Risk Of Cancer Induction Research Articles

Risk Estimation of Thyroid Cancer for Children Undergoing Brain CT Examinations

Background: Despite significant diagnosis benefits, the usage of ionizing radiation is not risk-free. The aim of this study was to determine the risk of thyroid cancer for children who exposed from brain computed tomography (CT) scan. Method: In this a cross-sectional study, 90 patients under 20 years of age who underwent brain CT-scan were selected. Parameters such as age, sex, imaging technique, imaging characteristics, and thyroid absorbed dose were considered. We used SPSS software, version 21, at 95% confidence interval to analyze the absorbed dose and risk for each individual. Results: The mean and standard deviation of absorbed the dose for girls and boys for the spiral technique were 3.954±0.393 and 4.72±0.000 mGy and in sequential technique, they were 2.282±0.461 and 1.985±0.431 mGy, respectively. The mean and standard deviation of the absorbed dose in <5 years age group was 5.65±2.00, 3.03±1.34 in 6 to 10 years, 2.63±0.98 in11 to 15 years, and in 16 to 20 years was 2.57±1.04 mGy (P<0.001). There was a significant negative correlation between the absorbed dose and field dimensions (r = -0.604, P<0.001) and slice thickness (r = -0.777, P<0.001). The mean and standard deviation of Lifetime risk for thyroid cancer induction (×105) in <5 years age group in spiral technique was 158.79±322.50 for female subjects and 16.5±42.90 for male patients, which was significantly more than those of other groups and techniques (P<0.001). Conclusion: The rate of thyroid absorbed dose during brain CT-scan was found to be noticeable, especially in spiral CT imaging, for female patients < 5 years. Based on our results, it was associated with an increased risk of thyroid cancer in this age group.

Volumetric modulated arc therapy versus intensity-modulated proton therapy in the irradiation of infra diaphragmatic Hodgkin Lymphoma in female patients

Purpose To investigate the role of infra diaphragmatic intensity-modulated proton therapy (IMPT) compared to volumetric modulated arc therapy (VMAT) for female Hodgkin Lymphoma (HL) patients and to estimate the risk of secondary cancer and ovarian failure. Methods A comparative treatment planning study was performed on 14 patients, and the results were compared according to conventional dose-volume metrics. In addition, estimates of the excess absolute risk (EAR) of secondary cancer induction were determined for the bowel, the bladder and the rectum. For the ovaries, the risk of ovarian failure was estimated. Results The dosimetric findings demonstrate the equivalence between VMAT and IMPT in terms of target coverage. A statistically significant reduction of the mean and near-to-maximum doses was proven for the organs at risk. The EAR ratio estimated for IMPT to VMAT was 0.51 ± 0.32, 0.32 ± 0.35 and 0.05 ± 0.11 for the bowel, bladder and rectum, respectively. Concerning the risk of ovarian failure for the chronologic age ranging from 18 to 46 years, the expected net loss in fertility years ranged from 4.8 to 3.0 years for protons and 12.0 to 5.7 years for photons. Conclusion This in-silico study confirmed the beneficial role of IMPT from a dosimetric point of view. Mathematical models suggested that the use of protons might be further advantageous due to the expected reduction of the risk of secondary cancer induction and its milder impact on the reduction of fertility.

Development of clinical application program for radiotherapy induced cancer risk calculation using Monte Carlo engine in volumetric-modulated arc therapy

BackgroundThe purpose of this study is to develop a clinical application program that automatically calculates the effect for secondary cancer risk (SCR) of individual patient. The program was designed based on accurate dose calculations using patient computed tomography (CT) data and Monte Carlo engine. Automated patient-specific evaluation program was configured to calculate SCR.MethodsThe application program is designed to re-calculate the beam sequence of treatment plan using the Monte Carlo engine and patient CT data, so it is possible to accurately calculate and evaluate scatter and leakage radiation, difficult to calculate in TPS. The Monte Carlo dose calculation system was performed through stoichiometric calibration using patient CT data. The automatic SCR evaluation program in application program created with a MATLAB was set to analyze the results to calculate SCR. The SCR for organ of patient was calculated based on Biological Effects of Ionizing Radiation (BEIR) VII models. The program is designed to sequentially calculate organ equivalent dose (OED), excess absolute risk (EAR), excess relative risk (ERR), and the lifetime attributable risk (LAR) in consideration of 3D dose distribution analysis. In order to confirm the usefulness of the developed clinical application program, the result values from clinical application program were compared with the manual calculation method used in the previous study.ResultsThe OED values calculated in program were calculated to be at most approximately 13.3% higher than results in TPS. The SCR result calculated by the developed clinical application program showed a maximum difference of 1.24% compared to the result of the conventional manual calculation method. And it was confirmed that EAR, ERR and LAR values can be easily calculated by changing the biological parameters.ConclusionsWe have developed a patient-specific SCR evaluation program that can be used conveniently in the clinic. The program consists of a Monte Carlo dose calculation system for accurate calculation of scatter and leakage radiation and a patient-specific automatic SCR evaluation program using 3D dose distribution. The clinical application program that improved the disadvantages of the existing process can be used as an index for evaluating a patient treatment plan.

Risk for second bladder and rectal malignancies from cervical cancer irradiation.

The objective of this study was to estimate the risk of developing second malignancies to partially in‐field organs from volumetric modulated arc therapy (VMAT) of cervical cancer and to compare the above risks with those from the conventional three‐dimensional conformal radiotherapy (3D‐CRT). Seventeen consecutive patients with uterine cervix carcinoma were selected. VMAT and 3D‐CRT plans were generated with 6 and 10 MV photons, respectively. The prescribed tumor dose was 45 Gy given in 25 fractions. Differential dose‐volume histogram data from the treatment plans were obtained for the partially in‐field organs such as bladder and rectum. These data were used to estimate the patient‐specific lifetime attributable risk (LAR) for bladder and rectal cancer induction with a non‐linear model based on a mixture of plateau and bell‐shaped dose–response relationships. The estimated risks per 10000 people were compared with the baseline risks for unexposed population. The patient‐specific rectal cancer risk estimates from VMAT were significantly lower than those from 3D‐CRT (P = 0.0144). The LARs for developing bladder malignancies from VMAT were significantly high compared to those from conventional irradiation (P = 0.0003). The mean difference between the patient‐specific LARs for radiation‐induced bladder and rectal malignancies as derived from 3D‐CRT and VMAT plans was 6.6% and 2.0%, respectively. The average LAR for developing bladder and rectal malignant diseases due to VMAT was 9.2 × 10‐4 and 43.7 × 10‐4, respectively. The corresponding risks following 3D‐CRT were 8.6 × 10‐4 and 44.6 × 10‐4. These average risks showed that pelvic irradiation increases the baseline probability for cancer induction by 12.6‐19.1%. The differences in the second cancer risks associated with the VMAT and 3D‐CRT for cervical cancer were found to be small. Both treatment techniques resulted in considerable increased probabilities for developing bladder and rectal malignancies relative to those of unirradiated population.

Radiation exposure to infants undergoing voiding cystourethrography: The importance of the digital imaging technology.

To determine the radiation burden to infants undergoing voiding cystourethrography (VCUG) in a single institution and investigate the effect of shifting from analogue to digital imaging that allowed the use of a radiography-free examination protocol. Anthropometric and exposure data were prospectively collected for 35 consecutive infants undergoing VCUG on a digital system with a standardized examination protocol not including radiographs. Thermoluminescent dosimeters were used to determine entrance-skin dose. Monte Carlo simulations and patient-specific anthropomorphic phantoms were employed to determine organ/tissue doses and effective dose (ED). The associated theoretical risk of radiation-induced cancer was determined and compared to the nominal risk of cancer induction. The radiation burden from VCUG on a modern digital system with a contemporary examination protocol was compared to corresponding data reported previously for an analogue system in the same institution. The median ED from VCUG was found 47 μSv. The associated total life attributable risk of radiation-induced cancer was found 10x10-6 and 13x10-6 for boys and girls, respectively. VCUG was found to increase the nominal risk of cancer by a factor of 1.000025 in boys and 1.000034 in girls. Shifting from analogue to digital imaging system resulted in 89% reduction of the radiation burden from VCUG. The theoretical radiation risks for infants undergoing VCUG using a modern digital imaging system and a radiography-free protocol were found to be minor. The transition from analogue to digital equipment resulted in considerable reduction of the radiation burden from VCUG.

VMAT for prostate cancer with 6‑MV and 10‑MV photons: Impact of beam energy on treatment plan quality and model‑based secondary cancer risk estimates

The aim of the present study was to examine the effect of the photon beam energy on the volumetric modulated arc therapy (VMAT) plan quality for prostate cancer and on the risk of secondary carcinogenesis. Separate VMAT plans with 6-MV and 10-MV photons were created for 11 low-risk patients with prostate cancer. The prescribed tumor dose was 70 Gy delivered in 28 fractions. The normal tissue integral dose and parameters associated with planning target volume and organs at risk were determined by the treatment planning data. A non-linear mechanistic model considering the effects of tumor dose fractionation and cell proliferation was employed for estimating the patient-specific lifetime attributable risk (LAR) for bladder and rectal cancer induction. Data from differential dose-volume histograms were used for these risk assessments. The mean values of the planning parameters from 6-MV treatment plans differed by 0.2-3.4% from those associated with irradiation using 10-MV photons. The LAR range for developing secondary bladder malignancies varied between 0.041 and 0.129% by the patient under investigation and the beam energy used. The corresponding range for the appearance of rectal malignant diseases was 0.047-0.153%. The mean percentage difference between the bladder cancer risks from VMAT with 6-MV and 10-MV photons was 2.6±2.3%. The corresponding difference for secondary rectal malignancies was 0.7±0.6%. Therefore, VMAT for prostate cancer with both 6-MV and 10-MV photons leads to clinically equivalent treatment plans and to similar secondary bladder and rectal cancer risks.

Survey of Mean Glandular Dose to Patients During Mammography Examinations: A Retrospective Study

The radiation dose delivered to patients undergoing mammography examination is of utmost importance because of the risk of cancer induction due to the process. In this work, we analyze the dose to 109 patients (214 images) who underwent mammographic examinations with a full-field digital mammography (FFDM) system. Quality control assessment was first performed using the International Atomic Energy Agency (IAEA) Human Health Series 2 and 17 protocol and the European guidelines for quality assurance in breast cancer screening and diagnosis. The results from the quality control test performed indicates that the system is functioning well. The mean glandular dose of patients analyzed shows that 23 out of 109 patients received averaged doses higher than the acceptable level at the same equivalent breast thickness of a phantom. The mammography system at the department is recommended for continuous use for imaging and screening of patients.

Radiation exposure during the treatment of spinal deformities.

To benchmark the radiation dose to patients during the course of treatment for a spinal deformity. Our radiation dose database identified 25,745 exposures of 6,017 children (under 18 years of age) and adults treated for a spinal deformity between 1 January 2008 and 31 December 2016. Patients were divided into surgical (974 patients) and non-surgical (5,043 patients) cohorts. We documented the number and doses of ionizing radiation imaging events (radiographs, CT scans, or intraoperative fluoroscopy) for each patient. All the doses for plain radiographs, CT scans, and intraoperative fluoroscopy were combined into a single effective dose by a medical physicist (milliSivert (mSv)). There were more ionizing radiation-based imaging events and higher radiation dose exposures in the surgical group than in the non-surgical group (p < 0.001). The difference in effective dose for children between the surgical and non-surgical groups was statistically significant, the surgical group being significantly higher (p < 0.001). This led to a higher estimated risk of cancer induction for the surgical group (1:222 surgical vs 1:1,418 non-surgical). However, the dose difference for adults was not statistically different between the surgical and non-surgical groups. In all cases the effective dose received by all cohorts was significantly higher than that from exposure to natural background radiation. The treatment of spinal deformity is radiation-heavy. The dose exposure is several times higher when surgical treatment is undertaken. Clinicians should be aware of this and review their practices in order to reduce the radiation dose where possible. Cite this article: Bone Joint J2021;103-B(4):1-7.

Thyroid dose and cancer risk from head and neck computed tomography at two selected centres in Nigeria.

The objective of this study was to evaluate the thyroid glands' radiation dose and the risk of thyroid cancer induction from head or neck computed tomography (CT) examinations. In a prospective study, we evaluated all participants of all ages and sex referred for Head or Neck CT Scan at the University College Hospital, Ibadan and Me Cure Healthcare Limited, Ibadan, Oyo State, Nigeria. Thyroid radiation dose was estimated with impact scan calculator, and real-time dose measurement with thermoluminescent badge dosimeters (TLDs). Data were analysed and P < 0.05 was considered statistically significant. One hundred and sixty-three participants (128 adults and 35 children) participated in the study. In most participants (74%), the tube voltage was 120 kVp. The estimated median thyroid gland dose by the imPACT scan calculator was 4.95 mGy (range = 1.20-30.0 mGy) and 4.40 mGy (range = 3.0-5.10 mGy), while the real-time dose measured by the TLD was 4.79 mGy (range = 1.73-96.7 mGy) and 2.33 mGy (range = 1.20-3.73 mGy) at Centre A and B, respectively. The estimated median thyroid cancer risk was 2.88 × 10-6 (maximum range of 52 × 10-6) at centre A and a median value of 3.20 × 10-6 with a cancer risk estimate that may reach 17.9 × 10-6 recorded at centre B, compared to a cumulative thyroid cancer risk of 0.12 × 10-5 among the general Nigerian population. Scanner specifications and technique may significantly contribute to variations seen in thyroid radiation doses. There may be a need to optimise centre protocols and apply dose reference levels for head and neck CT examinations to reduce thyroid cancer risk in Nigeria.

Examining the frequency and concomitant dose of geometric verification imaging for patients undergoing proton beam therapy for ocular tumours; an audit of current clinical practice.

Objectives:This paper uses clinical audit to determine the extent and dosimetric impact of additional imaging for patients undergoing ocular proton beam therapy who have no clips visible in the collimated beam.Methods:An audit was conducted on 399 patients treated at The National Centre for Eye Proton Therapy between 3 July 2017 and 14 June 2019. The mean total number of image pairs over the course of treatment for patients with and without clips visible in the collimated beam were compared.Results:Among 364 evaluable patients, 333 had clips visible in the collimated beam and 31 did not. There was a statistically significant increase of five image pairs required for patients with no clips visible compared with those with clips visible (mean 14.6 vs 9.6 image pairs, respectively; p = 2.74 × 10–6). This equated to an additional 1.5 mGy absorbed dose, representing an increase in secondary cancer induction risk from 0.0004 to 0.0007%.Conclusions:The small increase in concomitant dose and set-up time for patients with no clips visible in the collimated beam is not clinically significant.Advances in knowledge:This novel work highlights clinical audit from real on-treatment geometric verification data and frequencies, rather than protocols, for ocular proton beam therapy; something not present in the literature. The simple and straightforward methodology is easily and equally applicable to clinical audits (especially those under Ionising Radiation (Medical Exposure) Regulations) for photon techniques.

IONIZING RADIATION EXPOSURE REVIEW IN CHILDREN WITH INTESTINAL FAILURE

Introduction: Intestinal failure (IF) is a chronic condition with increasing incidence and survival rates. Children with IF undergo many radiological studies and procedures involving ionizing radiation. There is no evidence regarding its long-term outcomes. The aim of this study is to estimate cumulative radiation dose (CRD), in order to optimize imaging studies prescription. Methods: Retrospective study. Cohort. Inclusion criteria: children with IF under 18 y.o., 2007-2019. Clinical records review: age, follow up time, type of study/procedure and CRD (mSv). The CRD was established according to existing normative data. Three average doses were calculated for fluoroscopy procedures, according to the difficulty described in surgical reports. Results: N 95. Age 6.19 y.o. (R: 0.15 - 20), follow up 4.78 years (R: 0.08 - 12.41). Mean number of imaging studies/ procedures 49.43/patient. CRD 74.64 mSv/patient: 43% due to CT scans (28.2 mSv), 17% enema contrast studies (10.97 mSv), 14% fluoroscopy during central venous access placement (8.81 mSv). The remaining 26% due to plain X ray films, voiding cystourethrography, upper GI contrast studies, scyntigraphy and bone densitometry. Discussion: According to investigations about nuclear bomb survivors, an association has been established between exposure doses in the range of 30 and 90 mSv and radiation induced cancer risk. Children are at a greater risk than adults at a given dose, both because they are more radiosensitive and also they have more remaining years of life during which radiation induced cancer can develop. Our cohort received a CRD of 74.64 mSv, which is considered as a high risk CRD. Although it is not possible to predict its consequences, this fact means a warning sign for future potential morbidity. Conclusions: Our cohort received a CD higher than current recommendations. A concerted effort should be made to reduce and optimize studies and procedures involving radiation. A future plan for improvement will include standardized indication of radiological studies and introduction of radiology- free techniques for diagnosis and placement of central lines.

Extremity Exposure with 99mTc - Labelled Radiopharmaceuticals in Diagnostic Nuclear Medicine.

Extremity exposures may raise the risk of cancer induction among radiographers involved in the preparation and administration of technetium-99m labelled radiopharmaceuticals. To estimate finger doses on radiographers at a South African tertiary hospital. Adhesive tape was used to securely fix a calibrated thermoluminescent dosimeter (TLD) on fingertips and bases of ring and index fingers of both hands of five radiographers who prepared and administered technetium-99m labelled radiopharmaceuticals. Rubber gloves were worn to avoid TLD contamination. TLDs doses were read with a Harsaw TLD Reader (Model 3500) after a week. Five radiographers prepared and administered technitium-99m labelled radiopharmaceuticals (activity range; 78.20 GBq - 132.78 GBq during a one-week measurement period). A radiographer handling 132.78 GBq received 4.74±0.52 mSv on both hands; 5.52, 4.55, 5.11 and 4.60 mSv on the fingertip of the index finger of the dominant hand (FIDH), fingertip of the ring finger of the dominant hand (FRDH), fingertip of the index finger of the non-dominant hand (FINDH) and fingertip of the ring finger of the non-dominant hand (FRNDH), respectively. The respective doses received on the finger bases were 4.50 mSv, 4.60, 4.21 and 3.48 mSv. The radiographer handling 78.20 GBq received 0.85±0.18 mSv on both hands, 1.04, 1.17, 0.77 and 1 mSv for the FIDH, FRDH, FINDH and FRNDH, respectively, while respective doses for the bases were 0.8, 0.9, 0.6 and 0.8 mSv. The extremity exposures were below the annual limit (500 mSv). However, the use of syringe shields could still reduce the finger doses further.

Volumetric modulated arc therapy versus intensity-modulated proton therapy in the postoperative irradiation of thymoma.

To investigate the role of intensity-modulated proton therapy (IMPT) compared to volumetric modulated arc therapy (VMAT) for the radiation treatment of thymoma cancer. Twenty patients were retrospectively planned for IMPT [with (IMPT_R1 or IMPT_R2 according to the approach adopted) and without robust optimization] and VMAT. The results were compared according to dose-volume metrics on the clinical and planning target volumes (CTV and PTV) and the main organs at risk (heart, breasts, lungs, spinal cord and oesophagus). Estimates of the excess absolute risk (EAR) of secondary cancer induction were determined for the oesophagus, the breasts and the composite lungs. For the heart, the relative risk (RR) of chronic heart failure (CHF) was assessed. IMPT and VMAT plans resulted equivalent in terms of target coverage for both the CTV and the PTV. The CTV homogeneity index resulted in 0.03 ± 0.01 and 0.04 ± 0.01 for VMAT and all IMPT plans, respectively. The conformality index resulted in 1.1 ± 0.1 and 1.2 ± 0.1 for VMAT and all IMPT plans. The mean dose to the breasts resulted in 10.5 ± 5.0, 4.5 ± 3.4, 4.7 ± 3.5 and 4.6 ± 3.4Gy for VMAT, IMPT, IMPT_R1 and IMPT_R2. For the lungs, the mean dose was 9.6 ± 2.3, 3.5 ± 1.5, 3.6 ± 1.6 and 3.8 ± 1.4Gy; for the heart: 8.7 ± 4.4, 4.3 ± 1.9, 4.5 ± 2.0 and 4.4 ± 2.4Gy and for the oesophagus 8.2 ± 3.5, 2.2 ± 3.4, 2.4 ± 3.6 and 2.5 ± 3.5Gy. The RR for CHF was 1.6 ± 0.3 for VMAT and 1.3 ± 0.2 for IMPT (R1 or R2). The EAR was 3.6 ± 0.v vs 1.0 ± 0.6 or 1.2 ± 0.6 (excess cases/10,000 patients year) for the oesophagus; 17.4 ± 6.5 vs 5.7 ± 3.2 or 6.1 ± 3.8 for the breasts and 24.8 ± 4.3 vs 8.1 ± 2.7 or 8.7 ± 2.3 for the composite lungs for VMAT and IMPT_R, respectively. The data from this in-silico study suggest that intensity-modulated proton therapy could be significantly advantageous in the treatment of thymoma patients with particular emphasis to a substantial reduction of the risk of cardiac failure and secondary cancer induction. Robust planning is a technical pre-requisite for the safety of the delivery.

Excessive radon-based radiation in indoor air caused by soil building materials in traditional homes on Đồng Văn karst plateau, northern Vietnam

Radon-based radiation from natural soil building materials is an important factor likely influencing residents’ health as a contributing source of natural radiation. This survey aims to quantify the nuclide-specific α-radiation of isotopes 222Rn and 220Rn in common types of houses in a region of northern Vietnam, Đồng Văn karst plateau, to preliminarily (i) evaluate the total annual effective dose rates and (ii) assess the relative risk of cancer induction from indoor α-radiation for inhabitants. The average 222Rn concentrations in all house types were lower than 100 Bq m−3, but 220Rn abundances were far higher than 222Rn, even up to >1000 Bq m−3 in air close to a wall of unfired-soil bricks. The estimated total annual effective dose rates from indoor 222Rn and 220Rn and their progenies to residents with daily exposure of 13 h in the various types of houses range from 3.1 to 4.3 mSv a−1 for houses constructed with modified materials, but up to higher than 6 mSv a−1 in houses with raw building materials. The average risk of developing lung cancer as a consequence of a lifetime exposure to indoor α-radiation in affected homes ranges from 3.9% to 14.6%. 220Rn and its metallic progenies contribute more than 80% of the total average lung cancer risk from total radon, being responsible for a range of 2.7–14.6% of the risk of developing lung cancer.

Volumetric modulated arc therapy versus intensity-modulated proton therapy in neoadjuvant irradiation of locally advanced oesophageal cancer

BackgroundTo investigate the role of intensity-modulated proton therapy (IMPT) compared to volumetric modulated arc therapy (VMAT), realised with RapidArc and RapidPlan methods (RA_RP) for neoadjuvant radiotherapy in locally advanced oesophagal cancer.MethodsTwenty patients were retrospectively planned for IMPT (with two fields, (IMPT_2F) or with three fields (IMPT_3F)) and RA_RP and the results were compared according to dose-volume metrics. Estimates of the excess absolute risk (EAR) of secondary cancer induction were determined for the lungs. For the cardiac structures, the relative risk (RR) of coronary artery disease (CAD) and chronic heart failure (CHF) were estimated.ResultsBoth the RA_RP and IMPT approached allowed to achieve the required coverage for the gross tumour volume, (GTV) and the clinical and the planning target volumes, CTV and PTV (V98% > 98 for CTV and GTV and V95% > 95 for the PTV)). The conformity index resulted in 0.88 ± 0.01, 0.89 ± 0.02 and 0.89 ± 0.02 for RA_RP, IMPT_2F and IMPT_3F respectively. With the same order, the homogeneity index for the PTV resulted in 5.6 ± 0.6%, 4.4 ± 0.9% and 4.5 ± 0.8%. Concerning the organs at risk, the IMPT plans showed a systematic and statistically significant incremental sparing when compared to RA_RP, especially for the heart. The mean dose to the combined lungs was 8.6 ± 2.9 Gy for RA_RP, 3.2 ± 1.5 Gy and 2.9 ± 1.2 Gy for IMPT_2F and IMPT_3F. The mean dose to the whole heart resulted to 9.9 ± 1.9 Gy for RA_RP compared to 3.7 ± 1.3 Gy or 4.0 ± 1.4 Gy for IMPT_2F or IMPT_3F; the mean dose to the left ventricle resulted to 6.5 ± 1.6 Gy, 1.9 ± 1.5 Gy, 1.9 ± 1.6 Gy respectively. Similar sparing effects were observed for the liver, the kidneys, the stomach, the spleen and the bowels.The EAR per 10,000 patients-years of secondary cancer induction resulted in 19.2 ± 5.7 for RA_RP and 6.1 ± 2.7 for IMPT_2F or 5.7 ± 2.4 for IMPT_3F. The RR for the left ventricle resulted in 1.5 ± 0.1 for RA_RP and 1.1 ± 0.1 for both IMPT sets. For the coronaries, the RR resulted in 1.6 ± 0.4 for RA_RP and 1.2 ± 0.3 for protons.ConclusionWith regard to cancer of the oesophagogastric junction type I and II, the use of intensity-modulated proton therapy seems to have a clear advantage over VMAT. In particular, the reduction of the heart and abdominal structures dose could result in an optimised side effect profile. Furthermore, reduced risk of secondary neoplasia in the lung can be expected in long-term survivors and would be a great gain for cured patients.

Secondary bladder and rectal cancer risk estimates following standard fractionated and moderately hypofractionated VMAT for prostate carcinoma.

To estimate the risk for bladder and rectal cancer induction due to standard fractionated (SF) and moderately hypofractionated (HF) volumetric modulated arc therapy (VMAT) for prostate carcinoma. Twelve patients with low or intermediate-risk of prostate cancer referred for external-beam radiotherapy were included in this study. Three computed tomography-based VMAT plans were created for each study participant. The first plan was generated by assuming patient's irradiation with SF-VMAT (78Gy in 39 fractions). The second and third plans were created on the basis of two different HF schedules (HF-VMAT1 : 70Gy in 30 fractions, HF:VMAT2 : 60Gy in 20 fractions). Data from differential dose-volume histograms obtained by the above treatment plans were employed to calculate the organ equivalent dose (OED) of the bladder and rectum with the aid of a nonlinear model accounting for fractionation and proliferation effects. The calculated OED values were used to estimate the average lifetime attributable risk (LARav ) for the appearance of radiotherapy-induced secondary bladder and rectal malignancies. The lifetime risk of radiation carcinogenesis was compared with the respective organ-, and age-dependent lifetime intrinsic risk (LIR) of cancer development for unexposed males. The average OED of the rectum from SF-VMAT, HF-VMAT1 and HF-VMAT2 for prostate cancer was 972.0, 900.2, and 815.7cGy, respectively. The corresponding values for bladder were 73.4, 72.3, and 71.0cGy. The LARav for rectal cancer induction varied from 0.06% to 0.4% by the fractionation schedule used for irradiation and by the age of the patient at the time of treatment. The corresponding risk range related to the development of secondary bladder malignancies was 0.06-0.33%. The SF-VMAT, HF-VMAT1 and HF-VMAT2 led to an increase of the lifetime rectal cancer risk with respect to LIR by 2.2-9.8%, 2.0-9.1% and 1.8-8.2%, respectively, depending upon the patient's age. The corresponding elevation for bladder cancer induction was up to 8.0%, 7.9% and 7.7%. The use of VMAT for prostate carcinoma leads to a noteworthy increase of the lifetime risk for bladder and rectal cancer induction compared to that of unexposed people irrespective of the patient's age at the time of treatment and the applied fractionation scheme. The cancer risk data presented in this study may be taken into account by radiation oncologists and medical physicists in the selection of the optimal radiation therapy plan.

Practical advices for optimal CT scanner dose in children

Radiation protection and dose optimisation in computerized tomography (CT) for pediatric patients are of utmost importance because of the potential risk of cancer induction by exposure to ionizing radiation. A review of available technical features in modern CT machines aiming at reducing and/or optimizing patient dose was performed. Practical advices to operators were listed according to dose-related technical solutions studied to decrease the doses and to practically implement dose optimisation.

Organ dose measurements using an adult anthropomorphic phantom and risk estimation of cancer incidence from CBCT exposures

Cone-beam CT (CBCT) has become an essential tool for pre-treatment verification of the patient's position and for targeting the tumor volume localization in Image Guided Radiotherapy (IGRT). CBCT imaging is employed generally on a daily-basis, for each treatment fraction, and several times per patient, to ensure the correct patient's set-up. This leads to cumulative imaging doses to the tissues surrounding the exposed target-organs. The objective of this work is to determine the patient organ doses from a thorax CBCT scan in order to estimate risk of cancer incidence due to CBCT exposures.A thorax CBCT scan was performed in an anthropomorphic phantom of an adult male (CIRS ATOM) and the organ doses were assessed from point measurements using Thermo Luminescent Detectors (TLDs). The measurements were performed using a CBCT imaging system mounted on a LINAC (EdgeTM, Varian Medical Systems). The lifetime attributable risk (LAR) of cancer incidence was determined using the BEIR risk models. Considering a single thorax CBCT scan, the highest organ doses were calculated for heart and left lung which registered values of 5.84 ± 0.99 mGy and 4.90 ± 0.83 mGy, respectively. In contrast, the lowest organ dose was determined for right lung, with an absorbed dose of 3.07 ± 0.52 mGy. Regarding risk estimation, after a complete course of IGRT treatment for lung cancer (24 fractions) and assuming that, at least, one CBCT scan is performed per fraction, the LAR of cancer incidence varies between 27 to 309 cases per 100.000 exposed persons, depending on the organ evaluated. This work highlights the need to determine radiation induced cancer risks arising from CBCT repeated exposures in order to optimize the selected scanning protocols and consequently the radiological protection of patient. Furthermore, accurate organ dose calculation is fundamental to reduce the uncertainties associated with radiological risk estimation in imaging procedures.

Intensity modulated proton therapy compared to volumetric modulated arc therapy in the irradiation of young female patients with hodgkin\u2019s lymphoma. Assessment of risk of toxicity and secondary cancer induction

BackgroundTo investigate the role of intensity modulated proton therapy (IMPT) compared to volumetric modulated arc therapy (VMAT) for advanced supradiaphragmatic Hodgkin’s lymphoma (HL) in young female patients by assessing dosimetric features and modelling the risk of treatment related complications and radiation-induced secondary malignancies.MethodsA group of 20 cases (planned according to the involved-site approach) were retrospectively investigated in a comparative planning study. Intensity modulated proton plans (IMPT) were compared to VMAT RapidArc plans (RA). Estimates of toxicity were derived from normal tissue complication probability (NTCP) calculations with either the Lyman or the Poisson models for a number of endpoints. Estimates of the risk of secondary cancer induction were determined for lungs, breasts, esophagus and thyroid. A simple model-based selection strategy was considered as a feasibility proof for the individualized selection of patients suitable for proton therapy.ResultsIMPT and VMAT plans resulted equivalent in terms of target dose distributions, both were capable to ensure high coverage and homogeneity. In terms of conformality, IMPT resulted ~ 10% better than RA plans. Concerning organs at risk, IMPT data presented a systematic improvement (highly significant) over RA for all organs, particularly in the dose range up to 20Gy. This lead to a composite average reduction of NTCP of 2.90 ± 2.24 and a reduction of 0.26 ± 0.22 in the relative risk of cardiac failures. The excess absolute risk per 10,000 patients-years of secondary cancer induction was reduced, with IMPT, of 9.1 ± 3.2, 7.2 ± 3.7 for breast and lung compared to RA. The gain in EAR for thyroid and esophagus was lower than 1. Depending on the arbitrary thresholds applied, the selection rate for proton treatment would have ranged from 5 to 75%.ConclusionIn relation to young female patients with advanced supradiaphragmatic HL, IMPT can in general offer improved dose-volume sparing of organs at risk leading to an anticipated lower risk of early or late treatment related toxicities. This would reflect also in significantly lower risk of secondary malignancies induction compared to advanced photon based techniques. Depending on the selection thresholds and with all the limits of a non-validated and very basic model, it can be anticipated that a significant fraction of patients might be suitable for proton treatments if all the risk factors would be accounted for.

Estimating the whole-body effective dose and health risks as well as introducing a new easy method for eye lens dosimetry in interventional cardiology procedures

This study aimed to introduce a new method for eye lens thermo-luminescent dosimetry and also estimate the dose associated with induced cancer risk due to the ionizing radiation exposure received by physicians and other staff cooperating in interventional cardiology (IC) procedures. The measurements were performed with six TLDs (thermoluminescent dosimeters): four TLDs for eye lens dosimetry (2 positioned on respiratory/surgical mask under the eye region as the new method; and 2 near the outside border of the eye as the common method) and two TLDs for whole-body dosimetry. Whole-body doses were used to calculate the cancer risks induced by IC procedures. The results of the new proposed method for eye lens dosimetry were similar to common TLD positioning (mean differences <5%) and mask displacement had no significant effect on eye dose measurement in our new method. Our proposed method for eye lens dosimetry is simpler and more comfortable compared to the common method and it can be used as an alternative method without using TLD holders to monitor lens dose for IC workers wearing masks during the procedure. The estimated excess cancer incidence risk induced by IC procedures was 29.58 ± 5.71 and 46.68 ± 7.77 (per 100000 individuals) for men and women, respectively.