Cerebral Oximetry Measurements Results Depending on a Preclinical Skull Phantom Model

It is more common to perform non-invasive examination during general anaesthesia to ensure effective perioperative patient care. To achieve these results, researchers and clinicians are seeking out different technologies and developing new equipment. One such apparatus is a cerebral oximeter, which is used during cardiac surgery with cardiopulmonary bypass for neuroprotection management for reducing risk of postoperative neurological injury (cerebral stroke, neurocognitive dysfunction, and cerebral haemorrhage). A cerebral oximeter performs non-invasive transcutaneous measurements using near infrared radiation to assess the oxygenation of tissues. The objective of the study was to determine if the angle and thickness of a patient’s skull affects measurements. Intralipid water solution, gelatine, and ink were used to make six phantoms with skull thickness ranging from 6 to 11 mm. All phantoms were bent froma0to20 degrees angle. The cerebral oximeter SOMETICS INVOS 5100C was used to perform regional oximetry measurements. For skull thickness of 11 mm, the rSO2 was 45.8% (SD 0.96); for skull thickness of 10 mm, the rSO2 was 45.25% (SD 2.22); for skull thickness of 9 mm, the rSO2 was 32% (SD 1.63); for skull thickness of 8 mm, the rSO2 was 17% (SD 1.83); for skull thickness of 7 mm, the rSO2 was 15% (SD 0); for skull thickness of 6 mm, the rSO2 was 15% (SD 0). No significant changes were observed regarding the angle of the skull phantom. The thickness of the bone layer of the skull phantom affected the regional oximetry results, whereas the angle of the skull did not affect it.

PSIII-4 Determining the Efficacy and Safety of Differing Caliber/Ammunition Combinations for the Humane Euthanization and Subsequent Mass Depopulation of Market Weight Pigs

The objective of this proof of concept exercise was to validate a field applicable methodology designed to objectively assess the multiple caliber/ammunition combinations available for the safe and humane euthanization of market weight pigs during mass depopulation events. Heads of an equal number of barrows and gilts (n = 64) were randomly assigned to one of four caliber/ammunition combinations consisting of the .22 LR, .22 Mag, 0.38 Special, and 9mm. Fully jacketed (FMJ) ammunition was discharged from each of four unique firearms while ensuring that the distance from the muzzle to the forehead was consistent. The MIXED procedure of SAS was used to test the fixed effects of sex and caliber. No differences in skull thickness existed between sex (P = 0.32) or caliber/ammunition combination (P = 0.34). There was no difference in entrance wound diameter between the .38 Special and the 9mm (P = 0.15) yet the entrance wound diameter of the .38 Special and 9mm was larger than both the .22 LR and .22 Mag, respectfully (P < 0.0001). The 9mm bullets traveled further into the ballistic gel (P < 0.0001) and the furthest total distance (P < 0.0001). Bullets from the .38 Special traveled further into the ballistic gel and a further total distance than both the .22 LR and .22 Mag (P < 0.0001). There was no difference in the measurable trauma area of the brain for the 9mm bullets compared to .38 Special bullets (P = 0.83). The measurable trauma area of the brain was greater for the 9mm and .38 Special bullets when compared to both the .22 LR and .22 Mag (P < 0.0001). In conclusion, the efficacy and safety of the multiple caliber/ammunition combinations available for use in the euthanization of market weight pigs can be objectively quantified, replicated, and reported.

Acoustic properties across the human skull

Transcranial ultrasound is emerging as a noninvasive tool for targeted treatments of brain disorders. Transcranial ultrasound has been used for remotely mediated surgeries, transient opening of the blood-brain barrier, local drug delivery, and neuromodulation. However, all applications have been limited by the severe attenuation and phase distortion of ultrasound by the skull. Here, we characterized the dependence of the aberrations on specific anatomical segments of the skull. In particular, we measured ultrasound propagation properties throughout the perimeter of intact human skulls at 500 kHz. We found that the parietal bone provides substantially higher transmission (average pressure transmission 31±7%) and smaller phase distortion (242±44 degrees) than frontal (13±2%, 425±47 degrees) and occipital bone regions (16±4%, 416±35 degrees). In addition, we found that across skull regions, transmission strongly anti-correlated (R = −0.79) and phase distortion correlated (R = 0.85) with skull thickness. This information guides the design, positioning, and skull correction functionality of next-generation devices for effective, safe, and reproducible transcranial focused ultrasound therapies.

Technical and radiographic considerations for magnetic resonance imaging–guided focused ultrasound capsulotomy

OBJECTIVEMagnetic resonance imaging–guided focused ultrasound (MRgFUS) is an emerging treatment modality that enables incisionless ablative neurosurgical procedures. Bilateral MRgFUS capsulotomy has recently been demonstrated to be safe and effective in treating obsessive-compulsive disorder (OCD) and major depressive disorder (MDD). Preliminary evidence has suggested that bilateral MRgFUS capsulotomy can present increased difficulties in reaching lesional temperatures as compared to unilateral thalamotomy. The authors of this article aimed to study the parameters associated with successful MRgFUS capsulotomy lesioning and to present longitudinal radiographic findings following MRgFUS capsulotomy.METHODSUsing data from 22 attempted MRgFUS capsulotomy treatments, the authors investigated the relationship between various sonication parameters and the maximal temperature achieved at the intracranial target. Lesion volume and morphology were analyzed longitudinally using structural and diffusion tensor imaging. A retreatment procedure was attempted in one patient, and their postoperative imaging is presented.RESULTSSkull density ratio (SDR), skull thickness, and angle of incidence were significantly correlated with the maximal temperature achieved. MRgFUS capsulotomy lesions appeared similar to those following MRgFUS thalamotomy, with three concentric zones observed on MRI. Lesion volumes regressed substantially over time following MRgFUS. Fractional anisotropy analysis revealed a disruption in white matter integrity, followed by a gradual return to near-baseline levels concurrent with lesion regression. In the patient who underwent retreatment, successful bilateral lesioning was achieved, and there were no adverse clinical or radiographic events.CONCLUSIONSWith the current iteration of MRgFUS technology, skull-related parameters such as SDR, skull thickness, and angle of incidence should be considered when selecting patients suitable for MRgFUS capsulotomy. Lesions appear to follow morphological patterns similar to what is seen following MRgFUS thalamotomy. Retreatment appears to be safe, although additional cases will be necessary to further evaluate the associated safety profile.

Kranion, an open-source environment for planning transcranial focused ultrasound surgery: technical note

Transcranial focused ultrasound (FUS) ablation is an emerging incision-less treatment for neurological disorders. The factors affecting FUS treatment efficiency are not well understood. Kranion is open-source software that allows the user to simulate the planning stages of FUS treatment and to “replay” previous treatments for off-line analysis. This study aimed to investigate the relationship between skull parameters and treatment efficiency and to create a metric to estimate temperature rise during FUS. CT images from 28 patients were analyzed to validate the use of Kranion. For stereotactic targets within each patient, individual transducer element incident angles, skull density ratio, and skull thickness measurements were recorded. A penetration metric (the “beam index”) was calculated by combining the energy loss from incident angles and the skull thickness. Kranion accurately estimated the patient’s skull and treatment parameters. The authors observed significant changes in incident angles with different targets in the brain. Using the beam index as a predictor of temperature rise in a linear-mixed-effects model, they were able to predict the average temperature rise at the focal point during ablation with < 21% error (55°C ± 3.8°C) in 75% of sonications, and with < 44% (55°C ± 7.9°C) in 97% of sonications. This research suggests that the beam index can improve the prediction of temperature rise during FUS. Additional work is required to study the relationship between temperature rise and lesion shape and clinical outcomes.

Implantation of bone-anchored hearing device using a three-dimensional template in a child

BackgroundImplantation of bone-anchored hearing devices is performed to improve hearing in patients with chronic suppurative otitis media who cannot wear a conventional hearing aid. The surgical procedure can be safely performed in children aged over five years.Case reportA 15-year-old patient with bilateral chronic suppurative otitis media and conductive hearing loss underwent the procedure to implant a bone-anchored hearing device but was found to have skull thickness of less than 2.5 mm and the procedure was abandoned. A computed tomography scan of the skull was undertaken and a three-dimensional template was reconstructed to identify appropriate thickness of the skull to implant the abutment during a second procedure.ConclusionBone-anchored hearing devices can be implanted by prior imaging and using a template to identify the area of appropriate skull thickness to implant the abutment safely.