1. Design considerations for piezoelectric polymer ultrasound transducers
L F Brown IEEE Trans Ultrason Ferroelectr Freq Control. 2000;47(6):1377-96. doi: 10.1109/58.883527.
Much work has been published on the design of ultrasound transducers using piezoelectric ceramics, but a great deal of this work does not apply when using the piezoelectric polymers because of their unique electrical and mechanical properties. The purpose of this paper is to review and present new insight into seven important considerations for the design of active piezoelectric polymer ultrasound transducers: piezoelectric polymer materials selection, transducer construction and packaging requirements, materials characterization and modeling, film thickness and active area design, electroding selection, backing material design, and front protection/matching layer design. Besides reviewing these design considerations, this paper also presents new insight into the design of active piezoelectric polymer ultrasonic transducers. The design and fabrication of an immersible ultrasonic transducer, which has no adhesive layer between the active element and backing layer, is included. The transducer features direct deposition of poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] copolymer onto an insulated aluminum backing substrate. Pulse-echo tests indicated a minimum insertion loss of 37 dB and -6 dB bandwidth of 9.8 to 22 MHz (71%). The use of polymer wear-protection/quarter-wave matching layers is also discussed. Test results on a P(VDF-TrFE) transducer showed that a Mylar/sup TM/ front layer provided a slight increase in pulse-echo amplitude of 15% (or 1.2 dB) and an increase in -6 dB pulse-echo fractional bandwidth from 86 to 95%. Theoretical derivations are reported for optimizing the active area of the piezoelectric polymer element for maximum power transfer at resonance. These derivations are extended to the special case for a low profile (i.e., thin) shielded transducer. A method for modeling the non-linear loading effects of a commercial pulser-receiver is also included.
2. Identification of Risk Factors for Postoperative Cerebrospinal Fluid Leakage and Comparison of Two Alternative Dural Augmentation Techniques in Posterior Fossa and Spinal Surgeries
Muhammed Taha Eser, Sahin Hanalioglu, Mehmet Ziya Cetiner, Samet Dinc, Halil Olgun Peker, Mehmet Sorar, Habibullah Dolgun, Erhan Turkoglu Turk Neurosurg. 2019;29(3):377-385. doi: 10.5137/1019-5149.JTN.24432-18.0.
Aim: To investigate comparative efficacy of a novel absorbable adhesive membrane (TissuePatchDuralTM "TPD") and a fibrin glue (Tisseel "T") in reducing cerebrospinal fluid (CSF) leaks after posterior fossa and spinal procedures, and also to identify potential risk factors for CSF leakage. Material and methods: This is a single-center, retrospective cohort study of 123 consecutive posterior fossa (n=77) and spinal (n=46) surgeries. Patients were grouped based on dural sealants used 2-group comparison: TPD (n=56) vs. no-TPD (n=67) and 3-group comparison: T only (n=43), TPD only (n=32) vs TPD+T (n=35). Results: Mean age was 38.9 ± 22.2 years (62 males, 61 females). Baseline characteristics were similar between groups. Neither 2-group (TPD: 10.4% vs no-TPD: 8.9%; p=0.778) nor 3-group (T: 9.3% vs TPD: 6.3% vs TPD+T: 14.3%; p=0.539) comparisons revealed a significant difference in postoperative CSF leakage rates. Multivariate analysis showed that diagnosis (non-tumoral vs. tumor) (OR: 5.487; 95% CI: 1.118-26.937; p=0.036); previous surgery (OR: 9.268; 95% CI: 1.911-44.958; p=0.006), postoperative hydrocephalus (OR: 5.456; 95% CI: 1.250-23.821; p=0.024) were independent predictors of postoperative CSF leakage. Conclusion: TissuePatchDural < sup > TM < /sup > is a novel dural sealant patch which can be safely used to reinforce dural closure in posterior fossa and spinal surgeries, and its efficacy is comparable to widely used fibrin glue (Tisseel). Non-tumoral pathologies, previous surgery, and postoperative hydrocephalus appear to be independent risk factors for postoperative CSF leakage.
3. Endovascular Stroke Therapy Focused on Direct Clot Aspiration Using the SOFIATM Catheter for Acute Ischemic Stroke
Ilkay Akmangit, Bige Sayin, Ayberk Karaman, Ergun Daglioglu, Berna Arli, Mustafa Harun Sahin, Gurdal Orhan Turk Neurosurg. 2022;32(5):720-726. doi: 10.5137/1019-5149.JTN.34409-21.3.
Aim: To report our experience of mechanical thrombectomy using the SOFIA < sup > TM < /sup > catheter, in terms of its effectivenessicacy and safety. Material and methods: Acute ischemic stroke patients with large vessel occlusions who underwent mechanical thrombectomy, with the SOFIA < sup > TM < /sup > aspiration catheter as the first-line approach, were retrospectively identified. For all patients, the data, including reperfusion success (modified Thrombolysis in Cerebral Infarction [mTICI]), procedural details, clinical status at the baseline and post-discharge at 90 days, and complications, were analysed. Results: During the study period (January 2017-July 2020), 73 patients underwent endovascular thrombectomy. The mean age and the baseline National Institutes of Health Stroke scores were 72 (41-83) and 16 (12-25), respectively. Successful reperfusion (mTICI≥2b-3) was obtained in 80.8 % (n=59) of the patients. Using ADAPT, a first-pass effect was achieved in 63.01% (n=46) of the patients. Rescue stent retriever (SRV) had to be utilized in 36.98% (n=27) of the patients; all presented with a favourable clinical outcome (modified Rankin score ≤0-2) at 90 days. The complication rate in the study was 13.7% (n=10). Conclusion: The contact aspiration approach with SOFIA < sup > TM < /sup > catheters as a first-line device appears to be fast, safe, and effective. Our results were comparable to the findings of other series. In the case of insufficient response on contact aspiration, we could easily modify the SOFIA < sup > TM < /sup > catheter approach for an additional stent retriever rescue treatment.
