"When will I be back?" is the number one question posed by an athlete to the trainer, physical therapist or sports medicine doctor following a sports related injury. At the Hospital for Special Surgery (HSS), a multidisciplinary institution specializing in orthopedics and managing care for numerous professional sports teams, this question is pervasive, and MR is relied upon for answers. Given its excellent soft tissue contrast and sensitivity to osseous stress injuries, MR plays a prominent role in sports medicine including accurate diagnosis and prognostication for return to play.
As in sports, size and speed matter in MR. This is perhaps most true with regards to imaging athletes who may be broad-shouldered and require a wide-bore magnet, or who are in significant pain following a recent injury or surgery and require an accelerated exam. The SIGNA™ Premier 3.0T system, four of which HSS has installed within the past three years, affords both a wide bore and accelerated exam without compromising image quality. The 3.0T system boasts exceptional field homogeneity, which allows the technologist to place the athlete off-isocenter yet still maintain adequate signal-to-noise ratio (SNR), and limits distortion over both small and large fields-of-view. This is particularly important to identify additional injuries, possibly clinically unsuspected, that may be near the edge of the surface coil (Figure 1).
Figure 1.
A 56-year-old runner with acute, plantar left foot pain. (A) Axial inversion recovery (IR) and (B) proton density (PD) images, obtained on a SIGNA™ Premier and reconstructed using AIR™ Recon DL, demonstrate avulsion of the plantar fascia lateral cord (solid arrow) from the fifth metatarsal base (dashed arrow). (C) The sagittal IR image, as part of the same hindfoot MR exam, also reveals marrow edema within the proximal second metatarsal (arrows) at the edge of the FOV. (D) Coronal PD image from a subsequent, dedicated midfoot MR confirms an obliquely oriented fracture through the second metatarsal base (arrow) that was clinically unsuspected.
When evaluating injuries to the wrist, hand and digits, the technologist can also comfortably place the athlete in the supine position, with the arm by the side rather than in the prone superman (arm-over-head) position, and not be concerned about compromising image quality. Additionally, the highperformance gradients of the SIGNA™Premier system provide tight echo spacing for a given bandwidth to reduce blurring. Image sharpness is critical to identifying and characterizing chondral injuries that may accompany meniscal tears, which if not identified and treated promptly can lead to a degenerative cascade of joint damage (Figure 2).
Figure 2.
A 40-year-old runner with left knee pain and swelling for three weeks. (A) Coronal and (B, C) sagittal proton density images obtained on a SIGNA™ Premier and reconstructed using AIR™ Recon DL demonstrate a radial split tear of the medial meniscus posterior horn/root junction with displaced flap (ovals) and concomitant full thickness chondral shear over the medial condyle (arrows).
The SIGNA™ Premier also accommodates a broad complement of extremely flexible and thin AIR™ Coils that enable the injured joint or body region to be comfortably wrapped, thereby bringing coil elements closer to the region of interest and increasing SNR. This is relevant in the context of joint dislocations or bony contractures wherein conventional coils may not otherwise adequately cover the anatomy. The flexibility of the AIR™ Coils also allows them to be placed closer to soft tissue structures, such as the pectoralis and latissimus dorsi, that are frequently injured in high-performance athletes but notoriously difficult to image given their oblique course around the chest wall (Figure 3). The highdensity profile of the AIR™ Coils also accommodates high parallel imaging factors to accelerate acquisitions, which is imperative to mitigate respiratory motion in this region.
Figure 3.
(A,B) Oblique coronal T2-weighted Dixon and (C) proton density of the chest wall in a 29-year-old male with chest pain following bench pressing. Images demonstrate acute myotendinous rupture of the sternal head (arrows) of the pectoralis major. Axial images in the same exam through the glenohumeral joint, at the edge of the FOV,Xdemonstrate a posterior labral tear (C, arrow) that was addressed surgically at the same time as the pectoralis repair. (D) Oblique coronal and (E) axial IR images of a 28-year-old professional baseball pitcher with pain were obtained on a SIGNA™ Premier using AIR™ Coils and reconstructed with AIR™ Recon DL. Images demonstrate high grade insertional tear of the humeral insertion of the latissimus dorsi tendon (oval and arrow).
At HSS, we recently modified our protocols both at 1.5T and 3.0T to include AIR™ Recon DL, a deeplearning reconstruction pipeline that performs denoising, de-ringing and interpolation. The denoising component of the reconstruction has enabled faster image acquisition and higher acquired spatial resolution. At 3.0T, for example, we can scan most joints 40-50% faster while simultaneously improving in-plane spatial resolution by approximately 0.1 mm or throughplane resolution (slice thickness) by 1 mm for most sequences (Figure 4). The time savings can then be used to acquire additional planes of imaging for targeted questions or simply for throughput, which is particularly important during the injury-prone American football season!
Figure 4.
Sagittal PD MR of the ankle joint obtained on a SIGNA™ Premier of the same volunteer demonstrate increased sharpness of the tibiotalar and subtalar cartilage when images are obtained with (A) a matrix size of 512 x 480 and a conventional reconstruction method compared to (B) a matrix size of 640 x 480 and reconstructed using AIR™ Recon DL. The higher spatial resolution acquisition shown in (B) is acquired in 2:45 min. versus 3:55 min. for the lower resolution acquisition shown in (A). In this case, AIR™ Recon DL increased resolution and shortened scan time.
As MR lacks ionizing radiation, it is well-suited for longitudinal evaluation of injury in adolescent athletes. The recent introduction of the threedimensional zero-time-to echo (oZTEo) application, which provides exceptional bone contrast and like CT can be reformatted into any arbitrary plane. For example, in the setting of a shoulder dislocation, a referring physician may order an MR exam primarily to evaluate the extent of soft tissue capsulolabral injury and the extent of osseous impaction injuries by instead requesting an oZTEo sequence as part of the MR study (Figure 5). Additionally, the oZTEo sequence is used to increase the conspicuity of abnormal, soft tissue ossification that can help differentiate acute from chronic injuries, an important distinction in the competitive athlete who may have a long injury history. While soft tissue edema is frequently present in the acute setting, abnormal ossification (or bony deposition) may be seen in the chronic setting and is welldepicted on the oZTEo scan (Figure 6). Furthermore, chronic repetitive injury may result in abnormal osseous offset, or cam-type deformity, at the femoral head/neck junction, often evident in young athletes who place their hip joints under an extreme range of motion. Such a deformity can predispose the athlete to femoroacetabular impingement and early osteoarthritis. Utilization of oZTEo can help detect and measure this type of deformity that may require surgical correction (Figure 7).
Figure 5.
A 55-year-old woman following recent anterior shoulder dislocation. (A) Axial and (B) oblique sagittal proton density images demonstrate (A, arrow) Hill Sachs and (B, arrow) displaced Bankart impaction injuries. (C, D) Accompanying oZTEo images, reformatted from a single acquisition, allow for more conspicuous detection of these fractures, which is important for management.
Figure 6.
(A) Coronal and (C) axial oZTEo and (B, D) CT images of the left hip in a 22-year-old male basketball player. There is punctate ossification (arrows) of the posterosuperior acetabular labrum, compatible with chronic injury/degeneration, that can be reliably diagnosed on the oZTEo sequences.
Figure 7.
(A) Oblique axial CT and (B) oZTEo images of the left hip in a 29-year-old female runner with groin pain. Images demonstrate a cam-type deformity at the femoral head-neck junction with decreased head-neck offset. Measurement of head-neck offset is traditionally performed on CT but can also be performed on oZTEo images.
Returning athletes to the field most efficiently and safely is perhaps the ultimate goal of sports medicine and is an area ripe for research. MR already plays an important role in achieving these objectives, particularly as it relates to determining healing of stress-related osseous and soft tissue injuries. Continued advances in gradient performance, surface coils and pulse sequence designs will make MR even more valuable in assessing suitability of return to play.
