3D-localisation of cochlear implant electrode contacts in relation to anatomical structures from in vivo cone-beam computed tomography.

Positioning of the cochlear implant (CI) electrode in relation to the anatomical structures is a key factor for the hearing outcome and the preservation of residual hearing after cochlear implantation. Determining the exact electrode's location is therefore expected to play an important role in optimisation of the electrode design, the surgical techniques and the post-operative device fitting. The aim of this study is the development and validation of a robust and efficient computerised algorithm for three-dimensional (3D) localisation of the CI-electrode contacts with respect to the relevant cochlear structures, such as the basilar membrane and the modiolus, from modern clinical in vivo cone-beam computed tomography (CBCT). In the presented algorithm, the pre- and post-implantation CBCT are spatially aligned. To localise the anatomical structures, a cochlear microanatomical template derived from lab-based X-ray computed microtomography (µCT) measurements is warped to match the patient-specific cochlear shape acquired from pre-implantation CBCT. The electrode-contact locations, determined from the post-operative CBCT, are superimposed onto the cochlear fine-structure of the microanatomical template to localise the array. The accuracy of this method was validated in a temporal bone study by comparing the distance of the electrode contacts from the modiolar wall, as derived by the algorithm from CBCTs, with the distance determined from synchrotron-radiation (SR) µCT on the same specimens. Due to the achievable spatial resolution, good tissue contrast and limited presence of metallic artifacts, the SRµCT technique is considered to be a golden standard in the proposed approach. In contrast to other approaches, this validation method allowed for the evaluation of the final electrode-to-modiolus distance (EMD) error, and covers the error in co-alignment of the images, in the determination of the electrode contact location and in the localisation of the cochlear structures. The absolute mean error on the EMD parameter was determined at 0.11 mm (max = 0.29 mm, SD = 0.07 mm) across five samples, slightly lower than the voxel size of the CBCT-scans. In a retrospective study, the algorithm was applied to identify scalar translocations of the electrode from clinical in vivo CBCT datasets of 23 CI-recipients, which showed perfect (100%) agreement with the blinded opinion of two experienced neuroradiologists.

Reusability of P3 Facial Filter in a Pandemic Emergency: A 3D Analysis of Filter Microstructure with X-ray Microtomography Images after Dry Heat and UV Sterilization Procedures.

OBJECTIVE: Our goal is to evaluate the effects of heat and ultraviolet (UV) irradiation on P3 facial respirator microstructure. INTERVENTION: P3 facial filters were exposed to dry heat and UV sterilization procedures. METHODS: P3 facial filter samples underwent a standardized sterilization process based on dry heat and UV irradiation techniques. We analyzed critical parameters of internal microstructure, such as fiber thickness and porosity, before and after sterilization, using 3D data obtained with synchrotron radiation-based X-ray computed microtomography (micro-CT). The analyzed filter has two inner layers called the "finer" and "coarser" layers. The "finer" layer consists of a dense fiber network, while the "coarser" layer has a less compact fiber network. RESULTS: Analysis of 3D images showed no statistically significant differences between the P3 filter of the controls and the dry heat/UV sterilized samples. In particular, averages fiber thickness in the finer layer of the control and the 60° dry heated and UV-irradiated sample groups was almost identical. Average fiber thickness for the coarser layer of the control and the 60° dry heated and UV-irradiated sample groups was very similar, measuring 19.33 µm (±0.47), 18.33 µm (±0.47), and 18.66 µm (±0.47), respectively. There was no substantial difference in maximum fiber thickness in the finer layers and coarser layers. For the control group samples, maximum thickness was on average 11.43 µm (±1.24) in the finer layer and 59.33 µm (±6.79) in the coarser layer. Similarly, the 60° dry heated group samples were thickened 12.2 µm (±0.21) in the finer layer and 57.33 µm (±1.24) in the coarser layer, while for the UV-irradiated group, the mean max thickness was 12.23 µm (±0.90) in the finer layer and 58.00 µm (±6.68) in the coarser layer. Theoretical porosity analysis resulted in 74% and 88% for the finer and coarser layers. The finer layers' theoretical porosity tended to decrease in dry heat and UV-irradiated samples compared with the respective control samples. CONCLUSIONS: Dry heat and UV sterilization processes do not substantially alter the morphometry of the P3 filter samples' internal microstructure, as studied with micro-CT. The current study suggests that safe P3 filter facepiece reusability is theoretically feasible and should be further investigated.

Presentation of gaps around endodontic access cavity restoration by phase contrast-enhanced micro-CT.

OBJECTIVE: To evaluate the feasibility of synchrotron-based phase-contrast (PC) µCT for visualization of the gaps and differentiation between the gaps, restorative, and endodontic materials at the tooth-restoration interface. MATERIALS AND METHODS: Standardized access cavities were prepared in human maxillary molars and subjected to materials, simulating endodontic treatment: (1) saline irrigation; (2) NaOCl and 17% EDTA irrigation; (3) same as group 2, followed by application of Ca(OH)2; and (4) same as group 2, followed by application of root canal sealer. The access cavities were cleaned and restored using an etch-and-rinse adhesive and a composite material in multilayering technique. The samples were thermocycled (1000 cycles, 5-55 °C). Synchrotron-based µCT imaging was performed obtaining absorption and PC µCT images before and after the immersion of the samples into 50% AgNO3. PC µCT images were compared to absorption µCT and conventional optical microscopy images. RESULTS: PC µCT of unstained samples enabled the best visualization of gaps and differentiation of restorative and endodontic materials, contaminating the cavity surface. PC µCT revealed that AgNO3 staining leads to an overestimation of gap size due to anterograde and retrograde AgNO3 infiltration into dentinal tubules and underestimation of large gaps due to lack of AgNO3 penetration. CONCLUSION: Synchrotron PC µCT imaging enables better visualization of gap and differentiation of materials at the tooth-restoration interface. µCT imaging with AgNO3 staining has shown certain over- and underestimations. Future research should be aimed at incorporating PC µCT imaging of unstained samples for the validation of results obtained with other methods. CLINICAL SIGNIFICANCE: Contamination of cavity walls with an endodontic sealer or Ca(OH)2 leads to increased gap formation at the tooth-restoration interface.

Virtual histological assessment of the prenatal life history and age at death of the Upper Paleolithic fetus from Ostuni (Italy).

The fetal remains from the Ostuni 1 burial (Italy, ca 27 ka) represent a unique opportunity to explore the prenatal biological parameters, and to reconstruct the possible patho-biography, of a fetus (and its mother) in an Upper Paleolithic context. Phase-contrast synchrotron X-ray microtomography imaging of two deciduous tooth crowns and microfocus CT measurements of the right hemimandible of the Ostuni 1b fetus were performed at the SYRMEP beamline and at the TomoLab station of the Elettra - Sincrotrone laboratory (Trieste, Italy) in order to refine age at death and to report the enamel developmental history and dental tissue volumes for this fetal individual. The virtual histology allowed to estimate the age at death of the fetus at 31-33 gestational weeks. Three severe physiological stress episodes were also identified in the prenatal enamel. These stress episodes occurred during the last two months and half of pregnancy and may relate to the death of both individuals. Compared with modern prenatal standards, Os1b's skeletal development was advanced. This cautions against the use of modern skeletal and dental references for archaeological finds and emphasizes the need for more studies on prenatal archaeological skeletal samples.

Improving FTIR imaging speciation of organic compound residues or their degradation products in wall painting samples, by introducing a new thin section preparation strategy based on cyclododecane pre-treatment.

Fourier transform infrared (FTIR) imaging in transmission mode, employing a bidimensional focal plane array (FPA) detector, was applied for the detection and spatially resolved chemical characterisation of organic compounds or their degradation products within the stratigraphy of a critical group of fragments, originating from prehistoric and roman wall paintings, containing a very low concentration of subsisted organic matter or its alteration products. Past analyses using attenuated total reflection (ATR) or reflection FTIR on polished cross sections failed to provide any evidence of any organic material assignable as binding medium of the original painting. In order to improve the method's performance, in the present study, a new method of sample preparation in thin section was developed. The procedure is based on the use of cyclododecane C12H24 as embedding material and a subsequent double-side polishing of the specimen. Such procedure provides samples to be studied in FTIR transmission mode without losing the information on the spatial distribution of the detected materials in the paint stratigraphy. For comparison purposes, the same samples were also studied after opening their stratigraphy with a diamond anvil cell. Both preparation techniques offered high-quality chemical imaging of the decay products of an organic substance, giving clues to the painting technique. In addition, the thin sections resulting from the cyclododecane pre-treatment offered more layer-specific data, as the layer thickness and order remained unaffected, whereas the samples resulting from compression within the diamond cell were slightly deformed; however, since thinner and more homogenous, they provided higher spectral quality in terms of S/N ratio. In summary, the present study illustrates the appropriateness of FTIR imaging in transmission mode associated with a new thin section preparation strategy to detect and localise very low-concentrated organic matter subjected to deterioration processes, when the application of FTIR in reflection mode or FTIR-ATR fails to give any relevant information.

Synchrotron light-based µCT to analyse the presence of dentinal microcracks post-rotary and reciprocating NiTi instrumentation.

OBJECTIVES: The purpose of this study was to determine in vitro using a synchrotron radiation-based µCT (SRCT) whether rotary and reciprocating nickel titanium (NiTi) instrumentations lead to the formation of dentine microcracks. MATERIAL AND METHODS: Fourteen extracted human molars were obtained with ethical approval. Seven distobuccal roots of the maxillary molars and seven mesial roots of the mandibular molars were assigned to two experimental groups: (A) prepared with rotary Pro Taper instrumentation (n = 6) and (B) reciprocating WaveOne (n = 6). Irrigation with 1 % NaOCl and 17 % EDTA solutions was carried out. The remaining roots served as positive control with induced fractures (group C). SRCT was used to scan all samples pre and post-operatively. An imaging software was used to determine the number and length of microcracks. Statistical analyses weighed differences between pre and post-instrumentation and between shaping methods. RESULTS: A significant increase in the number and length of microcracks was detected post-shaping. No significant difference between rotary and reciprocating instrumentation was observed. CONCLUSIONS: Within the limitations of this in vitro study, an increased number and length of microcracks was induced by mechanical instrumentation. Reciprocating and rotary instrumentation are similar in terms of effect. CLINICAL SIGNIFICANCE: Dentinal damage may occur following rotary and reciprocating instrumentation.

Evaluation of microstructural properties of coffee beans by synchrotron X-ray microtomography: a methodological approach.

UNLABELLED: Synchrotron radiation microtomography was used as a nondestructive imaging technique to investigate the microstructural properties of green and roasted coffee beans. After image acquisition, 2D images have been reconstructed and 3D images of the beans have been then obtained. Qualitative and quantitative analysis of the images allow to fully characterize the morphological and structural features of the coffee beans. Roasting causes meaningful changes in the microstructure of the coffee bean tissue with the development in the entire bean of a porous structure with pores of different shape and size depending on the zone of the bean and cracks occurring mainly in the more external regions and between parenchyma and mucilage. The highly contrasted X-ray images have been analyzed to determine the pore size and its distribution in different regions of the coffee beans by selecting Volume-of-Interest (VoI). The use of phase-contrast hard X-rays imaging techniques represents an interesting tool of investigation of the internal structure, morphology, as well as the quality of whole coffee beans. Moreover, the high potentiality of 3D X-ray imaging and the approach used in this study could be applied in understanding the effects of roasting process conditions on the evolution of microstructural properties of the bean that may affect the stability as well the grinding and brewing performances. PRACTICAL APPLICATION: Synchrotron radiation microtomography is an elegant nondestructive imaging technique to investigate the microstructural properties of porous cellular matrices like the green and roasted coffee beans. The quantitative analysis of the resulting 2D and 3D images allows a more comprehensive and objective characterization of the sample under investigation as a whole or of extracted Volumes-of-Interest in the bean. This imaging technique could have a major role in understanding the effects of roasting process conditions on the microstructural properties of the bean.