Purpose:
The aim of this work was the assessment of the physical performance of the new hybrid PET/CT system: Discovery-690.
Methods:
The Discovery-690 combines a lutetium-yttrium-orthosilicate ...(LYSO) block detector designed PET tomograph with a 64-slice CT scanner. The system is further characterized by a dedicated powerful computing platform implementing fully 3D-PET iterative reconstruction algorithms. These algorithms can account for time of flight (TOF) information and/or a 3D model of the PET point spread function (PSF). PET physical performance was measured following NEMA NU-2-2007 procedures. Furthermore, specific tests were used: (i) to measure the energy and timing resolution of the PET system and (ii) to evaluate image quality, by using phantoms representing different clinical conditions (e.g., brain and whole body). Data processing and reconstructions were performed as required by standard procedures. Further reconstructions were carried out to evaluate the performance of the new reconstruction algorithms. In particular, four algorithms were considered for the reconstruction of the PET data: (i) HD = standard configuration, without TOF and PSF, (ii) TOF = HD + TOF, (iii) PSF = HD + PSF, and (iv) TOFPSF = HD + TOF + PSF.
Results:
The transverse (axial) spatial resolution values were 4.70 (4.74) mm and 5.06 (5.55) mm at 1 cm and 10 cm off axis, respectively. Sensitivity (average between 0 and 10 cm) was 7.5 cps/kBq. The noise equivalent count rate (NECR) peak was 139.1 kcps at 29.0 kBq/ml. The scatter fraction at the NECR peak was 37%. The correction accuracy for the dead time losses and random event counts had a maximum absolute error below the NECR peak of 2.09%. The average energy and timing resolution were 12.4% and 544.3 ps, respectively. PET image quality was evaluated with the NEMA IEC Body phantom by using four reconstruction algorithms (HD, TOF, PSF, and TOFPSF), as previously described. The hot contrast (after 3 iterations and for a lesion/background activity ratio of 4:1) for the spheres of 10, 13, 17, and 22 mm was (HD) 29.8, 45.4, 55.4, and 68.1%; (TOF) 39.9, 53.5, 62.7, and 72.2%; (PSF) 28.3, 47.3, 60.4, and 71.8%; (TOFPSF) 43.8, 62.9, 70.6, and 76.4%. The cold contrast for the spheres of 28 and 37 mm was (HD) 62.4 and 65.2%; (TOF) 77.1 and 81.4%; (PSF) 62.0 and 65.2%; (TOFPSF) 77.3 and 81.6%. Similar hot and cold contrast trends were found during the analyses of other phantoms representing different clinical conditions (brain and whole body). Nevertheless, the authors observed a predominant role of either TOF or PSF, depending on the specific characteristics and dimensions of the phantoms.
Conclusions:
Discovery-690 shows very good PET physical performance for all the standard NEMA NU-2-2007 measurements. Furthermore, the new reconstruction algorithms available for PET data (TOF and PSF) allow further improvements of the D-690 image quality performance both qualitatively and quantitatively.
Aim
To evaluate the resistance to cyclic fatigue of ProTaper Next (PTN; Dentsply Sirona, Ballaigues, Switzerland), Revo‐S (Micro‐Mega, Besançon, France), Mtwo (Sweden & Martina, Padova, Italy), ...Twisted Files (TF, SybronEndo, Orange, CA, USA) and EndoWave (J Morita Corporation, Osaka, Japan) used in continuous rotation or in reciprocation of Optimum Torque Reverse motion (OTR).
Methodology
A total of 120 nickel‐titanium files were tested. Twenty‐four instruments for each brand were divided into two groups (n = 12) on the basis of the motion tested: continuous rotation (Group 1) or reciprocation of OTR motion (Group 2). Resistance to cyclic fatigue was determined by recording time to fracture (TtF) in a stainless steel artificial canal with a 60° angle of curvature and 5 mm radius of curvature. The TtF data were analysed by using two‐way analysis of variance (anova) and Bonferroni's post hoc tests at 0.05.
Results
Mtwo and TF had significantly higher TtF when compared with all other instruments, both in continuous rotation and in reciprocation of OTR motion (P < 0.0001 and P < 0.05, respectively). No difference was observed between Mtwo and TF (P > 0.05), in both motions. PTN was associated with higher cyclic fatigue resistance than Revo‐S and EndoWave, both in continuous rotation and in reciprocation of OTR motions (P < 0.0001). No difference was observed between Revo‐S and EndoWave, in both motions (P > 0.05). Reciprocating OTR motion improved TtF of all instruments (P < 0.0001).
Conclusions
Reciprocation of OTR motion improved significantly cyclic fatigue resistance of all instruments tested compared with continuous rotation. Mtwo and TF had significantly higher cyclic fatigue than the other instruments, in both continuous rotation and reciprocation of OTR motion.
The interest in positron emission tomography (PET) and particularly in hybrid integrated PET/CT systems has significantly increased in the last few years due to the improved quality of the obtained ...images. Nevertheless, one of the most important limits of the PET imaging technique is still its poor spatial resolution due to several physical factors originating both at the emission (e.g. positron range, photon non-collinearity) and at detection levels (e.g. scatter inside the scintillating crystals, finite dimensions of the crystals and depth of interaction). To improve the spatial resolution of the images, a possible way consists of measuring the point spread function (PSF) of the system and then accounting for it inside the reconstruction algorithm. In this work, the system response of the GE Discovery STE operating in 3D mode has been characterized by acquiring (22)Na point sources in different positions of the scanner field of view. An image-based model of the PSF was then obtained by fitting asymmetric two-dimensional Gaussians on the (22)Na images reconstructed with small pixel sizes. The PSF was then incorporated, at the image level, in a three-dimensional ordered subset maximum likelihood expectation maximization (OS-MLEM) reconstruction algorithm. A qualitative and quantitative validation of the algorithm accounting for the PSF has been performed on phantom and clinical data, showing improved spatial resolution, higher contrast and lower noise compared with the corresponding images obtained using the standard OS-MLEM algorithm.
Pedullà E, Genovese C, Campagna E, Tempera G, Rapisarda E. Decontamination efficacy of photon‐initiated photoacoustic streaming (PIPS) of irrigants using low‐energy laser settings: an ex vivo study. ...International Endodontic Journal, 45, 865–870, 2012.
Aim To assess ex vivo, the antibacterial effectiveness of photon‐initiated photoacoustic streaming (PIPS) of irrigants using an Er:YAG laser equipped with a newly designed, stripped and tapered tip in extracted teeth with infected root canals.
Methodology One hundred and forty‐eight single‐rooted extracted teeth were prepared to a size 25, 0.06 taper. The specimens were sterilized, and all teeth except ten (negative control group) were inoculated with Enterococcus faecalis and incubated in a CO2 chamber at 37 °C for 15 days in Eppendorf tubes filled with trypticase soy broth medium changed every 2 days. Infected teeth were then randomly divided into four test groups (n = 32 for each): pulsed erbium/YAG laser at nonablative settings for 30 s with sterile bi‐distilled water (Group A) or 5% sodium hypochlorite (NaOCl) (Group B); without laser‐activated sterile bi‐distilled water irrigation for 30 s (Group C) or 5% NaOCl irrigation for 30 s (Group D); the positive control group received no treatment in infected teeth (n = 10). Colony‐forming units (CFUs) were counted from bacteriologic samples taken before (S1) and after treatment (S2). Data were analysed by Kruskal–Wallis and post hoc Dunn’s multiple comparison tests.
Results CFU counts were significantly lower in 5% NaOCl groups with or without laser activation than in sterile bi‐distilled water without laser activation group (P < 0.001). Moreover, there was a significant difference between bi‐distilled water groups with or without laser activation (P < 0.001). Sodium hypochlorite with laser activation group had the greatest CFU reduction, which was significantly greater than that evident in bi‐distilled water groups with or without laser activation (P < 0.001). There were no significant differences between 5% NaOCl groups with or without laser activation (P > 0.05). None of the four groups generated negative samples predictably.
Conclusions Under the conditions of this ex vivo study, there were no significant differences in bacterial reduction between the laser and NaOCl or NaOCl alone groups.
Correction added after online publication, 18th April 2012: The following statement has been deleted: ‘Thus, the use of a laser did not improve microbial killing over and above use of NaOCI alone.’
Aim
To investigate the retreatability of two calcium silicate‐based materials (BioRoot RCS, Septodont, Saint–Maur‐des‐Fossés, France and GuttaFlow Bioseal, Colténe/Whaledent AG, Langenau, Germany) ...using rotary instrumentation combined with supplementary irrigant agitation techniques using extracted teeth in a laboratory setting.
Methodology
The root canals of extracted single‐rooted mandibular premolars were prepared to size 40, .04 taper and randomly divided into two experimental groups (n = 36) depending on the root filling material. Root canals were filled with gutta‐percha and GuttaFlow Bioseal (GB, group 1) or BioRoot RCS (BR, group 2), scanned using a micro‐CT scanner and stored in phosphate‐buffered saline for 4 months. Removal of root filling was performed with rotary instruments, and specimens were randomly allocated to one of the subgroups for supplementary irrigant agitation (n = 12): subgroup A, syringe irrigation (control); subgroup B, Tornado Brush (M.I.B, Suresnes, France) and subgroup C, ultrasonically activated irrigation. Specimens were re‐scanned with micro‐CT to calculate the volume of remnant root filling material. Data were analysed statistically by two‐way ANOVA and post hoc Tukey's tests (P = 0.05).
Results
Specimens filled with GuttaFlow Bioseal were associated with a significantly smaller volume of root filling remnants compared with BioRoot RCS (P < 0.05). There was no significant difference between the supplementary irrigant agitation subgroups in the removal of GB (P > 0.05). In group 2 (BioRoot RCS), subgroups B (Tornado Brush) and C (ultrasonically activated irrigation) were associated with a significantly smaller volume of root filling remnants compared with subgroup A (syringe irrigation) (P < 0.05). There was no significant difference between subgroups B and C (P > 0.05).
Conclusions
Significantly smaller volumes of root filling remnants of GuttaFlow Bioseal, than BioRoot RCS, were present after their removal with rotary instruments and irrigation. Supplementary irrigant agitation techniques were associated with smaller volumes of remnants during the removal of BioRoot RCS but not that of GuttaFlow Bioseal.
Aim
To evaluate the effect of different torsional preloads on cyclic fatigue resistance of endodontic rotary instruments constructed from conventional nickel‐titanium (NiTi), M‐Wire or CM‐Wire.
...Methodology
Eighty new size 25, 0.06 taper Mtwo instruments (Sweden & Martina), size 25, 0.06 taper HyFlex CM (Coltene/Whaledent, Inc) and X2 ProTaper Next (Dentsply Maillefer) were used. The Torque and distortion angles at failure of new instruments (n = 10) were measured, and 0% (n = 10), 25%, 50% and 75% (n = 20) of the mean ultimate torsional strength as preloading condition were applied according to ISO 3630‐1 for each brand. The twenty files tested for every extent of preload were subjected to 20 or 40 torsional cycles (n = 10). After torsional preloading, the number of cycles to failure was evaluated in a simulated canal with 60° angle of curvature and 5 mm of radius of curvature. Data were analysed using two‐way analysis of variance. The fracture surface of each fragment was examined with a scanning electron microscope (SEM). Data were analysed by two‐way analyses of variance.
Results
Preload repetitions did not influence the cyclic fatigue of the three brands; however, the 25%, 50% and 75% torsional preloading significantly reduced the fatigue resistance of all instruments tested (P < 0.01, P < 0.001 and P < 0.0001, respectively) except for the HyFlex CM preloaded with 25% of the maximum torsional strength (P > 0.05).
Conclusions
Torsional preloads reduced the cyclic fatigue resistance of conventional and treated (M‐wire and CM‐wire) NiTi rotary instruments except for size 25, 0.06 taper HyFlex CM instruments with a 25% of torsional preloading.
Objectives
The objective of the study was to evaluate the shaping ability of curved root canals using Twisted File Adaptive (TFA) files (SybronEndo, Orange, CA) and Mtwo (Sweden & Martina, Padova, ...Italy) activated by continuous rotation or adaptive motion.
Materials and methods
Thirty-two mandibular molars with two separate mesial canals and severe angles of curvature were selected. Each canal was randomly assigned to one of the four experimental groups (
n
= 16): TFA and Mtwo files used in continuous rotation (groups 1 and 3) or in adaptive motion (groups 2 and 4). Root canals before and after preparation were assessed by micro-computed tomography. Volume, surface area, canal transportation, and centering ability were recorded and analyzed using two-way analyses of variance.
Results
Volume and surface area increased less with TFA files in continuous rotation than in other groups (
P
< 0.001 and
P
< 0.01, respectively, for each comparison) that were not different (
P
> 0.05). TFA files had significantly less transportation and higher centering ability than Mtwo both in continuous and adaptive motion (
P
< 0.0001). Centering ratio, but not canal transportation, was improved by adaptive motion compared with continuous rotation for both instruments (
P
< 0.01). However, no differences were found in canal transportation and centering ability in the apical third for both instruments and motions (
P
> 0.05).
Conclusions
No difference between the devices and kinematics was found in the apical third; TFA performed significantly better in the middle and coronal parts of the root canal.
Clinical relevance
The use of NiTi files made by heat-treated alloy and/or adaptive motion could improve the qualities of root canal shaping rather than the use of conventional NiTi instruments and/or continuous rotation in the coronal and middle thirds of the root canals, but not in the apical one. Moreover, these findings encourage the use of adaptive motion with conventional NiTi files to improve centering ability without affecting other preparation qualities of root canals.
Nuclear fragmentation measurements are necessary when using heavy-ion beams in hadrontherapy to predict the effects of the ion nuclear interactions within the human body. Moreover, they are also ...fundamental to validate and improve the Monte Carlo codes for their use in planning tumor treatments. Nowadays, a very limited set of carbon fragmentation cross sections are being measured, and in particular, to our knowledge, no double-differential fragmentation cross sections at intermediate energies are available in the literature. In this work, we have measured the double-differential cross sections and the angular distributions of the secondary fragments produced in the (12)C fragmentation at 62 A MeV on a thin carbon target. The experimental data have been used to benchmark the prediction capability of the Geant4 Monte Carlo code at intermediate energies, where it was never tested before. In particular, we have compared the experimental data with the predictions of two Geant4 nuclear reaction models: the Binary Light Ions Cascade and the Quantum Molecular Dynamic. From the comparison, it has been observed that the Binary Light Ions Cascade approximates the angular distributions of the fragment production cross sections better than the Quantum Molecular Dynamic model. However, the discrepancies observed between the experimental data and the Monte Carlo simulations lead to the conclusion that the prediction capability of both models needs to be improved at intermediate energies.
Aim
To compare the cutting efficiency of several glide path files: HyFlex EDM Glidepath File (HEGF), One G (OG), R‐Pilot (RP) and WaveOne Gold Glider (WOGG) at different cutting inclinations.
...Methodology
Cutting efficiency of 120 new HEGF, OG, RP and WOGG was tested at 90°, 70° and 45° inclination in relation to the sample. Depending on manufacturer instructions, instruments were tested in continuous rotation or reciprocating motion against standardized gypsum samples for 120 s using a customized apparatus. Cutting efficiency was determined by measuring the weight loss and the length of the sample cut. Data were analysed using two‐way analysis of variance and Tukey t‐test (P < 0.05).
Results
RP and WOGG had greater cutting ability than HEGF and OG in all tested angles. RP tested at 45° had significantly greater cutting efficiency than when tested at 90° and 70° (P < 0.05). OG was not significantly different in terms of cutting ability at 90°, 70° and 45° (P > 0.05). HEGF and WOGG had significantly greater cutting efficiency at 45° and 70° compared to 90° (P < 0.05), with no significant difference between 45° and 70° (P > 0.05). RP had the greatest cutting ability at all tested angles.
Conclusions
Reciprocating glide path instruments had greater cutting efficiency compared to those in continuous rotation. An inclined insertion (45° or 70°) increased the cutting ability of glide path files except for One G conventional NiTi files.
Aim
To assess resistance to cyclic fatigue of reciprocating nickel–titanium (
NiTi
) files (Reciproc and WaveOne) after immersion in
NaOCl
solution over several time periods.
Methodology
A total of ...90 new Reciproc R25 and WaveOne Primary were tested. The 45 files of the same brand were randomly assigned to three groups (n = 15) and submitted to the following immersion protocol in 5%
NaOCl
at 37 °C for 16 mm: no immersion (control), 1 or 5 min dynamically. The dynamic immersion and the following cyclic fatigue tests were performed using the appropriate preset reciprocation modes (‘RECIPROC ALL’ or ‘WAVEONE ALL’) in a specially designed endodontic motor. Resistance to cyclic fatigue was determined by recording time to fracture (TtF) in a stainless steel artificial canal with a 60° angle of curvature and 5 mm radius of curvature. The artificial canal was manufactured reproducing the instrument's size and taper. Data were analysed by 2‐way analyses of variance.
Results
Resistance to cyclic fatigue of the same
NiTi
file was not significantly affected by immersion in
NaOCl
. Reciproc R25 was associated with a higher cyclic fatigue resistance in all groups compared to WaveOne Primary (P < 0.0001).
Conclusions
Reciprocating dynamic immersion in
NaOCl
for 1 or 5 min did not reduce the cyclic fatigue resistance of
NiTi
files significantly. However, the type of reciprocating instrument influenced cyclic fatigue resistance with Reciproc R25 being more resistant than WaveOne Primary.
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