Safety and Feasibility of a Novel Externally Cooled Bronchoscopic Radiofrequency Ablation Catheter for Ablation of Peripheral Lung Tumours: A First-In-Human Dose Escalation Study.

BACKGROUND: Radiofrequency ablation (RFA) is an established modality for percutaneous ablation of non-small cell lung cancer (NSCLC) in medically inoperable patients but is underutilized clinically due to side effects. We have developed a novel, completely endobronchial RFA catheter with an externally cooled electrode. OBJECTIVES: The objective of this study was to establish the safety and feasibility of bronchoscopic RFA using a novel, externally cooled catheter for ablation of peripheral NSCLC. METHODS: Patients with stage I biopsy-confirmed NSCLC underwent bronchoscopic RFA of tumour 7 days prior to lobectomy. The RFA catheter was delivered bronchoscopically to peripheral NSCLC lesions, guided by radial endobronchial ultrasound, with positioning confirmed using intra-procedural cone beam CT. Pre-operative CT chest and histologic examination of resected specimens were used to establish distribution/uniformity of ablation and efficacy of tumour ablation. RESULTS: RFA in the first patient was complicated by dispersal of heated saline due to cough, resulting in ICU admission. The patient recovered fully and underwent uncomplicated lobectomy. Subsequently, the protocol was altered to mandate neuromuscular blockade with a pre-determined dose escalation, with algorithm-restricted energy (kJ) and irrigated saline volume (mL) constraints. A further 10 patients consented and seven underwent successful bronchoscopic RFA of peripheral NSCLC. No significant adverse events were noted. Ablation zone included tumour in all cases (proportion of tumour ablated ranged 8-72%), with uniform necrosis of tissue within ablation zones observed at higher energy levels. Ablation zone diameter correlated with RFA energy delivered (R2 = 0.553), with maximum long axis diameter of ablation zone 3.1 cm (22.9 kJ). CONCLUSION: Bronchoscopic RFA using an externally cooled catheter is feasible, appears safe, and achieves uniform ablation within the treatment zone. Uncontrolled escape of heated saline poses a major safety risk but can be prevented procedurally through neuromuscular blockade and by limiting irrigation.

Apparent diffusion coefficient and T2* mapping on 3T MRI in normal and degenerative lumbar intervertebral discs.

Purpose: To assess the utility of diffusion-weighted imaging (DWI) with apparent diffusion coefficient (ADC) maps and T2* mapping in quantitative analysis of nucleus pulposus (NP) and annulus fibrosus (AF) of lumbar intervertebral discs with its correlation with modified Pfirrmann grading (MPG) for lumbar degenerative disc disease (LDDD). Material and methods: One hundred subjects (20-74 years of age) underwent T2-weighted, DWI with ADC and T2* magnetic resonance imaging. MPG was applied to L3-L4, L4-L5, and L5-S1 discs, and ADC and T2* values of NP and AF were calculated in the mid-sagittal plane by segmenting each disc into 5 regions of interest (ROI) (NP-3, AF-2). Mean ADC and T2* values, their correlation, and cut-offs among different grades were calculated at different ROIs across different levels. Results: Out of total 300 discs analysed; 68 were normal (grade I) discs and 232 were degenerated (grade II to VIII) discs, based on MPG. T2* and ADC values in NP, AF, and the entire disc were significantly lower in degenerated discs than in normal discs. There was significant (p < 0.001) negative correlation between ADC and T2* values with MPG. ADC and T2* cut-off values were statistically significant across grades, with area under the curve (AUC) values in moderate to high accuracy range (0.8 to > 0.9) for assessing the degree of LDDD. Conclusions: T2* and ADC value-based grade scales are highly accurate in evaluating the degree of disc degeneration with a high degree of objectivity in comparison to visual assessment-based MPG. Reduced ADC and T2* values of NP could serve as markers of early LDDD.

Effect of choice of recovery patterns on handrim kinetics in manual wheelchair users with paraplegia and tetraplegia.

BACKGROUND: Impact forces experienced by the upper limb at the beginning of each wheelchair propulsion (WCP) cycle are among the highest forces experienced by wheelchair users. OBJECTIVE: To determine whether the magnitude of hand/forearm velocity prior to impact and effectiveness of rim impact force are dependent on the type of hand trajectory pattern chosen by the user during WCP. Avoiding patterns that inherently cause higher impact force and have lower effectiveness can be another step towards preserving upper limb function in wheelchair users. METHODS: Kinematic (50 Hz) and kinetic (2500 Hz) data were collected on 34 wheelchair users (16 with paraplegia and 18 with tetraplegia); all participants had motor complete spinal cord injuries ASIA A or B. The four-hand trajectory patterns were analyzed based on velocity prior to contact, peak impact force and the effectiveness of force at impact. RESULTS: A high correlation was found between the impact force and the relative velocity of the hand with respect to the wheel (P<0.05). The wheelchair users with paraplegia were found to have higher effectiveness of force at impact as compared to the users with tetraplegia (P<0.05). No significant differences in the impact force magnitudes were found between the four observed hand trajectory patterns. CONCLUSION: The overall force effectiveness tended to be associated with the injury level of the user and was found to be independent of the hand trajectory patterns.

IN.PACT™ Admiral™ drug-coated balloon: Durable, consistent and safe treatment for femoropopliteal peripheral artery disease.

Endovascular management of peripheral artery disease was until recently limited to percutaneous balloon angioplasty, atherectomy, stent grafts, and bare-metal stents. These therapies have been valuable, but plagued by high restenosis and revascularization rates. Important progress has been made with the introduction of combination devices, including drug-eluting stents and drug-coated balloons (DCB), designed to combat restenosis by locally delivering anti-proliferative drugs. In particular, promising clinical performance has been seen with the Medtronic IN.PACT™ Admiral™ DCB, with durable, consistent and safe results. Rigorous, randomized controlled trials have directly compared this and other drug-delivering devices to their non-drug-coated counterparts with data available through two years. Additionally, trials are ongoing to assess use of drug-coated technologies in combination with traditional therapies in hope of synergistic effects. This review gathers data from currently published clinical trials with the IN.PACT Admiral DCB for the treatment of femoropopliteal peripheral artery disease and explores the possible impact on continuing clinical practice.

Modifications in Wheelchair Propulsion Technique with Speed.

OBJECTIVE: Repetitive loading of the upper limb joints during manual wheelchair (WC) propulsion (WCP) has been identified as a factor that contributes to shoulder pain, leading to loss of independence and decreased quality of life. The purpose of this study was to determine how individual manual WC users with paraplegia modify propulsion mechanics to accommodate expected increases in reaction forces (RFs) generated at the pushrim with self-selected increases in WCP speed. METHODS: Upper extremity kinematics and pushrim RFs were measured for 40 experienced manual WC users with paraplegia while propelling on a stationary ergometer at self-selected free and fast propulsion speeds. Upper extremity kinematics and kinetics were compared within subject between propulsion speeds. Between group and within-subject differences were determined (α = 0.05). RESULTS: Increased propulsion speed was accompanied by increases in RF magnitude (22 of 40, >10 N) and shoulder net joint moment (NJM, 15 of 40, >10 Nm) and decreases in pushrim contact duration. Within-subject comparison indicated that 27% of participants modified their WCP mechanics with increases in speed by regulating RF orientation relative to the upper extremity segments. CONCLUSIONS: Reorientation of the RF relative to the upper extremity segments can be used as an effective strategy for mitigating rotational demands (NJM) imposed on the shoulder at increased propulsion speeds. Identification of propulsion strategies that individuals can use to effectively accommodate for increases in RFs is an important step toward preserving musculoskeletal health of the shoulder and improving health-related quality of life.

Effect of increased load on scapular kinematics during manual wheelchair propulsion in individuals with paraplegia and tetraplegia.

Repetitive loading of the upper extremity musculature during activities like wheelchair propulsion can lead to fatigue of surrounding musculature causing irregular segment kinematics. The goal of this study was to determine the effect of increase in load on the kinematics of the scapula in users with paraplegia and tetraplegia. Data were collected on 18 participants (11 with paraplegia and 7 with tetraplegia) using an electromagnetic motion tracking system (100Hz) and force sensing pushrim (200Hz). The participants propelled under no load and loaded conditions at their customary propulsion velocity. On average a 60N increase in force was elicited with the experimental protocol. Users with tetraplegia showed significant increases (p<.05) in the rate of change of scapular angles in the upward/downward rotation and the retraction/protraction direction under the loaded conditions, whereas users with paraplegia only showed difference in the retraction/protraction rotation direction. Overall both user populations moved towards position of increased downward rotation, anterior tilt and protraction with increase in load hence increasing the risk of impingement. This experiment adds depth to our understanding of dynamic scapular kinematics during wheelchair propulsion under different loading conditions and differences in scapular control between users with paraplegia and tetraplegia.

Support torques during simulated sit-to-stand movements.

Sit-to-stand movements are a fundamental daily activity and a prerequisite to upright posture. Previous simulations of spinal cord injured individuals using functional neuromuscular stimulation (FNS) suggested a forward foot placement would reduce hand-support forces. However, this recommendation has proved to be difficult for able-bodied individuals standing hands-free and for individuals with spinal cord injuries standing with a walker. This inverse model is a step towards the goal of using forward simulations to determine efficient sit-to-stand strategies. Initial seated postures varied from 80-110 degrees of knee flexion and 90-120 degrees of hip flexion. Realistic progressions of lower extremity joint angles including development of linear momentum were created using sigmoid functions. These kinematic values were used to estimate the required resultant joint torques to complete sit-to-stand. Joint torque values that act to raise the body were combined to indicate sit-to-stand difficulty from different seated postures. A representative foot-forward placement (knee 80 degrees, hip 90 degrees) resulted in a maximum combined torque of 544 Nm. In contrast, a representative foot-back placement (knee 110 degrees, hip 120 degrees) resulted in a maximum combined torque of 661 Nm. An intermediate seated posture (knee 97 degrees, hip 90 degrees) produced the lowest maximum combined torque of 401 Nm (2 Nm ankle plantarflexion, 201 Nm knee extension, 198 Nm hip extension). Foot-forward placement required substantial ankle dorsiflexion torques. The most efficient strategy appeared to be combining a foot back placement with momentum generation using hip flexion. By generalizing the sit-to-stand model beyond FNS-driven movements, further insight may be gained into other populations (i.e., elderly).

NMES-assisted standing model from varied seated postures.

After spinal cord injury (SCI), intact lower motor neurons can be electrically activated to produce functional muscular contractions and enhance one's capabilities beyond seated activities. Even with neuromuscular electrical stimulation (NMES), significant amounts of hand-support forces are commonly required to move from a sitting to standing position. The goal of this project was to determine initial seated postures that reduce vertical hand-support forces while keeping anterior/posterior hand-support forces below levels that would cause walker slipping or tipping. A multi-segment biomechanical model was further developed and expanded to test multiple combinations of initial postures. The muscles that were analyzed included the vastus lateralis and semimembranosus. Varying the initial knee and hip angles created alternative seated postures. For vastus lateralis stimulation, the lowest vertical hand-support forces (63-66% of body weight) were predicted at the lower (70-74 degrees) and upper (110 degrees) ranges of initial knee flexion. With combined vastus lateralis and semimembranosus stimulation, the lowest predicted vertical hand-support forces were 2-10% of body weight at initial knee flexion angles between 70-82 degrees. Initial hip flexion angles above 110 degrees were required to prevent walker slipping and tipping in these cases. The development of hip extensor torque with semimembranosus stimulation was critical in reducing the vertical hand-support forces. One implication is that when training with parallel bars for NMES-assisted standing, hand-support forces should be monitored to avoid conditions that would tip a walker. In future models, optimizing the timing sequence for stimulating muscles may produce smoother coordination of joint rotations and further reduce the vertical hand-support forces.