White Paper: Multitom Rax Real3D for Musculoskeletal and Trauma Imaging - Imaging Technique and Clinical Application

White paper Multitom Rax Real3D for musculoskeletal and trauma imaging Imaging technique and clinical application Anna Rasche, PhD; Marcel Beister, PhD siemens-healthineers.com/robotic-x-ray SIEMENS Healthineers White paper · Multitom Rax Real3D for musculoskeletal imaging Contents 1. Real3D: The technique and its added value 3 3D imaging in supine and natural weight-bearing patient positions 3 High spatial resolution for bony structures 5 Dose-saving potential for extremities 9 2. Real3D: Applications in clinical practice 11 Trauma evaluation of extremities: Fracture detection and surgical follow-up 11 Arthrography: Taking advantage of Multitom Rax’s multifunctionality 15 Weight-bearing imaging for new approaches in orthopedics 17 3. Conclusion: Shaping the future of orthopedic and trauma imaging with Real3D 20 Abbreviations 20 References 21 2 Multitom Rax Real3D for musculoskeletal imaging · White paper 1. Real3D: The technique and its added value The Twin Robotic X-ray system Multitom Rax provides conventional radiography, fluoroscopic examinations for functional assessment, the slot scanning function True2scale Body Scan for extended orthopedic examinations, and Real3D as cone-beam computed tomography on the same system. The focus of this white paper is on Real3D that offers three-dimensional information on the scanned body region – free from magnification and distortion – in sagittal, coronal, and axial views as well as a rendered bone volume to meet the requirements of musculoskeletal and trauma departments. 3D imaging in supine and natural weight-bearing patient positions Real3D enables examinations of different body regions with the patient in a supine or weight-bearing position as shown in Figure 1. Lumbar spine Hip Knee Foot/ankle OR Head Elbow Hand/wrist Knee Foot/ankle a Scanned in a weight-bearing patient position b Scanned in a supine patient position 1 Recommended body regions for Real3D 3 White paper · Multitom Rax Real3D for musculoskeletal imaging To capture 3D information, Real3D uses a flat panel In contrast to Real3D, multi-detector computed tomo- detector for image acquisition that results in a cone graphy (MDCT) uses a combination of a fan-beam X-ray geometry of the X-ray beam (Figure 2a). During a scan, configuration and multiple detector rows for image tube and detector rotate around the patient and a acquisition to subsequently reconstruct a volume specific number of projection images are taken depen- dataset. Because of the much smaller cone angle, ding on the application. The projection data is used multiple rotations around the patient are performed to calculate 3D datasets that are familiar and well- in a spiral or helical pattern to cover the entire region established in computed tomography (CT). of interest.[1],[2] a b 2 X-ray geometry in Real3D (a) and multi-detector CT (b) Multitom Rax uses a ceiling-mounted tube and a in the system to enable imaging of different body parts ceiling-mounted amorphous silicon flat-panel detector with the patient in either a supine or an upright position for Real3D image acquisition (with an active area of (Figure 3). Depending on the trajectory, tube and 42.0 cm x 42.5 cm and a cesium iodide scintillator). detector capture projection data over an angular range Tube and detector both have three translational and two of between 171° and 200° around the patient with a rotational degrees of freedom for moving on defined scan duration of between 12 and 16 seconds. For a paths (trajectories) around the patient and acquiring precise and stable reconstruction of a region of interest, the projections. Three types of trajectories are installed angular ranges of less than 360° are sufficient.[3] a Tableside trajectory for hand b Table trajectory for head, foot, c Upright trajectory for foot, knee, and elbow examinations and knee examinations hip, and lumbar spine examinations 3 Different trajectories for Multitom Rax Real3D 4 Multitom Rax Real3D for musculoskeletal imaging · White paper High spatial resolution for bony structures For diagnostic evaluations, the radiologist can use multi-planar reconstruction (MPR) views in sagittal, coronal, and axial planes, corresponding to MDCT (Figure 4). A 3D view using a volume-rendering technique (VRT) allows for an additional assessment of anatomical structures. Study-ID 5aaa943 4 MPR and VRT of an elbow: axial, sagittal, coronal, and VRT view of a fracture of the radial head (Courtesy of Krankenhaus der Augustinerinnen, Cologne, Germany) The user can choose up to four different image comparable image impression. The smooth impression impressions for the generated Real3D slices: smooth, is mainly intended for VRT renderings, while the medium medium, sharp, and very sharp. The image impression impression is a good, balanced choice between image is influenced primarily by the underlying reconstruction resolution and noise. The sharp and very sharp image kernels. These are chosen to be similar to the ones impressions with a higher image resolution are intended used in Siemens Healthineers’ clinical MDCT systems, for diagnosing fractures and fine bony structures which enables Real3D on Multitom Rax to provide a (Figure 5). Study-ID 5aac203 a Smooth b Medium c Sharp d Very sharp1 5 Real3D image impressions (Courtesy of Krankenhaus der Augustinerinnen, Cologne, Germany) 1 Only available for Real3D Hi-Res 5 Study-ID 5aac203 White paper · Multitom Rax Real3D for musculoskeletal imaging The maximum volume that can be imaged using Multitom Rax Real3D is a cylinder with a diameter and height of approximately 23 to 26 cm at an isotropic spatial resolution of up to 15 lp/cm, depending on the trajectory and image impression selected for reconstruction. The coronal image resolution in the z-direction is higher in Real3D than in MDCT due to the isotropic smaller pixels of Multitom Rax’s flat panel detector (Figure 6). a High-resolution MDCT scanner using an ultra-high-resolution, b Real3D Hi-Res using the image impression “very sharp” sharp reconstruction kernel (Ur77) 6 Coronal slices of a wrist examination (Courtesy of University Hospital Wuerzburg, Germany) Real3D Hi-Res is an additional scan mode with a higher To fully exploit the smaller pixel size, the circular spatial resolution of up to 25 lp/cm, that allows a trajectory is modified so that the examined body part is reconstruction of a cylinder with a diameter and height closer to the detector. This reduces the limiting effect of of 15 cm. The high-resolution scan mode works with an the focal spot size on the spatial resolution of the X-ray un-binned partial detector readout, in contrast to the system (Figure 7). normal mode of 2 x 2 binned readout mode. X-ray source X-ray source Focal spot 0.6 mm Focal spot 0.6 mm Object Object Detector Detector 2x2 binned pixel 1x1 unbinned pixel 0.296 mm 0.148 mm Area of less sharpness Area of less sharpness a Normal scan mode b High-resolution scan mode 7 X-ray source and detector for the Real3D scan modes 6 Multitom Rax Real3D for musculoskeletal imaging · White paper The higher spatial resolution when using the high- and reveals more details (Figure 8). Table 1 shows an resolution scan mode has advantages for assessing overview of the differences between both scan modes anatomical structures. The visualization of the bone implemented in Multitom Rax. and its trabeculae is sharper than the normal scan mode a Axial slice in normal scan mode b Axial slice in high-resolution scan mode c Coronal slice in normal scan mode d Coronal slice in high-resolution scan mode 8 Real3D phantom examination of a hand Normal scan mode High-resolution scan mode Real3D Real3D Hi-Res Spatial resolution 15 lp/cm 25 lp/cm Reconstructable volume Cylinder with diameter and height of 23 to 26 cm Cylinder with diameter and height of 15 cm Body regions Hand/wrist, elbow, head, hip, lumbar spine, knee, foot/ankle Hand/wrist, elbow Table 1: Differences between Real3D’s normal and high-resolution scan modes ! Even higher spatial resolution using Real3D Hi-Res: 32 lp/cm compared with 16 lp/cm in the normal scan mode. 7 White paper · Multitom Rax Real3D for musculoskeletal imaging Metal artifact reduction for excellent bone visualization in the presence of implants For body parts containing metallic implants, markers, reduction. A study of cadaveric wrist scans confirmed or external fixators, Real3D offers dedicated acquisition that Real3D Hi-Res with metal artifact reduction modes with modified parameters that automatically implemented “Facilitates excellent visualization of trigger a metal artifact reduction method during the appendicular skeleton in the presence of metal the computation of the slice images and the VRT. The implants.”[4] advanced interpolation method in conjunction with the preservation of high-frequency details can reduce The artifact reduction method can be chosen for recon- the number of streaks and very bright and dark areas struction even if a regular acquisition mode was used: for surrounding metallic implants in the image to a large example, if the presence of the metal was unknown to extent. In Figure 9, you can see an example of an ankle the user before the acquisition. Conversely, it is possible examination with and without metal artifact reduction: to turn off the artifact reduction for reconstruction even Dark streaks close to the visible screw and three dark if an acquisition mode for metal implants was used for phantom holes created by out-of-plane screws are the data acquisition. substantially reduced by Real3D’s metal artifact a Without metal artifact reduction b With metal artifact reduction 9 Sagittal slice of a foot examination with a bone fracture plate and multiple fixation screws (Courtesy of Krankenhaus der Augustinerinnen, Cologne, Germany) 8 Multitom Rax Real3D for musculoskeletal imaging · White paper Dose-saving potential for extremities Dose declaration The applied radiation dose plays an important role in impact the desired image quality. The radiation dose evaluating modalities. The dose specification describes cannot be considered separately, but only in the context the energy that the patient is exposed to. The unit for of the achieved image quality. this dose is Gray (1 Gy = 1 J/kg). In contrast to the effective dose – which is specified in the unit Sievert (Sv) – the applied dose does not provide an evaluation of the potential damage that the ionizing radiation can cause in the patient’s body; rather, it describes Integrated ionization the radiation of the X-ray beams. chamber for DAP in real time A value for the dose area product (DAP) is documented in conventional X-ray examinations. Due to its different acquisition technique compared to 2D radiography, CTDI phantom with in MDCT examinations a dose length product (DLP) a diameter of 16 cm and a computed tomography dose index (CTDI) are documented. Dose probe As described above, Real3D captures a number of projection images using a fluoroscopy acquisition mode. As a result, the dose for each image is measured as DAP using an ionization chamber at the X-ray source (Figure 10). The applied dose is stated as the DAP sum of the individual projection images for the entire Real3D 10 Measuring positions for DAP and for calculation of DLP and CTDIvol16 dataset. In addition, Real3D offers computed values for DLP, CTDIvol16, and CTDIvol32 (see description above). As a basis ! Dose area product for 2D radiography for calculating these values, conversion factors were According to IEC 60601-2-54, conventional X-ray determined in dose measurements with a 16-cm CTDI devices measure or calculate a value for the dose phantom, because this entire phantom fits inside the area product (DAP) in Gy·m². The DAP is the surface Real3D beam path (Figure 10).2 Lund University in integral of the air kerma – the kinetic energy Malmö has independently validated this calculation and released in air – along a sectional plane confirmed the accuracy of the method implemented on through the radiation field. Multitom Rax.[5] A calculated value for CTDIvol32 based on simulations can also be displayed by the system. ! Dose length product for 3D computed tomography The DLP takes the actual source-to-object-distance According to IEC 60601-2-44, a value for the dose of the acquisition into account, which varies across length product (DLP) in mGy·cm and a computed different trajectory types in Real3D and across different tomography dose index (CTDI) in mGy must be MDCT models. That is why we recommend CTDIvol16 and specified for CT scanners. The DLP is calculated CTDIvol32 of Real3D and MDCT scanners to serve as a basis as the line integral of the air kerma along the for comparing the applied radiation dose between both system axis of the computer tomograph. The CTDIvol systems. represents the average energy dose (expressed as air kerma) within a phantom, a PMMA cylinder with The dose declaration values from Real3D allow for a a diameter of 16 or 32 cm, aligned with the scanner comparison of conventional X-ray devices with MDCT axis and centered in the scan plane. A value for scanners. Nevertheless, users should take into account CTDIvol must be derived that includes information the fact that comparing the dose delivered by different about the CTDI phantom. The DLP can also be modalities is subject to a certain degree of inaccuracy calculated as the product of the CTDIvol value and due to different measurement methods, and this will the scan length. 2 The measurements are derived from IEC 60601-2-44. Due to the different acquisition methods of Real3D and MDCT, the measurements cannot be adopted exactly as described in IEC 60601-2-44. 9 White paper · Multitom Rax Real3D for musculoskeletal imaging Applied radiation dose at the extremities Several studies of human specimens compared the especially suitable for evaluating bone cortex and applied radiation dose and the achieved image quality trabeculae and therefore for fracture diagnosis and of Real3D to MDCT scanners when imaging extremities. during the healing process.[6],[7] All publications conclude that there were substantial dose savings using Real3D compared to MDCT scanners The image quality of the Real3D high-resolution scan at a comparable image quality for bony structures. mode was analyzed compared to a high-resolution MDCT [6],[7],[8],[9] scanner for wrist and elbow imaging. The overall image quality of Real3D Hi-Res was rated as similar to a high- Table 2 shows the CTDIvol16 values from cadaveric studies. resolution MDCT scanner. Artifacts in bone using Real3D In the normal Real3D scan mode, the applied radiation Hi-Res were considered minimal or few – comparable to dose from the MDCT scanner was five to eight times high-resolution MDCT – and image noise in bone was higher than from Real3D – and the high-resolution MDCT inferior to high-resolution MDCT. Similar to the results scanner applied a radiation dose four times higher than from normal scan mode, artifacts and noise in soft tissue Real3D Hi-Res. The results of another study of cadaveric were rated lower in Real3D Hi-Res compared to high- wrist and elbow scans indicate a further dose-saving resolution MDCT. It was concluded that by using Real3D potential using Real3D Hi-Res at a low dose compared Hi-Res, an even better image quality for evaluating bony to the standard protocol while maintaining the desired structures could be achieved compared to the normal diagnostic image quality.[10] scan mode, similar to comparing a high-resolution MDCT scanner to a conventional MDCT scanner.[8],[9] As stated above, the radiation dose affects the achieved image quality. Looking at the results of Real3D in normal The normal scan mode of Real3D produces a similar scan mode for the wrist, the overall image quality was image quality for bone visualization while applying less rated higher for Real3D than for MDCT and slightly lower radiation dose compared to a conventional MDCT for images of the ankle. Artifacts and image noise in scanner and the Hi-Res scan mode compared to high- bone were comparable in the wrist images and slightly resolution MDCT scanner. This indicates that substantial more prominent in the ankle images. The assessment dose savings using Real3D for extremity imaging may of artifacts and image noise in soft tissue was inferior be possible depending on the clinical situation. compared to MDCT. It was concluded that Real3D is Normal scan mode High-resolution scan mode Wrist [6] Ankle [7] Wrist [8] Elbow [9] Wrist / Elbow [10] Real3D High- Real3D MDCT Real3D MDCT Real3D High- Real3D Hi-Res Hi-Res resolution Hi-Res resolution MDCT MDCT Low Dose CTDIvol16 (mGy) 1.8±0.2 15.0 2.9±0.6 15.0 3.3 13.8 3.3 13.8 1.2 Table 2: Applied radiation dose in cadaveric studies ! Real3D offers a dose-saving potential for the evaluation of bony structures in the upper and lower extremities. Applied radiation dose at the body trunk The applied radiation dose is different when imaging of human specimens. The authors proposed a protocol extremities than it is using the cone-beam imaging with a CTDIvol32 of 11.9 ± 2.6 mGy for clinical use, which technique at the body trunk. More tissue is present in was the most balanced choice after considering the the beam path, which causes more scattered radiation. overall image quality, the clarity of the posterior wall, That is why a higher radiation dose is needed to achieve the applied radiation dose, and noise. When the radiation an adequate image quality at the body trunk than at the dose used in the proposed Real3D protocol was com - extremities. The applied radiation dose for imaging the pared to values from multi-detector CT, similar or even lumbar spine at the body trunk was analyzed in a study higher dose levels are reported in the literature.[11] 10 Multitom Rax Real3D for musculoskeletal imaging · White paper 2. Real3D: Application in clinical practice Multitom Rax offers diverse clinical applications of Real3D that range from trauma and functional evaluation of extremities to the assessment of joints in a natural weight-bearing patient position. Trauma evaluation of extremities: Fracture detection and surgical follow-up For trauma imaging, Multitom Rax and its Real3D For acute elbow traumas, Real3D Hi-Res allowed for functionality can add diagnostic value compared to 2D a greater sensitivity compared to radiography in the X-ray examinations, especially for the assessment of assessment of fractures, articular surface involvement, complex anatomies with high superposition of adjacent and multi-fragment patterns.[14] bony structures like joints. Real3D can be used right after the 2D image if required or instead of a 2D examination The diagnostic accuracy for detecting various post- to evaluate traumas to the extremities and their surgical surgical complications, screw dislocation, implant follow-up. When evaluating small bone and joint trauma, loosening, fragment displacement, and delayed healing Real3D may help physicians by detecting and excluding was superior for Real3D compared to X-ray examinations extremity fractures, fracture-related findings, and post- in a study that included patients after osteoplasty surgical complications more reliably than 2D radiographs, of hand/wrist, elbow, and ankle/foot. In addition, as shown in Table 3.[12],[13],[14],[15] the post-operative management decision changed in 23.8 percent of patients with Real3D images compared It has been reported that there are a larger number of to X-ray information. In one case, the Real3D image fractures, joint involvement, and multi-fragment injuries showed no intra-articular positions of four screws – being assessed using Real3D compared to conventional thanks to reducing over-projection of anatomical X-ray images. The orthopedic surgeon changed the structures compared to conventional X-ray – and this treatment decision based on radiological reports after prevented unnecessary surgeries.[15] the Real3D scan was compared to the report from the radiograph for 31.5 percent of the patients, and six The studies of fracture detection presented had a higher fractures suspected in radiographs were ruled out by sensitivity for detecting fractures and fracture-related the Real3D information.[12] findings using Real3D compared to conventional radiography; they also confirmed the readers’ greater Comparable benefits can be shown for Real3D Hi-Res. diagnostic confidence when reading Real3D images, In a study of severe wrist trauma, Real3D Hi-Res was as shown in Table 4. superior for imaging scaphoid fractures, multi-fragment radius injuries, articular affliction, proximal pole or waist involvement, and comminuted patterns.[13] ! Physicians ruled out more fractures, fracture-related findings, and post-surgical complications at extremities using Real3D compared to conventional radiography. ! Higher diagnostic confidence for physicians for ruling out fractures and fracture-related findings at extremities using Real3D compared to conventional radiography. 11 White paper · Multitom Rax Real3D for musculoskeletal imaging Real3D/ X-ray Real3D Hi-Res Diagnostic accuracy of upper/lower extremity traumas [12]: Fractures 98% 71% Joint involvement 98% 79% Multi-fragment injuries 98% 76% Diagnostic accuracy of wrist traumas [13]: Radius fracture 100% 100% Articular affliction 99% 84% Multi-fragment situation in radius 100% 92% Scaphoid fracture 100% 70% Waist or proximal pole involvement 100% 68% Multi-fragment injury in scaphoid 100% 73% Sensitivity of elbow traumas [14]: Fracture 96% 75% Articular involvement 95% 79% Multi-fragment injury 96% 71% Diagnostic accuracy of post-surgical complications [15]: Articular screw position 99% 84% Screw loosening 99% 86% Implant failure 100% 96% Fragment dislocation 99% 85% Delayed healing / non-union 98% 89% Table 3: Average diagnostic accuracy/sensitivity of findings among different readers Real3D X-ray p value Diagnostic confidence: traumas of the upper and lower extremities [12] 5 4 < 0.001 Diagnostic confidence: wrist traumas [13] 5 4 < 0.001 Diagnostic confidence: elbow traumas [14] 5 4 < 0.001 Table 4: Median diagnostic confidence when reading Real3D compared to conventional X-ray examinations from “1 = no” to “5 = absolute” among different readers 12 Multitom Rax Real3D for musculoskeletal imaging · White paper Clinical cases: Trauma evaluation of extremities and post-surgical follow-up The following presents two examples from clinical routine radiographs six days later did not display any fracture that show the benefits of Real3D compared to conventional line (Figure 11b), Real3D was requested to exclude 2D radiographs. a radiographically occult fracture of the radial head (Figure 11c). Figure 11 illustrates the clinical case of a radial head fracture. The patient fell from an e-scooter onto his right Multitom Rax Real3D was able to depict a non-displaced elbow. He presented to the trauma surgery department fracture in the anterior portion of the radial head with pressure pain, especially over the radial head, and (Mason type I). Aside from the radial head injury, other extensive swelling that resulted in limited motion range. fractures were excluded in the Real 3D examination. No bony injury could be ascertained in the initial X-ray Surgical therapy was not required, because the elbow scans. However, a subtle anterior fat pad sign in the joint showed no signs of instability. Instead, the patient lateral radiogram (arrow) suggested the presence of was given conservative treatment that included tempo- joint effusion (Figure 11a). When the second set of rary immobilization and subsequent physical therapy. Study ID 5aac390 Study ID 5aac391 a X-ray examinations on date of injury b X-ray examinations six days later Study ID 5aac379 c Axial, sagittal, and coronal view of Real3D Hi-Res examination using standard protocol (tube voltage 80 kV, CTDIvol32 1.9 mGy, CTDIvol16 5.5 mGy, scan time 14 sec) 11 Multitom Rax examinations of a radial head fracture (Courtesy of University Hospital Wuerzburg, Germany)3 3 Please visit our Clinical Case Library to explore more applications of Multitom Rax Real3D 13 White paper · Multitom Rax Real3D for musculoskeletal imaging The clinical case of a scaphoid screw dislocation In addition to the complete fracture healing, Real3D demonstrates the clinical use of Real3D for surgical images with metal artifact reduction revealed screw follow-up (Figure 12). The patient fell on her left wrist displacement into the scaphotrapezial joint. The proximal three months before the present examination and articular surface of the trapezium displayed a small notch suffered a scaphoid waist fracture (Herbert B2). (arrow on the coronal view) congruent to the distal Conventional screw osteosynthesis was performed with portion of the dislocated screw. Signs of secondary subsequent cast immobilization for six weeks. The osteoarthritis were visible (joint space narrowing, patient reported subtle pressure pain over the radial side subchondral sclerosis). of the distal carpal row. The 2D radiography (Figure 12a) was unable to visualize accurate screw placement and remained inconclusive with regard to fracture healing, so that a Real3D scan was ordered (Figure 12b). Study ID 5aab935 Study ID 5aab557 a X-ray examinations b Coronal, sagittal, axial, and MIP (maximum intensity projection) view of Real3D Hi-Res examination using dedicated metal protocol (tube voltage 116 kV, CTDIvol32 5.0 mGy, CTDIvol16 18.0 mGy, scan time 14 sec) 12 Multitom Rax examinations of a scaphoid screw dislocation (Courtesy of University Hospital Wuerzburg, Germany)4 14 4 Please visit our Clinical Case Library to explore more applications of Multitom Rax Real3D Multitom Rax Real3D for musculoskeletal imaging · White paper Arthrography: Taking advantage of Multitom Rax’s multifunctionality The combination of its different functionalities means A study of human specimens proved the feasibility that Multitom Rax offers the potential for an improved of Multitom Rax for 3D arthrography of the wrist in patient workflow and associated time savings. With a “one-stop shop” approach without repositioning Multitom Rax, arthrographies can be performed for the region of interest by using fluoroscopy to inject a simultaneous evaluation of chondral injuries, the contrast medium and Real3D Hi-Res to create surrounding cartilage, and subchondral bone. After the the tomography. The median examination time for injection of the contrast medium using the fluoroscopy 3D arthrography was 5.4 min from contrast injection functionality of the system, the Real3D scan can be to finishing the Real3D scan.[16] performed immediately without changing rooms. ! With its fluoroscopic and Real3D functionalities, Multitom Rax offers a one-stop shop approach for 3D arthrography. Clinical case: Arthrography The case shown in Figure 13 shows this application in Chauffeur fracture of the distal radius (arrow), while clinical routine. The patient presented with pain and ruling out any discontinuity of the scapholunate swelling over the radial side of the wrist after falling on interosseous ligament (marked with a circle on the his outstretched left hand in a bicycle accident. With the coronal view). Axial reformatting supported the 2D radiography (Figure 13a), a slightly displaced fracture presumed integrity of the scapholunate interosseous of the radial styloid process was ascertained (marked ligament. Its dorsal segment in particular, which with an arrow on the X-ray examination). functions as one of the key stabilizers of the proximal Before beginning surgical treatment of this Chauffeur- carpal row, appeared intact (marked with a circle on type fracture, trauma surgeons requested a pre-operative the axial view). The lunotriquetral ligament displayed assessment of scapholunate ligament integrity. To a subtle discontinuity in its proximal membranous assess the anatomical structure, an arthrography using portion. However, this finding is mainly associated Multitom Rax was performed with the patient remaining with degenerative alterations and insignificant for in the same position for the fluoroscopy and Real3D carpal stability. imaging using the tableside scan trajectory for wrist imaging. While the patient had surgery for re-fixation of the distal radius, the need for additional treatment of the Fluoroscopy-guided two-compartment wrist arthrography scapholunate ligament was ruled out in a minimally (midcarpal, radiocarpal) depicted no communicating invasive procedure using Multitom Rax Real3D lesions of the intrinsic carpal ligaments (Figure 13b). arthrography. Subsequent Real3D imaging (Figure 13c) visualized the 15 White paper · Multitom Rax Real3D for musculoskeletal imaging Study ID 5aac389 a X-ray examination Study ID 5aac378 b Fluoroscopy-guided injection c Coronal and axial views of Real3D Hi-Res examination using standard protocol (tube voltage 80 kV, CTDIvol32 1.6 mGy, CTDIvol16 4.5 mGy, scan time 14 sec) 13 Multitom Rax examinations of a wrist arthrography (Courtesy of University Hospital Wuerzburg, Germany)5 16 5 Please visit our Clinical Case Library to explore more applications of Multitom Rax Real3D Multitom Rax Real3D for musculoskeletal imaging · White paper Weight-bearing imaging for new approaches in orthopedics The examination of disorders in a natural weight-bearing Another scientific publication analyzed the spinal position is well established in 2D radiography. Now stability of six patients in a weight-bearing, neutral Real3D makes this approach possible for 3D imaging. A standing position and with flexion and extension using Real3D scan with the patient in a natural weight-bearing Real3D. The Real3D scan in a functional physiological position may provide additional information for the standing position offered three-dimensional information evaluation of osteoarticular deformities. Because the with no geometric distortion compared to conventional position of certain anatomical structures, especially radiographs of fractures, spinal canal, exit foramina, complex joints, changes with weight loading, a Real3D facet joints, and implanted metal. In one of the patients, scan with the patient in an upright position could make this information prevented fusion surgery by showing a difference in diagnosis and treatment planning spinal stability. The authors conclude that neutral, compared to supine imaging: for example, for an flexion, and extension imaging using Real3D allows improved prosthesis or surgery planning and for patients for an accurate assessment of spinal instabilities. For who have pain in a weight-bearing position, and for patients for whom no diagnosis was possible using a whom a scan in a supine position does not provide a supine 3D imaging modality, weight-bearing Real3D finding.[17] examinations offered new opportunities to identify the cause of occult back and leg pain.[19] Weight-bearing imaging of the lumbar spine With its Real3D functionality, Multitom Rax is the only When combining the advantages of cross-sectional and generally available scanner that enables weight-bearing weight-bearing imaging of the lumbar spine, it is found CT imaging of the lumbar spine. that Real3D offers a promising alternative for imaging diseases of the lumbar spine. The static forces that apply The first clinical results show a valid use case for this in weight-bearing conditions and the resulting changes kind of examination in the assessment of the lumbar in anatomical size are believed to be the main reason for foramina. A study of 48 patients confirmed that the an often recognizable mismatch between clinical and lumbar foramina were smaller in a weight-bearing magnetic resonance imaging findings for the diagnosis position compared to a supine patient position of lower back pain. However, future clinical research is (Figure 14). There was a statistically significant needed to investigate how patients’ clinical outcomes decrease in neuroforaminal size – the cross-sectional can be improved by these differences.[20] areas as well as the cranio-caudal and ventro-dorsal diameters of the foramina – from the supine to the weight-bearing position. These results may indicate the ! Weight-bearing Real3D examinations of the lumbar added value of the weight-bearing 3D information for spine show a decrease in the neuroforaminal size diagnosis and treatment planning.[18] compared to supine patient position. Weight-bearing imaging of the lower extremities In addition to its unique application for the lumbar spine, Multitom Rax Real3D offers weight-bearing examinations of the lower extremities similar to other systems that use the cone-beam technique for computed tomography. This type of imaging offers quantification of biomechanical parameters, including the relative positions of bones, angles, and ligaments as well as joint Area 1.243 cm2 Area 1.131 cm2 space width.[21] a MDCT slice acquired b Real3D slice acquired For the knee, the diagnosis and treatment of osteoarthritis in a supine patient in a weight-bearing patient and patellofemoral diseases can be impacted by the fact position position that femorotibial rotation, the tibial tuberosity-trochlear groove, and medial joint space width differ between Marked neural foramina in the lumbar spine weight-bearing and non-weight-bearing images.[22] 14 (Courtesy of University Hospital Basel, Switzerland) 17 White paper · Multitom Rax Real3D for musculoskeletal imaging Foot and ankle examinations that are performed been observed in recent years, which has led to a better in a weight-bearing position can add clinical value understanding of the anatomy and biomechanics of when evaluating complex deformities, joint alignment, scans performed in a natural weight-bearing position.[21] congruence and coverage of articulating facets, impingement, joint degeneration, and decreases Similar to the lumbar spine, the application fields for in joint space width when standing.[21] weight-bearing foot, knee, or hip examinations using Real3D open the door for more clinical research: for A growing number of international studies of weight- example, to standardize approaches for diagnosis and bearing 3D examinations of the lower extremities has treatment planning. Clinical cases: Weight-bearing imaging An example of Real3D in clinical routine for osteoarthritis The 3D examination under weight load shows that of the knee scanned with the patient in a natural weight- the lateral joint space has completely closed up bearing patient position is shown in Figure 15. The (marked with a circle in the sagittal view). In addition, patient had lateral knee pain for several years, and the there are signs of activated osteoarthritis of the knee: symptoms increased significantly under weight load, spotty, periarticular osteopenia that most resembles especially when walking and climbing stairs. A Real3D inactivity osteopenia; lateralized patella with incipient scan was performed to look for degenerative changes retropatellar arthrosis; and concomitant joint effusion. and the position of the bones and to assess the situation The option to implant a knee endoprosthesis was under weight-bearing conditions. discussed with the patient. Coronal, axial, and sagittal views of Real3D examination using standard protocol (tube voltage 117 kV, CTDIvol32 4.6 mGy, CTDIvol16 9.5 mGy, scan time 16 sec) 15 Multitom Rax examinations of an osteoarthritis of the knees under weight-bearing conditions (Courtesy of Artemed Hospital Munich, Germany)6 18 6 Please visit our Clinical Case Library to explore more applications of Multitom Rax Real3D Multitom Rax Real3D for musculoskeletal imaging · White paper The following clinical case shows a perfect example of The physiological angle between talus and calcaneus the clinical value of weight-bearing Real3D for foot and (kite angle) of the left foot was 13°. On the right side, ankle examinations in clinical routine. In Figure 16, the kite angle was reduced by 3°, which presumably weight-bearing examinations of both of the patient’s feet resulted from compensating for the angle deformity are shown. The patient suffered a calcaneus fracture of of the lower leg. Additional rotational differences were the left foot 12 years previously, with several surgeries found in the rotation measurements of both legs. The and subtalar arthrodesis that resulted in a rotational error new information led to a re-evaluation of the previous of the foot. In particular, the supination error bothered imaging of the lower leg, which revealed a rotational him when walking and made it hard to place his foot error on the left lower leg of 25° and a varus deformity straight on the ground. To compensate, the patient had of the knee. The mobile right foot could compensate for to perform an internal rotation of the entire leg of 20 to some of the changes, whereas the left foot was fixated 25°. The Real3D examination (Figures 16b and c) was by subtalar arthrodesis. The treatment required a needed to analyze the subtalar position under weight- rotation-correcting osteotomy of the left tibia and fibula. bearing conditions in both feet in order to find rotational differences after the trauma and surgeries. Study ID 5aac675 Study ID 5aac195 Study ID 5aac195 a X-ray examination b Sagittal views of both feet in a Real3D c Axial views of both feet in a Real3D examination using dedicated metal examination protocol for left and right foot (tube voltage per scan 117 kV, CTDIvol32 as sum of both scans 19.1 mGy, CTDIvol16 32.0 mGy, scan time per scan 16 sec) 16 Multitom Rax examinations of both feet under weight-bearing conditions (Courtesy of University Hospital Carl Gustav Carus, Dresden, Germany)7 7 Please visit our Clinical Case Library to explore more applications of Multitom Rax Real3D 19 White paper · Multitom Rax Real3D for musculoskeletal imaging 3. Conclusion: Shaping the future of orthopedic and trauma imaging with Real3D The Real3D functionality in the Multitom Rax Twin- Multitom Rax’s multifunctionality provides integrated Robotic X-ray system can be a useful enhancement fluoroscopic and Real3D imaging, offering a one-stop for musculoskeletal and trauma departments, because shop approach for 3D arthrography – from contrast it provides tomographic information on the scanned injection under fluoroscopy to the Real3D examination – anatomical region. without repositioning the patient.[16] In the initial publications, Real3D showed a similar Weight-bearing examinations with Real3D offer new image quality in the evaluation of bony structures in options and the potential to enhance diagnosis and the extremities compared to conventional MDCT achieve a sustainable improvement in patient treatment. scanners – and a dose-saving potential at the same time. Images that are taken with the patient in an upright Using the high-resolution scan mode, an even higher position may provide more information for diagnosis and resolution can be achieved. The 3D information can allow treatment planning, for example, precise positioning of the radiologist to detect and rule out extremity fractures, the joints for implant and prosthesis planning and fracture-related findings, and post-surgical complications malposition of anatomical structures.[17] more reliably than conventional radiography.[12] Weight-bearing 3D imaging in clinical routine remains an important research topic for orthopedic imaging. Abbreviations BMI Body mass index CT Computed tomography CTDI Computed-tomography dose index DAP Dose area product DLP Dose length product Hi-Res High-resolution MAR Metal artifact reduction MDCT Multi-detector computed tomography MIP Maximum-intensity projection MPR Multi-planar reconstruction VRT Volume-rendering technique 20 Multitom Rax Real3D for musculoskeletal imaging · White paper References [1] Scarfe WC. Clinical applications of cone-beam [9] Grunz JP, Weng AM, Kunz AS, Veyhl-Wichmann M, computed tomography in dental practice. J Can Schmitt R, Gietzen CH, Pennig L, Herz S, Ergün S, Dent Assoc 2006; 72(1):75–80. PMID: 16480609. Bley TA, Gassenmaier T. 3D cone-beam CT with a [2] Scarfe WC and Farman AG. What is cone-beam CT twin robotic X-ray system in elbow imaging: and how does it work? Dent Clin North Am 2008; Comparison of image quality to high-resolution 52(4):707-30. doi: 10.1016/j.cden.2008.05.005. multidetector CT. Eur Radiol Exp. 2020 Sep 8;4(1):52. PMID: 18805225. [3] Noo F, Defrise M, Clackdoyle R, Kudo H. Image [10] Luetkens KS, Ergün S, Huflage H, Kunz AS, Gietzen reconstruction from fan-beam projections on less CH, Conrads N, Pennig L, Goertz L, Bley TA, than a short scan. Phys. Med. Biol. 2002; Gassenmaier T, Grunz JP. Dose reduction potential 47(14):2525–46. in cone-beam CT imaging of upper extremity joints with a twin robotic X-ray system. Sci Rep. 2021 Oct [4] Kunz AS, Patzer TS, Grunz JP, Luetkens KS, Hartung 11;11(1):20176. doi: 10.1038/s41598-021- V, Hendel R, Fieber T, Genest F, Ergün S, Bley TA, 99748-1. PMID: 34635787; PMCID: PMC8505435. Huflage H. Metal artifact reduction in ultra-high- resolution cone-beam CT imaging with a twin [11] Feldle P, Grunz JP, Kunz AS, Patzer TS, Huflage H, robotic X-ray system. Sci Rep. 2022 Sep Hendel R, Luetkens KS, Ergün S, Bley TA, Conrads N. 16;12(1):15549. doi: 10.1038/s41598-022- Weight-bearing gantry-free cone-beam CT of the lumbar spine: Image quality analysis and dose 19978-9. PMID: 36114270. efficiency. Eur J Radiol. 2023 Aug;165:110951. doi: [5] Fransson V, Tingberg A. Dose length product 10.1016/j.ejrad.2023.110951. Epub 2023 Jun 25. determination in cone-beam computed tomography PMID: 37379623. through experimental measurements and dose area product conversion. Proc. SPIE 11595, Medical [12] Grunz JP, Pennig L, Fieber T, Gietzen CH, Imaging 2021: Physics of Medical Imaging, Heidenreich JF, Huflage H, Gruschwitz P, Kuhl PJ, 115952Y. 2021 Feb 15 Petritsch B, Kosmala A, Bley TA, Gassenmaier T. Twin robotic X-ray system in small bone and joint [6] Grunz JP, Gietzen CH, Kunz AS, Weng AM, Veyhl- trauma: Impact of cone-beam computed Wichmann M, Ergün S, Bley TA, Schmitt R, tomography on treatment decisions. Eur Radiol. Gassenmaier T. Twin robotic X-ray system for 3D 2020 Dec 5. cone-beam CT of the wrist: An evaluation of image quality and radiation dose. AJR Am J Roentgenol. [13] Grunz JP, Jordan MC, Schmitt R, Luetkens KS, 2020 Feb;214(2):422-427. Huflage H, Meffert RH, Bley TA, Kunz AS. Gantry- free high-resolution cone-beam CT: Efficacy for [7] Grunz JP, Kunz AS, Gietzen CH, Weng AM, Veyhl- distal radius and scaphoid fracture detection and Wichmann M, Ergün S, Schmitt R, Bley TA, characterization. Acad Radiol. 2023 Jul;30(7):1358- Gassenmaier T. 3D cone-beam CT of the ankle using 1366. doi: 10.1016/j.acra.2022.08.030. Epub 2022 a novel twin robotic X-ray system: Assessment of Sep 25. PMID: 36167629 image quality and radiation dose. Eur J Radiol. 2019 Oct;119:108659. [14] Kunz AS, Schmalzl J, Huflage H, Luetkens KS, Patzer TS, Kuhl PJ, Gruschwitz P, Petritsch B, Schmitt R, [8] Grunz JP, Weng AM, Gietzen CH, Veyhl-Wichmann Bley TA, Grunz JP. Twin robotic gantry-free cone- M, Pennig L, Kunz A, Schmitt R, Ergün S, Bley TA, beam CT in acute elbow trauma radiology. 2023 Gassenmaier T. Evaluation of ultra-high resolution Mar;306(3):e221200. doi: 10.1148/radiol.221200. cone-beam CT prototype of twin robotic Epub 2022 Nov 8. PMID: 36346312.] radiography system for cadaveric wrist imaging. Acad Radiol. 2020 Jul 9:S1076-6332(20)30368-8. 21 White paper · Multitom Rax Real3D for musculoskeletal imaging [15] Patzer TS, Grunz JP, Huflage H, Conrads N, [20] Benz RM, Harder D, Amsler F, Voigt J, Fieselmann A, Veldhoen S, Schmalzl J, Pennig L, Bley TA, Luetkens Falkowski AL et al. Initial assessment of a prototype KS, Kunz AS. Combining gantry-free cone-beam 3D cone-beam computed tomography system for computed tomography with iterative metal artefact imaging of the lumbar spine, evaluating human reduction for surgical follow-up imaging of the cadaveric specimens in the upright position. appendicular skeleton. Eur J Radiol. 2022 Investigative Radiology 2018; 53(12):714-9. Oct;155:110465. doi: 10.1016/j. ejrad.2022.110465. Epub 2022 Aug 10. PMID: [21] Brinch S, Wellenberg RHH, Boesen MP, Maas M, Johannsen FE, Nybing JU, Turmezei T, Streekstra GJ, 35973302. Hansen P. Weight-bearing cone-beam CT: The need [16] Luetkens KS, Grunz JP, Paul MM, Huflage H, for standardized acquisition protocols and Conrads N, Patzer TS, Gruschwitz P, Ergün S, Bley measurements to fulfill high expectations: A review TA, Kunz AS. One-stop shop CT arthrography of the of the literature. Skeletal Radiol. 2023 wrist without subject repositioning by means of Jun;52(6):1073-1088. doi: 10.1007/s00256-022- gantry-free cone-beam CT. Sci Rep. 2022 Aug 04223-1. Epub 2022 Nov 9. Erratum in: Skeletal 24;12(1):14422. doi: 10.1038/s41598-022- Radiol. 2023 Jul;52(7):1431. PMID: 36350387. 18395-2. PMID: 36002544; PMCID: PMC9402709. [22] Hirschmann A, Buck FM, Fucentese SF, Pfirrmann [17] Benz RM, Hirschmann A. 3D Imaging of joints in the CWA. Upright CT of the knee: The effect of weight- upright weight-bearing position using Multitom bearing on joint alignment. Eur Radiol 2015; Rax. J Trauma Treat 2016; 5:291. 25(11):3398–404 [18] Falkowski AL, Kovacs BK, Benz RM, Tobler P, Schön S, Stieltjes B, Hirschmann A. In vivo 3D tomography of the lumbar spine using a twin robotic X-ray system: Quantitative and qualitative evaluation of the lumbar neural foramina in supine and upright position. Eur Radiol. 2020 Oct 29. [19] Winn N, Kaur S, Cassar-Pullicino V, Ockendon M. A novel use of cone beam CT: Flexion and extension weight-bearing imaging to assess spinal stability. Eur Spine J. 2022 Jul;31(7):1667-1681. doi: 10.1007/s00586-022-07233-8. Epub 2022 May 19. 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