Assessment of radiation-induced cancer risk to patients undergoing computed tomography angiography scans

Background: Computed tomography angiography [CTA] scan is a suitable imaging technique to evaluate the blood vessels. However, one major disadvantage is the potential risk of cancer related to ionizing radiation exposure during the procedures. The aim of this investigation was to estimate the risk of exposure induced cancer death [REID] values for some common computed tomography angiography [CTA] scans

Materials and Methods: The scan parameters and patient gender and age were collected for a total of 251 patients undergoing CTA scans of the head [51], carotid [50], abdomen [50], thoracic [50] and the lower extremities [50]. The effective diameter, scan length, effective tube current and the dose-length product [DLP] values were obtained for each patient. The organ doses and the effective dose were calculated by the ImpactDose program. The REID values were estimated for the different CTA scans by the calculated organ doses and corresponding age- and sex- specific risk factors

Results: The REID values for the CTA scans of head were 17+/-4 and 20+/-3 per million, carotid were 35+/-9 and 67+/-14 per million, the lower extremities were 60+/-26 and 64+/-24 per million, thoracic were 97+/-28 and 204+/-72 per million, and for abdomen were 101+/-25 and 194+/-72 per million, for males and females, respectively

Conclusion: The results of this investigation showed that CTA scans are associated with non-negligible risk of exposure induced cancer. A variation in radiation cancer risk as a function of age and gender of the patients was demonstrated and found that the younger female patients were at the highest risk

Evaluation of radiation-induced cancer risk to patients undergoing intra-oral and panoramic dental radiographies using experimental measurements and Monte Carlo calculations

Background: Radiation doses associated with the conventional dental radiographies are relatively low, but their number is high. Therefore, justification is necessary to ensure that radiation doses to patients, particularly children, are kept as low as reasonably achievable

Materials and Methods: The exposure factors applied for real patients in four age groups [5, 10, 15-year-old and adult] were obtained for conventional dental radiographies, periapical, bitewing, and panoramic. The dose-area product [DAP] values were measured for every dental radiographies. The risk of exposure-induced cancer death [REID] was estimated for every dental radiographies in different age groups and in both genders

Results: The range of the REID values in periapical radiography were 1.3 to 20.9 per ten million for male patients, and 1.6 to 28.3 per ten million for female patients in different age groups. The range of REID values in bitewing radiography were 1.5 to 11.2 per ten million for male, and 1.9 to 13.2, per ten million for female in different age groups. The mean of REID values in panoramic radiography were 7.32, 4.70, 3.55, and 2.1 per ten million for male patients in 5-, 10-, and 15-year-old and adult age groups, respectively, and were 9.43, 5.86, 4.25 and 2.41 per ten million for female patients in 5, 10, 15-year-old and adult age groups, respectively

Conclusion: In accordance with the results of the present study, the overall risk of cancer from radiation in children was more than adult and in female patients is more than male patients in dental X-ray examinations

Assessment of radiation treatment chain for cervical cancer with combined external and brachy radiation therapy

Performing radiotherapy of cervical cancer by combined external radiotherapy and brachytherapy includes several stages. Inaccuracy of each stage may cause insufficient dose delivery and produce complications in neighboring radiosensitive organs. In this study a technique was developed in order to assure the quality of treatment delivery. A solid pelvic phantom was designed and fabricated for simulation of the entire radiotherapy procedure of the cervical cancer. Treatment planning for external radiotherapy was accomplished using computed tomography images and for intracavitary brachytherapy using orthogonal radiographs. Dose measurements were performed with an intracavitary ionization chamber. External radiotherapy was done using linear accelerator. The Nucletron Selectron low dose rate [LDR] machine was used for brachytherapy. For both modalities, the software calculated dose values were compared to the values measured in the pelvic phantom. The calculated data obtained from the treatment planning system was consistent with the measured data. The comparison between measurements and calculations showed a maximum variation of +/- 2 % for external radiation therapy and +/- 3.6 % for brachytherapy. The phantom and the procedure developed in this study successfully provided a tool for comprehensive evaluation of each step in the chain of radiation therapy under the same conditions found in actual treatment. This method can be used to verify the accuracy and reproducibility of this treatment in any department and also during commissioning of the treatment planning systems

Acquiring molecular interference functions of X-ray coherent scattering for breast tissues by combination of simulation and experimental methods

Recently, it has been indicated that X-ray coherent scatter from biological tissues can be used to access signature of tissue. Some scientists are interested in studying this effect to get early detection of breast cancer. Since experimental methods for optimization are time consuming and expensive, some scientists suggest using simulation. Monte Carlo [MC] codes are the best option for radiation simulation; however, one permanent defect with MC codes has been the lack of a sufficient physical model for coherent [Rayleigh] scattering, including molecular interference effects. It was decided to obtain molecular interference functions of coherent X-ray scattering for normal breast tissues by combination of modeling and experimental methods. A Monte Carlo simulation program was written to simulate the angular distribution of scattered photons for the normal breast tissue samples. Moreover, experimental diffraction patterns of these tissues were measured by means of energy dispersive X-ray diffraction [EDXRD] method. The simulation and experimental data were used to obtain a tabulation of molecular interference functions for breast tissues. With this study a tabulation of molecular interference functions for normal breast tissues was prepared to facilitate the simulation diffraction patterns of the tissues without any experimental. The method may lead to design new systems for early detection of breast cancer