T1ρ Magnetic Resonance Imaging Research Articles

T1ρ Magnetic Resonance Imaging to Assess Cartilage Damage After Primary Shoulder Dislocation

Objectives:Anterior shoulder dislocation is a common injury with an estimated incidence of 23.1/100,000 person-years. In anterior dislocation, associated injuries typically involve the anteroinferior glenoid and posterosuperior humeral head. Patients who suffer a shoulder dislocation are at higher risk of developing glenohumeral arthropathy; the risk increases with recurrent dislocations. However, little is known about the initial cartilage damage after a primary shoulder dislocation. T1ρ is a magnetic resonance imaging (MRI) modality that allows quantification of cartilage proteoglycan content and can be used to detect physiologic changes in cartilage without intravenous contrast. Cartilage degeneration is characterized by decreased proteoglycan content, which results in an increased T1ρ relaxation constant. T1ρ MRI can detect differences in knee cartilage between Kellgren-Lawrence grades as well as acetabular cartilage changes in patients with femoroacetabular impingement. The objectives of this prospective study were to determine if T1ρ MRI can detect cartilage damage following primary shoulder dislocation and to assess for patterns in cartilage damage in anterior dislocations.Methods:This study received Institutional Review Board approval. Nine patients (mean age 31.3 years, range 20-59) who had sustained anterior shoulder dislocations underwent a 3T T1ρ MRI within ten days of their injury. Five control patients without prior dislocation or glenohumeral arthritis also underwent 3T T1ρ MRI. The T1ρ relaxation constant was determined for the entire glenoid and humeral head for dislocation and control patients. In addition, the glenoid was divided into nine zones, and T1ρ values were determined for each zone in dislocated and control patients to assess for differences between the two groups and to identify any patterns in cartilage damage in dislocated patients.Results:T1ρ mapping of glenohumeral cartilage in dislocated shoulders showed significant cartilage damage. Overall T1ρ values were increased in dislocated shoulders compared to control shoulders for glenoid and humeral head cartilage (53.46±0.99 vs. 36.60±3.6 and 46.50±1.1 vs. 36.19±1.7, respectively; mean±SEM, p = 0.0025, Fig. 1A). Furthermore, T1ρ values were significantly increased in all glenoid zones in dislocated shoulders compared to controls except for posterior/inferior (p = 0.064 for posterior/inferior, p < 0.02 for all other zones, Fig. 1B). However, there were no significant differences in T1ρ values between glenoid zones in dislocated shoulders across patients, reflecting widespread cartilage damage.Conclusion:T1ρ MRI is sensitive for detecting cartilage damage and proteoglycan loss after shoulder dislocation. T1ρ values were significantly higher (lower proteoglycan content) in nearly all glenoid zones in dislocated shoulders compared to controls and approached significant difference in the posterior/inferior zone. Although the anteroinferior glenoid and posterosuperior humeral head are characteristically affected in anterior dislocation, cartilage damage was surprisingly more widespread and affected the entire joint. The etiology of diffuse cartilage damage is unknown but may be due to hemarthrosis or additional trauma to the joint during humeral head relocation. Longer-term studies are needed to determine if the initial cartilage damage persists and if cartilage damage worsens with repeat dislocations.

Pingyangmycin-induced in vivo lumbar disc degeneration model of rhesus monkeys.

Animal experimental study. To establish a slowly progressive and reproducible intervertebral disc degeneration model and determine the performance of T1ρ magnetic resonance imaging in the evaluation of disc degeneration. Recently, one of the hotspots of research efforts was related to management of early stage of disc degeneration. To our knowledge, a functional animal model that mimics ischemic and slowly progressive disc degeneration of humans does not exist. The subchondral bone adjacent to the lumbar intervertebral discs (from L3-L4 to L6-L7) of 8 rhesus monkeys was randomly injected with 4 mL of Pingyangmycin (PYM) solution (1.5 mg/mL, PYM), or 4 mL of phosphate buffered saline (Vehicle control), or exteriorized but not injected anything (Sham), respectively. The degenerative process was investigated by using radiography and T1ρ magnetic resonance imaging at 1, 3, 6, 9, 12, and 15 months postoperatively. Histological scoring, immunohistochemistry, and real-time polymerase chain reaction were performed at 15 months. The mean T1ρ values of nucleus pulposus and annulus fibrosus in the PYM group significantly decreased after 3 and 6 months, respectively, followed by slow decrease, and the histological score was significantly higher at 15 months, compared with the control groups. The results of molecular analysis revealed a significant increase matrix metalloprotease-3, A disintegrin and metalloproteinase with thrombospondin motifs -5, tumor necrosis factor α, interleukin-1β, interleukin-6 expressions, and marked reduction in aggrecan, type II collagen, von Willebrand factor expressions at the messenger RNA levels in the PYM group. Spearman correlation analysis of Pfirrmann grades showed significantly inverse correlation with T1ρ values of nucleus pulposus and annulus fibrosus (r = -0.634, -0.617, respectively, P < 0.01). Injection of PYM into the subchondral bone adjacent to the lumbar intervertebral discs of rhesus monkeys can results in mild, slowly progressive disc degeneration, which mimics the onset of human disc degeneration, and the T1ρ magnetic resonance imaging is suited for evaluating intervertebral disc degeneration. N/A.

Subclinical cartilage degeneration in young athletes with posterior cruciate ligament injuries detected with T1ρ magnetic resonance imaging mapping.

Prediction of the risk of osteoarthritis in asymptomatic active patients with an isolated injury of the posterior cruciate ligament (PCL) is difficult. T1ρ magnetic resonance imaging (MRI) enables the quantification of the proteoglycan content in the articular cartilage. The purpose of this study was to evaluate subclinical cartilage degeneration in asymptomatic young athletes with chronic PCL deficiency using T1ρ MRI. Six athletes with chronic PCL deficiency (median age 17, range 14-36years) and six subjects without any history of knee injury (median age 31.5, range 24-33years) were recruited. Regions of interest were placed on the articular cartilage of the tibia and the distal and posterior areas of the femoral condyle, and T1ρ values were calculated. On stress radiographs, the mean side-to-side difference in posterior laxity was 9.8mm. The T1ρ values at the posterior area of the lateral femoral condyle and the superficial layer of the distal area of the medial and lateral femoral condyle of the patients were significantly increased compared with those of the normal controls (p<0.05). At the tibial plateau, the T1ρ values in both the medial and lateral compartments were significantly higher in patients compared with those in the normal controls (p<0.05). T1ρ MRI detected unexpected cartilage degeneration in the well-functioning PCL-deficient knees of young athletes. One should be alert to the possibility of subclinical cartilage degeneration even in asymptomatic patients who show no degenerative changes on plain radiographs or conventional MRI. IV.

Early intervertebral disc degeneration changes in asymptomatic weightlifters assessed by t1ρ-magnetic resonance imaging.

Case-control study. To evaluate early intervertebral disc degeneration quantified by T1ρ- and T2-weighted magnetic resonance imaging (MRI) in asymptomatic weightlifters compared with a healthy control group matched for sex and age. Athletes consistently recruit or transfer high levels of repetitive forces through the spine, and MRI has documented a higher rate of intervertebral disc degeneration in athletes compared with matched controls. This study aims to analyze the potential role of T1ρ-MRI in the assessment of early degenerative changes occurring in intervertebral discs of young asymptomatic weightlifters compared with healthy controls. Twenty-six asymptomatic young male weightlifters versus a sedentary control group matched for age and sex, both having no lower back pain nor any spinal symptoms, underwent MRI (1.5 T). Degenerative grade was assessed using T2-weighted images, according to the Pfirrmann scale. T1ρ mapping and values in the nucleus pulposus (n=130) were obtained. Differences in T1ρ value between among the groups and linear regression analyses with degenerative grade were determined. Pfirrmann degenerative grade did not show significant differences among groups. Instead, T1ρ values were significantly lower in the lumbar spine of weightlifters compared with controls (P<0.05). T1ρ values decreased linearly with degenerative grade. T1ρ values were significantly lower in athletes compared with a sedentary matched control group showing differences in intervertebral disc degeneration onset among individuals with lifestyle and environmental factors leading to back pain. T1ρ can be potentially used as a valid clinical tool to identify early changes in intervertebral disc on the verge of new emerging intervertebral discs regenerative strategies and treatments. 4.

T₁ρ MRI of human musculoskeletal system.

Magnetic resonance imaging (MRI) offers the direct visualization of the human musculoskeletal (MSK) system, especially all diarthrodial tissues including cartilage, bone, menisci, ligaments, tendon, hip, synovium, etc. Conventional MRI techniques based on T1 - and T2 -weighted, proton density (PD) contrast are inconclusive in quantifying early biochemically degenerative changes in MSK system in general and articular cartilage in particular. In recent years, quantitative MR parameter mapping techniques have been used to quantify the biochemical changes in articular cartilage, with a special emphasis on evaluating joint injury, cartilage degeneration, and soft tissue repair. In this article we focus on cartilage biochemical composition, basic principles of T1ρ MRI, implementation of T1ρ pulse sequences, biochemical validation, and summarize the potential applications of the T1ρ MRI technique in MSK diseases including osteoarthritis (OA), anterior cruciate ligament (ACL) injury, and knee joint repair. Finally, we also review the potential advantages, challenges, and future prospects of T1ρ MRI for widespread clinical translation.

Evaluation of liver fibrosis with T1ρ MR imaging.

Chronic liver disease is a major public health problem worldwide. Liver fibrosis, a common feature of almost all chronic liver diseases, involves the accumulation of collagen, proteoglycans, and other macromolecules in the extracellular matrix. The accumulation of proteins in the extracellular matrix promotes the formation of scars that bridge together adjacent portal triads and central veins. Ultimately, progressive hepatic fibrosis leads to cirrhosis, a characteristic of all end-stage liver disease. Clinically, liver fibrosis usually has an insidious onset and progresses slowly over decades. Patients remain asymptomatic or have only mild, nonspecific symptoms until the development of cirrhosis (1). To date, the conventional imaging diagnostic tests available in clinical practice are not sensitive or specific enough to function as screening tests for detecting liver fibrosis. In patients with precirrhotic stages of liver fibrosis, as well as patients with early cirrhosis, the liver parenchyma usually has a normal appearance or may exhibit only subtle, nonspecific heterogeneity on conventional MR images. A number of MR imaging techniques have been investigated to identify or to assign a grade to liver cirrhosis. These include double contrast material-enhanced MR imaging (2), MR elastography (3-5), and diffusion weighted imaging (3,5,6). The reproducibility and intersite variability of these techniques have not been well established. A mechanism for magnetic resonance (MR) tissue contrast, spin-lattice relaxation time in the rotating frame (T1ρ), has been investigated in biomedical applications. In T1ρ imaging, the equilibrium magnetization, M0, established by the static magnetic field, B0, is flipped into the transverse plane first. This magnetization in the transverse plane relaxes like a normal free induction decay but in the presence of an onresonant continuous wave radiofrequency pulse, which is much weaker than B0 and is called spin-lock radiofrequency pulse. The relaxation rate constant of this transverse magnetization

T1ρ Magnetic Resonance Imaging for Detection of Early Cartilage Changes in Knees of Asymptomatic Collegiate Female Impact and Nonimpact Athletes

To determine if T1ρ magnetic resonance imaging (T1ρ MRI) could assess early articular cartilage changes in knees of asymptomatic female collegiate athletes. It was hypothesized that impact cohort would demonstrate greater changes than nonimpact cohort. An institutional review board-approved prospective cohort study. Blinded MRI analyses. Participants from collegiate athletic program. Imaging at university hospital, February 2008 to July 2009. Inclusion criteria were female collegiate athletes in athletic season and asymptomatic. Exclusion criteria were previous/current knee injuries/surgeries. Twenty-one female NCAA Division I athletes, 11 impact (basketball players) and 10 nonimpact (swimmers) participants were consented and imaged with 3.0-T MRI (Siemens) and T1ρ sequence (University of Pennsylvania). One patient was removed (injury diagnosis). Final roster was 10 impact and 10 nonimpact participants. No difference in cohort body mass index, height, or weight. Average T1ρ relaxation times (ART) for patellar and femoral cartilage to analyze defined regions and depth and modified International Cartilage Repair Society classification. Statistical analyses showed that ART of radial zone of central third weight-bearing region of cartilage in basketball players was significantly greater (P = 0.041) than swimmers and ART of the superficial zone in basketball players was significantly less (P = 0.003) than that of swimmers. For both groups, the ART of superficial zones were significantly greater than that of radial zones (P < 0.001). Four impact athletes showed macroscopic changes (none in nonimpact cohort). T1ρ MRI detected early changes in articular cartilage of asymptomatic collegiate female impact athletes, with significant differences between cohorts in radial zone of central third weight-bearing region and superficial zones ART. Both cohorts showed increased ART in superficial zone. Four impact athletes showed macroscopic changes. This study demonstrates a quantitative MRI sequence able to detect signal differences in articular cartilage in asymptomatic athletes.

Assessing Myocardial Disease Using T1ρ MRI.

There is great interest to use magnetic resonance imaging (MRI) for non-invasive assessment of myocardial disease in ischemic and non-ischemic cardiomyopathies. Recently, there has been a renewed interest to use a magnetic resonance imaging (MRI) technique utilizing spin locking radiofrequency (RF) pulses, called T1ρ MRI. The spin locking RF pulse creates sensitivity to some mechanisms of nuclear relaxation such as 1H exchange between water and amide, amine and hydroxyl functional groups in molecules; consequently, there is the potential to non-invasively, and without exogenous contrast agents, obtain important molecular information from diseased myocardial tissue. The purpose of this article is to review and critically examine the recent published literature in the field related to T1ρ MRI of myocardial disease.

Evaluation of Fibrotic Liver Disease with Whole-Liver T1ρ MR Imaging: A Feasibility Study at 1.5 T

To test at 1.5 T whether T1ρ magnetic resonance (MR) imaging of fibrotic liver disease is feasible, to investigate whether liver T1ρ imaging allows assessment of the severity of liver cirrhosis, and to assess the normal liver T1ρ range in healthy patients. This prospective study was approved by the institutional ethics committee. Written informed consent was obtained. Healthy volunteers (n = 25) and patients (n = 34) with cirrhosis underwent whole-liver T1ρ MR imaging at 1.5 T. Mean T1ρ values were calculated from liver regions of interest. Mean T1ρ values were correlated to clinical data and histopathologic analysis by analysis of variance. Receiver operating characteristic curves were calculated to determine the accuracy of mean T1ρ values for the assessment of Child-Pugh class. Mean T1ρ values of volunteers (mean, 40.9 msec ± 2.9 [standard deviation]; range, 33.9-46.3 msec) were significantly lower than those of patients who were Child-Pugh class A (P < .004), B (P < .001), or C (P < .001), and significant differences were found between each Child-Pugh stage (A vs B, P < .002; B vs C, P < .009; A vs C, P < .001). Liver cirrhosis was confirmed via histologic analysis in all patients with liver biopsy. Mean T1ρ values did not correlate with necroinflammatory activity (r = 0.31; P = .23), degree of steatosis (r = -0.016; P = .68), or presence of iron load (r = 0.22; P = .43). Mean T1ρ values performed well by assessing the Child-Pugh stage, with receiver operating characteristic areas of 0.95-0.98. Intraclass correlation coefficient values ranged between 0.890 and 0.987, which indicated excellent imaging and reimaging reproducibility and interobserver and intraobserver variability. Whole-liver T1ρ MR imaging at 1.5 T to detect and assess human liver cirrhosis is feasible. Further investigation and optimization of this technique are warranted to cover the entire spectrum of fibrotic liver disease.

Novel Imaging of the Intervertebral Disk and Pain

T-1-rho (T1ρ) magnetic resonance imaging (MRI) and disc height ratio (DHR) are potential biomarkers of degenerative disk disease (DDD) related to biochemical composition and morphology of the intervertebral disk (IVD), respectively. To objectively detect DDD at an early stage, the hypothesis was tested that the average T1ρ relaxation time of the nucleus pulposus (NP) correlates with the disk height of degenerate IVDs, measured by MRI. Studies were performed on a 3-T Siemens Tim Trio clinical MRI scanner (Siemens Healthcare, Malvern, Pennsylvania, United States) on patients being treated for low back pain whose disks were categorized into (1) painful and (2) nonpainful subgroups based on provocative diskography and (3) age-matched healthy controls. Painful disks presented both low DHR and T1ρ values, nonpainful disks measured the highest DHR and extended to a higher range of T1ρ, and control disks presented a midrange DHR with the highest T1ρ values. T1ρ MRI evaluated in the NP of IVDs may be useful to establish a threshold (120 milliseconds here) above which indicates a healthy disk, and disks measuring low NP T1ρ (50 to 120 milliseconds here) would require disk height analysis to further categorize the disk. Combining T1ρ MRI and disk height analysis may hold promise in predicting painful disks without provocative diskography, and predictive models should be developed.

Intervertebral Disk Degeneration: T1ρ MR Imaging of Human and Animal Models

To evaluate disk degeneration in human and animal models by using a T1ρ magnetic resonance (MR) imaging technique to help in understanding the natural history and progression of intervertebral disk degeneration. After institutional review board approval was obtained, 80 subjects (54 men and 26 women; mean age ± standard deviation, 31.6 years ± 6.20) with 400 lumbar intervertebral disks were examined at MR imaging. With approval from the animal care committee, six rhesus monkeys received two levels of either annulus fibrosus puncture or pingyangmycin subendplate injection at L3-4 and L5-6 to mimic disk degeneration. Lumbar spines of all the animals were examined at radiography and MR imaging preoperatively and 1 day and 1, 3, 6, 9, and 13 months postoperatively. Pfirrmann grading system and T1ρ quantification were used to evaluate the degenerative degree of the disks of both humans and animals. The mean T1ρ values of lumbar intervertebral disks of human subjects were 136.0 msec ± 31.4 and 76.1 msec ± 14.2 at Pfirrmann grades II and III, respectively. The T1ρ values in lumbar intervertebral disks of the rhesus monkey models of disk degeneration had a rapid decrease from approximately 110 msec to 80 msec and then tended to stabilize after operation. There was a large T1ρ value decrease between Pfirrmann grades II and III in human subjects that coincided with the rapid degeneration process of lumbar intervertebral disks in the rhesus monkeys. Pfirrmann grades were significantly correlated with T1ρ values in both humans (r = -0.681, P < .001) and rhesus monkeys (r = -0.824, P < .001). The data demonstrate that rapid intervertebral disk degeneration occurs early in the degenerative cascade, between Pfirrmann grades II and III.

Image quality considerations for accurate quantitative T1ρ magnetic resonance imaging

Image quality considerations for accurate quantitative T1ρ magnetic resonance imaging

T1ρ at Adjacent Level Discs after Surgery

Introduction Disk degenerative disease (DDD) is a strong etiologic risk factor of chronic low back pain (LBP) and is a common disabling condition for millions of individuals. Total disk arthroplasty is rapidly growing in popularity as an alternative to fusion to treat disc-related back pain. One motivation for arthroplasty is to preserve motion in order to prevent DDD at adjacent disk levels, a serious side effect of fusion surgery1. However, standard diagnostic tools such as x-ray measurements of disk height and T2 magnetic resonance imaging (MRI) signal intensity measurements are insensitive to adjacent level DDD.2 A better approach is to utilize noninvasive imaging methods that are responsive to subtle chemical biomarkers. To this end, T1ρ MRI, which has been demonstrated to correlate with disk degeneration, proteoglycan content, and disk pressure in cadaver tissue,3–6 was used as a quantitative biomarker to assess discs adjacent to surgically fused discs pre- and postsurgery. We evaluated whether a change in T1ρ value was related to presurgical discography opening pressure7 or T2-MRI based Pfirrmann degenerative grades8 of discs adjacent to fused discs. The hypothesis tested is that adjacent discs with low opening pressure (indicating low osmotic pressure and proteoglycan content) are more prone to degeneration and manifest decreased T1ρ values. The objective of this study is to determine changes in T1ρ relaxation times in adjacent level discs in patients following surgery to relate these to presurgical opening pressure as measured by provocative discography. Materials and Methods All MRI scans were performed on a 3 Tesla Siemens Tim Trio clinical scanner (using the vendor-supplied spine array coil with approval from the IRB and with subjects' consent). T1ρ and T2-weighted MRI were performed on patients pre- and postsurgery ( n = 4, 12 levels {2 points per level - nucleus &amp; total disc}, mean age 42 ± 3 years, range 39–45) at time points ∼2 years apart. Discography opening pressure (OP), the pressure where an injected contrast dye first overcomes the internal osmotic pressure, was obtained following the placement of 22 gauge needles into the center of the L2/L3 through L5/S1 disks, using the IntelliSystem with digital pressure display. Lohexol (Omnipaque 300), a low osmolar, nonionic, iodinated-contrast agent, was injected into each disk under continuous fluoroscopic imaging. Following coregistration and segmentation procedures, average T1ρ (in milli seconds) was recorded from the discs a level above or below the surgically treated disk using algorithms written in Matlab. Pfirrmann grading was performed on T2 MRI of the same discs by a single-reader with several years of experience in disk MRI analysis. Statistical descriptives and regressions were performed in SPSS 19.0 to evaluate any relationships between changes in T1ρ pre- and postsurgery 2 years apart (δT1ρ) in the discs adjacent to fused discs and presurgery opening pressure and Pfirrmann grade of the adjacent discs. Results There was a significant (p1ρ and presurgery opening pressure of discs (Fig. 1) that were above surgically fused discs. Adjacent discs were with low OP (T1ρ 2 years postsurgery). Dashed lines indicate 95% confidence intervals. Graph of δT1ρ and presurgery Pfirrmann grade (Fig. 2) shows poor correlation (r = 0.25, p = 0.16) demonstrating the inability of Pfirrmann grade to predict T1ρ, and hence adjacent level DDD. Conclusion Presurgical opening pressure measurements of adjacent discs were significantly related to changes in T1ρ pre- and postsurgery. The data suggests that a low OP may be used to establish a threshold below which these disks are likely to degenerate following surgical intervention at an adjacent disc. At the same time, in this limited number of subjects, Pfirrmann grading could not be related to changes in T1ρ. We are continuing recruitment of more patients with an aim to develop T1ρ MRI to detect adjacent level DDD to evaluate patient outcomes from back surgery. I confirm having declared any potential conflict of interest for all authors listed on this abstract Yes Disclosure of Interest None declared Bertagnoli R, et al. European Spine Journal 2002;11(2):S131-S136 Chou R, et al. Annals of Internal Medicine 2007;147(7):478–491 Johannessen W, et al. Spine 2006;31(11):1253–1257 Auerbach J, et al. European Spine Journal 2006;15 Suppl 3:S338–344 Blumenkrantz G, et al. Magnatic Resonance in Medicine2010;63(5):1193–1200 Borthakur A, et al. Spine 2011;36(25):2190–6 Tehranzadeh J. Radiologic Clinics of North America 1998;36(3):463–495 8.Pfirrmann CW, et al. Spine 2001;26(17):1873–1878

T1ρ magnetic resonance imaging quantification of early lumbar intervertebral disc degeneration in healthy young adults.

Cross-sectional study using T1ρ magnetic resonance imaging (MRI) of lumbar spine in healthy young adults. To evaluate early intervertebral disc degeneration (IDD) quantified by T1ρ- and T2-weighted MRI in asymptomatic young adults and to correlate T1ρ value with Pfirrmann degenerative grade, sex, and body mass index (BMI). Intervertebral disc starts early to degenerate losing proteoglycan content in the nucleus pulposus (NP). A potential tool for the study of early stage of IDD is T1ρ MRI. T1ρ relaxation time of human discs has been correlated to proteoglycan content in previous studies. T1ρ- and T2-weighted images of the lumbar spine were obtained for 63 asymptomatic young subjects (34 men and 29 women; mean age, 22.95 ± 1.8 yr), with a 1.5-T MRI scanner. T1ρ mapping and values in the NP and anulus fibrosus (n = 315) were obtained. Degenerative grade was assessed using T2-weighted images, according to the Pfirrmann scale. Differences in T1ρ value between sexes, BMI, and linear regression analyses with degenerative grade were determined. T1ρ values of NPs were significantly higher than those of anulus fibrosus at all levels. T1ρ values were significantly lower in women at L3-L4 and L4-L5 discs (P < 0.05). T1ρ values decreased linearly with degenerative grade. However, nondegenerated discs (Pfirrmann grades 1 and 2) showed a wide range of T1ρ relaxation time. No significant correlation was observed between T1ρ value and BMI. The data of this study showed a significant difference in IDD onset between sexes. T1ρ values correlate with Pfirrmann degenerative grade in young adults. However, the wide distribution of T1ρ values in healthy intervertebral disc highlights the low sensitivity of Pfirrmann grade to detect the early IDD changes. T1ρ can be potentially used as a clinical tool to identify early IDD and to create a reliable quantitative scale.

MR T1ρ as an imaging biomarker for monitoring liver injury progression and regression: an experimental study in rats with carbon tetrachloride intoxication

Recently it was shown that the magnetic resonance imaging (MRI) T1ρ value increased with the severity of liver fibrosis in rats with bile duct ligation. Using a rat carbon tetrachloride (CCl(4)) liver injury model, this study further investigated the merit of T1ρ relaxation for liver fibrosis evaluation. Male Sprague-Dawley rats received intraperitoneal injection of 2 ml/kg CCl(4) twice weekly for up to 6 weeks. Then CCl(4) was withdrawn and the animals were allowed to recover. Liver T1ρ MRI and conventional T2-weighted images were acquired. Animals underwent MRI at baseline and at 2 days, 2 weeks, 4 weeks and 6 weeks post CCl(4) injection, and they were also examined at 1 week and 4 weeks post CCl(4) withdrawal. Liver histology was also sampled at these time points. Liver T1ρ values increased slightly, though significantly, on day 2, and then increased further and were highest at week 6 post CCl(4) insults. The relative liver signal intensity change on T2-weighted images followed a different time course compared with that of T1ρ. Liver T1ρ values decreased upon the withdrawal of the CCl(4) insult. Histology confirmed the animals had typical CCl(4) liver injury and fibrosis progression and regression processes. MR T1ρ imaging can monitor CCl(4)-induced liver injury and fibrosis. • MR T1ρ is a valuable imaging biomarker for liver injury/fibrosis. • Liver T1ρ was only mildly affected by oedema and acute inflammation. • Liver MR T1ρ decreased when liver fibrosis and injury regressed.

T1ρ Magnetic Resonance Imaging and Discography Pressure as Novel Biomarkers for Disc Degeneration and Low Back Pain

Prospective magnetic resonance imaging (MRI) study of patients low back pain (LBP) requiring discography as part of their routine clinical diagnoses and asymptomatic age-matched volunteers. To determine whether T1ρ MRI and discography opening pressure (OP) are quantitative biomarkers of disc degeneration in LBP patients and in asymptomatic volunteers. Disc degenerative disease, a common cause of LBP, is related to the patient's prognosis and serves as a target for therapeutic interventions. However, there are few quantitative measures in the clinical setting. Discography OP and T1ρ MRI are potential biomarkers of disc degenerative disease related to biochemical composition of the intervertebral disc. The institutional review board approved all experiments, and informed consent was provided by each subject. Patients being treated for LBP (n = 17; 68 levels; mean age, 44 ± 6 years; and range, 30-53) and control subjects (n = 11; 44 levels; mean age, 43 ± 17 years; and range, 22-76) underwent T1ρ and T2 MRI on a Siemens 3T Tim Trio clinical scanner (Siemens Medical Solutions, Malvern, PA). The LBP patients also received multilevel provocative discography before their MRI. OP was recorded as the pressure when fluid first enters the nucleus of the intervertebral disc. T1ρ was significantly lower in the painful discs (55.3 ± 3.0 ms, mean ± SE) from control (92.0 ± 4.9 ms, P < 0.001) and nonpainful discs (83.6 ± 3.2 ms, P < 0.001). Mean OP for the painful discs (11.8 ± 1.0 psi, mean ± SE) was significantly lower than that for nonpainful discs (19.1 ± 0.7 psi, P < 0.001). Both T1ρ and OP correlated moderately with Pfirrmann degenerative grade. Receiver-operating-characteristic area under the curve was 0.91 for T1ρ MRI and 0.84 for OP for predicting painful discs. T1ρ and OP are quantitative measures of degeneration that are consistent across both control subjects and LBP patients. A significant and strong correlation exists between T1ρ values and in vivo OP measurements obtained by discography in LBP patients.

Longitudinal analysis of T1ρ and T2 quantitative MRI of knee cartilage laminar organization following microfracture surgery

ObjectiveTo quantitate longitudinally the radiographic properties of different layers of repaired tissue following microfracture (MFx) surgery using T1ρ and T2 magnetic resonance imaging (MRI). Design10 patients underwent MFx surgery to treat symptomatic focal cartilage defects (FCD). Sagittal three-dimensional (3D) water excitation high-spatial resolution (HR) spoiled gradient recalled (SPGR) for quantitative T1ρ and T2 mapping were acquired for each patient 3–6months and 1year after surgery. Cartilage compartments were segmented on HR-SPGR images, and T1ρ and T2 maps were registered to the HR-SPGR images. T1ρ and T2 values for the full thickness of deep and superficial layers of repaired tissue (RT) and normal cartilage (NC) were calculated, and compared within and between respective time points. A p-value <0.05 is considered statistically significant. ResultsThe majority of FCD were found in the MFC. The average surface area of the lesions did not differ significantly overtime. At 3–6months, RT had significantly higher full thickness T1ρ and T2 values relative to NC. At 1year, this significant difference was only observed for T1ρ values. At 3–6months follow-up, the RT's superficial layer had significantly higher T1ρ and T2 values than the deep layer of the RT and the superficial layer of NC. At 12months, the superficial layer of the RT had significantly higher T1ρ values than the RT's deep layer and the NC's superficial layer. ConclusionT1ρ and T2 MRI are feasible methods for quantitatively and noninvasively monitoring the maturation of repaired tissue following microfracture surgery over time.

Evaluation of cartilage degradation in arthritis using T1ρ magnetic resonance imaging mapping

T1ρ magnetic resonance imaging (MRI) can be used to map proteoglycan (PG) loss in cartilage. Here, we used T1ρ MRI to map cartilage degradation in osteoarthritis (OA) and rheumatoid arthritis (RA). Tissue samples were obtained from five RA patients and 14 OA patients following total knee arthroplasty (TKA). Three parameters were measured: First, macroscopic grading of cartilage sample tissues was performed on a 5-grade scale (G0: normal, G1: swelling, G2: superficial fibrillation, G3: deep fibrillation, G4: subchondral bone exposure). Second, semi-quantitative values of PG were assessed by measuring the optical density of Safranin-O-stained paraffin sections that had been digitally photographed. Third, cartilage was divided into superficial and deep layers and the T1ρ values were quantified. T1ρ values of OA and RA in the superficial layers showed significant differences between groups (G0/1 and G0/2 for OA; G0/2 and G1/2 for RA). In the deep layers, T1ρ values of OA and RA also differed significantly between groups. In both the superficial and deep layers, there was a significant correlation between the mean T1ρ values and macroscopic grading (P < 0.01 for OA, P < 0.001 for RA). We found a negative correlation between the score of Safranin-O staining and T1ρ values (r = -0.61 for OA, r = -0.79 for RA). In addition, RA subjects had significantly higher T1ρ values than OA subjects of similar morphologic grade. In conclusion, T1ρ MRI is able to detect and map the early stages of cartilage degradation in OA and RA. This method is reliable and useful for the evaluation of macromolecular changes in arthritic cartilage.

T1ρ MR Imaging Is Sensitive to Evaluate Liver Fibrosis: An Experimental Study in a Rat Biliary Duct Ligation Model

To correlate spin-lattice relaxation time in the rotating frame (T1ρ) measurements with degree of liver fibrosis in a rat model. The protocols and procedures were approved by the local Animal Experimentation Ethics Committee. Liver fibrosis was induced with biliary duct ligation (BDL). Two studies, 1 month apart, were performed with a 3-T clinical imager. The first study involved longitudinal magnetic resonance (MR) imaging follow-up of BDL rats (n = 8) and control rats (n = 4) on days 8, 15, 21, and 29 after BDL. The second study involved MR imaging of another group of BDL and control rats (n = 5 for each) on days 24 and 38 after BDL. Hematoxylin-eosin and picrosirius red staining were performed in liver specimens from days 8, 15, 24, and 38 after BDL. Repeated-measures analysis of variance was used, and treatment groups were compared (Bonferroni adjustment). On day 8, there were proliferation of bile duct and inflammatory cell infiltration around portal triads. While there was overlap, BDL rats (n = 8) demonstrated higher mean liver T1ρ values than did control rats (n = 4) on day 8 (46.7 msec ± 2.9 [standard deviation] vs 44.7 msec ± 1.2, P = .4). On day 15, BDL rats demonstrated liver fibrosis with a background of inflammatory infiltration. On day 15, mean T1ρ values in BDL rats could be largely separated from those in control rats (52.6 msec ± 6.0 vs 43.8 msec ± 1.5, P = .02). On day 24, BDL rats had liver T1ρ values 23.5% higher than in control rats (n = 5 for each group, P = .0007). Histomorphometric analysis showed that collagen content increased after surgery from days 8 to 24 (n = 6 for each group, P < .0001), with no further increase between days 24 and 38 (n = 6 for each group, P >.99). In this model, liver fibrosis was detected with T1ρ MR imaging; the degree of fibrosis was correlated with degree of increase in T1ρ measurements. http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.11101638/-/DC1.

High-Field Magnetic Resonance Imaging Assessment of Articular Cartilage before and after Marathon Running

Background There is continuing controversy whether long-distance running results in irreversible articular cartilage damage. New quantitative magnetic resonance imaging (MRI) techniques used at 3.0 T have been developed including T1rho (T1ρ) and T2 relaxation time measurements that detect early cartilage proteoglycan and collagen breakdown. Hypothesis Marathon runners will demonstrate T1ρ and T2 changes in articular cartilage on MRI after a marathon, which are not seen in nonrunners. These changes are reversible. Study Design Cohort study; Level of evidence, 2. Methods Ten asymptomatic marathon runners had 3-T knee MRI scans 2 weeks before, within 48 hours after, and 10 to 12 weeks after running a marathon. The T1ρ and T2 MRI sequences in runners were compared with those of 10 age- and gender-matched controls who had MRI performed at baseline and 10 to 12 weeks. Results Runners did not demonstrate any gross morphologic MRI changes after running a marathon. Postmarathon studies, however, revealed significantly higher T2 and T1ρ values in all articular cartilage areas of the knee (P < .01) except the lateral compartment. The T2 values recovered to baseline except in the medial femoral condyle after 3 months. Average T1ρ values increased after the marathon from 37.0 to 38.9 (P < .001) and remained increased at 3 months. Conclusion Runners showed elevated T1ρ and T2 values after a marathon, suggesting biochemical changes in articular cartilage, T1ρ values remain elevated after 3 months of reduced activity. The patellofemoral joint and medial compartment of the knee show the highest signal changes, suggesting they are at higher risk for degeneration.