Estimation of endurance performance markers using a metabolic model in cycling: a pilot study

Introduction: Metabolic models can be used to simulate dose-time responses in physiological parameters like blood lactate concentration. Likewise, these models can be applied to observed data from graded exercise tests to estimate endurance performance markers like maximal oxygen consumption (V̇O2max) and maximal lactate accumulation rate (ċLamax). Currently, this method is not explained in the literature. The aim of this pilot study is 1) to transparently report an algorithm for estimation, 2) to compare the theoretical and practical maximal lactate steady-state (MLSS), and 3) to inform a rigorous study design to optimize and validate this approach. Methods: Ten Participants from two labs participated in this non-experimental study. Body composition, a submaximal ergometer test, and a 30-minute one-trial MLSS test at the intensity of the theoretical MLSS were conducted on two separate days. Maximal post-lactate values were fitted to the metabolic model from Mader & Heck (1986) to estimate V̇O2max and ċLamax, which consequently determined the theoretical MLSS. The increase in blood lactate concentration from minute 10 to 30 was analyzed and a sensitivity analysis was conducted, using the advanced model from Mader (2003). Results: The average blood lactate concentration increase in the one-trial MLSS test from minute 10 to 30 was 1.38 ± 1.27 mmol/L. The sensitivity analysis shows that for 50 % of the measurements the actual difference between the power at the theoretical and practical MLSS is less than 1.8%. Conclusion: This study provides a proof-of-concept for using metabolic simulations to derive estimates for endurance performance markers that determine the metabolic profile of an athlete. This study can inform the design of future validation studies on this approach

Validity of a simulation-based performance testing model in cycling: a study protocol

Background: Metabolic simulations as described by Mader (2003) can be used to model the physiological response (e.g. blood lactate, phosphocreatine, pH, aerobic and anaerobic energy contribution) to exercise. While some parameters of the model were derived from the literature and are assumed to be constant, the individual performance markers V̇O2max (maximal oxygen consumption) and ċLamax (maximal lactate production rate) can be used as input to create individual performance predictions. Further, the MLSS (maximal lactate steady-state) can be estimated via the model. In practice, this model is already used to infer those performance markers from observed testing data. However, a thorough evaluation of this approach is still missing. Objective: To assess the concurrent validity of simulation-based performance testing (sim) in cycling compared to experimental estimates from performance testing (exp). Study Design: Agreement Study Participants: Recreational cyclists and triathletes Methods: Five exercise tests will be conducted on at least 5 days. On day 1, body composition, a 15-second sprint (ċLamaxexp) and a ramp test until exhaustion (V̇O2maxexp) will be conducted. On day 2 and 3, an individualized test protocol and a standard graded exercise test are conducted to observe model-based performance markers (V̇O2maxsim, ċLamaxsim, MLSSsim) with each procedure. From day 4 on, multiple 30-minute constant workload tests are performed to measure MLSSexp. Agreement analyses will be conducted via Bland-Altman analyses using a priori defined Limits of Agreement. Registration: This study protocol will be pregistered via the Open Science Framework (OSF) upon an ethical vote. Ethics: A vote by the ethics committee of the Ruhr University Bochum is still pending

Peripheral artery disease: how much inter-leg symmetry? A contrast-enhanced magnetic resonance angiography study

The aim of this observational retrospective study was to qualitatively and quantitatively evaluate the symmetry of atherosclerotic plaques in patients with peripheral artery disease (PAD) undergoing contrast-enhanced magnetic resonance angiography of lower limbs. We retrospectively evaluated the peripheral magnetic resonance angiography of 82 patients considering the iliac, femoral and tibial arteries. Stenosis was scored 0 (none), 1 (<50%), 2 (50%-74%), 3 (75%-99%), and 4 (occluded). Symmetry was quantified as the percentage of bilaterally-diseased arteries and using the inter-leg absolute score difference (0-4). Signs test and Cohen \u3ba were also calculated. Seventy-one (87%) patients had 651 bilaterally-diseased artery, and 168 (20%) of 820 artery pairs were bilaterally affected. At least 1 bilateral stenosis was observed from 11% (right internal iliac) to 73% (right superficial femoral). All 10 arteries showed symmetry, none of the inter-leg comparisons being significantly different (P 65 .100). Cohen \u3ba ranged from 0.208 (common femoral) to 0.533 (internal iliac). This study showed that PAD was symmetrically distributed between the 2 legs, with the internal iliac artery being the most symmetric segment. Symmetry of PAD was quantified in 20%

Fluid preinjection for microwave ablation in an ex vivo bovine liver model assessed with volumetry in an open MRI system

PURPOSEWe aimed to detect possible differences in microwave ablation (MWA) volumes after different fluid preinjections using magnetic resonance imaging (MRI).MATERIALS AND METHODSMWA volumes were created in 50 cuboid ex vivo bovine liver specimens (five series: control [no injection], 10 mL water, 10 mL 0.9% NaCl, 10 mL 6% NaCl, and 10 mL 12% NaCl preinjections; n=10 for each series). The operating frequency (915 megahertz), ablation time (7 min), and energy supply (45 watts) were constant. Following MWA, two MR sequences were acquired, and MR volumetry was performed for each sequence.RESULTSFor both sequences, fluid preinjection did not lead to significant differences in MWA ablation volumes compared to the respective control group (sequence 1: mean MWA volumes ranged from 7.0±1.2 mm [water] to 7.8±1.3 mm [12% NaCl] vs. 7.3±2.1 mm in the control group; sequence 2: mean MWA volumes ranged from 4.9±1.4 mm [12% NaCl] to 5.5±1.9 mm [0.9% NaCl] vs. 4.7±1.6 mm in the control group). The ablation volumes visualized with the two sequences differed significantly in general (P < 0.001) and between the respective groups (control, P ≤ 0.001; water, P < 0.001; 0.9% NaCl, P < 0.001; 6% NaCl, P ≤ 0.001; 12% NaCl, P < 0.001). The volumes determined with sequence 1 were closer to the expected ablation volume of 8 mL compared to those determined with sequence 2.CONCLUSIONFor the fluid qualities and concentrations assessed, there is no evidence that fluid preinjection results in larger coagulation volumes after MWA. Because ablation volumes determined by MRI vary with the sequence used, interventionalists should gain experience in how to interpret postinterventional imaging findings (with the MR scanner, sequences, and parameters used) to accurately estimate the outcome of the interventions they perform

Applications for diagnostic noninvasive and therapeutically-invasive imaging in an open 1.0 tesla MRI

Einleitung: Die in dieser Promotionsschrift vorgelegten Originalarbeiten wurden allesamt in einem 1,0-Tesla-MRT mit offenem Scannerkonzept durchgeführt. Es handelt sich um Studien sowohl zu diagnostischer (1.+2.) sowie interventionell-therapeutischer (3.) Bildgebung. 1.+2.: Ein nicht invasives 2D-Time-of-Flight-Magnetresonanz-Angiographie-Protokoll ohne Kontrastmittel (TOF-MRA) bzw. ein triggered-angiography-non-contrast-enhanced- Protokoll (TRANCE-MRA) wurden für die arterielle Darstellung der unteren Extremität mit der digitalen Subtraktionsangiographie (DSA) als Goldstandard, verglichen. 3.: Die Ergebnisqualität der im oMRT in nahezu Echtzeit-Bildgebung durchgeführten minimalinvasiven Zystenaspiration wurde an Patienten mit symptomatischen, nervenkomprimierenden lumbosakralen Zysten untersucht. Methodik: 1.+2.: Es wurden 1134 bzw. 1782 Gefäßdurchmesser (TOF-MRA bzw. TRANCE-MRA) in jeweils 81 definierten Segmenten prospektiv gemessen und mit der entsprechenden DSA patientenspezifisch bei 7 (4 Frauen, 3 Männer; Durchschnittsalter: 68 Jahre) bzw. 11 Patienten (8 Männer, 3 Frauen; Durchschnittsalter: 66 Jahre) verglichen. Aufgrund evidenter Symmetrie (rechts/links) wurden die 81 Segmente zu 41 Segmenten für eine höhere statistische Aussagekraft konsolidiert. 3.: 11 Patienten mit symptomatischen lumbosakralen Zysten wurden mittels interventioneller Freihand- Zystenaspiration behandelt. Ergebnisse: 1.: Für die 41 symmetrischen Segmente konnten 25 ausgezeichnete, sehr gute und gute (n=11 > 0,8; n=4 > 0,7; n=10 > 0,5), 7 mäßige bis geringe (n=4 > 0,3 und n=3 ≤ 0,3), sowie 2 statistisch nicht aussagekräftig korrelierbare, 3 inverse und 4 nicht messbare Korrelationen verzeichnet werden. Die arterielle Becken- und Oberschenkel- Hauptstrombahn erzielte die besten Korrelationen und ließ sich am solidesten darstellen. 2.: Insgesamt wurden 34 ausgezeichnete, sehr gute und gute (n=13 > 0,8, n=0 > 0,7; n=11 > 0,5), sowie 4 mäßige bis geringe (n=2 > 0,3; n=2 ≤ 0,3) Korrelationen erhoben. In der Becken-Bein-Etage wurden alle Segmente in der DSA vergleichsweise etwas größer gemessen als in der TRANCE-MRA. In der Oberschenkeletage maßen 6 Segmente kleiner, 3 gleich und 2 größer als in der DSA. In der Unterschenkeletage waren bis auf den Tractus tibiofibularis die gemessenen Segmente in der TRANCE-MRA größer. Schlussfolgerung: 1. Die TOF-MRA ist im oMRT in ca. 60-90 Minuten durchführbar und führt zu guten Ergebnissen in der Visualisierung der arteriellen Hauptstrombahn des Beckens sowie der Oberschenkeletage, während die Visualisierung der Unterschenkeletage optimierungsbedürftiger ist. 2. Die TRANCE-MRA ist in ca. 50 Minuten durchführbar. Gefäßdurchmesser werden im Vergleich zur DSA in größeren Arterien dabei tendenziell etwas kleiner, in kleineren etwas größer gemessen. 3. Jeder Patient verspürte eine Besserung nach erfolgreicher Zystenaspiration. Im Follow-up nach einem Jahr konnten keine Rezidive verzeichnet werden.Introduction: All original studies presented in this doctorate thesis were implemented in an open MRI at 1.0 Tesla. They deal with diagnostic (1+2) and interventional-therapeutic (3) imaging. 1+2: A non-invasive non-contrast- enhanced 2D-time-of-flight-magnetic-resonance-angiography-protocol (TOF-MRA) respectively triggered-angiography-non-contrast-enhanced-protocol (TRANCE-MRA) were compared for the arterial imaging of the lower extremity using the digital subtraction angiography (DSA) as the gold standard. 3: The quality of the almost real-time imaging results of minimally invasive cyst aspiration performed in an oMRI was investigated on patients suffering from nerve- compressing lumbosacral cysts. Methods: 1+2: 1134 respectively 1782 vascular diameters (TOF-MRA respectively TRANCE-MRA) in 81 defined segments each were prospectively measured in 7 patients (4 women, 3 men; average age 68), respectively 11 patients (8 men, 3 women; average age 66) and compared with the corresponding DSA. For symmetry considerations (right/left), 81 segments were consolidated to 41 segments for a higher statistical validity. 3: 11 patients with symptomatic lumbosacral cysts were treated using interventional freehand cyst aspiration. Results: 1: For the 41 symmetric segments, a total of 25 excellent, very good and good correlations (n=11 > 0.8; n=4 > 0.7; n=10 > 0.5), 7 mediocre to low (n=4 > 0.3 and n=3 ≤ 0.3), 2 statistically insignificantly correlatable, 3 inverse and 4 non-measurable correlations were determined. The pelvic and femoral arteries achieved the best correlations with the most reliable images. 2: A total of 34 excellent, very good and good (n=13 > 0.8, n=10 > 0.7; n=11 > 0.5), as well as 4 mediocre to low (n=2 > 0.3; n=2 ≤ 0.3) correlations were ascertained. At pelvis-leg-level, the results of the DSA-measured segments were slightly larger compared to TRANCE-MRA. At thigh level, the measurements of 6 segments were smaller, 3 the same and 2 larger than measured with DSA. At lower leg level, segments measured with TRANCE-MRA were larger except the tractus tibiofibularis. 3: Seven of eleven cysts in the lumbosacral area were aspirated successfully. Four cysts (8.8±3.8 mm) could not be aspirated. Conclusion: 1. The TOF-MRA in the oMRI takes approximately 60-90 minutes with good visualization results for the pelvic and femoral arteries. The visualization results of the lower leg level require improvement. 2. The TRANCE-MRA takes approximately 50 minutes. Compared to the DSA, the measurements of vascular diameters tend to be slightly smaller in larger and slightly larger in smaller arteries. 3\. All patients felt better after successful cyst aspiration. No relapses were recorded during the follow- up one year later