Quantitative magnetization transfer ultrashort echo time imaging of the Achilles tendon

Ultrashort echo time imaging allows the short T₂ Achilles tendon to be directly visualized with MRI. Radiofrequency saturation 1 kHz or less off‐resonance has been used previously to improve image contrast. In this study, magnetization transfer was investigated in the Achilles tendon of eight normal volunteers and one patient with psoriatic arthritis. 2D Ultrashort echo time images were acquired using saturation pulses 2–100 kHz off‐resonance at 4 pulse powers. On‐resonance saturation recovery images were also obtained to estimate T₁. The results were fitted to a two compartment quantitative magnetization transfer model. The estimated bound proton fraction for the eight healthy volunteers was 21.0 ± 1.2% (mean ± standard deviation) compared to 16.4% in the patient with psoriatic arthritis (P < 0.05). The T₂ of the bound protons was measured as 6.1 ± 0.3 μsec in the healthy volunteers and 6.0 μsec in the patient. This technique appears clinically feasible and may be useful for assessing the collagen and water changes which occur in Achilles tendinopathy. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.     

Ultrashort echo time MR imaging with off‐resonance saturation for characterization of pathologically altered Achilles tendons at 3 T

Off‐resonance radiofrequency saturation pulses applied prior to regular excitation in MR sequences can be used to modify signal contrast based on magnetization transfer and direct saturation effects. Clinical applicability and value of ultrashort echo time sequences combined with off‐resonance saturation pulses was tested in 16 healthy and 14 tendinopathic as well as paratendinopathic Achilles tendons in vivo at 3 T. A 3D ultrashort echo time sequence in combination with a gaussian off‐resonance saturation pulse (frequency offset: 1000–5000 Hz) was used to modify the detectable MR signal intensity from the Achilles tendon. Off‐resonance saturation ratio was calculated as the relative reduction in signal intensity under selective off‐resonance saturation in relation to a reference measurement without any saturation pulse. Off‐resonance saturation ratio in tendons of healthy volunteers ranged from 0.52 ± 0.06 (1000 Hz) to 0.24 ± 0.02 (5000 Hz), whereas symptomatic tendinopathic tendons (0.35 ± 0.04 to 0.17 ± 0.02) and asymptomatic tendinopathic tendons (0.41 ± 0.06 to 0.21 ± 0.02) showed significantly lower mean off‐resonance saturation ratio values. Off‐resonance saturation ratio values might provide a sensitive and quantitative marker for assessment of pathological microstructure alterations of the Achilles tendon. Magn Reson Med, 2013. © 2012 Wiley Periodicals, Inc.     

Ultrashort TE imaging with off‐resonance saturation contrast (UTE‐OSC)

Short T₂ species such as the Achilles tendon and cortical bone cannot be imaged with conventional MR sequences. They have a much broader absorption lineshape than long T₂ species, therefore they are more sensitive to an appropriately placed off‐resonance irradiation. In this work, a technique termed ultrashort TE (UTE) with off‐resonance saturation contrast (UTE‐OSC) is proposed to image short T₂ species. A high power saturation pulse was placed +1 to +2 kHz off the water peak to preferentially saturate signals from short T₂ species, leaving long T₂ water and fat signals largely unaffected. The subtraction of UTE images with and without an off‐resonance saturation pulse effectively suppresses long T₂ water and fat signals, creating high contrast for short T₂ species. The UTE‐OSC technique was validated on a phantom, and applied to bone samples and healthy volunteers on a clinical 3T scanner. High‐contrast images of the Achilles tendon and cortical bone were generated with a high contrast‐to‐noise ratio (CNR) of the order of 12 to 20 between short T₂ and long T₂ species within a total scan time of 4 to 10 min. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.     

Microcirculation after Achilles tendon rupture correlates with functional and patient‐reported outcomes

Patients with acute Achilles tendon rupture (ATR ) display an extended healing process with varying clinical outcome. Poor microcirculatory blood flow has been suggested to be a significant factor for the healing process. However, whether microcirculation may predict healing outcome has been mostly unknown. Therefore, we investigated whether blood flow in the Achilles tendon may be associated with patient‐reported and functional outcomes after ATR . In vivo laser‐Doppler flowmetry was used to assess microvascular blood flow bilateral in the Achilles tendons, during post‐occlusive reactive hyperemia, of nine patients with acute total ATR at 2 weeks post‐operatively. At 3 months post‐operatively, patient‐reported outcome was assessed using Achilles tendon Total Rupture Score (ATRS ). At 1 year a uniform outcome score, Achilles Combined Outcome Score (ACOS ), was obtained by combining validated, independent, patient‐reported (ATRS ), and functional outcome (heel‐rise test) measures. An improved combined patient‐reported and functional outcome, ACOS , at 1 year was significantly correlated with higher maximum blood flow (r=.777, P =.040) in the injured limb. Furthermore, enhanced patient‐reported outcome, ATRS , at 3 months, was associated with an elevated ratio of maximum to resting blood flow (r=.809, P =.015) in the uninjured limb. Blood flow in early tendon healing is associated with long‐term patient‐reported and functional outcomes after ATR . The microcirculatory blood flow of both the healing and contralateral Achilles tendon seems to determine the healing potential after injury.     

The prevalence of Achilles and patellar tendon injuries in Australian football players beyond a time‐loss definition

Little is known about the prevalence and associated of morbidity of tendon problems. With only severe cases of tendon problems missing games, players that have their training and performance impacted are not captured by traditional injury surveillance. The aim of this study was to report the prevalence of Achilles and patellar tendon problems in elite male Australian football players using the Oslo Sports Trauma Research Centre (OSTRC ) overuse questionnaire, compared to a time‐loss definition. Male athletes from 12 professional Australian football teams were invited to complete a monthly questionnaire over a 9‐month period in the 2016 pre‐ and competitive season. The OSTRC overuse injury questionnaire was used to measure the prevalence and severity of Achilles and patellar tendon symptoms and was compared to traditional match‐loss statistics. A total of 441 participants were included. Of all participants, 21.5% (95% CI : 17.9‐25.6) and 25.2% (95% CI 21.3‐29.4) reported Achilles or patellar tendon problems during the season, respectively. Based on the traditional match‐loss definition, a combined 4.1% of participants missed games due to either Achilles or patellar tendon injury. A greater average monthly prevalence was observed during the pre‐season compared to the competitive season. Achilles and patellar tendon problems are prevalent in elite male Australian football players. These injuries are not adequately captured using a traditional match‐loss definition. Prevention of these injuries may be best targeted during the off‐ and pre‐season due to higher prevalence of symptoms during the pre‐season compared to during the competitive season.     

Non‐uniform displacement and strain between the soleus and gastrocnemius subtendons of rat Achilles tendon

Achilles tendon (AT ) comprises of 3 subtendons arising from the soleus (SOL ) and the lateral (LG ) and medial (MG ) heads of the gastrocnemius muscle. While recent human studies show differential displacement within AT , these displacements have not been attributed to specific subtendons. We tested the hypothesis that the SOL and LG subtendons show differential displacement and strain during various combinations of SOL , LG , and MG excitations. Movement of knots, sutured onto SOL and LG subtendons of 12 Wistar rats, was videotaped, while the muscles were stimulated intramuscularly and ankle torque was assessed. When SOL only was stimulated, the plantar flexion torque was the smallest among the different conditions (P  < .001). In this condition, from passive to active state, the displacement (0.57 vs 0.47 mm, P  = .002) and strain (8.4% vs 2.4%, P  < .001) in the SOL subtendon were greater than in LG subtendon. When LG only was stimulated, a higher ankle torque was measured as compared to SOL stimulation (P  < .001); the displacement was similar in both subtendons (~0.6 mm), while the strain was greater in LG than in SOL (4.7% vs 1.7%, P  < .001). When all 3 muscles were stimulated simultaneously, ankle torque was highest and the displacement (0.79 vs 0.74 mm, P  = .002) and strain (7.7% vs 4.4%, P  = .003) were greater in SOL than in LG . These data show that the different subtendons of AT can experience relative displacement and differential strains. Together with anatomical dissections, the results revealed that such uniformities may be due to a lower stiffness of SOL subtendon compared to LG .     

Regional variations of T2* in healthy and pathologic achilles tendon in vivo at 7 Tesla: Preliminary results

The aim of this study was to investigate T in the Achilles tendon (AT), in vivo, using a three‐dimensional ultrashort time echo (3D‐UTE) sequence, to compare field strength differences (3 and 7 T) and to evaluate a regional variation of T in healthy and pathologic tendon. Ten volunteers with no history of pain in the AT and five patients with chronic Achilles tendinopathy were recruited. 3D‐UTE images were measured with the following echo times, at echo time = [0.07, 0.2, 0.33, 0.46, 0.59, 0.74, 1.0, 1.5, 2.0, 4.0, 6.0, and 9.0 ms]. T values in the AT were calculated by fitting the signal decay to biexponential function. Comparing volunteers between 3 and 7 T, short component T was 0.71 ± 0.17 ms and 0.34 ± 0.09 ms (P < 0.05); bulk long component T was 12.85 ± 1.87 ms and 10.28 ± 2.28 ms (P < 0.05). In patients at 7 T, bulk T was 0.53 ± 0.17 ms (P = 0.045, compared to volunteers), T was 11.49 ± 4.28 ms (P = 0.99, compared to volunteers). The results of this study suggest that the regional variability of AT can be quantified by T in in vivo conditions. Advanced quantitative imaging of the human AT using a 3D‐UTE sequence may provide additional information to standard clinical imaging. Finally, as the preliminary patient data suggest, T may be a promising marker for the diagnosis of pathological changes in the AT. Magn Reson Med, 2012. © 2012 Wiley Periodicals, Inc.     

Changes in leisure‐time physical activity and physical and mental health functioning: a follow‐up study

Functioning will be an increasingly important issue in Finland over the coming decades as the proportion of the population aged 65 and older is growing significantly. However, the associations between changes in physical activity and subsequent health functioning are poorly understood. The aim of this study was to examine how changes in physical activity relate to concurrent and prospective levels of health functioning. Cohort data from the Helsinki Health Study were used. Phase 1 (n = 8960, response rate 67%, 80% women) was conducted among 40‐ to 60‐year‐old employees of the City of Helsinki in 2000–2002, phase 2 in 2007 (n = 7332, response rate 83%), and phase 3 in 2012 (n = 6814, response rate 79%). Linear mixed models were used as the main statistical method. Increasing physical activity was associated with higher concurrent and prospective levels of physical health functioning, whereas decreasing activity was associated with lower levels of physical health functioning. The associations were stronger with physical than with mental health functioning. Promoting physical activity among aging people may help to maintain their level of health functioning.     

Evaluation of sonoelastography in Achilles tendon of healthy volunteers and patients with symptomatic Achilles tendon

Aim and objectives: To assess the role of SEL in evaluation of Achilles tendon. Methodology: This study included 40 healthy volunteers and 40 patients with symptomatic Achilles tendon. All patients were examined by conventional B-mode ultrasound, sonoelastography and MRI. Results: Achilles tendons of the volunteers were characterized by hard texture with higher strain ratios than those of the patients with Achilles tendinopathy. No significant differences could be detected between SR of male and female volunteers yet significant differences could be detected in the volunteer group above and below forty being lower with softer tendon properties in the group above forty with a cut-off value of ≤1.84 between healthy and diseased group. Sonoelastography had the sensitivity of 89.1% and specificity of 96.1% for diagnosis of tendinopathy with results superior to those of conventional B-mode ultrasonography. Conclusion: SEL is a reliable tool in the evaluation of Achilles tendinopathy with sensitivity and specificity superior to B-mode US. Strain ratio provides excellent non-invasive diagnostic data adds strongly in more objective evaluation of Achilles tendon properties.