Nanoparticle contrast agents offer the potential to significantly improve existing methods of cancer diagnosis and treatment. Advantages include biocompatibility, selective accumulation in tumor cells, and reduced toxicity. Considerable research is underway into the use of nanoparticles as enhancement agents for radiation therapy and photodynamic therapy, where they may be used to deliver treatment agents, produce localized enhancements in radiation dose and selectively target tumor cells for localized damage. This paper reviews the current status of nanoparticles for cancer treatment and presents preliminary results of a pilot study investigating titanium dioxide nanoparticles for dual-mode enhancement of computed tomography (CT) imaging and kilovoltage radiation therapy. Although titanium dioxide produced noticeable image contrast enhancement in the CT scans, more sensitive detectors are needed to determine whether the nanoparticles can also produce localized dose enhancement for targeted radiation therapy.

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Background: The objective of the study is to describe temporal trends and regional variations in the use of knee magnetic resonance imaging (MRI), knee arthroscopy and total knee replacement surgery in Australians older than 55 years.

Backscatter factors are essential in the determination of radiation dose for kilovoltage X-ray beams. The accurate measurement of backscatter factors in water (B (W)) is difficult and published values are based largely on Monte Carlo calculations. A number of studies have found that the measurement of B (W) in the energy range from 50 to 300 kVp is possible using Gafchromic EBT film, but this film is no longer commercially available. In this work, we evaluated whether the newer Gafchromic EBT2 film is suitable for the determination of B (W) for kilovoltage X-ray beams. B (W) were measured with Gafchromic EBT2 film for beam qualities of 50, 100 and 280 kVp and field sizes of 2, 3, 4 and 6 cm diameter and compared with tabulated values published in the AAPM TG-61 protocol. We found that rotation of the film position during readout had a small but non-negligible effect on the optical density readings. The agreement between measured and published B (W) was better than 3%, with the largest difference of occurring for the 2 cm diameter field with the 50 kVp X-ray beam. However, these differences are consistent with the total estimated uncertainty for the measurements, as calculated by the ISO GUM. Our results demonstrate that Gafchromic EBT2 film is a suitable dosimeter for B (W) measurements for clinical kilovoltage X-ray beams.

The development of nanoparticle agents for MRI-guided radiotherapy is growing at an increasing pace, with clinical trials now underway and many pre-clinical evaluation studies ongoing. Gadolinium and iron-oxide-based nanoparticles remain the most clinically advanced nanoparticles to date, although several promising candidates are currently under varying stages of development. Goals of current and future generation nanoparticle-based contrast agents for MRI-guided radiotherapy include achieving positive signal contrast on T1-weighted MRI scans, local radiation enhancement at clinically relevant concentrations and, where applicable, avoidance of uptake by the reticuloendothelial system. Exploiting the enhanced permeability and retention effect or the use of active targeting ligands on nanoparticle surfaces is utilised to promote tumour uptake. This review outlines the current status of promising nanoparticle agents for MRI-guided radiation therapy, including several platforms currently undergoing clinical evaluation or at various stages of the pre-clinical development process. Challenges facing nanoparticle agents and possible avenues for current and future development are discussed.