Design, fabrication, and evaluation of single- and multi-level 3D-printed non-covering cervical spinal fusion surgery templates.

Background: Cervical spinal fusion surgeries require accurate placement of the pedicle screws. Any misplacement/misalignment of these screws may lead to injuries to the spinal cord, arteries and other organs. Template guides have emerged as accurate and cost-effective tools for the safe and rapid insertions of pedicle screws. Questions/Purposes: Novel patient-specific single- and multi-level non-covering templates for cervical pedicle screw insertions were designed, 3D-printed, and evaluated. Methods: CT scans of two patients were acquired to reconstruct their 3D spine model. Two sets of single-level (C3-C7) and multi-level (C4-C6) templates were designed and 3D-printed. Pedicle screws were inserted into the 3D-printed vertebrae by free-hand and guided techniques. For single-level templates, a total of 40 screws (2 patients × 5 vertebrae × 2 methods × 2 screws) and for multi-level templates 24 screws (2 patients × 3 vertebrae × 2 methods × 2 screws) were inserted by an experienced surgeon. Postoperative CT images were acquired to measure the errors of the entry point, 3D angle, as well as axial and sagittal plane angles of the inserted screws as compared to the initial pre-surgery designs. Accuracy of free-hand and guided screw insertions, as well as those of the single- and multi-level guides, were also compared using paired t-tests. Results: Despite the minimal removal of soft tissues, the 3D-printed templates had acceptable stability on the vertebrae during drillings and their utilization led to statistically significant reductions in all error variables. The mean error of entry point decreased from 3.02 mm (free-hand) to 0.29 mm (guided) using the single-level templates and from 5.7 mm to 0.76 mm using the multi-level templates. The percentage reduction in mean of other error variables for, respectively, single- and multi-level templates were as follows: axial plane angle: 72% and 87%, sagittal plane angle: 56% and 78%, and 3D angle: 67% and 83%. The error variables for the multi-level templates generally exceeded those of the single-level templates. The use of single- and multi-level templates also considerably reduced the duration of pedicle screw placements. Conclusion: The novel single- and multi-level non-covering templates are valuable tools for the accurate placement of cervical pedicle screws.

Mass Sensors Based on Capacitive and Piezoelectric Micromachined Ultrasonic Transducers-CMUT and PMUT.

Microelectromechanical system (MEMS)-based mass sensors are proposed as potential candidates for highly sensitive chemical and gas detection applications owing to their miniaturized structure, low power consumption, and ease of integration with readout circuits. This paper presents a new approach in developing micromachined mass sensors based on capacitive and piezoelectric transducer configurations for use in low concentration level gas detection in a complex environment. These micromachined sensors operate based on a shift in their center resonant frequencies. This shift is caused by a change in the sensor's effective mass when exposed to the target gas molecules, which is then correlated to the gas concentration level. In this work, capacitive and piezoelectric-based micromachined sensors are investigated and their principle of operation, device structures and configurations, critical design parameters and their candidate fabrication techniques are discussed in detail.

Methodological issues in the recruitment of primary care patients with depression.

OBJECTIVE: To compare two strategies of patient recruitment, waiting room (WR) screening and screening after physician referral (PR), for participation in a treatment-outcome study of minor depression and dysthymia in primary care. The influence of demographic factors on patients' refusal to participate in WR screening was also examined. METHOD: Of a convenience sample of 3,344 first stage patients, a total of 609 patients were evaluated in a semi-structured manner using a two-stage screening procedure from the mood module of the Primary Care Evaluation of Mental Disorders (PRIME-MD). RESULTS: Male and older patients were more likely to refuse participation in screening than female and younger patients. Waiting room screens yielded a higher number of qualified patients compared to PR screens, but PR screens yielded a higher percentage of patients who qualified for further participation. CONCLUSIONS: The recruitment of male and older primary care patients is complicated by their tendency to refuse participation in WR screening for a treatment-outcome study of milder depression. Although each recruitment strategy offers advantages and disadvantages, the simultaneous use of both is recommended to recruit the most patients in the least amount of time.