Imaging of Ulnar-Sided Wrist Pain

Bilateral lunotriquetral coalition: a dynamic four-dimensional computed tomography technical case report

Lunotriquetral coalitions are the most common form of carpal coalition wherein the cartilage between the lunate and triquetrum ossification centers failed to undergo apoptosis. This technical case report examines the arthrokinematics of bilateral lunotriquetral coalitions with dissimilar Minnaar types in one participant with one asymptomatic wrist and one wrist with suspected distal radioulnar joint injury. Static and dynamic (four-dimensional) CT images during pronosupination were captured using a photon-counting detector CT scanner. Interosseous proximity distributions were calculated between the lunotriquetral coalition and adjacent bones in both wrists to quantify arthrokinematics. Interosseous proximity distributions at joints adjacent to the lunotriquetral coalition demonstrate differences in median and minimum interosseous proximities between the asymptomatic and injured wrists during resisted pronosupination. Altered kinematics from lunotriquetral coalitions may be a source of ulnar-sided wrist pain and discomfort, limiting the functional range of motion. This case report highlights potential alterations to wrist arthrokinematics in the setting of lunotriquetral coalitions and possible associations with ulnar-sided wrist pain, highlighting anatomy to examine in radiographic follow-up. Furthermore, this case report demonstrates the technical feasibility of four-dimensional CT using photon-counting detector technology in assessing arthrokinematics in the setting of variant wrist anatomy.

Ulnar Variance in Athletes: A Scoping Review

CONTEXT

Ulnar variance (UV) is a measurement of the relative locations of the radius and ulna that may become perturbed in athletic populations. Positive UV can be associated with wrist pathologies often treated conservatively or surgically and may result in interruption of sports participation.

OBJECTIVE

This scoping review aims to summarize diagnostic measures of UV in athletes, describe its relation to separate wrist conditions, and present treatment strategies for symptomatic UV.

DATA SOURCES

A systematic search was created and modified for PubMed, CINAHL, Embase, and SPORTDiscus including articles from inception until February 2, 2022.

STUDY SELECTION

Articles including UV characterization, imaging modality style, and an athletic population were searched across multiple databases.

STUDY DESIGN

A scoping review was designed to identify the methods for imaging UV in athletic populations following the PRISMA Extension for Scoping Reviews (PRISMA-ScR).

LEVEL OF EVIDENCE

Level 4.

DATA EXTRACTION

The specific athletic population, imaging modality, measurement style, wrist pathology association, and surgical management of UV were extracted.

RESULTS

A total of 4321 records were screened independently for eligibility: 22 met inclusion criteria. Eight sports comprised the analysis. All studies referenced conventional radiography to diagnose UV; 50% specified the posteroanterior, 18.2% anteroposterior, and 13.6% pronated, gripping radiographs. Hafner's method (7×), Palmer's technique (2×), and the method of perpendiculars (3×) were used to measure UV. Athletes displayed more positive UV than nonathletes and UV became more positive over time in longitudinal studies. Triangular fibrocartilage complex tears, focal lunate necrosis, and ulnar abutment were associated with positive UV. Ulnar shortening osteotomy was the most performed operation for positive UV.

CONCLUSION

Conventional radiography is the gold standard for imaging UV in athletes. Hafner's method is the most commonly used radiograph measurement technique. Wrist pathology in athletic populations may indicate positive UV in need for operative management.

Dynamic Computed Tomography of the Distal Radioulnar Joint Versus Magnetic Resonance Imaging in Detecting Foveal Tears of the Triangular Fibrocartilage Complex

BACKGROUND

Diagnosis of foveal triangular fibrocartilage complex (TFCC) tears remains difficult. The purpose of this study was to evaluate whether dynamic computed tomography (CT) of the distal radioulnar joint (DRUJ) has a higher sensitivity in detecting foveal tears of the TFCC when compared with magnetic resonance imaging (MRI).

METHODS

A database query identified all patients above the age of 18 years with suspected foveal TFCC injuries who underwent bilateral dynamic CT imaging of the DRUJ, static 3T MRI, and subsequent wrist arthroscopy. All patients had evidence of foveal tenderness on clinical examination. The imaging results were validated with wrist arthroscopy.

RESULTS

Twelve patients with a mean age of 31 years (range, 18-53 years) were identified. Eight patients were diagnosed with a complete foveal detachment of the TFCC on wrist arthroscopy. Of the 8 patients with a foveal tear on DRUJ arthroscopy, only 3 had a preoperative physical examination suggestive of DRUJ instability. Magnetic resonance imaging identified foveal injuries in 4 of these 8 patients (sensitivity, 50%), and 3 of these were identified as only partial tears. Dynamic CT identified instability of DRUJ in 6 of 8 patients (sensitivity, 75%). Seven of 8 patients had imaging findings suggestive of a foveal tear when including either MRI or CT imaging (sensitivity, 88%). Of the 4 patients with an intact foveal attachment on arthroscopy, 3 (specificity, 75%) had a stable DRUJ on CT and all 4 (specificity, 100%) had an intact foveal attachment on MRI.

CONCLUSION

Sixty-two percent of patients with foveal tears on arthroscopy have a stable DRUJ on clinical examination. When combining MRI and dynamic CT imaging of the DRUJ, the sensitivity of detecting a foveal TFCC tear approaches 88% compared with a gold standard of wrist arthroscopy.

How to Report: Wrist MRI

Knowledge of the imaging anatomy of the wrist is essential for reporting magnetic resonance imaging (MRI). This familiarity should include the carpal bones, tendons (extensor and flexor compartments), triangular fibrocartilage complex (TFCC), intrinsic and extrinsic ligaments, and nerves, especially the median and ulnar nerves. Limitations of MRI in visualizing these structures, particularly the intrinsic ligaments and the TFCC, need to be considered. This article outlines the main features to comment on when reporting common conditions of the wrist on MRI, with some examples of terminology that can be used to describe these abnormalities.

Advanced Imaging of Ulnar Wrist Pain

Ulnar-sided wrist pain can be a diagnostic challenge for clinicians and radiologists. The ulnar wrist has complex morphology and is composed of many small bone and soft tissue structures. Within these structures, a wide variety of pathologic conditions can occur. To successfully diagnose and treat these pathologic conditions, clinicians and radiologists must have a strong understanding of the advanced imaging techniques available to them. In this review, the authors present a brief review of the normal ulnar wrist anatomy, discuss the differential diagnosis of ulnar-sided wrist pain, and examine the indications for different advanced imaging modalities.

Ulnar-Side Wrist Pain Management Guidelines: All That Hurts is Not the TFCC!

BACKGROUND

Ulnar-sided wrist pain is a common clinical problem, most often misdiagnosed as triangular fibrocartilage complex (TFCC) injury. It may be frustrating to the patient, as one may end up wearing a wrist splint for an unusually long period, disrupting their routine.

PURPOSE

Because of the dilemmas in the diagnosing the cause of ulnar-sided wrist pain, various algorithms have been suggested but it is an individual's choice to do a systematic assessment and follow in their routine clinical practice. We propose the 'storey concept' for examining the ulnar side of the wrist, with ulnar styloid as the reference point. The lower storey identifies the pathologies of the DRUJ, the intermediate storey identifies the pathologies of the radiocarpal joint and the upper storey identifies the pathologies of midcarpal and carpometacarpal joint.

CONCLUSION

Also, it is important to ramify the cause of pain into stable or unstable wrist, with or without arthritis, as this will guide us in managing the pain arising from distal radioulnar joint. In addition to methodical clinical examination, ideal radiographs and high-resolution MRI are critical to diagnose wrist pathologies. The role of wrist arthroscopy has consistently increased, and complements in both diagnosis and treatment of wrist pain especially in ambiguous situations.

Acute Distal Radioulnar Joint Instability: Evaluation and Treatment

This article reviews the anatomy and mechanics of pronation and supination (axial rotation) of the forearm through the distal radioulnar joint (DRUJ), and the proximal radioulnar joint (PRUJ). Injuries to the bones and/or ligaments of the forearm, wrist, or elbow can result in instability, pain, and limited rotation. Acute dislocations of the DRUJ commonly occur along with a fracture to the distal radius, radial metadiaphysis, or radial head. These injuries are all caused by high-energy trauma. Outcomes are predicated on anatomic reduction and restoration of stability to the DRUJ and PRUJ with or without ligamentous repair or reconstruction.

Wrist Arthroscopy in Athletes

Arthroscopy is a surgical technique whose indication for wrist injuries has grown in recent years. Athletes are subject to traumatic injury to the wrist due to training overload or the intensity of the activity during competition. The need of a quick return to sports practice makes arthroscopy a very useful minimally invasive technique in these situations. The authors present indications of sports-related injuries to the wrist that can be treated by arthroscopy. A literature review is also presented.

Comparison between conventional MRI and MR arthrography in the diagnosis of triangular fibrocartilage tears and correlation with arthroscopic findings

PURPOSE

The triangular fibrocartilage complex is one of the most important stabilizers of the wrist and a defect in its anatomical structure is a possible cause of ulnar sided wrist pain. The aim of this study is to compare the diagnostic accuracy between conventional MRI and MR arthrography (MRA) in the depiction of triangular fibrocartilage complex (TFCC) tears.

METHODS-MATERIALS

A total of 60 patients with clinical findings that suggested TFCC tears underwent wrist MRI and MRA. All the MRI and MRA results were compared with the arthroscopic findings.

RESULTS

40 tears were confirmed by arthroscopy. 38/40 tears were identified by MRA while MRI identified 26/40 tears. There were also 8 false positives and 13 false negative results identified by MRI. Two false negative results were identified by MRA. No false positive results were identified.

CONCLUSION

MR arthrography is more sensitive and specific method in terms of the diagnosis of TFCC tears compared to conventional wrist MRI. There was no difference in the diagnostic accuracy between wrist arthroscopy and MRA.

Current perspectives in conventional and advanced imaging of the distal radioulnar joint dysfunction: review for the musculoskeletal radiologist

Distal radioulnar joint (DRUJ) dysfunction is a common cause of ulnar sided wrist pain. Physical examination yields only subtle clues towards the underlying etiology. Thus, imaging is commonly obtained towards an improved characterization of DRUJ pathology, especially multimodality imaging, which is frequently resorted to arrive at an accurate diagnosis. With increasing use of advanced MRI and CT techniques, DRUJ imaging has become an important part of a musculoskeletal radiologist's practice. This article discusses the normal anatomy and biomechanics of the DRUJ, illustrates common clinical abnormalities, and provides a comprehensive overview of the imaging evaluation with an insight into the role of advanced cross-sectional modalities in this domain.

Pisiform malalignment associated with distal radius fractures

BACKGROUND

The association of scaphoid or other carpal bone fractures with distal radius fractures is frequently reported, whereas few studies have described pisiform malalignment associated with distal radius fractures. The purpose of this study was to investigate the frequency and characteristics of pisiform malalignment associated with distal radius fractures.

METHODS

We performed a retrospective study by reviewing the data of 152 consecutive patients with a mean age of 63 years who were treated surgically for distal radius fractures during a five-year period. We evaluated the pisotriquetral joint via preoperative sagittal computed tomography (CT) and assessed pisiform malalignment. Pisiform malalignment was defined as follows: (1) wide type, joint space ≥4.0 mm; (2) non-parallel type, loss of parallelism of the joint surface of ≥20°; or (3) overriding type, proximal or distal overriding of the pisotriquetral joint ≥2.0 mm. We investigated the relationship between pisiform malalignment and the patterns of distal radius fractures. Pisiform malalignment was assessed using postoperative CT to determine whether it had been reduced.

RESULTS

Pisiform malalignment was observed in 48 cases involving 44 patients with a mean age of 58 (17-81) years. The patients included 16, 17, and 15 cases of the wide type, non-parallel type, and overriding type, respectively. Distal radius fractures with dorsal displacement exhibited pisiform malalignment significantly more frequently than those with volar displacement. No significant difference was noted between intra- and extra-articular fractures or between patients with and without distal ulnar fractures. Among the 22 pisiform malalignment cases assessed via postoperative CT, 15 cases were reduced, and 7 cases remained malaligned. The non-parallel type exhibited the lowest reduction rate among the 3 types.

CONCLUSIONS

Among distal radius fractures, 29% were complicated by pisiform malalignment. Distal radius fractures with dorsal displacement exhibited a significantly increased frequency of pisiform malalignment compared to those with volar displacement.

Dynamic ulnar impaction syndrome in tennis players: report of two cases

In this report, two tennis players with symptoms of ulnar impaction syndrome are reviewed. Both players have neutral ulnar variance. These cases represent dynamic ulnar impaction syndrome, when the impact between ulna and carpus occurs during conditions of pronated grip. The literature and the treatment of these two cases are discussed.

Diagnostic modalities for distal radioulnar joint

The first imaging modality in patients suspected of distal radioulnar joint pathology should be conventional radiography to exclude or diagnose wrist pathology including osteoarthritis, rheumatoid arthritis, calcium pyrophosphate deposition disease, (healed) fractures, or impaction syndromes. When conventional radiography is inconclusive, high resolution 3 Tesla magnetic resonance imaging is advised. We provide a broad overview of the literature regarding the use of intra-articular contrast both with computed tomography (CTA) or magnetic resonance imaging (MRA). Conventional arthrography and unenhanced computed tomography are not indicated. This article discusses the most useful imaging techniques in terms of clinical indications, patient positioning, technical imaging requirements, and diagnostic performance in patients with suspected distal radioulnar joint pathology. Furthermore, the most prevalent pathologies are discussed, with the focus on imaging characteristics in both stable and unstable distal radioulnar joints.

Imaging of Sports-related Hand and Wrist Injuries: Sports Imaging Series

Hand and wrist injuries are common occurrences in amateur and professional sports and many of them are sport-specific. These can be divided into two categories: traumatic injuries and overuse injuries. The aim of this article is to review the most common hand and wrist sports-related lesions. Acute wrist injuries are predominantly bone fractures, such as those of the scaphoid, hamate hook, and ulnar styloid. Ligament lesions are more challenging for radiologists and may lead to carpal instability if undiagnosed. Overuse wrist injuries are mainly represented by tendinous disorders, with De Quervain syndrome and extensor carpi ulnaris tendon disorders being the most common among them; however, there are other possible disorders such as impaction syndromes, stress fractures, and neurovascular lesions. Finally, finger lesions, including closed-tendon injuries (mallet and boutonniere injuries, jersey finger, and boxer's knuckle), flexor pulley injuries, and skier's thumb, should also be detected. (©) RSNA, 2016 Online supplemental material is available for this article.

[Detection of intrinsic ligament and TFCC lesions of the wrist. Direct versus indirect MRI arthrography]

BACKGROUND

The purpose of this study was to validate the diagnostic value of direct magnetic resonance imaging (dMRI) arthrography and indirect MRI (iMRI) arthrography concerning intrinsic ligament injuries and tears of the triangular fibrocartilage complex (TFCC).

PATIENTS AND METHODS

A randomized prospective trial was conducted with patients who presented with wrist pain potentially due to carpal lesions and 10 patients aged 19-60 years (3 female and 7 male) were included. Between the clinical examination and the diagnostic and therapeutic arthroscopy, dMRI and iMRI arthrography were performed for the diagnostics of injuries of the intrinsic ligaments or the TFCC. The results of dMRI and iMRI arthrography were evaluated by two radiologists blinded to the injuries of the patients and a consensus was reached. The results were compared with the findings obtained by arthroscopy.

RESULTS

In the arthroscopy five lesions of the scapholunate ligament (SL), one of the lunotriquetral ligament (LT) and seven of the TFCC were identified. The sensitivity of iMRI and dMRI for carpal ligament lesions (SL and LT) was low (50 %) whereas the specificity was high (93 %). For injuries of the TFCC the sensitivity (up to 100 %) and the specificity (100 %) were both excellent. The area under the curve (AUC) in the receiver operating characteristics (ROC) analysis was high for TFCC lesions in both dMRI and iMRI arthrography.

CONCLUSION

Indirect MRI arthrography is a suitable method for detection of injuries of the TFCC and intrinsic ligaments of the wrist with good sensitivity and specificity. Despite the low number of patients the results of this study showed that there were no essential differences between dMRI and iMRI arthrography with respect to the diagnostic value for carpal injuries of the wrist.

The role of imaging in diagnosing diseases of the distal radioulnar joint, triangular fibrocartilage complex, and distal ulna

OBJECTIVE

The purpose of this article is to review the anatomy, biomechanics, and multimodality imaging findings of common and uncommon distal radioulnar joint (DRUJ), triangular fibrocartilage complex, and distal ulna abnormalities.

CONCLUSION

The DRUJ is a common site for acute and chronic injuries and is frequently imaged to evaluate chronic wrist pain, forearm dysfunction, and traumatic forearm injury. Given the complex anatomy of the wrist, the radiologist plays a vital role in the diagnosis of wrist pain and dysfunction.

A new definition of wrist sprain necessary after findings in a prospective MRI study

INTRODUCTION

Wrist injuries with negative X-rays are diagnosed as acute wrist sprains. The prognosis is usually good, but some patients suffer from long-lasting pain and reduced wrist function, probably due to missed diagnosis followed by inappropriate treatment. The aim of this study was to investigate acute wrist sprains with MRI to detect the pathoanatomy of the injury.

PATIENTS AND METHODS

This prospective magnetic resonance imaging (MRI) study included patients between 18 and 49 years, who attended the Accident and Emergency Department (A&E) Bergen, Norway, after sustaining an acute wrist trauma within the previous week. Initial X-rays of the wrist were normal. MRI was done within a median of 1 day (range 0-31 days) after the trauma, 80% within 4 days. The study period lasted from 5 November 2009 to 4 November 2010.

RESULTS

A total of 155 acute MRIs were done, out of which 30 were completely normal. Patients with positive MRI had a median of two (range 0-8) pathological findings. We found 54 fractures and 56 bone bruises, mostly located to the radius followed by the scaphoid, the triquetrum, the capitate and the lunate. There were 73 soft-tissue injuries, which included 15 injuries to the triangular fibrocartilage complex (TFCC) and five scapho-lunate (SL) ligament lesions.

CONCLUSIONS

Wrist sprain is an inaccurate diagnosis. In four out of five patients with normal X-rays, MRI identified pathological findings and a large variety of injuries in different structures. We suggest that wrist sprain should be defined as "occult partial or complete soft tissue (ligament, tendon, muscle) or bony injury in relation to a trauma with negative X-ray". The MRI findings led to a more differentiated treatment in more than a third of the patients. We recommend that MRI should be considered as a part of an early investigation, especially when the wrist pain does not settle within the first couple of weeks.

Diagnostic accuracy of magnetic resonance imaging and magnetic resonance arthrography for triangular fibrocartilaginous complex injury: a systematic review and meta-analysis

BACKGROUND

Triangular fibrocartilaginous complex (TFCC) tears are common sources of ulnar-sided wrist pain and resultant functional disability. Diagnosis is based on the history and clinical examination as well as radiographic evidence of a TFCC central perforation or a radial/ulnar tear. The purpose of this study was therefore to evaluate the diagnostic accuracy of magnetic resonance imaging (MRI) and magnetic resonance arthrography (MRA) in the detection of TFCC injury in the adult population.

METHODS

Published and unpublished literature databases were searched. Two-by-two tables were constructed to calculate the sensitivity and specificity of MRI or MRA investigations against arthroscopic outcomes. Pooled sensitivity and specificity values and summary receiver operating characteristic curve evaluations were performed. The methodological quality of each study was assessed with use of the QUADAS (Quality Assessment of Diagnostic Accuracy Studies) tool.

RESULTS

Twenty-one studies were included in the review, and these series included a total of 982 wrists. On meta-analysis, MRA was superior to MRI in the investigation of full-thickness TFCC tears, with a pooled sensitivity of 0.75 and a pooled specificity of 0.81 for MRI compared with 0.84 and 0.95, respectively, for MRA. MRA and MRI performed at greater field strengths were reported to have greater sensitivity and specificity than those performed at lower field strengths. There were insufficient data to assess the diagnostic test accuracy for partial-thickness TFCC tears.

CONCLUSIONS

Given its acceptable diagnostic test accuracy, it is recommended that MRA, rather than MRI, be performed in when there are questions about the diagnosis and subsequent management of patients with ulnar-sided wrist pain.

Subluxation of the distal radioulnar joint as a predictor of foveal triangular fibrocartilage complex tears

PURPOSE

The triangular fibrocartilage complex (TFCC) with its ulnar foveal attachment is the primary stabilizer of the distal radioulnar joint (DRUJ). The purpose of this study was to describe a technique for measuring the degree of subluxation of the DRUJ in wrist magnetic resonance imaging (MRI) examinations to predict tears involving the foveal attachment of the TFCC.

METHODS

We measured DRUJ geometry in wrist MRI examinations of 34 patients who were found to have foveal TFCC tears at surgery. We compared the results with DRUJ geometry in 11 asymptomatic controls. Subluxation of the ulnar head was assessed using transaxial MRI images obtained at the level of the DRUJ with the wrist in pronation. We quantified subluxation with a line spanning the sigmoid notch of the radius and a perpendicular line through the center of curvature of the articulating surface of the ulna. We calculated the ratio of the lengths of the dorsal and volar segments and normalized it to the center of the sigmoid notch.

RESULTS

A total of 34 patients with intraoperatively confirmed tears of the foveal attachment of the TFCC had a mean dorsal ulnar subluxation measurement of 16% ± 4%, whereas the 11 controls had a mean subluxation measurement of 5% ± 4%.

CONCLUSIONS

The results confirm the hypothesis that subluxation of the ulnar head relative to the sigmoid notch of the radius, as assessed by MRI with the wrist in pronation, is a predictor of tears of the foveal attachment of the TFCC.

TYPE OF STUDY/LEVEL OF EVIDENCE

Diagnostic II.

Ulnar-sided wrist pain. II. Clinical imaging and treatment

Pain at the ulnar aspect of the wrist is a diagnostic challenge for hand surgeons and radiologists due to the small and complex anatomical structures involved. In this article, imaging modalities including radiography, arthrography, ultrasound (US), computed tomography (CT), CT arthrography, magnetic resonance (MR) imaging, and MR arthrography are compared with regard to differential diagnosis. Clinical imaging findings are reviewed for a more comprehensive understanding of this disorder. Treatments for the common diseases that cause the ulnar-sided wrist pain including extensor carpi ulnaris (ECU) tendonitis, flexor carpi ulnaris (FCU) tendonitis, pisotriquetral arthritis, triangular fibrocartilage complex (TFCC) lesions, ulnar impaction, lunotriquetral (LT) instability, and distal radioulnar joint (DRUJ) instability are reviewed.

Diagnostic comparison of 1.5 Tesla and 3.0 Tesla preoperative MRI of the wrist in patients with ulnar-sided wrist pain

PURPOSE

The diagnostic sensitivity, specificity, and accuracy of 1.5 Tesla (T) and of 3.0T magnetic resonance imaging (MRI) are correlated with wrist arthroscopy findings in patients presenting with ulnar-sided wrist pain.

METHODS

The records and diagnostic MRI scans of 102 patients who presented between 1997 and 2006 with ulnar-sided wrist pain were evaluated. Preoperative MRI scans at 1.5T (n = 70) and 3.0T (n = 32) were evaluated by 2 experienced musculoskeletal radiologists with different levels of experience who were blinded to the arthroscopic findings. Preoperative MRI findings for the triangular fibrocartilage complex (TFCC), scapholunate, ulnotriquetral, and lunotriquetral ligaments were recorded and compared with findings at diagnostic arthroscopy. The sensitivity, specificity, and accuracy were calculated for both the 1.5T and 3.0T preoperative MRI scans. Statistical comparisons were made using chi-square test and JMP 6.0 software.

RESULTS

A tear of the TFCC was identified retrospectively on 1.5T images in 49 of 58 patients and on 3.0T images in 15 of 16 patients. Compared with the gold standard of arthroscopy, 1.5T wrist MRI in this patient population had a sensitivity of 85%, a specificity of 75%, and an accuracy of 83% for reader 1 for the detection of a tear of the TFCC. In the same patient population, 3.0T wrist MRI had a sensitivity of 94%, a specificity of 88%, and an accuracy of 91% for reader 1. For reader 2, the improvement in sensitivity for the lunotriquetral ligament between the 1.5T and 3.0T images was statistically significant.

CONCLUSIONS

The sensitivity, specificity, and accuracy of 3.0T wrist MRI for the TFCC is consistently higher compared with those of 1.5T wrist MRI. The trend suggests that 3.0T wrist MRI provides improved capability for detection of TFCC injuries. Given the available sample size, however, the confidence intervals around the point estimates are wide and overlapping. Further studies are needed to confirm or refute our results of the estimated sensitivity, specificity, and accuracy parameters.

Modern imaging of the hand, wrist, and forearm

A review of the current state of the relevant diagnostic imaging technologies and methods and their clinical application in imaging common conditions of the hand, wrist, and forearm is presented. Evolving and future imaging technologies are also considered.