Gated brachytherapy minimizes dose to the heart
Brachytherapy treatment of the left breast can result in unwanted radiation dose to non-target organs such as the heart. Elekta of Sweden has proposed a respiration-state-gated brachytherapy system that minimizes dose to the heart (WO/2009/080085). The apparatus comprises an X-ray source that's small enough to insert into the patient, a respiration-state monitor, and a control apparatus that receives information from the monitor and controls the X-ray output accordingly. The control system operates the X-ray source at one output level when the respiration-state monitor indicates a degree of lung inflation above a first preset threshold, and operates the source at a second, lower output level when the monitor indicates lung inflation below a second preset threshold.
PDT promises less invasive cardiac ablation
Researchers at St. Jude Medical (Maple Grove, MN) have developed a means of using photodynamic therapy (PDT) for ablation of cardiac tissue via the oesophagus (WO/2009/085653). Employing PDT in this way eliminates the need for surgical incisions and manoeuvring of the ablation catheter through the circulatory system, thus minimizing the risk of complications and reducing recovery time. The scheme involves the introduction of a photosensitive drug to the cardiac tissue. A deformable, elongated body is then inserted into the oesophagus with its distal end located next to the cardiac tissue. Reflective and opaque surfaces at the distal end direct electromagnetic radiation towards the cardiac tissue, activating the photosensitizer and leading to necrosis. An expandable membrane at the distal end can be used to urge the elongated body to a predetermined position within the oesophagus.
Hot nanoparticles enhance radiotherapy efficacy
A method that uses nanoparticles to boost the efficacy of treatments such as radiation therapy is described by Nanospectra Biosciences (Houston, TX) in international patent application WO/2009/091597. The nanoparticles create focused hyperthermia within the target area, which has direct anti-tumour effects, as well as enhancing other therapies by increasing perfusion or reducing hypoxia in the treatment area. A scheme for treating a target area could comprise: systemically introducing nanoparticles into the circulation; allowing the nanoparticles to preferentially accumulate in the target area; applying external energy to the target so that the nanoparticles transduce some of this energy into heat to create localized hyperthermia; and then applying ionizing radiation to the target area.
Treatment planning optimizes ocular radiotherapy
Oraya Therapeutics (Newark, CA) has devised a method for planning image-guided radiation therapy of a lesion on or adjacent to the retina (WO/2009/075714). The first step involves establishing at least two beam paths, based on an aligned patient-eye position, along which collimated X-rays are directed at the retinal lesion. Based on the known spectral and intensity characteristics of the beam, a total irradiation time along each beam path is then determined to produce the desired radiation dose at the lesion. From the coordinates of the optic nerve in the aligned eye position, the system determines the extent and duration of eye movement away from this position - in a direction that moves the optic nerve toward the beam - that can be allowed during treatment while maintaining the dose to the optic nerve below a predetermined level.
Dosimeter exploits synthetic diamonds
Diamond is an ideal material for radiotherapy dosimetry: it is nearly tissue equivalent, radiation-hard and potentially offers a very fast response time. Devices based on natural diamond, however, are expensive and exhibit low performance uniformity, while chemical vapour deposition (CVD)-grown synthetic diamonds are generally polycrystalline, leading to low signal stability and poor response time. Researchers at the University of Rome Tor Vergata in Italy have now developed a dosimeter based on CVD-grown monocrystalline synthetic diamond (WO/2009/087104). The dosimeter comprises two layers of the synthetic diamond, intrinsic or doped, the second of which has much lower electrical conductivity than the first. Contacts with each layer enable measurement of the electrical signal produced when radiation is incident upon the sensitive second diamond layer. The dosimeter can be battery powered, making it suitable for in-vivo dosimetry and the realization of portable devices.
Tracking QA: monoscopic imaging may be enough
Robot-based image-guided radiation treatment systems, such as the CyberKnife from Accuray (Sunnyvale, CA), perform patient tracking by comparing 2D in-treatment X-ray images with digitally reconstructed radiographs derived from 3D pre-treatment diagnostic imaging data. In general, two stereoscopic images are used to align the target volume with a reference position, to directly track the tumour, and/or to check the validity of and update a correlation model. At times, however, one of the images of the stereo pair may not be usable, for example if the beam path is blocked by the radiation treatment source, a robotic arm or the treatment couch. In international patent application WO/2009/091382, Accuray describes a method by which monoscopic imaging data can be used for quality assurance of tracking when one of the images of the stereo pair is not usable.
X-rays keep an eye on thermal ablation progress
INTIO (formerly Abla-Tx) of Broomfield, CO, has developed a thermal ablation system that uses an X-ray system to measure temperature changes during the ablation procedure (WO/2009/100098). The image data sets captured by the X-ray system provide temperature change information throughout the volume-of-interest being ablated (using radiofrequency ablation, microwave therapy, high-intensity focused ultrasound, laser ablation or other interstitial heat-delivery methods). Intermediate image data sets captured during treatment are fed into a system controller, which can modify or update the thermal ablation plan to achieve volume necrosis targets. The filing also describes methods of performing thermal ablation using the X-ray temperature measurements as a feedback source, plus ways to assess the patient's post-ablation status and the system performance.