Validation of a pseudo-3D phantom for radiobiological treatment plan verifications.

Performing realistic and reliable in vitro biological dose verification with good resolution for a complex treatment plan remains a challenge in particle beam therapy. Here, a new 3D bio-phantom consisting of 96-well plates containing cells embedded into Matrigel matrix was investigated as an alternative tool for biological dose verification. Feasibility tests include cell growth in the Matrigel as well as film dosimetric experiments that rule out the appearance of field inhomogeneities due to the presence of the well plate irregular structure. The response of CHO-K1 cells in Matrigel to radiation was studied by obtaining survival curves following x-ray and monoenergetic 12C ion irradiation, which showed increased radioresistance of 3D cell cultures in Matrigel as compared to a monolayer. Finally, as a proof of concept, a 12C treatment plan was optimized using in-house treatment planning system TRiP98 for uniform cell survival in a rectangular volume and employed to irradiate the 3D phantom. Cell survival distribution in the Matrigel-based phantom was analyzed and compared to cell survival in a reference setup using cell monolayers. Results of both methods were in good agreement and followed the TRiP98 calculation. Therefore, we conclude that this 3D bio-phantom can be a suitable, accurate alternative tool for verifying the biological effect calculated by treatment planning systems, which could be applied to test novel treatment planning approaches involving multiple fields, multiple ion modalities, complex geometries, or unconventional optimization strategies.

Kill painting of hypoxic tumors with multiple ion beams.

We report on a novel method for simultaneous biological optimization of treatment plans for hypoxic tumors using multiple ion species. Our previously introduced kill painting approach, where the overall cell killing is optimized on biologically heterogeneous targets, was expanded with the capability of handling different ion beams simultaneously. The current version (MIBO) of the research treatment planning system TRiP98 has now been augmented to handle 3D (voxel-by-voxel) target oxygenation data. We present a case of idealized geometries where this method can identify optimal combinations leading to an improved peak-to-entrance effective dose ratio. This is achieved by the redistribution of particle fluences, when the heavier ions are preferentially forwarded to hypoxic target areas, while the lighter ions deliver the remaining dose to its normoxic regions. Finally, we present an in silico skull base chordoma patient case study with a combination of 4He and 16O beams, demonstrating specific indications for its potential clinical application. In this particular case, the mean dose, received by the brainstem, was reduced by 3%-5% and by 10%-12% as compared to the pure 4He and 16O plans, respectively. The new method allows a full biological optimization of different ion beams, exploiting the capabilities of actively scanned ion beams of modern particle therapy centers. The possible experimental verification of the present approach at ion beam facilities disposing of fast ion switch is presented and discussed.

Oxygen beams for therapy: advanced biological treatment planning and experimental verification.

Nowadays there is a rising interest towards exploiting new therapeutical beams beyond carbon ions and protons. In particular, [Formula: see text]O ions are being widely discussed due to their increased LET distribution. In this contribution, we report on the first experimental verification of biologically optimized treatment plans, accounting for different biological effects, generated with the TRiP98 planning system with [Formula: see text]O beams, performed at HIT and GSI. This implies the measurements of 3D profiles of absorbed dose as well as several biological measurements. The latter includes the measurements of relative biological effectiveness along the range of linear energy transfer values from ≈20 up to ≈750 keV µ [Formula: see text], oxygen enhancement ratio values and the verification of the kill-painting approach, to overcome hypoxia, with a phantom imitating an unevenly oxygenated target. With the present implementation, our treatment planning system is able to perform a comparative analysis of different ions, according to any given condition of the target. For the particular cases of low target oxygenation, [Formula: see text]O ions demonstrate a higher peak-to-entrance dose ratio for the same cell killing in the target region compared to [Formula: see text]C ions. Based on this phenomenon, we performed a short computational analysis to reveal the potential range of treatment plans, where [Formula: see text]O can benefit over lighter modalities. It emerges that for more hypoxic target regions (partial oxygen pressure of ≈0.15% or lower) and relatively low doses (≈4 Gy or lower) the choice of [Formula: see text]O over [Formula: see text]C or [Formula: see text]He may be justified.

Regulation of heme oxygenase activity in rat liver during oxidative stress induced by cobalt chloride and mercury chloride.

Activities of heme oxygenase and tryptophan-2,3-dioxygenase and cytochrome P450 content in liver as well as absorption of the Soret band and optical density at 280 nm in serum were determined 2 and 24 h after administration of HgCl(2) and CoCl(2) and after co-administration of the metal salts with alpha-tocopherol. Administration of HgCl(2) and CoCl(2) increased the contents of hemolysis products in the serum, induced heme oxygenase, and decreased cytochrome P450 content in the liver. Injection of HgCl(2) increased the activity of tryptophan-2,3-dioxygenase holoenzyme and enzyme saturation with the heme, but administration of CoCl(2) decreased these parameters. Pretreatment with alpha-tocopherol completely blocked the changes induced by HgCl(2) after 24 h. Induction of heme oxygenase induced by CoCl(2) was not blocked by alpha-tocopherol, but this antioxidant normalized the increase in the level of hemolysis products in the serum and decrease in tryptophan-2,3-dioxygenase holoenzyme activity and cytochrome P450 content. Mechanisms of regulation of heme oxygenase by mercury and cobalt ions are discussed.

[Metabolism of heme and hemoproteins in rat liver upon administration of mercuric chloride]. / Metabolizm gema i gemoproteinov v pecheni krys pri vvedenii khlorida rtuti.

Rat liver delta-aminolevulinate synthase (delta-ALAS) activity in the early period after mercury chloride administration (0.7 mg per 100 g body weight) was found to be followed by free heme level increase, which was registered by the increase of heme saturation of the heme-binding protein tryptophan-2,3-dioxygenase (T-2,3-DO). delta-ALAS and heme oxygenase activity increase was observed 24 h after action. Microsomal cytochromes P450 and b5 levels decrease. Heme saturation of the T-2,3-DO returned to control level. Heme oxygenase and T-2,3-DO induction promoted hepatocytes free heme level normalization. Heme oxygenase and delta-ALAS induction role in the liver cells defense from the oxidative damage is discussed.

Water loss and nitrogen excretion in sharp-nosed reed frogs (Hyperolius nasutus: anura, Hyperoliidae).

Sharp-nosed African reed frogs, Hyperolius nasutus Gunther, are small (0.4 g) hyperoliids which have minimal rates of evaporative water loss (4.5 mg g-1 h-1; 0.3 mg cm-2 h-1) that are only 1/10 to 1/20 that of a typical frog, Hylaregilla, of comparable size (171 mg g-1 h-1, 4.8 mg cm-2 h-1). The surface-area-specific resistance to water flux of H. nasutus dorsal skin (96-257 sec cm-1) is similar to that of other 'waterproof' frogs (300-400), of cocooned frogs (40-500), and of desert reptiles (200-1400). However, H. nasutus can greatly increase the rate of evaporative water loss during radiative heat stress by mucous gland discharge, and by exposing the ventral skin. Urea is the principal nitrogenous waste product of H. nasutus and uric acid comprises less than 1% of the total nitrogen excretion for both H. nasutus and H. regilla. Other 'waterproof' frogs, in contrast, are uricotelic. Lethal dehydration requires less than two weeks in H. nasutus, despite its low surface-area-specific rate of water loss, because of its small size and concomitantly high surface-to-volume ratio. The rate of urea accumulation during dehydration was 23 mM g-1 day-1, which is sufficiently low that urea accumulation would not be lethal before the frog had succumbed to dehydrational death. Consequently, there appears to be little or no selective advantage for uricotely in small 'waterproof' frogs, such as H. nasutus.

The free swimming Pipa larvae, with a review of pipid larvae and pipid phylogeny (Anura: Pipidae).

This paper describes the morphology of the free swimming Pipa larvae, compares them with Xenopus, Hymenochirus, and to some extent, Rhinophrynus larvae, and presents a morphological diagnosis of pipid larvae. Pipa and Xenopus have very similar chondrocrania. Hymenochirus is superficially different but has the same diagnostic features. The differences appear related to its small size and predatory habitus. Other aspects of anatomy, especially the filter apparatus are very different in each genus. The filter apparatus of Pipa is somewhat reduced and seems modified for the retention of relatively large (20+ microns) particles. Similar adaptations may have been annectant to predations in Hymenochirus, which lacks a filter apparatus. However, varying states of seven character complexes, which cut across the varying ecology, show that there are two basic pipid lineages, each currently confined to Africa or South America, respectively. Recent finds of fossil South American Xenopus indicate that these two lineages separated before the continents did. This does not warrant the recognition of two subfamilies because Xenopus and Hymenochirus are too different. Pseudhymenochirus is not an intermediate between them; it is primitive Hymenochirus. Eight character states separate pipid and rhynophrynid larvae.