Cholelithiasis patients have a higher risk of gastrointestinal cancer, particularly of gallbladder and extrahepatic bile duct cancer. Post-cholecystectomy patients have a risk of colorectal and stomach cancer within the first 5 years and persisting after 5 years, respectively. This paper proposes strategies for preventing gastrointestinal cancer.

The EBT2 film together with a flatbed scanner is a convenient dosimetry QA tool for verification of clinical radiotherapy treatments. However, it suffers from a relatively high degree of uncertainty and a tedious film calibration process for every new lot of films, including cutting the films into several small pieces, exposing with different doses, restoring them back and selecting the proper region of interest (ROI) for each piece for curve fitting. In this work, we present a percentage depth dose (PDD) method that can accurately calibrate the EBT2 film together with the scanner non-uniformity correction and provide an easy way to perform film dosimetry. All films were scanned before and after the irradiation in one of the two homemade 2 mm thick acrylic frames (one portrait and the other landscape), which was located at a fixed position on the scan bed of an Epson 10 000XL scanner. After the pre-irradiated scan, the film was placed parallel to the beam central axis and sandwiched between six polystyrene plates (5 cm thick each), followed by irradiation of a 20 × 20 cm² 6 MV photon beam. Two different beams on times were used on two different films to deliver a dose to the film ranging from 32 to 320 cGy. After the post-irradiated scan, the net optical densities for a total of 235 points on the beam central axis on the films were auto-extracted and compared with the corresponding depth doses that were calculated through the measurement of a 0.6 cc farmer chamber and the related PDD table to perform the curve fitting. The portrait film location was selected for routine calibration, since the central beam axis on the film is parallel to the scanning direction, where non-uniformity correction is not needed (Ferreira et al 2009 Phys. Med. Biol. 54 1073-85). To perform the scanner non-uniformity calibration, the cross-beam profiles of the film were analysed by referencing the measured profiles from a Profiler™. Finally, to verify our method, the films were exposed to 60° physical wedge fields and the compositive fields, and their relative dose profiles were compared with those from the water phantom measurement. The fitting uncertainty was less than 0.5% due to the many calibration points, and the overall calibration uncertainty was within 3% for doses above 50 cGy, when the average of four films were used for the calibration. According to our study, the non-uniformity calibration factor was found to be independent of the given dose for the EBT2 film and the relative dose differences between the profiles measured by the film and the Profiler were within 1.5% after applying the non-uniformity correction. For the verification tests, the relative dose differences between the measurements by films and in the water phantom, when the average of three films were used, were generally within 3% for the 60° wedge fields and compositive fields, respectively. In conclusion, our method is convenient, time-saving and cost-effective, since no film cutting is needed and only two films with two exposures are needed.

Our findings suggest that PD with treatment is associated with a significantly reduced overall risk of cancer and reduced risks of certain types of cancers.

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This paper presents a population-based retrospective cohort study to identify the differences in secondary primary cancer (SPC) among hypopharyngeal, laryngeal, and other sites of head and neck cancer (HNC). Data were collected from the Taiwan National Health Insurance Research Database (NHIRD) for the period 1979-2010. The study cohort comprised 5914 newly diagnosed hypopharyngeal and laryngeal patients from the registry of the Catastrophic Illness Patients Database (CIPD). The comparison cohort comprised 5914 patients with other sites of HNC. We used a multivariate Cox proportional-hazards regression model to assess the risk of developing SPC. The incidence of SPC in the study cohort was 68% higher compared with the comparison cohort (23.9 vs. 14.2 per 1000 person-years, Incident Rate Ratio = 1.68). The study cohort had a higher adjusted hazard ratio (HR) in oesophageal cancer (HR = 3.47) and lung cancer (HR = 1.89). The difference in SPC incidence between the study and comparison cohort was significant.

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The drawbacks of adaptive histogram equalization techniques are the loss of definition on the edges of the object and overenhancement of noise in the images. These drawbacks can be avoided if the noise is excluded in the equalization transformation function computation. A method has been developed to separate the histogram into zones, each with its own equalization transformation. This method can be used to suppress the nonanatomic noise and enhance only certain parts of the object. This method can be combined with other adaptive histogram equalization techniques. Preliminary results indicate that this method can produce images with superior contrast.

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