A randomized, controlled, double-blind study of light emitting diode photomodulation for the prevention of radiation dermatitis in patients with breast cancer Permalink https://escholarship.org/uc/item/0jv6d41x Dermatologic Surgery, 36(12) Journal

A major goal of the MAX program is to detect and measure gamma rays produced following the nuclear reactions that take place in a supernova explosion. To detect a reasonable number of supernovae, sensitivities of the order of a few times 10-7 γ cm-2sec-1 are needed -much better than possible with current instruments. The approach in the MAX program is to use a crystal diffraction lens to collect photons over a large area and concentrate them on a small well-shielded detector, greatly improving the signal to noise ratio. The crystals need to have both high diffraction efficiency and a relatively broad energy bandwidth. With mosaic crystals there is a trade-off between bandwidth and diffraction efficiency -one can have either high efficiency or large bandwidth, but not both without losing too much intensity through atomic absorption. A recent breakthrough in our understanding of crystal diffraction for high-energy gamma rays has made it possible to develop crystals that have both high diffraction efficiency and a relatively broad energy bandwidth. These crystals have near perfect crystal structure, but the crystalline planes are slightly curved. Such curved planes can be obtained in 3 different ways, by using mixed crystals with a composition gradient, by applying a thermal gradient, and by mechanically bending a near perfect crystal. A series of experiments have been performed on all three types of crystals using high-energy x-ray beams from the Advanced Photon Source at the Argonne National Laboratory. Experiments performed at 3 energies, 93 keV, 123 keV and 153 keV, with both the thermal gradient Si crystals and with the mechanically bent Si crystals, demonstrated that one can achieve diffraction efficiencies approaching 100% with moderate energy bandwidths ( E/E = 1.4%) and low atomic absorption (transmission = 0.65), in excellent agreement with theory. The use of this type of diffraction crystal is expected to increase the sensitivity of gamma ray telescopes by a factor of 5 over that possible with normal mosaic crystals.

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The objective of this project is to develop and construct an innovative imaging system for nuclear medicine and molecular imaging that uses photon diffraction and is capable of generating 1-2 mm spatial resolution images in two or three dimensions. The proposed imaging system would be capable of detecting radiopharmaceuticals that emit 100-200 keV gamma rays which are typically used in diagnostic nuclear medicine and in molecular imaging. The system is expected to be optimized for the 140.6 keV gamma ray from a Tc-99m source, which is frequently used in nuclear medicine. This new system will focus the incoming gamma rays in a manner analogous to a magnifying glass focusing sunlight into a small focal point on a detector's sensitive area. Focusing gamma rays through photon diffraction has already been demonstrated with the construction of a diffraction lens telescope for astrophysics and a scaled-down lens for medical imaging, both developed at Argonne National Laboratory (ANL). In addition, spatial resolutions of 3 mm have been achieved with a prototype medical lens. The proposed imaging system would be comprised of an array of photon diffraction lenses tuned to diffract a specific gamma ray energy (within 100-200 keV) emitted by a common source. The properties of photon diffraction make it possible to diffract only one specific gamma ray energy at a time, which significantly reduces scattering background. The system should be sufficiently sensitive to the detection of small concentrations of radioactivity that can reveal potential tumor sites at their initial stages of development. Moreover, the system's sensitivity would eliminate the need for re-injecting a patient with more radiopharmaceutical if this patient underwent a prior nuclear imaging scan.Detection of a tumor site at its inception could allow for an earlier initiation of treatment and wider treatment options, which can potentially improve the chances for cure.

PURPOSE Our objective was to demonstrate the efficacy of a telehealth training course on high-dose-rate (HDR) brachytherapy for gynecologic cancer treatment for clinicians in low- and middle-income countries (LMICs) METHODS A 12-week course consisting of 16 live video sessions was offered to 10 cancer centers in the Middle East, Africa, and Nepal. A total of 46 participants joined the course, and 22 participants, on average, attended each session. Radiation oncologists and medical physicists from 11 US and international institutions prepared and provided lectures for each topic covered in the course. Confidence surveys of 15 practical competencies were administered to participants before and after the course. Competencies focused on HDR commissioning, shielding, treatment planning, radiobiology, and applicators. Pre- and post-program surveys of provider confidence, measured by 5-point Likert scale, were administered and compared. RESULTS Forty-six participants, including seven chief medical physicists, 16 senior medical physicists, five radiation oncologists, and three dosimetrists, representing nine countries attended education sessions. Reported confidence scores, both aggregate and paired, demonstrated increases in confidence in all 15 competencies. Post-curriculum score improvement was statistically significant ( P < .05) for paired respondents in 11 of 15 domains. Absolute improvements were largest for confidence in applicator commissioning (2.3 to 3.8, P = .009), treatment planning system commissioning (2.2 to 3.9, P = .0055), and commissioning an HDR machine (2.2 to 4.0, P = .0031). Overall confidence in providing HDR brachytherapy services safely and teaching other providers increased from 3.1 to 3.8 and 3.0 to 3.5, respectively. CONCLUSION A 12-week, low-cost telehealth training program on HDR brachytherapy improved confidence in treatment delivery and teaching for clinicians in 10 participating LMICs.

Positron production in 238 U 1 232 Th and 238 U 1 181 Ta collisions near the Coulomb barrier has been studied. Earlier experiments reported narrow lines in the spectra of positrons, accumulated without the requirement of electrons detected in coincidence. No evidence of such structure is observed in the present data. The positron energy spectra are compared with estimates from dynamic atomic processes, and from internal pair conversion of electromagnetic transitions from the excited nuclei. [S0031-9007(96)02277-6] PACS numbers: 25.70. Bc, Positron production in the collisions of very heavy nuclei at Coulomb-barrier energies has attracted a great deal of attention over the past 15 years. This process is of particular interest since the positron production mechanism is intimately linked to the very strong electromagnetic fields which occur in these collisions. These fields become "supercritical" when the united charge of the two ions (Z U ) is greater than approximately 173, and when the nuclei approach to within approximately 100 fm [1]. This phenomenon has been previously investigated in a number of experiments (e.g., [2,3]). In later experiments with Z U 180 to 188, the energy spectra of positrons displayed unexpected narrow structures at energies near 300-400 keV, with widths of 60 to 80 keV. The initial observation of such peaks in the 238 U 1 248 Cm system (Z U 188) [4] prompted the suggestion that they might be related to the spontaneous production of positrons associated with the overcritical binding of vacant electron orbitals in a relatively long-lived quasiatomic system. The analysis of data from subsequent experiments, however, showed evidence for similar structures in a number of other systems, with characteristics which were inconsistent with the expectations for the spontaneous production mechanism [5]. In particular, the expected very strong Z U dependences of the peak energy and yield (~Z N U where N ഠ 20) were not observed.Structures were also observed in a different set of measurements for the 238 U 1 238 U and 238 U 1 232 Th systems [6,7]. While the energies of the peaks in these data were lower, the general features appeared to be similar to those described previously. In particular, the narrow widths of the lines were taken to imply that the source velocities in the laboratory frame were relatively low, close to that of the center-of-mass of the colliding heavy ions. Finally, weaker evidence has been reported for peaks in subcritical (Z U , 173) systems, including 238 U 1 181 Ta (Z U 165) [8].The characteristics of these structures suggested that their source might be the decay of a light neutral particle X 0 into a positron-electron pair, which would lead to almost monoenergetic positrons of kinetic energy E e 1 ഠ ͑m X 0 2 2m e ͒c 2 ͞2. Sharp sum-energy lines consistent with this hypothesis have been reported in positron-electron coincidence spectra, from collisions in 618 0031-9007͞97͞78(4)͞618(4)$10.00

Hydroxyurea (HU) induces fetal hemoglobin (Hb F) production in patients with sickle cell anemia. The therapeutic dosage of HU used for Hb F induction often elicits myelosuppression, which becomes its major associated complication. We examined the effect of HU on hemoglobin modulation and the role of radical scavengers on these induced changes. In vitro exposure of human blood to various concentrations of HU at predetermined time intervals induced a progressive dose‐dependent oxidation (MetHb formation) of both adult (Hb AA) and sickle (Hb SS) hemoglobins. The oxidative effect of HU on Hb SS was 3 times greater than its effect on Hb AA. Similar but less profound changes were observed in H2O2‐treated samples. Hb F was, however, observed to be relatively resistant to HU‐induced oxidative damage. A substantial protective effect of Hb by α‐tocopherol, ascorbic acid, and D‐mannitol was observed during pretreatment of Hb AA and Hb SS blood samples. Analyses of the hemoglobins and their globin chain components by high‐performance liquid chromatography revealed a considerable protective effect by these free radical scavengers. These results indicate that the HU‐induced damage of hemoglobin and their component globin chains can be reduced by radical scavengers. J. Clin. Lab. Anal. 15:1–7, 2001. © 2001 Wiley‐Liss, Inc.