[en] An expression is derived for the electron density resolution of proton computed tomography obtained from algebraic reconstruction methods. The dependence of the resolution on system parameters is clarified and methods for achieving the best resolutions possible are suggested. Comparison of our results with previous ones from the literature is included as well as a discussion of the limitations of the results.

[en] The scanner is based on the nuclear scattering of high energy protons by the nucleons (protons and neutrons) included in the atomic nuclei. It has been described elsewhere and we just recall here the main properties. The future improvements are notified

[en] Nuclear reaction transmutation doping in GaN - 2D layer-based MOSFETs, crucial for precise dose measurements in heavy ion radiotherapy machines, poses potential long-term radiation damage. These MOSFETs are optimal for satisfying restricted stopping power conditions and delta-ray equilibrium across various charged particles in proton and heavy ion therapy. Yet, producing new reaction residues during their use can significantly alter dosimeter calibration, warranting thorough research. Hence, this study delves into the impact of nuclear reaction transmutation doping on dosimetry, as its effect remains unexplored despite being a significant concern. Studied the α impact on GaN MOSFET for Dose-Drain current calibration shifts. Nuclear transmutation doping in GaN 2D layers had a significant influence on calibrations

[en] Nuclear scattering radiography (N.S.R.) allows to obain directly a three dimensional representation of the objects. It is sensitive to the product of the specific gravity by the nuclear scattering cross-sections of the elements in the objects. We call it simple radiographs. N.S.R. allows to obtain simultaneously the distribution of the hydrogen contained in the objects (hydrogen radiographs). Results obtained on an anatomical specimen (head) are given and the future possibilities of the technique are estimated

[en] Comprehensive tests on single slice CT scanner was carried out using in-house fabricated phantoms/test tools following AAPM recommended methods to independently validate the auto-performance test (APT) results. Test results of all the electromechanical parameters were found within the specified limits. Radiation and sensitivity profile widths were within ± 0.05 cm of the set slice thickness. Effective energy corresponding to nominal kVp of 80, 110 and 130 were 49.99, 55.08 and 59.48 keV, respectively. Percentage noise obtained by APT was 1.32% while the independently measured value was 0.38%. Observed contrast resolutions by independent method at 0.78% and 12% contrast difference were 4 mm and 1.25 mm ( = 4 Ip/cm) respectively. However, high contrast resolution (limiting spatial resolution) by APT at 50, 10 and 2% MTF levels were 9, 12.5 and 14.1 Ip/cm respectively. Difference in calculated and measured CT numbers of water, air, teflon, acrylic, polystyrene and polypropylene were in the range of 0 to 24 HU, while this difference was 46 and 94 HU in case of nylon and bakelite respectively. The contrast scale determined using CT linearity phantom was 1.998 x 10^-4 cm^-1/CT number. CT dose index (CTDI) and weighted CTDI (CTDl_w) measured at different kVp for standard head and body phantoms were smaller than manufacturer-specified and system-calculated values and were found within the manufacturer-specified limit of ± 20%. Measured CTDIs on surface (head: 3.6 cGy and body: 2.6 cGy) and at the center (3.3 cGy, head; and 1.2 cGy, body) were comparable to reported values of other similar CT scanners and were also within the industry-quoted CTDI range. Comprehensive QA and independent validation of APT results are necessary to obtain baseline data for CT virtual simulation. (author)

[en] The present invention concerns a procedure and an image forming apparatus for a section of the object examined, the relative nuclear densities of the object yielding the image information. In particular, the application of nuclear magnetic resonance techniques to obtain in vivo nuclei density lines at resonance is described, human or animal applications being envisaged

No abstract available

[en] Proton Computed Tomography (pCT) can improve the accuracy of both patient positioning and dose calculation in proton therapy, enabling to accurately reconstruct the electron density distribution of irradiated tissues. A pCT prototype, equipped with a silicon tracker and a YAG:Ce calorimeter, has been manufactured by an Italian collaboration. First tests under proton beam allowed obtaining good quality tomographic images of a non-homogeneous phantom. Manufacturing of a new large area system with real-time data acquisition is under way.

[en] The aim of this study was to evaluate the feasibility of using [¹⁸F] 3'-deoxy-3'-fluorothymidine (FLT) positron emission tomography (PET) for the diagnosis and grading of brain tumors. The patient population comprised 26 patients (15 males, 11 females) with brain tumors (n=18) or nontumorous lesions (n=8). 2-[¹⁸F]fluoro-2-deoxy-d-glucose (FDG) and FLT PET images were obtained using a dedicated PET scanner 1 h after the injection of 370 MBq of FDG or FLT. Uptake of FDG and FLT by the lesions was visually and semiquantitatively assessed in comparison with normal brain tissue. Of 26 brain lesions, four showed increased FDG uptake compared with normal gray matter (grade 5). These four lesions showed intensely increased FLT uptake and were all high-grade tumors. Twenty-two lesions with similar (grade 4) or decreased (grades 1-3) FDG uptake compared with normal gray matter showed variable pathology. Among the 18 brain tumors, FLT PET showed increased uptake in all 12 high-grade tumors but FDG uptake was variable. In 22 brain lesions with similar or decreased uptake compared with normal gray matter on FDG PET, the sensitivity and specificity of FLT PET for the diagnosis of brain tumor were 79% (11/14) and 63% (5/8), respectively. The uptake ratios of 14 brain tumors on FLT PET were significantly higher than the lesion to gray matter ratios (p=0.012) and lesion to white matter ratios (p=0.036) of FDG uptake and differed significantly between high (5.1±2.6) and low (2.1±1.1) grade tumors (p=0.029). In nine gliomas, FLT uptake was significantly correlated with the Ki-67 proliferation index (rho=0.817, p=0.007). These findings indicate that FLT PET is useful for evaluating tumor grade and cellular proliferation in brain tumors. It displayed high sensitivity and good contrast in evaluating brain lesions that showed similar or decreased uptake compared with normal gray matter on FDG PET. FLT PET, however, did not appear to be sufficiently useful for differentiating tumors from nontumorous lesions. (orig.)

[en] The aim of this study was to evaluate image quality and lesion detectability with and without attenuation correction in patients with abdominal tumors, using a free-response receiver operating characteristic (FROC) methodology. Thirty-four patients with various abdominal tumors were evaluated (11 men, 23 women, median age 48 years). Whole-body emission scans were performed 68 min (35-102 min) after intravenous injection of 4.3 MBq/kg fluorine-18 fluorodeoxyglucose (FDG). Images were reconstructed using the OS-EM algorithm and corrected for attenuation either using postinjection singles transmission (n=27) or by calculation and body outline (n=7). Total scan duration did not exceed 70 min. Studies were read independently by four observers unaware of any clinical data. The uncorrected (UC) images were systematically read before the attenuation-corrected (AC) images. All studies were given an image quality score ranging from 1 (unreadable) to 5 (excellent). Each focus of increased activity was then localized and given a probability of malignancy using a five-point scale. The average image quality score was similar for both UC and AC images. At the time of the positron emission tomography (PET) scans, 127 lesions (63 liver metastases, 9 retroperitoneal lesions, 50 peritoneal or bowel lesions, and 5 pancreatic carcinomas) were revealed by pathological or correlative studies. The areas under the FROC curves were consistently greater for AC images (range 0.8663-0.8867) than for UC images (range 0.7774-0.8613). Overall, the difference between the AC images and the UC images was significant (P=0.019). In particular, correction for attenuation increased the sensitivity regardless of the location of the lesions. In conclusion, correction for attenuation significantly improves the diagnostic accuracy of FDG-PET for abdominal staging of neoplasms, without impairing the image quality. (orig.)