Periodontal disease with treatment reduces subsequent cancer risks.

AIM: The aim of our study was to evaluate the relationship between routine treatment of periodontal disease (PD) and the subsequent risks for cancers in Taiwan. METHODS: Study participants were selected from the Taiwan National Health Insurance (NHI) system database. The PD with a routine treatment cohort contained 38 902 patients. For each treatment cohort participant, two age- and sex-matched comparison (control) cohort participants were randomly selected. Cox's proportional hazards regression analysis was used to estimate the effects of PD with treatment on the subsequent risk of cancer. RESULTS: The overall risk of developing cancer was significantly lower in the treatment cohort than in the patients without treatment (adjusted Hazard ratio = 0.72, 95% confidence interval = 0.68-0.76). The risks of developing most gastrointestinal tract, lung, gynecological and brain malignancies were significantly lower in the treatment cohort than in the comparison cohort. In contrast, the risks of prostate and thyroid cancers were significantly higher in the treatment cohort than in the comparison cohort. CONCLUSIONS: 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.

Cancer risk in patients with cholelithiasis and after cholecystectomy: a nationwide cohort study.

BACKGROUND: This study examined the association of cholelithiasis post-cholecystectomy with subsequent cancers and evaluated the risk of cancer in patients with both cholelithiasis and cholecystectomy. METHODS: The Taiwanese National Health Insurance Research Database was used to identify 15545 newly diagnosed cholelithiasis patients from 2000 to 2010, and 62180 frequency-matched non-cholelithiasis patients. A total of 5850 (37.6 %) with cholelithiasis patients received a cholecystectomy. The risk of developing cancer after cholecystectomy was measured using the Cox proportional-hazards model. RESULTS: The incidence of developing cancer in the cholelithiasis cohort was 1.52-fold higher than that in the comparison cohort (p < 0.001). Compared with patients aged 20-34 years, patients in older age groups had a higher risk of developing cancer. The hazard ratio (HR) for developing gallbladder, extrahepatic bile duct, pancreatic, liver, stomach, and colorectal cancer was 59.3, 10.7, 3.12, 1.90, 1.71, and 1.36-fold higher for patients with cholelithiasis, respectively. After a cholecystectomy, the HR for developing stomach and colorectal cancer was 1.81-fold and 1.56-fold, respectively. The incidence rate ratio was higher for the first 5 years and over 5 years (5.05 and 4.46, respectively) (95 % confidence interval 4.73-5.39 and 4.11-4.84, respectively) in proximal colon and stomach cancer patients with cholecystectomies. CONCLUSIONS: 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.

Calibration of EBT2 film by the PDD method with scanner non-uniformity correction.

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.

Scatter correction for 3D PET using beam stoppers combined with dual-energy window acquisition: a feasibility study.

Fully three-dimensional (3D) positron emission tomography (PET) can achieve high sensitivity of coincidence events, but the absence of inter-slice septa inevitably leads to increased scattered events. The scattered events can represent as much as 50% of the total detected events. In this research, we proposed a scatter correction method for 3D PET based on beam stoppers and dual-energy window acquisition. The beam stoppers were placed surrounding the object to attenuate primary beams. The scatter fractions were directly estimated at those blocked lines of response and then the entire scatter fraction distribution was recovered using the dual-energy window ratio as reference. The performance was evaluated by using Monte Carlo simulations of various digital phantoms. For the Utah phantom study, the proposed method accurately estimated the scatter fraction distribution, and improved image contrast and quantification based on four different quality indices as performance measures. For the non-homogeneous Zubal phantom, the simulated results also demonstrated that the proposed method achieved a better restoration of image contrast than the dual-energy window method. We conclude that the proposed scatter correction method could effectively suppress various kinds of scattered events, including multiple scatter and scatter from outside the field of view.

Antisense thymidylate synthase electrogene transfer to increase uptake of radiolabeled iododeoxyuridine in a murine model.

UNLABELLED: In vitro and in vivo experiments from our laboratory and others have suggested that the combination of thymidylate synthase (TS) inhibitor and radiolabeled iododeoxyuridine (IdUrd) is synergistic. Efficacy is limited by drug resistance, which is often mediated by TS overexpression. We designed an in vivo electrogene transfer (EGT) model for delivering antisense TS plasmid (ATS) into tumor to increase the subsequent efficacy of (131)I-IdUrd therapy. METHODS: Plasmid complementary to nucleotide 531-710 in the coding region of the mouse TS (mTS) mRNA was constructed. TS activity and (131)I-IdUrd DNA incorporation were determined 48 h after in vitro EGT of ATS to CT26 cells. In vivo therapeutic effect and radioactivity retained in tumor after various combinations of EGT ATS, 5-fluorouracil (5-FU), and continuous infusion of (131)I-IdUrd by osmotic minipump were determined. RESULTS: A reduction of TS activity was achieved after in vitro EGT ATS. Flow cytometry analysis indicated that ATS-treated cells were arrested at S phase. In the in vivo tumor model, the combination of EGT ATS and 5-FU was able to partially overcome 5-FU drug resistance. Sixty percent of tumors can be eradicated by the combination of EGT ATS, 5-FU, and infusion of (131)I-IdUrd. The tumors treated by EGT ATS had higher radioactivity retained 1 wk after (131)I-IdUrd therapy than after EGT of control plasmid. CONCLUSION: In situ EGT ATS can downregulate TS and increase the therapeutic effect of radiolabeled IdUrd therapy. The combination of EGT ATS, 5-FU, and (131)I-IdUrd may result in tumor eradication.

Quality degradation in lossy wavelet image compression.

The objective of this study was to develop a method for measuring quality degradation in lossy wavelet image compression. Quality degradation is due to denoising and edge blurring effects that cause smoothness in the compressed image. The peak Moran z histogram ratio between the reconstructed and original images is used as an index for degradation after image compression. The Moran test is applied to images randomly selected from each medical modality, computerized tomography, magnetic resonance imaging, and computed radiography and compressed using the wavelet compression at various levels. The relationship between the quality degradation and compression ratio for each image modality agrees with previous reports that showed a preference for mildly compressed images. Preliminary results show that the peak Moran z histogram ratio can be used to quantify the quality degradation in lossy image compression. The potential for this method is applications for determining the optimal compression ratio (the maximized compression without seriously degrading image quality) of an image for teleradiology.

A novel image quality index using Moran I statistics.

Measurement of image quality is very important for various applications such as image compression, restoration and enhancement. Conventional methods (e.g., mean squared error; MSE) use error summation to measure quality change pixel by pixel and do not correlate well with subjective quality measurement. This is due to the fact that human eyes extract structural information from the viewing field. In this study a new quality index using a Moran I statistics is proposed. The Moran statistic that measures the sharpness from a local area is a good index of quality as most image processing techniques alter the smoothness of the image. Preliminary results show that the new quality index outperforms the MSE significantly under various types of image distortions.

Determination of beam intensity in a single step for IMRT inverse planning.

In intensity modulated radiotherapy (IMRT), targets are treated by multiple beams at different orientations each with spatially-modulated beam intensities. This approach spreads the normal tissue dose to a greater volume and produces a higher dose conformation to the target. In general, inverse planning is used for IMRT treatment planning. The inverse planning requires iterative calculation of dose distribution in order to optimize the intensity profile for each beam and is very computation intensive. In this paper, we propose a single-step method utilizing a figure of merit (FoM) to estimate the beam intensities for IMRT treatment planning. The FoM of a ray is defined as the ratio between the delivered tumour dose and normal tissue dose and is a good index for the dose efficacy of the ray. To maximize the beam utility, it is natural to irradiate the tumour with intensity of each ray proportional to the value of the FoM. The nonuniform beam intensity profiles are then fixed and the weights of the beam are determined iteratively in order to yield a uniform tumour dose. In this study, beams are employed at equispaced angles around the patient. Each beam with its field size that just covers the tumour is divided into a fixed number of beamlets. The FoM is calculated for each beamlet and this value is assigned to be the beam intensity. Various weighting factors are incorporated in the FoM computation to accommodate different clinical considerations. Two clinical datasets are used to test the feasibility of the algorithm. The resultant dose-volume histograms of this method are presented and compared to that of conformal therapy. Preliminary results indicate that this method reduces the critical organ doses at a small expense of uniformity in tumour dose distribution. This method estimates the beam intensity in one single step and the computation time is extremely fast and can be finished in less than one minute using a regular PC.

Comprehensive measurement for clinical dosimetry of tertiary multileaf collimator.

To initiate the use of a tertiary multileaf collimator (MLC) in the clinic, a set of dosimetry data for clinical use of the MLC, the secondary field size jaw and the MLC tracked by the jaw were measured. The dose calculation technique from the commissioned jaw field data was established. The dosimetry characteristics included absolute output (Dw), collimator scatter factor (Sc), total scatter factor (Scp), phantom scatter factor (Sp), percentage depth dose (PDD), tissue-maximum ratio (TMR), and peak scatter factor (PSF). The absolute output of the MLC field was +5% to +2% greater than that of the same jaw size field from 4 x 4 to 24 x 24 cm2 fields. The variation of Sc and Scp ranged from 4 x 4 to 24 x 24 cm2 fields and were less than that of the jaw fields, while the Sp, PDD and TMR values remained the same. Importantly, when the MLC-only field was performed without the collimator jaws tracking close to the field segments, greater output was delivered, and PSFs should be used to calculate the MLC field output.