Precision of the PET activity range during irradiation with10C,11C, and12C beams.

Objective. Beams of stable ions have been a well-established tool for radiotherapy for many decades. In the case of ion beam therapy with stable12C ions, the positron emitters10,11C are produced via projectile and target fragmentation, and their decays enable visualization of the beam via positron emission tomography (PET). However, the PET activity peak matches the Bragg peak only roughly and PET counting statistics is low. These issues can be mitigated by using a short-lived positron emitter as a therapeutic beam.Approach.An experiment studying the precision of the measurement of ranges of positron-emitting carbon isotopes by means of PET has been performed at the FRS fragment-separator facility of GSI Helmholtzzentrum für Schwerionenforschung GmbH, Germany. The PET scanner used in the experiment is a dual-panel version of a Siemens Biograph mCT PET scanner.Main results.High-quality in-beam PET images and activity distributions have been measured from the in-flight produced positron emitting isotopes11C and10C implanted into homogeneous PMMA phantoms. Taking advantage of the high statistics obtained in this experiment, we investigated the time evolution of the uncertainty of the range determined by means of PET during the course of irradiation, and show that the uncertainty improves with the inverse square root of the number of PET counts. The uncertainty is thus fully determined by the PET counting statistics. During the delivery of 1.6 × 107ions in 4 spills for a total duration of 19.2 s, the PET activity range uncertainty for10C,11C and12C is 0.04 mm, 0.7 mm and 1.3 mm, respectively. The gain in precision related to the PET counting statistics is thus much larger when going from11C to10C than when going from12C to11C. The much better precision for10C is due to its much shorter half-life, which, contrary to the case of11C, also enables to include the in-spill data in the image formation.Significance. Our results can be used to estimate the contribution from PET counting statistics to the precision of range determination in a particular carbon therapy situation, taking into account the irradiation scenario, the required dose and the PET scanner characteristics.

Environmental enrichment from birth enhances visual acuity but not place learning in mice.

The effect of richness of the environment on behavioral function was investigated in C57B6 mice. Animals were raised in either enriched (group-housed in large clear plexiglas cages with stimulating objects) or restricted (group housed in opaque white plastic cages with no stimulating objects) environmental conditions and their spatial learning and visual acuity were measured as adults. The performance of enriched and restricted groups were indistinguishable in place and cued versions of the Morris water task; however, the visual acuity of the enriched group, measured in a grating versus gray version of the visual water task, was 18% higher than the restricted group. These data demonstrate that the function of the mouse visual system can be significantly influenced by the nature of early visual input. They also indicate that the effects of environmental enrichment are manifested differently in behavioral measures of spatial learning and visual acuity.

Common cuttlefish (Sepia officinalis) mortality at the National Zoological Park: implications for clinical management.

Six out of seven cuttlefish acquired by the Smithsonian National Zoological Park in July 1998 died before 1 November 1998. Postmortem examinations showed mantle ulcers, secondary bacterial infections, inanition, and cuttlebone fractures. The surviving cuttlefish developed a progressive focal mantle ulcer, was treated with oral chloramphenicol intermittently for 9 wk, and maintained a normal appetite and growth rate until death at 7 mo of age. The National Zoological Park pathology database showed signalments, histories, and causes of mortality of 186 common cuttlefish, each 1-14 mo old, that received gross and histologic examinations; for example, the largest group of cuttlefish of known sex, age, and body weight at postmortem were 7-9 mo old and weighed an average of 376.2 g (males, n = 18) and 299.0 g (females, n = 15). Many cuttlefish had multiple pathologic diagnoses. Significant diseases included inflammation and secondary bacterial infections, especially gastrointestinal, cardiovascular, respiratory, reproductive, and ophthalmic, and septicemia due to Vibrio spp. or other gram-negative bacteria. Mantle lesions, including ulceration/dermatitis, abscess/granuloma, necrosis/fibrosis/cellulitis, and laceration/abrasion/erosion, were also identified, along with inanition, cuttlebone lesions, and trauma. Mantle lesions were associated with secondary bacterial infections and death. On the basis of this information, if captive cuttlefish behavior creates risk for development of mantle lesions, administration of antibiotics effective against gram-negative bacteria may delay or halt disease progression. Cuttlefish exhibits require proper design, husbandry, economic resources, and staffing to minimize disease syndromes and mortality.