Clinical characterization of a proton beam continuous uniform scanning system with dose layer stacking.

A proton beam delivery system on a gantry with continuous uniform scanning and dose layer stacking at the Midwest Proton Radiotherapy Institute has been commissioned and accepted for clinical use. This paper was motivated by a lack of guidance on the testing and characterization for clinical uniform scanning systems. As such, it describes how these tasks were performed with a uniform scanning beam delivery system. This paper reports the methods used and important dosimetric characteristics of radiation fields produced by the system. The commissioning data include the transverse and longitudinal dose distributions, penumbra, and absolute dose values. Using a 208 MeV cyclotron's proton beam, the system provides field sizes up to 20 and 30 cm in diameter for proton ranges in water up to 27 and 20 cm, respectively. The dose layer stacking method allows for the flexible construction of spread-out Bragg peaks with uniform modulation of up to 15 cm in water, at typical dose rates of 1-3 Gy/min. For measuring relative dose distributions, multielement ion chamber arrays, small-volume ion chambers, and radiographic films were employed. Measurements during the clinical commissioning of the system have shown that the lateral and longitudinal dose uniformity of 2.5% or better can be achieved for all clinically important field sizes and ranges. The measured transverse penumbra widths offer a slight improvement in comparison to those achieved with a double scattering beam spreading technique at the facility. Absolute dose measurements were done using calibrated ion chambers, thermoluminescent and alanine detectors. Dose intercomparisons conducted using various types of detectors traceable to a national standards laboratory indicate that the measured dosimetry data agree with each other within 5%.

Kidney donation from a patient with cardiac myxoma: a case report.

INTRODUCTION: Renal transplantation has still become the preferred method to treat end-stage renal failure. The majority of organs are obtained from individuals with irreversible central nervous system injury. This group is nowadays unsatisfactory and small relative to the needs. A significant percentage of donors may be found among patients primarily suffering from benign neoplasms whose nature does not show malignant potential and do not metastasize. To date, there have been no reports about successful organ transplantation from an organ donor with cardiac myxoma. AIM: The aim of this report was to present a successful transplantation of cadaveric kidney grafts from a 61-year-old female donor with a left atrial cardiac myxoma, which initially appeared as an embolic cerebral infarct. The kidney graft recipients were a 51-year-old woman and a 57-year-old man with long-lasting histories of chronic renal failure under treatment by hemodialysis. The transplant function of both kidneys has been satisfactory with a 5-year follow-up. For the present, apart from single event of acute rejection in a male recipient, the patients have maintained stable renal function. Routine accessory examinations did not reveal any changes within the kidney or other organs. To date, a renal biopsy has not been taken. Both recipients are undergoing special follow-up. CONCLUSION: Patients with myxoma should be accepted as donors, since the risk of dying on the waiting list is greater than the tumor transfer risk. Exclusion of these potential donors decreases the donor pool and unnecessarily wastes valuable organs.

Conservation of Pitx1 expression during amphibian limb morphogenesis.

In contrast to the pattern of limb emergence in mammals, chicks, and the newt N. viridescens, embryos such as Xenopus laevis and Eleutherodactylus coqui initiate pelvic limb buds before they develop pectoral ones. We studied the expression of Pitx1 in X. laevis and E. coqui to determine if this paired-like homeodomain transcription factor directs differentiation specifically of the hindlimb, or if it directs the second pair of limbs to form, namely the forelimbs. We also undertook to determine if embryonic expression patterns were recapitulated during the regeneration of an amputated limb bud. Pitx1 is expressed in hindlimbs in both X. laevis and E. coqui, and expression is similar in both developing and regenerating limb buds. Expression in hindlimbs is restricted to regions of proliferating mesenchyme.