BackgroundRadiofrequency (RF) subthalamotomies have been proposed since the 1960s to treat patients suffering from Parkinson's disease (PD). Recently, the magnetic resonance (MR)-guided focused ultrasound technology (MRgFUS) offers the possibility to perform subthalamic thermocoagulations with reduced risks and optimized accuracy. We describe here the initial results of the MRgFUS pallidothalamic tractotomy (PTT), an anatomical and physiological update of the earlier subthalamotomies.MethodsThirteen consecutive patients suffering from chronic (mean disease duration 9.7 years) and therapy-resistant PD were treated unilaterally with an MRgFUS PTT. Primary relief assessment indicators were the score reduction of the Unified Parkinson Disease Rating Scale (UPDRS) and the patient estimation of global symptom relief (GSR) taken at 3 months follow-up. Final temperatures at target were between 52°C and 59°C. The MR examinations were performed before the treatment, 2 days and 3 months after it. The accuracy of the targeting was calculated on 2 days post-treatment MR pictures for each PTT lesion.ResultsThe first four patients received a PTT using the lesional parameters applied for thalamotomies. They experienced clear-cut recurrences at 3 months (mean UPDRS relief 7.6%, mean GSR 22.5%), and their MR showed no sign of thermal lesion in T2-weighted (T2w) images. As a consequence, the treatment protocol was adapted for the following nine patients by applying repetition of the final temperatures 4 to 5 times. That produced thermocoagulations of larger volumes (172 mm3 against 83 mm3 for the first four patients), which remained visible at 3 months on T2w images. These nine patients enjoyed a mean UPDRS reduction of 60.9% and a GSR of 56.7%, very close to the results obtained with radiofrequency lesioning. The targeting accuracy for the whole patient group was 0.5, 0.5, and 0.6 mm for the anteroposterior (AP), mediolateral (ML), and dorsoventral (DV) dimensions, respectively.ConclusionsThis study demonstrated the feasibility, safety, and accuracy of the MRgFUS PTT. To obtain similar results as the ones of RF PTT, it was necessary to integrate the fact that white matter, in this case, the pallidothalamic tract, requires repeated thermal exposition to achieve full lesioning and thus full therapeutic effect.
A sensor system for measurement of pressure and shear at the lower limb residuum/socket interface is described. The system comprises of a flexible sensor unit and a data acquisition unit with wireless data transmission capability. Static and dynamic performance of the sensor system was characterised using a mechanical test machine. The static calibration results suggest that the developed sensor system presents high linearity (linearity error ≤3.8%) and resolution (0.9kpa for pressure and 0.2kpa for shear). Dynamic characterisation of the sensor system shows hysteresis error of approximately 15% for pressure and 8% for shear. Subsequently, a pilot amputee walking test was conducted. Three sensors were placed at the residuum/socket interface of a knee disarticulation amputee and simultaneous measurements were obtained during pilot amputee walking test. The pressure and shear peak values as well as their temporal profiles are presented and discussed. * Corresponding Author: Piotr Laszczak, Engineering Materials Research Group, Faculty of Engineering and the Environment, University of Southampton, SO17 1BJ, Southampton, UK; Email, P.Laszczak@soton.ac.uk; Phone, 07513362435 Preprint submitted to Medical Engineering and PhysicsMarch 1, 2016In particular, peak pressure and shear of approximately 58kPa and 27kPa, respectively, were recorded. Their temporal profiles also provide dynamic coupling information at this critical residuum/socket interface. These preliminary amputee test results suggest strong potential of the developed sensor system for exploitation as an assistive technology to facilitate socket design, socket fit and effective monitoring of lower limb residuum health.Abstract word count: 200
BackgroundAlready in the late 1960s and early 1970s, targeting of the “posterior subthalamic area (PSA)” was explored by different functional neurosurgical groups applying the radiofrequency (RF) technique to treat patients suffering from essential tremor (ET). Recent advances in magnetic resonance (MR)-guided focused ultrasound (MRgFUS) technology offer the possibility to perform thermocoagulation of the cerebellothalamic fiber tract in the PSA without brain penetration, allowing a strong reduction of the procedure-related risks and increased accuracy. We describe here the first results of the MRgFUS cerebellothalamic tractotomy (CTT).MethodsTwenty-one consecutive patients suffering from chronic (mean disease duration 29.9 years), therapy-resistant ET were treated with MRgFUS CTT. Three patients received bilateral treatment with a 1-year interval. Primary relief assessment indicators were the Essential Tremor Rating Scale (Fahn, Tolosa, and Marin) (ETRS) taken at follow-up (3 months to 2 years) with accent on the hand function subscores (HF16 for treated hand and HF32 for both hands) and handwriting. The evolution of seven patients with HF32 above 28 points over 32 (group 1) differentiated itself from the others’ (group 2) and was analyzed separately. Global tremor relief estimations were provided by the patients. Lesion reconstruction and measurement of targeting accuracy were done on 2-day post-treatment MR pictures for each CTT lesion.ResultsThe mean ETRS score for all patients was 57.6 ± 13.2 at baseline and 25.8 ± 17.6 at 1 year (n = 10). The HF16 score reduction was 92 % in group 2 at 3 months and stayed stable at 1 year (90 %). Group 1 showed only an improvement of 41 % at 3 months and 40 % at 1 year. Nevertheless, two patients of group 1 treated bilaterally had an HF16 score reduction of 75 and 88 % for the dominant hand at 1 year after the second side. The mean patient estimation of global tremor relief after CTT was 92 % at 2 days and 77 % at 1-year follow-up.ConclusionsCTT with MRgFUS was shown to be an effective and safe approach for patients with therapy-refractory essential tremor, combining neurological function sparing with precise targeting and the possibility to treat patients bilaterally.
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