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Detectors, Relative Dosimetry, and Microdosimetry
Published in Harald Paganetti, Proton Therapy Physics, 2018
Radiochromic dosimeters are based on a change of color as a result of radiation-induced chemical reactions. Various chemicals have been used as radiochromic dosimeters, such as aminotriphenyl-methane dyes and leuco dyes. Commercial radiochromic films, such as MD-55, EBT, EBT2, EBT3, and EBT-XD (Ashland, NJ), are 2D detectors that are widely used in radiotherapy in recent years. These all contain pentacosa-10,12-diyonic acid (PCDA) or its lithium salt LiPCDA in the sensitive layer. The crystalline PCDA or LiPCDA polymerize after irradiation, forming an intense blue darkening [47] without a requirement for any postirradiation development process. One or more thin layers of the radiochromic material are embedded in polyester films, and the overall composition of the films is nearly tissue equivalent. This dosimeter exhibits energy dependence due to the LET dependence of the chemical yields (number of molecules formed per 100 eV of energy imparted) of initial reactive species formed and, in addition, due to recombination or termination reactions that depend on the ionization density. For very low-energy protons, response quenching can be up to 50% [18], while in the Bragg peak of clinical low-energy proton beams, the under response is typically between 10% and 20%.
Historical background, development, and construction of radiochromic films
Published in Indra J. Das, Radiochromic Film, 2017
Martin Butson, Azam Niroomand-Rad
The sensitivity of HD-810 and MD-55 films decreases with decreasing energy, therefore ISP developed XR type T and R (transmissive and reflective) specifically for use in the low-energy range, 20–200 kVp. The film has the same active layer as the previous films but included a high-Z material and has a dose range of 0.1–15 Gy. By the mid-2000s, a new film was released called external beam therapy (EBT). The active layer was a variation of the monomer used in the previous films and was a hair like version of the lithium salt of pentacosa-10, 12-diyonic acid crystal [42]. The atomic composition of EBT is (42.3% C, 39.7% H, 16.2% O, 1.1% N, 0.3% Li, and 0.3% Cl). The inclusion of the moderate atomic number element chlorine (Z = 17) provided a Zeff of 6.98 making it near tissue equivalent. The new active layer was also found to be more sensitive, providing a dose range of 0.01–8 Gy. The diacetylene monomers exposed to heat, UV, or ionizing radiation undergo progressive 1,4-polymerization leading to the production of colored polymer chains that grow in length with level of exposure as shown in Figure 2.3 [21,38,43]. The packing of the diacetylene monomers in the crystal lattice depends on the particular end groups (R1 and R2 in Figure 2.3), the monomers in EBT films are approximately 0.75 µm in diameter and for the polymerization to occur the triple bonds of adjacent monomers should be within 0.4 nm of each other [42]. The radiation sensitivity of the crystal is also dependent on the particular end groups, with the lithium salt of pentacosa diynoic acid used in EBT film being sensitive to doses as low as 1cGy, several orders of magnitude more sensitive than the earlier radiochromic films.
Comparison of immediate and sustained release formulations of lithium salts
Published in International Review of Psychiatry, 2022
Maurizio Pompili, Carlo Magistri, Cristiano Mellini, Giuseppe Sarli, Ross J. Baldessarini
The variety of lithium salt preparations and doses and of study participants, with few determinations (n = 1–5) of the same outcomes (Table 2), limited efforts to provide quantitative comparisons of SR vs. IR products and data were not sufficient to support formal meta-analysis. Nevertheless, an important observation is that in 11 of 14 outcomes rated, SR appeared to support more favourable responses than with IR lithium salt preparations. These differences included: 15% lower 48 h excretion of lithium, 16% less dilute urine (osmolality) with 10%, greater GFR, as well as 49% lesser cognitive symptoms, 51% less tremor, 43% less fatigue, 50% less weakness, and 35% less weight-gain, as well as 35% more favourable overall ratings of adverse effects, without significant mean differences regarding polyuria, headache, or gastrointestinal symptoms; moreover, treatment-adherence was, significantly, 32% greater. In one report, variance in serum concentrations of lithium was lower with SR lithium sulphate (Barbuti et al., 2021). Also based on a single study, the serum elimination half-life for lithium was 74% longer with SR (33.7 h) than IR (19.3 h) forms of lithium carbonate (Castrogiovanni, 2002). These generally more favourable outcomes with SR preparations of lithium salts as regards tolerability may reflect the reported, substantially (by ca. half) lower daily peak-to-trough differences in levels of circulating lithium (Alda, 2006).
Outcomes of acute exploratory pediatric lithium ingestions
Published in Clinical Toxicology, 2020
Faisal Syed Minhaj, Bruce D. Anderson, Joshua D. King, James B. Leonard
The primary objective of the study was to characterize acute unintentional exposures to lithium in children <6 years of age. As a secondary outcome, we sought to identify a weight-based threshold to empirically refer patients into a healthcare facility for symptoms consistent with moderate effect or worse. Only cases where either a specific dose of the lithium salt was identified or a quantity of a specific product was included. Liquid formulations of lithium were converted to milligrams of lithium carbonate (lithium citrate 8 mEq/5 mL = 300 mg of lithium carbonate). Despite minimal variability in the weight of young children and previous authors interpolation of weight in this population, no weights were interpolated [9,10]. Some additional exploratory analyses were performed. We analyzed the trend over time of the dose where patients were referred in to the hospital (e.g., call originated from home and patient was referred to a healthcare facility).
Pharmacotherapy for the peripartum management of bipolar disorder
Published in Expert Opinion on Pharmacotherapy, 2019
Raoul Belzeaux, Catherine Sanguinetti, Andrea Murru, Norma Verdolini, Isabella Pacchiarotti, Diego Hidalgo-Mazzei, Lola Cohen, Gerard Anmella, Margherita Barbuti, Eduard Vieta, Pierre-Michel Llorca, Ludovic Samalin
Bipolar disorder (BD) is a severe psychiatric disorder characterized by successive mood episodes (manic, depressive) and inter-episodic periods [1]. Numerous treatment guidelines have been established to support clinicians to choose the most appropriate pharmacological treatment in each phase of the illness course. Mood episodes are treated with ‘mood stabilizers’ defined as a heterogeneous class including lithium salt, anticonvulsants and second-generation antipsychotics (SGA, or dopamine antagonist/partial agonists), either as monotherapy or in combination [2,3]. During manic episodes, first-line treatments are anticonvulsants (mainly valproate acid), lithium salts, or antipsychotics [4,5]. During depressive episodes, first-line treatments are also some antipsychotics (quetiapine, olanzapine, and lurasidone), lithium salts or lamotrigine. There is still a debate about the effectiveness of antidepressants in BD [6]. Inter-episodic periods are often characterized by residual symptoms and poor functioning, although around 50% of patients demonstrate good level of functioning [7–9].