Wearable, Fiber-less, Multi-Channel System for Continuous Wave Functional Near Infrared Spectroscopy Based on Silicon Photomultipliers Detectors and Lock-In Amplification.

Development and in-vivo validation of a Continuous Wave (CW) functional Near Infrared Spectroscopy (fNIRS) system is presented. The system is wearable, fiber-less, multi-channel (16×16, 256 channels) and expandable and it relies on silicon photomultipliers (SiPMs) for light detection. SiPMs are inexpensive, low voltage and resilient semiconductor light detectors, whose performances are analogous to photomultiplier tubes (PMTs). The advantage of SiPMs with respect to PMTs is that they allow direct contact with the scalp and avoidance of optical fibers. In fact, the coupling of SiPMs and light emitting diodes (LEDs) allows the transfer of the analog signals to and from the scalp through thin electric cables that greatly increase the system flexibility. Moreover, the optical probes, mechanically resembling electroencephalographic electrodes, are robust against motion artifacts. In order to increase the signal-to-noise-ratio (SNR) of the fNIRS acquisition and to decrease ambient noise contamination, a digital lock-in technique was implemented through LEDs modulation and SiPMs signal processing chain. In-vivo validation proved the system capabilities of detecting functional brain activity in the sensorimotor cortices. When compared to other state-of-the-art wearable fNIRS systems, the single photon sensitivity and dynamic range of SiPMs can exploit the long and variable interoptode distances needed for estimation of brain functional hemodynamics using CW-fNIRS.

Dose reduction in multislice CT by means of bismuth shields: results of in vivo measurements and computed evaluation.

PURPOSE: We investigated the amount of patient dose reduction in the thyroid, lens of the eye and the breast when using bismuth protections in multislice computed tomography (CT) exams as well as their influence on the quality of diagnostic images. MATERIALS AND METHODS: The radiation dose was measured by using thermoluminescence dosimeters. The study was conducted on the two CT scanners installed in our radiology department (64 and eight slices). The shield effects on the CT image were evaluated by measuring the signal-to-noise ratio in a phantom and in vivo, and by verifying the presence of artefacts on patients' images. The obtained organ-dose reduction factors were used to evaluate the effects of shielding on the effective dose. RESULTS: The shielding attenuation ranged from 30% to 60% depending on the CT scan protocols and organs. The difference between shielded and unshielded signal-to-noise ratio was statistically significant but within the standard requirements for quality assurance. Results were in agreement with the radiologists' perception of image quality. The use of the shields allowed up to 38% reduction of effective dose. CONCLUSIONS: Use of bismuth shields significantly decreases both organ and effective radiation dose, with a consequent reduction in health risk for the patient, quantified in 1.4 fewer cases of radiation-induced tumours every 5 years in our centre (12,100 exams/year), in agreement with the risk factors proposed by Publication 60 of the International Commission on Radiological Protection (ICRP). The relative inexpensiveness of these protections, their easy application and their substantial lack of influence on image quality suggest their massive introduction into routine clinical practice.

[Arterial recanalization with the Kensey catheter. Preliminary results]. / Ricanalizzazione arteriosa con catetere di Kensey. Risultati preliminari.

Fifteen patients with chronic obstruction of leg arteries (mean length: 6 cm) were treated with the Kensey catheter and then with PTA. In 11 cases the procedure was successful (74%) and in 2 it was interrupted--in one case for dissection and in the other for vessel perforation. Two maneuvers, after dissection, were ended with PTA and stent placement (overall success rate: 87%). Emergency surgery was never needed. In the cases solved with the Kensey catheter, the cumulative patency rate was 51% at 6, 12 and 24 months. The Kensey catheter did not improve the results of conventional PTA, which means its role is complementary to that of PTA and an alternative to more expensive laser systems, if PTA fails.