Ocular Brachytherapy (Interventional Radiotherapy): Preserving the Vision.

Uveal melanoma represents the most common intraocular neoplasia among adults. Brachytherapy (interventional radiotherapy; IRT) has a great advantage, when compared with enucleation, both in terms of organ and function sparing. The Collaborative Ocular Melanoma Study introduced into clinical practice a standardised procedure that allowed the equivalence of IRT with enucleation in terms of overall survival to be demonstrated. IRT is carried out by placing a plaque in direct contact with the sclera under the uveal melanoma. Several radioactive sources may be used, including 106-ruthenium, 125-iodine, 103-palladium and 90-strontium. It is a multidisciplinary procedure requiring the collaboration of interventional radiation oncologists and ophthalmologists in the operating theatre and medical physicists for an accurate treatment time calculation. It also relies on ultrasound imaging to identify the lesion and verifiy the correct plaque placement. An emerging tool of paramount importance could be the use of artificial intelligence and predictive models to identify those patients at higher risk of developing late side-effects and therefore who may deserve preventive and supportive therapies.

Monte Carlo simulation of the dose to nuclear medicine staff wearing protective garments.

The literature contains both endorsements of, and advice against, the use of protective apparel in nuclear medicine procedures. The main issues usually centre around: Whether the shielding which can be provided by a protective garment light enough to wear (0 to 0.6 mm lead equivalent at the gamma energies commonly encountered in nuclear medicine) is enough to warrant its use; and (more recently); Whether the dose enhancement behind the protective garment from electron scatter in lead is sufficient to be of concern. In this work, the Monte Carlo code EGSnrc was used to investigate the effectiveness of lead of thicknesses of 0 to 0.6 mm, in shielding staff from photons of energies of 140 and 511 keV. Furthermore, dose escalation behind the lead was investigated. Reasonable dose reductions are obtained at 140 keV with protective garments of 0.5 mm lead equivalence. This perhaps warrants their use, in certain circumstances. At 511 keV, the reduction in dose is less than 10%, and their use is probably not justified (given the weight that has to be carried) from an ALARA point of view. It should be noted here that protective garments designed for X-ray shielding will generally not have the same lead equivalence at the gamma energies used in nuclear medicine. It should also be noted that protective garments which do not contain lead do not always attenuate as much as their stated lead equivalence claims. Dose escalation does occur, but the depth of penetration of the scattered electrons beyond the exit side of the lead shielding is such that it is highly unlikely that a significant dose would be delivered to viable tissue in wearers of protective garments.

On the use of Kodak CR film for quality assurance of needle loading in I-125 seed prostate brachytherapy.

Low dose rate brachytherapy using implanted I-125 seeds as a monotherapy for prostate cancer is now in use in many hospitals. In contrast to fractionated brachytherapy treatments, where the effect of incorrect positioning of the source in one treatment fraction can be diminished by correcting the position in subsequent fractions, the I-125 seed implant is permanent, making correct positioning of the seeds in the prostate essential. The seeds are inserted into the prostate using needles. Correct configuration of seeds in the needles is essential in order to deliver the planned treatment. A comparison of an autoradiograph obtained by exposing film to the seed-loaded needles with the patient treatment plan is a valuable quality assurance tool. However, the time required to sufficiently expose Kodak XOMAT V film, currently used in this department is significant. This technical note presents the use of Kodak CR film for acquisition of the radiograph. The digital radiograph can be acquired significantly faster, has superior signal-to-noise ratio and contrast and has the usual benefits of digital film, e.g. a processing time which is shorter than that required for non-digital film, the possibility of image manipulation, possibility of paper printing and electronic storage.

Photoproduction of eta-mesic 3He.

The photoproduction of eta-mesic 3He has been investigated using the TAPS calorimeter at the Mainz Microtron accelerator facility MAMI. The total inclusive cross section for the reaction gamma3He-->etaX has been measured for photon energies from threshold to 820 MeV. The total and angular differential coherent eta cross sections have been extracted up to energies of 745 MeV. A resonancelike structure just above the eta production threshold with an isotropic angular distribution suggests the existence of a resonant quasibound state. This is supported by studies of a competing decay channel of such a quasibound eta-mesic nucleus into pi(0)pX. A binding energy of (-4.4+/-4.2) MeV and a width of (25.6+/-6.1) MeV is deduced for the quasibound eta-mesic state in 3He.

The reaction gammap-->pi0gamma'p and the magnetic dipole moment of the Delta+ 1232 resonance.

The reaction gammap-->pi(0)gamma'p has been measured with the TAPS calorimeter at the Mainz Microtron accelerator facility MAMI for energies between sqrt[s]=1221-1331 MeV. The cross section's differential in angle and energy have been determined for the photon gamma' in three bins of the excitation energy. This reaction channel provides access to the magnetic dipole moment of the Delta(+)(1232) resonance and, for the first time, a value of mu(Delta(+))=[2.7(+1.0)(-1.3)(stat)+/-1.5(syst)+/-3(theor)]mu(N) has been extracted.