Feasibility, indications, and radiographically confirmed diagnoses of standing extremity cone beam computed tomography in the horse

Equine Standing Multidetector Computed Tomography of the Distal Thoracic Limb and Tarsus Has a Lower Cumulative Radiation Dose than Digital Radiography

Recent technological advancements in CT have improved the ability to scan standing sedated horses. However, the impact of radiation exposure on veterinary staff while scanning the extremities of standing horses using this technique, compared with digital radiography (DR), remains unknown. This study compares the radiation exposure of imaging technicians assisting with multidetector CT (MDCT) and DR of the distal thoracic limb and tarsus in standing horses. Personal dose equivalent was measured on four body locations: thyroid gland, gonads, hand, and feet. Images of the distal thoracic limb (n = 12) and tarsus (n = 12) were obtained from 24 Warmblood horses using DR and MDCT. The DR included four views of the front fetlock (dorsopalmar, lateromedial, dorso45lateral-palmaromedial oblique, and dorso45medial-palmarolateral oblique), three views of the front foot (dorsopalmar, lateromedial and dorso65proximal-palmarodistal oblique) and four views of the tarsus (dorsoplantar, lateromedial, dorso45lateral-plantaromedial oblique and dorso45medial-planterolateral oblique). The MDCT scans included the distal metacarpus to the foot and the tarsus. Noninferiority testing showed lower radiation exposure to the imaging technician during MDCT of the distal thoracic limb and tarsus compared with DR, measured at the thyroid gland, hand, and feet. The radiation exposure to the gonads during MDCT of the thoracic limb was significantly higher than with DR. Nevertheless, the lower cumulative radiation exposure for the assisting imaging technician during MDCT compared with DR suggests that the tested MDCT setup enables advanced imaging of the distal limb in standing sedated horses, offering both reduced radiation exposure and avoiding the patient-related risks of general anesthesia.

Magnetic resonance Imaging for diagnosing and managing deep digital flexor tendinopathy in equine athletes: Insights, advances and future directions

Deep digital flexor (DDF) tendinopathy is a significant cause of lameness and poor performance in equine athletes with substantial implications for their return to athletic performance. Magnetic resonance imaging (MRI) is increasingly integrated into the diagnostic workup of horses with foot pain and has revolutionised the diagnosis and management of these injuries. This review discusses the principles of MRI in the context of deep digital flexor tendon (DDFT) injury, comparing high-field and low-field systems and highlighting the clinical relevance of technical parameters, including field strength and sequence selection, in achieving an accurate diagnosis. This review also critically evaluates how different configurations and/or imaging features of tendon lesions may impact patient prognosis, considers the complementary role of computed tomography and ultrasonography in cases where MRI may not be feasible, and discusses emerging imaging techniques including positron emission tomography (PET)-MRI and quantitative MRI. Lastly, this review underscores the importance of serial imaging to monitor lesion progression and guide rehabilitation, while identifying knowledge gaps and proposing future research directions. Ultimately, a multidisciplinary approach incorporating advanced imaging and tailored rehabilitation is essential to improving clinical outcomes in horses with DDFT injuries.

Comparison of radiography and computed tomography for identification of third metacarpal structural change and associated assessment of condylar stress fracture risk in Thoroughbred racehorses

BACKGROUND

Catastrophic injury has a low incidence but leads to the death of many Thoroughbred racehorses.

OBJECTIVES

To determine sensitivity, specificity, and reliability for third metacarpal condylar stress fracture risk assessment from digital radiographs (DR) and standing computed tomography (sCT).

STUDY DESIGN

Controlled ex vivo experiment.

METHODS

A blinded set of metacarpophalangeal joint DR and sCT images were prepared from 31 Thoroughbreds. Four observers evaluated the condyles and parasagittal grooves (PSG) of the third metacarpal bone for the extent of dense bone and lucency/fissure and assigned a risk assessment grade for condylar stress fracture based on imaging features. Sensitivity and specificity for detection of subchondral structural changes in the condyles and PSG, and for risk assessment for condylar stress fracture were determined by comparison with a reference assessment based on sCT and joint surface examination. Agreement between observers and the reference assessment and reliability between observers were determined. Intra-observer repeatability was also assessed.

RESULTS

Sensitivity for detection of structural change was lower than specificity for both imaging methods and all observers. For agreement with the reference assessment of structural change, correlation coefficients were generally below 0.5 for DR and 0.49-0.82 for sCT. For horses categorised as normal risk on reference assessment, observer assessment often agreed with the reference. Sensitivity for risk assessment was lower than specificity for all observers. For horses with a reference assessment of high risk of injury, observers generally underestimated risk. Diagnostic sensitivity of risk assessment was improved with sCT imaging, particularly for horses categorised as having elevated risk of injury from the reference assessment. Assessment repeatability and reliability was better with sCT than DR.

MAIN LIMITATIONS

The ex vivo study design influenced DR image sets.

CONCLUSIONS

Risk assessment through screening with diagnostic imaging is a promising approach to improve injury prevention in racing Thoroughbreds. Knowledge of sensitivity and specificity of fetlock lesion detection provides the critical guidance needed to improve racehorse screening programs. We found improved detection of MC3 subchondral structural change and risk assessment for condylar stress fracture with sCT ex vivo.

Combined standing low-field magnetic resonance imaging and fan-beam computed tomographic diagnosis of fetlock region pain in 27 sports horses

BACKGROUND

There is no description of comparative magnetic resonance imaging (MRI) and fan-beam computed tomography (CT) findings in the fetlock of lame sports horses.

OBJECTIVES

To document low-field MRI and fan-beam CT diagnoses in the lame and nonlame limbs of sports horses with fetlock region pain, and to evaluate whether combined imaging provides superior information to either technique alone.

STUDY DESIGN

Retrospective descriptive study.

METHODS

Clinical records of sports horses with pain causing lameness localised to the metacarpo/metatarsophalangeal joint region that had undergone fan-beam CT and low-field MRI were reviewed. Images of both lame and nonlame contralateral limbs were assessed subjectively.

RESULTS

Images of 52 limbs (lame n = 31, nonlame n = 21) were analysed. In 16 lame limbs of 13 horses, the most significant abnormality was in the subchondral and trabecular bone of the proximal phalanx (sagittal groove n = 14, medial fovea n = 1, sagittal groove and medial fovea n = 1). All had hyperintense STIR signal that was more extensive than CT abnormalities; CT provided useful information in all limbs. In five lame limbs, the most significant lesion was in the metacarpal condyle(s): an incomplete fracture (n = 1) or resorptive lesions (n = 4); the fracture and two resorptive lesions were not detected using MRI. In nine limbs of eight horses, lesions in multiple locations possibly contributed to pain. In one limb, abnormalities in the medial proximal sesamoid bone and in the palmar ligament were the main findings.

MAIN LIMITATIONS

Small numbers of limbs with specific abnormalities. Comprehensive imaging of the contralateral limb was not performed in all horses. Absence of follow-up information.

CONCLUSIONS

Fan-beam CT and low-field MRI provided complementary information and yielded diagnoses and conclusions in some horses that could not have been achieved when using one modality only. Resorptive subchondral bone lesions in the fetlock may be present without associated low-field MRI abnormalities.

Visualization of anatomical structures in the carpal region of the horse using cone beam computed tomography in comparison with conventional multidetector computed tomography

Introduction

In the diagnostics of orthopedic diseases in the horse, diagnostic imaging often plays a decisive role. Cone beam computed tomography (CBCT) imaging is used in both human and small animal medicine and becoming increasingly popular. To see whether CBCT imaging can be useful in the diagnosis of orthopedic diseases of the carpal region of the horse and to explore possible limitations we compared CBCT images with multidetector computed tomography (MDCT) images of the carpal region of equine cadaveric specimens.

Materials and methods

Twenty-eight forelimbs from fifteen horses, slaughtered for reasons unrelated to this study, were examined. Native and contrast enhanced CBCT and MDCT scans were performed. Anatomical structures were blindly evaluated by three independent experienced observers using a visual scoring system previously reported and adapted to the equine carpal region. A descriptive evaluation was carried out as well as Spearman's rank correlation and interobserver agreement was shown by percent agreement (PA).

Results

Visualization of osseous structures was excellent in both MDCT and CBCT. Articular cartilage could only be assessed in contrast enhanced scans whereby MDCT showed a slightly better visualization than CBCT. Soft tissue structures were generally difficult to assess. An exception were the medial and lateral palmar intercarpal ligament, which could not be visualized in native but were well visualized in contrast enhanced scans in both MDCT and CBCT images.

Discussion/conclusion

For the evaluation of osseous structures and some intraarticular ligaments after contrast enhancement, CBCT serves as a reliable diagnostic imaging modality for the equine carpal region. However, soft tissue structures and cartilage are imaged more reliably using MDCT.

Cone beam computed tomography and cross-sectional anatomy of the region of the fetlock in the horse (Equus caballus)

This study aimed to delineate the detailed anatomy of the metacarpophalangeal (MCP) and metatarsophalangeal (MTP) joints in healthy horses using cone beam computed tomography (CBCT). The fetlock region of 15 cadaveric forelimbs and 14 cadaveric hindlimbs from nine adult horses without orthopaedic disease underwent CBCT scanning. Additionally, arthrography CBCT scans were conducted following intra-articular injection of a radiopaque contrast medium containing blue epoxy resin dye. Subsequently, limbs were frozen and sectioned to visualize anatomical structures in sectional planes corresponding to selected CBCT images. CBCT proved suitable for detailed visualization of the bony components of the fetlock region. Furthermore, the common digital extensor tendon, superficial and deep digital flexor tendons, suspensory ligament, and straight and oblique sesamoidean ligaments were identifiable on CBCT images. However, certain ligaments, such as the collateral sesamoidean ligaments and intersesamoidean ligaments, were not clearly identified. The hyaline cartilage of the MCP and MTP joint facets was assessable on the post-contrast sequence. In cases where a radiographic or ultrasound examination cannot provide a definitive diagnosis and determine the extent of disease, CBCT can provide additional valuable data on the equine MCP and MTP joint. The images obtained in this study can serve as a reference for CBCT examination of the equine MCP and MTP joint.

Visualization of anatomical structures in the fetlock region of the horse using cone beam computed tomography in comparison with conventional multidetector computed tomography

Introduction

Cone-beam computed tomography (CBCT) is regarded as a convenient and suitable alternative to conventional computed tomography. However, in the horse, the quality of obtained data sets needs to be evaluated. Therefore, the aim of this study was to compare the visibility and accessibility of clinically relevant anatomical structures displayed in CBCT and conventional multidetector computed tomography (MDCT).

Materials and methods

Twenty-nine limbs from horses euthanized for reasons unrelated to this study were used. Native and intraarticular contrast scans of the fetlock (CBCT vs. MDCT) were performed. The visibility and accessibility of selected anatomical structures were blindly scored by three independent experienced observers using a scoring system previously reported and adapted to the fetlock joint.

Results

Only minor differences between CBCT and MDCT were identified concerning the diagnostic quality of images for osseous structures. Soft tissue structures were better evaluated on MDCT images. In CBCT as well as in MDCT articular cartilage could only be visualized after intraarticular injection of contrast medium.

Discussion/conclusion

Cone beam computed tomography of the fetlock is a useful and reliable diagnostic tool when evaluating osseous structures and delineating articular cartilage with contrast medium. However, this modality is limited for assessing soft tissues structures.

Cone-beam computed tomography produces images of numerically comparable diagnostic quality for bone and inferior quality for soft tissues compared with fan-beam computed tomography in cadaveric equine metacarpophalangeal joints

Cone-beam computed tomography (CBCT) is an emerging modality for imaging of the equine patient. The objective of this prospective, descriptive, exploratory study was to assess visualization tasks using CBCT compared with conventional fan-beam CT (FBCT) for imaging of the metacarpophalangeal joint in equine cadavers. Satisfaction scores were numerically excellent with both CBCT and FBCT for bone evaluation, and FBCT was numerically superior for soft tissue evaluation. Preference tests indicated FBCT was numerically superior for soft tissue evaluation, while preference test scoring for bone was observer-dependent. Findings from this study can be used as background for future studies evaluating CBCT image quality in live horses.

Computed tomographic evaluation of the distal limb in the standing sedated horse: Technique, imaging diagnoses, feasibility, and artifacts

In several veterinary institutions, adjustments of CT machines have been made that allow for imaging of the standing horse. The risk of general anesthesia is eliminated and the shorter scan completion time reduces cost to clients. The objective of this retrospective, analytical study was to evaluate the technique, imaging diagnoses, feasibility, and image artifacts of multi-slice helical CT of horses' distal limbs acquired under standing sedation. The CT images of 250 horses of various breeds, aged 3-23 years, that underwent standing distal limb CT were evaluated. Three observers assessed the CT images for artifacts and inter-observer agreement was calculated. Eighty-six percent (95% confidence interval (CI), 81-90) of the scans were carried out on the forelimbs, while 14% (95% CI, 10-19) were of the hindlimbs. A total of 65% (95% CI, 59-71) of horses that underwent standing sedated CT had single imaging diagnoses. Seventy-one percent (95% CI, 65-77) of the cases had unilateral lesions, 27% (95% CI, 22-33) had bilateral lesions and 2% (95% CI, 1-4) had no diagnosed lesions. The average CT acquisition time was 17.5 minutes (range = 15-20). The average number of acquisitions per horse was 1.7 (median = 1; range = 1-4). There was good to excellent agreement between all three observers for the presence of motion artifact in the metacarpo/metatarsophalangeal joints, identification of marked beam hardening artifact, mild solar/ skin dirt, and photon starvation artifact (kappa 0.61-0.80). No complications were encountered. Standing examination of the distal limb achieved diagnostic image quality that was obtained with minimal acquisition attempts and in a timely manner.

Use of a novel helical fan beam imaging system for computed tomography of the distal limb in sedated standing horses: 167 cases (2019–2020)

OBJECTIVE

To evaluate the diagnostic capabilities of a novel helical fan beam CT system used for imaging of horses with a range of clinical distal limb problems.

ANIMALS

167 horses.

PROCEDURES

Medical records were reviewed of horses presented for CT of the distal limb at 2 university-based veterinary hospitals. The following data were recorded: age, sex, breed, presenting complaint, sedation used for imaging, scanning time, procedure time, other diagnostic imaging methods performed, imaging diagnosis, clinical diagnosis, and complications during imaging.

RESULTS

Most horses were Thoroughbreds and Quarter Horses. Procedure times ranged from 15 to 40 minutes, with scanning completed in 15 to 45 seconds for each region of interest. The foot or pastern region was commonly scanned (88/167 [53%] horses), with navicular bone disease diagnosed in 42 of 88 (48%) horses. The fetlock region was also commonly scanned (42/167 [40%] horses), with palmar or plantar osteochondral disease diagnosed in 17 of 42 (40%) horses. Horses were compliant during scanning, and no complications with sedation or damage to the scanner occurred. A specific imaging diagnosis for the lameness was achieved more frequently with CT imaging (166/167 [99%]) than with planar digital radiography (26/58 [45%]).

CLINICAL RELEVANCE

The helical fan beam CT system could be used safely to scan sedated standing horses from the carpal or tarsal region distally. Subjectively, the machine was easy to operate, allowing CT to be incorporated into lameness investigations. CT imaging was very likely to result in a clinical diagnosis in horses with distal limb lameness.

When radiography and ultrasonography are not enough: the use of computed tomography and magnetic resonance imaging for equine lameness cases

MRI and CT have enhanced our diagnostic abilities for equine lameness beyond what is available using radiography and ultrasonography. This has allowed veterinarians to better prognosticate and treat lameness conditions, improving patient outcomes. This article discusses the basic principles behind MRI and CT, their advantages and disadvantages, the different types of equipment available for clinical use in horses, the typical diagnostic workup prior to pursuing advanced imaging, and common regions where MRI and CT are used clinically. The companion Currents in One Health by Spriet, AJVR, July 2022, discusses even more advanced equine imaging in the form of positron emission tomography. Combined, these future directions of MRI, CT, and positron emission tomography may include improved ability to image standing horses or screen for injury prevention.

Other Clinical Problems of the Equine Foot

Many disorders affect the equine foot, and many hoof problems have multiple predisposing causes. Surgery may be necessary after conservative management has failed. Diseases of the hoof capsule may seem simple, but their effect on performance can be long-lasting and healing is often prolonged. Diagnosis of problems within the hoof capsule is enhanced with the use of computed tomography and MRI. The prognosis of fractures has improved with strategic placement of lag screws across fracture planes using aiming devices and advanced intraoperative imaging techniques. Collaboration between the clinician and a skilled farrier is important for successful management of hoof disorders.

Equine flexor tendon imaging part 2: Current status and future directions in advanced diagnostic imaging, with focus on the deep digital flexor tendon

Flexor tendon injuries are a common cause of lameness and early retirement in equine athletes. While ultrasonography is most frequently utilised, advanced diagnostic imaging modalities are becoming more widely available for detection and monitoring of flexor tendon lesions. Part two of this literature review details current experience with low- and high-field magnetic resonance imaging (MRI) and computed tomography (CT) for the diagnosis of equine flexor tendinopathy with a focus on the deep digital flexor tendon. Implications of the 'magic angle' artefact as well as injection techniques and the use of contrast media are discussed. Future developments in tendon imaging aim to gain enhanced structural information about the tendon architecture with the prospect to prevent injury. Techniques as described for the assessment of the human Achilles tendon including ultra-high field MRI and positron emission tomography are highlighted.