Evaluation of APD and SiPM Matrices as Sensors for Monolithic PET Detector Block

Gamma detectors based on monolithic scintillator blocks coupled to APDs matrices have proved to be a good alternative to pixelated ones for PET scanners. They provide comparable spatial resolution, improve the sensitivity and make easier the mechanical design of the system. In this study we evaluate by means of Geant4-based simulations the possibility of replacing the APDs by SiPMs. Several commercial matrices of light sensors coupled to LYSO:Ce monolithic blocks have been simulated and compared. Regarding the spatial resolution and linearity of the detector, SiPMs with high photo detection efficiency could become an advantageous replacement for the APD

Evaluation of a PET Prototype Using LYSO:Ce Monolithic Detector Block

We have analyzed the performance of a PET demonstrator formed by two sectors of four monolithic detector blocks placed face-to-face. Both front-end and read-out electronics have been evaluated by means of coincidence measurements using a rotating 22Na source placed at the center of the sectors in order to emulate the behavior of a complete full ring. A continuous training method based on neural network (NN) algorithms has been carried out to determine the entrance points over the surface of the detectors. Reconstructed images from 1 MBq 22Na point source and 22Na Derenzo phantom have been obtained using both filtered back projection (FBP) analytic methods and the OSEM 3D iterative algorithm available in the STIR software package [1]. Preliminary data on image reconstruction from a 22Na point source with Ø = 0.25 mm show spatial resolutions from 1.7 to 2.1 mm FWHM in the transverse plane. The results confirm the viability of this design for the development of a full-ring brain PET scanner compatible with magnetic resonance imaging for human studies

Nurses' perceptions of aids and obstacles to the provision of optimal end of life care in ICU

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Acute skin toxicity of ultra-hypofractionated whole breast radiotherapy with simultaneous integrated boost for early breast cancer

Background: Whole-breast irradiation (WBI) after breast conserving surgery (BCS) is indicated to improve loco-regional control and survival. Former studies showed that addition of tumor bed boost in all age groups significantly improved local control although no apparent impact on overall survival but with an increased risk of worse cosmetic outcome. Even though shortened regimens in 3 weeks are considered the standard, recent studies have shown the non-inferiority of a treatment regimen of 5 fractions in one-week in both locoregional control and toxicity profile, although simultaneous integrated boost (SIB) in this setting has been scarcely studied. Materials and Methods: From March-2020 to March-2022, 383 patients with early breast cancer diagnosis and a median age of 56 years-old (range 30–99)were included in a prospective registry of ultra-hypofractionated WBI up to a total dose of 26 Gy in 5.2 Gy/fraction with a SIB of 29 Gy in 5.8 Gy/fraction in 272 patients (71%), 30–31 Gy in 6–6.2 Gy/fraction in 111 patients (29%) with close/focally affected margins. Radiation treatment was delivered by conformal 3-D technique in 366 patients (95%), VMAT in 16patients (4%) and conformal 3-D with deep inspiration breath hold (DIBH) in 4patients (1%). Ninety-three per cent of patients received endocrine therapy and 43% systemic or targeted chemotherapy. Development of acute skin complications was retrospectively reviewed. Results: With a median follow-up of 18 months (range 7–31), all patients are alive without evidence of local, regional or distant relapse. Acute tolerance was acceptable, with null o mild toxicity: 182 (48%) and 15 (4%) patients developed skin toxicity grade 1 and 2 respectively; 9 (2%) and 2 (0.5%) patients breast edema grade 1and 2 respectively. No other acute toxicities were observed. We also evaluated development of early delayed complications and observed grade 1 breast edema in 6 patients (2%); grade 1 hyperpigmentation in 20 patients (5%); and grade 1 and 2 breast induration underneath boost region in 10(3%) and 2 patients (0.5%) respectively. We found a statistically significant correlation between the median PTVWBI and presence of skin toxicity (p = 0.028) as well as a significant correlation between late hyperpigmentation with the median PTVBOOST (p = 0.007) and the ratio PTVBOOST/PTVWBI (p = 0.042). Conclusion: Ultra-hypofractionated WBI + SIB in 5 fractions over one-week is feasible and well tolerated, although longer follow-up is necessary to confirm these results