IMPROVED MARKING AND CHARACTERIZING OF PULMONARY NODULES ON DIGITAL RADIOGRAPHS USING A COMPUTER-AIDED DIAGNOSIS SYSTEM

Objective To evaluate and reduce inter-observer variations in the detection and characterization of pulmonary nodules on digital radiograph （DR） chest images. Methods Two hundreds and thirty-two new posterior-anterior DR chest images were collected from out-patient screening patients. Consensus was reached by two experienced radiologists on the marking, rating, and segmentation of small actionable nodules ranged from 5 to 15 mm in diameter using a computer-aided diagnosis （CAD） system. Both their own nodule findings and the computer＇s automatic nodule detection results were analyzed to make the consensus. Nodules identified together with corresponding likelihood rating and segmentation results were referred as ＂Gold Stand- ard＂. Two un-experienced radiologists were asked to first mark and characterize suspicious nodules independently, then were allowed to consult the computer nodule detection results and change their decisions. Results Large inter-observer variations in pulmonary nodule identification and characterization on DR chest images were observed between un-experienced radiologists. Un-expefienced radiologists could greatly benefit from the CAD system, including substantial decrease of inter-observer variation and improvement of nodule detection rates. Moreover, radiologists with different levels of skillfulness could achieve similar high level performance after using the CAD system. Conclusion The CAD system shows a high potential for providing a valuable assistance to the examination of DR chest images.

INTER-OBSERVER VARIATIONS OF DIGITAL RADIOGRAPH PULMONARY NODULE MARKING BY USING COMPUTER TOOLKIT

Objective To assess inter-observer variations of pulmonary nodule marking in routine clinical chest digital radiograph (DR) softcopy reading by using a lung nodule computer toolkit.Methods A total of 601 chest posterior-anterior DR images were randomly selected from routine outpatient screening in Peking Union Medical College Hospital. Two chest radiologists with experience more than ten years were first asked to read the images and mark all suspicious nodules independently by using computer toolkit IQQA-Chest, and to indicate the likelihood for each nodule detected. They were also asked to draw the boundary of the identified nodule manually on an enlarged region of interest, which was instantly analyzed by IQQA-Chest. Two sets of diagnostic reports, including the marked nodules, likelihood, manually drawn boundaries, quantitative measurements, and radiologists’ names, were automatically generated and stored by the computer system. One week later, the two radiologists read the same images together by using the same computer toolkit without referring to their previous reading results. Marking procedure was the same except that consensus was reached for each suspicious region. Statistical analysis tools provided in the IQQA-Chest were used to compare all the three sets of reading results.Results In the independent readings, Reader 1 detected 409 nodules with a mean diameter of 12.4 mm in 241 patients, and Reader 2 detected 401 nodules with a mean diameter of 12.6 mm in 253 patients. In the consensus reading, a total of 352 nodules with a mean diameter of 12.4 mm were detected in 220 patients. Totally, 42.3% of Reader 1’s and 45.1% of Reader 2’s marks were confirmed by the consensus reading. About 40% of each reader’s marks agreed with the other. There were only 130 (14.4%) out of the total 904 unique nodules were confirmed by both readers and the consensus reading. Moreover, 5.6% (51/904) of the marked regions were rated identical likelihood in all three readings. Statistical analysis showed significant differences between Readers 1 and 2, and between consensus and Reader 2 in determining the likelihood of the marks (P<0.01), but not between consensus and Reader 1. No significant difference in terms of size was observed in nodule segmentation between either two of the three readings. Conclusion Large variations in nodule marking and nodule-likelihood determination but not in nodule size were observed between experts as well as between single-person reading and consensus reading.

A Method of Digitally Reconstructed Radiographs Based on Medical CT Images

A complete and detail method is described to get digitally reconstructed radiographs （DRRs）. Casting rays to traverse CT images, computing CT values of resample points by interpolation, then converting CT value to its attenuation coefficient by using simplified segment function. Finally, DRRs enhancement is made to get the better display of region of interest （ROI）, and a new way is adopted to adjust the customization coefficient. The experimental results show that the proposed method is effective in generating the satisfied DRRs.

Extra-Oral Digital Panoramic Radiographic Interpretation and Clinical Findings of Stage IV Periodontitis among Some Samples Concerning Saudi/Non-Saudi Nationality

Background: There are associations between the severity of periodontal diseases and some predisposing factors, such as age, race, and income rate. Therefore, the present study was designed to evaluate the extra-oral digital panoramic radiographic interpretation and clinical findings of stage IV periodontitis among some samples concerning Saudi/non-Saudi nationality. Material and Methods: The study comprised a random sample of 298 residents in Saudi Arabia referred to the internship program clinics at the College of Dentistry, King Khalid University. They were according to the age of participants as follows: youth (15 - 24 years), adults (25 - 64 years), and seniors (65 years and over) within two groups according to nationality (Saudi and non-Saudi). Clinical periodontal examination and radiographic extra oral digital panoramic radiographs were done, and then the periodontal parameters, the percentage of bone loss, and the pattern of bone loss were recorded. The data was collected, and the statistical analysis was performed with ANOVA test, Tukey’s test, Chi-square test, and T-test and considered a P-value at (p Results: The samples included 62 (20%) youth participants with mean of age (21.806 ± 3.390), 182 (57%) adults’ participants with mean age (42.802 ± 9.094), and 54 (23%) seniors participants with a mean age (69.074 ± 6.810). There were highly statistically significant differences in the comparison between the participants’ ages (P 0.05). Conclusion: At the end of this study, we concluded that there are alterations in clinical and radiographic and clinical findings of stage IV periodontitis with the alteration of participants’ ages and nationality.

A new projection model based robust 2D-3D registration method on Fourier-Mellin space for image guided intervention

An automatic method is proposed to solve the registration problem,which aligns a single 2D fluoroscopic image to a 3D image volume without demanding any additional media like calibration plate or user interactions.First,a mathematic projection model is designed which can reduce the influence of projection distortion on parameter optimization and improve the registration accuracy.Then,a two stage optimization method is proposed,which enables a robust registration in a wide parameter space.Furthermore,an automatic registration framework is proposed based on the FourierMellin robust image comparison descriptor.Experimental results show that the registration method has a high accuracy with average rotation error of 0.6 degree and average translation error of 1.4mm.