Endodontic working length measurements of premolars and molars in high-resolution dental MRI: a clinical pilot study for assessment of reliability and accuracy.

OBJECTIVES: To prospectively assess the reliability and accuracy of high-resolution, dental MRI (dMRI) for endodontic working length (WL) measurements of premolars and molars under clinical conditions. MATERIALS AND METHODS: Three-Tesla dMRI was performed in 9 subjects who also had undergone cone-beam computed tomography (CBCT) (mean age: 47 ± 13.5 years). A total of 34 root canals from 12 molars (4/8, upper/lower jaw; 22 root canals) and 11 premolars (2/9 upper/lower jaw; 12 root canals) were included. CBCT and dMRI datasets were reconstructed to visualize the root canal in one single slice. Subsequently, two radiologists measured the root canal lengths in both modalities twice in blinded fashion. Reliability and accuracy for both modalities were assessed using intraclass correlation coefficients (ICCs) and Bland-Altman analysis, respectively. RESULTS: Reliability (intra-rater I/II; inter-rater) of dental MRI measurements was excellent and comparable to CBCT for premolars (0.993/0.900; 0.958 vs. 0.993/0.956; 0.951) and for molars (0.978/0.995; 0.986 vs. 0.992/0.996; 0.989). Bland-Altman analysis revealed a mean underestimation/bias (95% confidence interval) of dMRI measurements of 0.8 (- 1.44/3.05) mm for premolars and 0.4 (- 1.55/2.39) mm for molars. In up to 59% of the cases, the accuracy of dMRI for WL measurements was within the underestimation margin of 0 to 2 mm short of the apical foramen AF. CONCLUSIONS: In vivo demonstration and measurement of WL are feasible using dMRI. The reliability of measurements is high and equivalent to CBCT. Nonetheless, due to lower spatial resolution and longer acquisition time, the accuracy of dMRI is inferior to CBCT, impeding its current use for clinical treatment planning. CLINICAL RELEVANCE: dMRI is a promising radiation-free imaging technique. Its reliability for endodontic working length measurements is high, but its accuracy is not satisfactory enough yet.

A comprehensive Monte Carlo study of out-of-field secondary neutron spectra in a scanned-beam proton therapy gantry room.

PURPOSE: To simulate secondary neutron radiation fields that had been measured at different relative positions during phantom irradiation inside a scanning proton therapy gantry treatment room. Further, to identify origin, energy distribution, and angular emission of the secondary neutrons as a function of proton beam energy. METHODS: The FLUKA Monte Carlo code was used to model the relevant parts of the treatment room in a scanned pencil beam proton therapy gantry including shielding walls, floor, major metallic gantry-components, patient table, and a homogeneous PMMA target. The proton beams were modeled based on experimental beam ranges in water and spot shapes in air. Neutron energy spectra were simulated at 0°, 45°, 90° and 135° relative to the beam axis at 2m distance from isocenter for monoenergetic 11×11cm2 fields from 200MeV, 140MeV, 75MeV initial proton beams, as well as for 118MeV protons with a 5cm thick PMMA range shifter. The total neutron spectra were scored for these four positions and proton energies. FLUKA neutron spectra simulations were crosschecked with Geant4 simulations using initial proton beam properties from FLUKA-generated phase spaces. Additionally, the room-components generating secondary neutrons in the room and their contributions to the total spectrum were identified and quantified. RESULTS: FLUKA and Geant4 simulated neutron spectra showed good general agreement with published measurements in the whole simulated neutron energy range of 10-10 to 103MeV. As in previous studies, high-energy (E≥19.6MeV) neutrons from the phantom are most prevalent along 0°, while thermalized (1meV≤E<0.4eV) and fast (100keV≤E<19.4MeV) neutrons dominate the spectra in the lateral and backscatter direction. The iron of the large bending magnet and its counterweight mounted on the gantry were identified as the most determinant sources of secondary fast-neutrons, which have been lacking in simplified room simulations. CONCLUSIONS: The results helped disentangle the origin of secondary neutrons and their dominant contributions and were strengthened by the fact that a cross comparison was made using two independent Monte Carlo codes. The complexity of such room model can in future be limited using the result. They may further be generalized in that they can be used for an assessment of neutron fields, possibly even at facilities where detailed neutron measurements and simulations cannot be performed. They may also help to design future proton therapy facilities and to reduce unwanted radiation doses from secondary neutrons to patients.

Radiation protection modelling for 2.5 Petawatt-laser production of ultrashort x-ray, proton and ion bunches: Monte Carlo model of the Munich CALA facility.

The 'Centre for Advanced Laser Applications' (CALA) is a new research institute for laser-based acceleration of electron beams for brilliant x-ray generation, laser-driven sub-nanosecond bunches of protons and heavy ions for biomedical applications like imaging and tumour therapy as well as for nuclear and high-field physics.The radiation sources emerging from experiments using the up to 2.5 petawatt laser pulses with 25 femtosecond duration will be mixed particle-species of high intensity, high energy and pulsed, thus posing new challenges compared to conventional radiation protection. Such worldwide pioneering laser experiments result in source characteristics that require careful a-priori radiation safety simulations.The FLUKA Monte-Carlo code was used to model the five CALA experimental caves, including the corridors, halls and air spaces surrounding the caves. Beams of electrons (<5 GeV), protons (<200 MeV),12C (<400MeV/u) and197Au (<10MeV/u) ions were simulated using spectra, divergences and bunch-charges based on expectations from recent scientific progress.Simulated dose rates locally can exceed 1.5 kSv h-1inside beam dumps. Vacuum pipes in the cave walls for laser transport and extraction channels for the generated x-rays result in small dose leakage to neighboring areas. Secondary neutrons contribute to most of the prompt dose rate outside caves into which the beam is delivered. This secondary radiation component causes non-negligible dose rates to occur behind walls to which large fluences of secondary particles are directed.By employing adequate beam dumps matched to beam-divergence, magnets, passive shielding and laser pulse repetition limits, average dose rates in- and outside the experimental building stay below design specifications (<0.5µSv h-1) for unclassified areas,<2.5µSv h-1for supervised areas,<7.5µSv h-1maximum local dose rate) and regulatory limits (<1mSv a-1for unclassified areas).

Optimization and performance study of a proton CT system for pre-clinical small animal imaging.

Proton computed tomography (pCT) promises to reduce or even eliminate range uncertainties inherent in the conversion of Hounsfield units into relative stopping power (RSP) for proton therapy treatment planning. This is of particular interest for proton irradiation studies in animal models due to the high precision required and uncertainties in tissue properties. We propose a dedicated single-particle tracking pCT system consisting of low material budget floating strip Micromegas detectors for tracking and a segmented time-projection-chamber with vertical Mylar absorbers, functioning as a range telescope. Based on Monte Carlo simulations of a realistic in silico beam and detector implementation, a geometrical optimization of the system components was conducted to safeguard an ideal operation close to intrinsic performance limits at 75 MeV. Moreover, the overall imaging capabilities relevant for pre-clinical proton therapy treatment planning were evaluated for a mouse model. In order to minimize extrinsic uncertainties in the estimated proton trajectories, a spacing of the two tracking planes of at least 7 cm is required in both tracking detectors. Additionally, novel in-house developed and produced aluminum-based readout electrodes promise superior performance with around 3 mm-1 spatial resolution due to the reduced material budget. Concerning the range telescope, an absorber thickness within 500 µm to 750 µm was found to yield the best compromise between water-equivalent path length resolution and complexity of the detector instrumentation, still providing sub-0.5% RSP accuracy. The optimized detector configuration enables better than 2% range accuracy for proton therapy treatment planning in pre-clinical data sets. This work outlines the potential of pCT for small animal imaging. The performance of the proposed and optimized system provides superior treatment planning accuracy compared to conventional x-ray CT. Thus, pCT can play an important role in translational and pre-clinical cancer research.

Ultrasonographic assessment of the spleen in 60 healthy sheep.

AIM: To evaluate the sonographic appearance, size, location and shape of the spleen in 60 healthy sheep. METHODS: A 7.5 MHz linear scanner was used to examine the location, extent and appearance of the spleen from the left side of the sheep, in intercostal spaces (ICS) 8-12 and caudal of the last rib. RESULTS: The ultrasonographic appearance of the splenic parenchyma was homogeneous with a thin, smooth echogenic capsule. The spleen could be visualized in intercostal spaces 9-12 in all sheep, in intercostal space 8 in 25/60 sheep (42%) and caudal of the last rib in 24/60 sheep (40%). In intercostal spaces 8-12 and caudal of the last rib the spleen was visible in 16/60 sheep (27 %). The distance from the dorsal margin of the spleen to the spinous processes of the thoracic vertebrae was greatest in the 8th intercostal space: mean 19.32 (SD 2.76) cm and smallest in the 12th intercostal space: mean 6.61 (SD 1.94) cm. The dorsoventral splenic extent was greatest in the 11th intercostal space: mean 13.69 (SD 2.2) cm and smallest in the 8th intercostal space: mean 7.13 (SD 2.5) cm. The thickness of the spleen ranged from 21 (SD 9.0) mm in the 8th intercostal space to 49 (SD 7.0) mm in the 11th intercostal space. The mean vessel diameter was 1.9 (SD 0.7) mm. Spleen size did not correlate with age, body weight, or thoracic and abdominal circumference. CONCLUSIONS: Ultrasonography is a useful, straightforward and non-invasive method for evaluation of the spleen in sheep. CLINICAL RELEVANCE: These findings provide information which can be used as a reference for sonographic spleen examination and diagnosis of splenic lesions in sheep.

Objective assessment of quality of life in female patients after esthetic, non-oncologic or oncologic surgery of their mammary glands--reality and perspectives.

UNLABELLED: The World Health Organisation defines health as a state of complete physical, mental and social well-being, and not merely the absence of a disease or infirmity. The female breast, surgically considered as a "troubled organ", can be affected by disorders of various types. Its normal morphology can be changed by deformities which may have a serious impact on the mental state of female patients. Assessment of these deformities is essential when doctors should define the inclusion and exclusion criteria for each breast operation that has elements of esthetic surgery in it, the breast being indisputably a symbol of female beauty. When we consider the parameters of normal breast morphology, it is only proper to take into account their dependence on race, national culture, folk psychology, etc. For Bulgarian women, P. Tepavicharova has found that the distance from fossa jugularis to the nipple-areolar complex can have the following characteristic proportions: 15.5-17 cm for a woman 155-160 cm in height and with breast circumference of 75-80 cm; 17-18.5 cm for woman 160-165 cm in height and with breast circumference of 89-95 cm; and 18-20 cm for a woman 165-170 cm in height and with breast circumference of 95-100 cm. J. Lalardie points out that breast stability is determined by three principal factors: skin and its elasticity, the condition of the underlying collagenous structure of the breast, and the firm bond between the skin and fibrous elements. RB Brinks defines the four forms of ptosis of the breast: glandular ptosis, true ptosis, parenchymal maldistribution, and pseudoptosis. According to P. Tepavicharova, the violation of breast symmetry is the major factor triggering a sequence of psychosomatic reactions. CONCLUSIONS: The basic parameters of female breast morphology are the mammary base, mammary perimeter, the forward projection of the breast, symmetry, breast volume, and the state of the axillary extension. The major deviations from normal breast morphology that can have an impact on the quality of life are mammary ptosis, hypertrophy, asymmetry, and deformations of the breast shape as well as the operation cicatrices on the breast. An assessment of the association of the deviations from normal morphology with the correction to normal morphology (with or without dealing with a pathological process) and with the impact on the quality of life is a possible base for objective assessment of the latter parameter.