Durable-polymer versus biodegradable-polymer drug-eluting stents in acute coronary syndromes: three-year outcomes of the HOST REDUCE POLYTECH RCT Trial.

BACKGROUND: Long-term follow-up is essential to evaluate the impact of polymer degradation in drug-eluting stents (DES). AIMS: We aimed to compare durable-polymer DES (DP-DES) and biodegradable-polymer DES (BP-DES) during a 3-year follow-up to evaluate the entire period of polymer resolution (before, during, and after degradation). METHODS: The HOST REDUCE POLYTECH RCT Trial was a randomised clinical trial enrolling patients with acute coronary syndrome (ACS) and comparing the efficacy and safety of DP-DES and BP-DES. The primary outcome was a patient-oriented composite outcome (POCO), and the key secondary outcome was a device-oriented composite outcome (DOCO). RESULTS: A total of 3,413 ACS patients were randomised to either the DP-DES (1,713 patients) or BP-DES (1,700 patients) group. During the 3-year follow-up, the risk of the POCO was similar between the DP-DES and BP-DES groups (14.8% vs 15.4%, hazard ratio [HR] 0.96, 95% confidence interval [CI]: 0.80-1.14; p=0.613). However, the risk of the DOCO was lower in the DP-DES group (6.0% vs 8.0%, HR 0.73, 95% CI: 0.57-0.95; p=0.020). In a landmark analysis, the lower risk of the DOCO for the DP-DES group was evident during the transition from the early to the late period after percutaneous coronary intervention (PCI) (from 8 to 16 months post-PCI; 1.8% vs 3.3%, HR 0.54, 95% CI: 0.34-0.84; p=0.007), which was mainly driven by a risk reduction of target lesion revascularisation. CONCLUSIONS: In ACS patients, DP-DES showed similar results to BP-DES regarding the POCO up to 3 years. For the DOCO, DP-DES were superior to BP-DES; this was due to the higher event rate during the period of polymer degradation.

Development of a PMMA phantom as a practical alternative for quality control of gamma knife® dosimetry.

BACKGROUND: To measure the absorbed dose rate to water and penumbra of a Gamma Knife® (GK) using a polymethyl metacrylate (PMMA) phantom. METHODS: A multi-purpose PMMA phantom was developed to measure the absorbed dose rate to water and the dose distribution of a GK. The phantom consists of a hemispherical outer phantom, one exchangeable cylindrical chamber-hosting inner phantom, and two film-hosting inner phantoms. The radius of the phantom was determined considering the electron density of the PMMA such that it corresponds to 8 g/cm2 water depth, which is the reference depth of the absorbed dose measurement of GK. The absorbed dose rate to water was measured with a PTW TN31010 chamber, and the dose distributions were measured with radiochromic films at the calibration center of a patient positioning system of a GK Perfexion. A spherical water-filled phantom with the same water equivalent depth was constructed as a reference phantom. The dose rate to water and dose distributions at the center of a circular field delimited by a 16-mm collimator were measured with the PMMA phantom at six GK Perfexion sites. RESULTS: The radius of the PMMA phantom was determined to be 6.93 cm, corresponding to equivalent water depth of 8 g/cm2. The absorbed dose rate to water was measured with the PMMA phantom, the spherical water-filled phantom and a commercial solid water phantom. The measured dose rate with the PMMA phantom was 1.2% and 1.8% higher than those measured with the spherical water-filled phantom and the solid water phantom, respectively. These differences can be explained by the scattered photon contribution of PMMA off incoming 60Co gamma-rays to the dose rate. The average full width half maximum and penumbra values measured with the PMMA phantom showed reasonable agreement with two calculated values, one at the center of the PMMA phantom (LGP6.93) and other at the center of a water sphere with a radius of 8 cm (LGP8.0) given by Leksell Gamma Plan using the TMR10 algorithm. CONCLUSIONS: A PMMA phantom constructed in this study to measure the absorbed dose rates to water and dose distributions of a GK represents an acceptable and practical alternative for GK dosimetry considering its cost-effectiveness and ease of handling.

Determination of the absorbed dose rate to water for the 18-mm helmet of a gamma knife.

PURPOSE: To measure the absorbed dose rate to water of (60)Co gamma rays of a Gamma Knife Model C using water-filled phantoms (WFP). METHODS AND MATERIALS: Spherical WFP with an equivalent water depth of 5, 7, 8, and 9 cm were constructed. The dose rates at the center of an 18-mm helmet were measured in an 8-cm WFP (WFP-3) and two plastic phantoms. Two independent measurement systems were used: one was calibrated to an air kerma (Set I) and the other was calibrated to the absorbed dose to water (Set II). The dose rates of WFP-3 and the plastic phantoms were converted to dose rates for an 8-cm water depth using the attenuation coefficient and the equivalent water depths. RESULTS: The dose rate measured at the center of WFP-3 using Set II was 2.2% and 1.0% higher than dose rates measured at the center of the two plastic phantoms. The measured effective attenuation coefficient of Gamma Knife photon beam in WFPs was 0.0621 cm(-1). After attenuation correction, the difference between the dose rate at an 8-cm water depth measured in WFP-3 and dose rates in the plastic phantoms was smaller than the uncertainty of the measurements. CONCLUSIONS: Systematic errors related to the characteristics of the phantom materials in the dose rate measurement of a Gamma Knife need to be corrected for. Correction of the dose rate using an equivalent water depth and attenuation provided results that were more consistent.