Very high dose per pulse
(
3
–
13
cGy
∕
pulse
)
high energy electron beams are currently produced by special linear accelerators (linac) dedicated to Intra Operative Radiation Therapy (IORT). The ...electron beams produced by such linacs are collimated by special Perspex applicators of various size and cylindrically shaped. The biggest problems from the dosimetric point of view are caused by the high dose-per-pulse values and the use of inclined applicators. In this work measurements of absolute dose for the inclined applicators were done by using a small cylindrical ionization chamber, type CC01 (Wellhofer), a parallel plane ionization chamber type Markus (PTW 23343) and radiochromic films type EBT. We show a method which allows calculating the quality correction factors for CC01 chamber with an uncertainty of 1% and the absolute dose value for the inclined applicators using CC01 with an uncertainty of 3.1% for electron beams of energy of 6 and
7
MeV
produced by the linac dedicated to IORT Novac7.
Abstract Background Pregnancy after kidney transplant has become possible thanks to the recent surgical and pharmacological breakthrough. Materials and Methods We performed a restrospective study ...including all childbearing women transplanted in our centers after 1997. The following variables were analyzed: type of nephropathy, patient age when dialysis started, age at transplantation, time between dialysis and transplantation and between transplantation and baby birth. We also considered immunosuppressive therapy, type of delivery, baby weight, Apgar score, and mother and baby follow-up. Results We followed up 13 pregnancies in 12 patients who were diagnosed with chronic pyelonephritys (n = 4), postpartum cortical necrosis (n = 1), immunoglobulin A GN (n = 4), diabetic nephropathy (n = 1), unknown nephropathy (n = 2). All patients received a cadaveric donor kidney. They were treated with calcium antagonists and alfamethyldopa for their high blood pressure. We observed 9 mother complications: nonnephrotic proteinuria (n = 1), urinary tract Infection (n = 1), pre-eclampsia (n = 4), internal placenta detachment (n = 1) and spontaneous abortions (n = 2); 4 fetal complications: IUGR (n = 2), acute distress respiaratory syndrome (n = 1), Klinefelter syndrome (n = 1) and preterm births (n = 4). In 2 cases the child weight was lower when compared to the gestational age, and 5 babies were admitted to the neonatal intensive care unit. The mother's follow-up showed no acute rejection episodes. Breastfeeding was discouraged due to the transmission of immunosuppressive medications into breast milk. We did not observe significant disease upon child follow-up. Conclusion Our data were in agreement with the literature confirming that pregnancy after kidney transplant though possible carries elevated risks. Patients therefore are referred to highly specialized centers where obstetricians, nephrologists, intensivists, and neonatologists provide surveillance and treatment.
Purpose
Appropriate use of SPECT imaging is regulated by evidence-based guidelines and appropriateness criteria in an effort to limit the burden of radiation administered to patients. We aimed at ...establishing whether the use of a low dose for stress–rest single-day nuclear myocardial perfusion imaging on an ultrafast (UF) cardiac gamma camera using cadmium-zinc-telluride solid-state detectors could be used routinely with the same accuracy obtained with standard doses and conventional cameras.
Methods
To this purpose, 137 consecutive patients (mean age 61 ± 8 years) with known or suspected coronary artery disease (CAD) were enrolled. They underwent single-day low-dose stress–rest myocardial perfusion imaging using UF SPECT and invasive coronary angiography. Patients underwent the first scan with a 7-min acquisition time 10 min after the end of the stress protocol (dose range 185 to 222 MBq of
99m
Tc-tetrofosmin). The rest scan (dose range 370 to 444 MBq of
99m
Tc-tetrofosmin) was acquired with a 6-min acquisition time. The mean summed stress scores (SSS) and mean summed rest scores (SRS) were obtained semiquantitatively.
Results
Coronary angiograms showed significant epicardial CAD in 83% of patients. Mean SSS and SRS were 10 ± 5 and 3 ± 3, respectively. Overall the area under the ROC curve for the SSS values was 0.904, while the areas under the ROC curves for each vascular territory were 0.982 for the left anterior descending artery, 0.931 for the left circumflex artery and 0.889 for the right coronary artery.
Conclusion
This pilot study demonstrated the feasibility of a low-dose single-day stress–rest fasting protocol performed using UF SPECT, with good sensitivity and specificity in detecting CAD at low patient exposure, opening new perspectives in the use of myocardial perfusion in ischaemic patients.
The challenge of saturation at the high dose rate employed in FLASH radiotherapy and the lack of real-time 2D and 3D dosimeters create an opportunity for the use of plastic scintillators. This study ...presents the development of an online dosimetric system designed for electron FLASH radiotherapy applications: an array of dosimeters, made by plastic scintillating fibers, each one coupled to an optical fiber, was evaluated as a proof-of-concept using a LINAC providing 9 MeV electrons, at the Centro Pisano Flash Radiotherapy. Signal linearity was established up to 10 Gy/pulse, with a pulse duration of 4μs. We also measured the signal variation across the beam profile using different applicators (30 mm, 50 mm and 100 mm in diameters) and we developed a geometrical model that accounts for the different amount of dose absorbed by the plastic scintillating fibers and the optical fibers. By fitting this model to the data, we estimated both the inter-calibration factors of the dosimeters, as well as the intrinsic ratio (i.e. for equal irradiated volumes) of spurious light in the optical fiber respect to the scintillation, which is equal to (4.7±0.1stat.±1.0syst.) %.
•Dosimeters made by an array of plastic scintillating fibers tested with a FLASH beam.•Beam profile measured with an array of five dosimeters.•New calibration method to equalize response and subtract spurious signal.
Probably the most important range of materials for consideration as the blanket material for the tokamak design for fusion reactors ITER and DEMO is the high alloy Fe–9Cr oxide dispersion ...strengthened ferritic steels. Ferritic steels possess exceptional thermal conductivity and low thermal expansion and are resistant to void swelling. Their main drawback is high ductile to brittle transition temperatures, particularly in the oxide dispersion strengthened versions. This paper describes attempts to reduce the DBTT in an un-irradiated ferritic steel by a novel heat treatment procedure. New batches of high alloy Fe–9Cr oxide dispersion strengthened (Eurofer) ferritic steel have been produced by a powder metallurgy route, and relatively homogeneous material has been produced by hot isostatic pressing (HIP). Mini-Charpy test specimens were made from materials which had been subjected to a matrix of heat treatments with varying solution treatment temperature (ST), cooling rate from the ST temperature, and tempering treatment. The initial DBTT was in the range of 150–200°C (423–473K). Downward shifts of up to approximately 200°C (473K) have been observed after solution treatment at 1300°C (1573K) followed by slow cooling. This paper describes the microstructure of this material, and discussion is made of the likely microstructural factors needed to produce these DBTT downward shifts.
By normalizing the values of its pixels with respect to the length of the used scale, a gray image can be interpreted as a fuzzy relation R which is divided in submatrices (possibly square) called ...blocks. Every block RB is compressed to a block GB, which in turn is decompressed to a block DB (unsigned) ⩾RB. Both GB and DB are obtained via fuzzy relation equations with continuous triangular norms in which fuzzy sets with Gaussian membership functions are used as coders. The blocks DB are recomposed in order to give a fuzzy relation D. We use the Lukasiewicz t-norm and a watermark (matrix) is embedded in every GB with the LSBM (Least Significant Bit Modification) algorithm by obtaining a block , decompressed to a block (signed). Both and are obtained by using the same fuzzy relation equations. The blocks are recomposed by obtaining the fuzzy relation (signed). By evaluating the quality of the reconstructed images via the PSNR (Peak Signal to Noise Ratio) with respect to the original image R, we show that the signed image is very similar to the unsigned image D for low values of the compression rate.
