Estimated Effective Lifetime Risks of Radiation-Induced Thyroid Cancer in Computed Tomography (CT) Brain Examination

Thyroid is one of the most radiosensitive organs in the human body. Although the scanning range of brain computed tomography (CT) does not include lower neck region, there is possibility for thyroid to be irradiated due to scattered radiation because of its location near to the external beam collimation. The objective of this study was to evaluate effective lifetime risk of radiation-induced thyroid cancer in young adults following brain CT examination. A total of 306 patient data within the age range between 18 and 39 years old were retrospectively analysed. Absorbed dose of the thyroid organ was obtained through the input of data using WAZA- ARI v2. Effective lifetime risk was calculated by multiplying equivalent dose of the thyroid organ with the lifetime attributable cancer risk adapted from Biological Effects in Ionising Radiation (BEIR) Report V11. The effective lifetime risks were recorded as 0.45 ± 0.70 per 100 000 and 0.93 ± 1.52 per 100 000 for single and multiple exposures, respectively. In terms of gender, woman data (0.99 ± 0.76; 1.95 ± 2.15) were found higher as compared to man data (0.13 ± 0.39; 0.35 ± 0.45) for both single and multiple exposure. The percentage difference of effective lifetime risks between single and multiple exposures was up to 107%. The effective lifetime risk noted in this study may be low, however, the long-term risk of cancer development should be considered. This study serves as preliminary reference when revising clinical protocol especially in those involving repeated exposures in young adult patients. Future study should include other radiosensitive organs exploring the effective lifetime risk of radiation induced cancer following CT procedure.

Bismuth Pelvic X-Ray Shielding Reduces Radiation Dose Exposure in Pediatric Radiography

Background. Radiation using conventional X-ray is associated with exposure of radiosensitive organs and typically requires the use of protection. This study is aimed at evaluating the use of bismuth shielding for radiation protection in pediatric pelvic radiography. The effects of the anteroposterior and lateral bismuth shielding were verified by direct measurements at the anatomical position of the gonads. Methods. Radiation doses were measured using optically stimulated luminescence dosimeters (OSLD) and CIRS ATOM Dosimetry Verification Phantoms. Gonad radiographs were acquired using different shields of varying material (lead, bismuth) and thickness and were compared with radiographs obtained without shielding to examine the effects on image quality and optimal reduction of radiation dose. All images were evaluated separately by three pediatric orthopedic practitioners. Results. Results showed that conventional lead gonadal shielding reduces radiation doses by 67.45%, whereas dose reduction using one layer of bismuth shielding is 76.38%. The use of two layers of bismuth shielding reduces the dose by 84.01%. Using three and four layers of bismuth shielding reduces dose by 97.33% and 99.34%, respectively. Progressively lower radiation doses can be achieved by increasing the number of bismuth layers. Images obtained using both one and two layers of bismuth shielding provided adequate diagnostic information, but those obtained using three or four layers of bismuth shielding were inadequate for diagnosis. Conclusions. Bismuth shielding reduces radiation dose exposure providing appropriate protection for children undergoing pelvic radiography. The bismuth shielding material is lighter than lead, making pediatric patients more comfortable and less apt to move, thereby avoiding repeat radiography.

Radiation Reduction and Protection for Radiosensitive Organs (Lens, Thyroid, and Genital Organs) of Patients Receiving Percutaneous Coronary Intervention—Real-World Measurement of Radiation Dose in a Single Center

Backgrounds: Reducing radiation exposure is the basic principle for performing percutaneous coronary intervention (PCI). Many studies have confirmed the effect of radiation protection for medical staff, but studies about the effectiveness of protection for patients and real measurement of radiation dose in patients’ specific organs are lacking. Aim: To measure the radiation doses absorbed by patients’ radiosensitive organs during PCI and the effectiveness of radiation protection. Methods: A total of 120 patients were included and allocated into three groups as the ratio of 1:1:2. A total of 30 patients received PCI at 15 frames rate per second (fps), 30 patients at 7.5 fps, and 60 patients wore radiation protective hat and glasses during PCI at 7.5 fps. The radiation doses were measured at right eyebrow (lens), neck (thyroid), back (skin), and inguinal area (genital organs) by using thermoluminescent dosimeters (TLDs). Results: Dose-area product (DAP) reduced by 58.8% (from 534,454 ± 344,660 to 220,352 ± 164,101 mGy·cm2, p < 0.001) after reducing the frame rate, without affecting successful rate of PCI. Radiation doses measured on skin, lens, genital organs, and thyroid decreased by 73.3%, 40.0%, 40.0%, and 35.3%, respectively (from 192.58 ± 349.45 to 51.10 ± 59.21; 5.29 ± 4.27 to 3.16 ± 2.73; 0.25 ± 0.15 to 0.15 ± 0.15; and 17.42 ± 12.11 to 11.27 ± 8.52 μSv, p < 0.05). By providing radiation protective equipment, radiation doses at lens and thyroid decreased further by 71.8% and 65.9% (from 3.16 ± 2.73 to 0.89 ± 0.79; 11.27 ± 8.52 to 3.84 ± 3.49 μSv, p < 0.05). Conclusions: By lowering the frame rate and providing protective equipment, radiation exposure in radiosensitive organs can be effectively reduced in patients.

Using patient shielding – What is the risk?

The practice of placing radiation protective shielding on patients (‘in contact’) in order to reduce the dose to certain radiosensitive organs for diagnostic X-ray examination, has been employed for decades. However, there has been a growing body of evidence that this practice is often ineffective or even counterproductive and the use of such shielding can also overemphasise the hazards of ionising radiation in the public mind. This has led to a growing disparity in the application of patient contact shielding and culminated in several professional bodies issuing guidance and statements to provide a consistent approach to patient contact shielding. This, in turn, has led to a healthy discussion and re-evaluation of when and why patient contact shielding should be used, where the main issue centres around the criteria used to arrive at the recommendations. The decision process involves considering, among others, the reported effectiveness of the shielding and a subjective assessment of the subsequent risks from their use. In order to improve the transparency of these recommendations, it is therefore suggested that a threshold for dose and/or risk should be clearly stated, below which no protection is required. A suggested starting point for defining this threshold is discussed. This would enhance uniformity of application and provide clarity for staff, patients and the public. It would also ensure that any future research in this area could be easily incorporated into the general guidance.

Clinical application of “black bone” imaging in paediatric craniofacial disorders

For decades, CT has been the primary imaging modality for the diagnosis and surveillance of paediatric craniofacial disorders. However, the deleterious effects of ionising radiation in the paediatric population are well established and remain an ongoing concern. This is especially so in the head and neck region, which has relatively poor soft tissue shielding with many radiosensitive organs. The development of “black bone” imaging utilising low flip angles and short echo time (TE) has shown considerable promise in alleviating the use of ionising radiation in many cases of craniofacial disorders. In this review article, we share our experience of utilising “black bone” sequence in children with craniofacial pathologies, ranging from traumatic injuries to craniosynostosis and focal osseous/fibro-osseous lesions such as fibrous dysplasia and Langerhans cell histiocytosis (LCH). A detailed discussion on the technical aspects of “black bone” sequence, including its potential pitfalls and limitations, will also be included.

MR-Guided Radiotherapy: The Perfect Partner for Immunotherapy?

During the last years, preclinical and clinical studies have emerged supporting the rationale to integrate radiotherapy and immunotherapy. Radiotherapy may enhance the effects of immunotherapy by improving tumor antigen release, antigen presentation, and T-cell infiltration. Recently, magnetic resonance guided radiotherapy (MRgRT) has become clinically available. Compared to conventional radiotherapy techniques, MRgRT firstly allows for daily on-table treatment adaptation, which enables both dose escalation for increasing tumor response and superior sparing of radiosensitive organs-at-risk for reducing toxicity. The current review focuses on the potential of combining MR-guided adaptive radiotherapy with immunotherapy by providing an overview on the current status of MRgRT, latest developments in preclinical and clinical radio-immunotherapy, and the unique opportunities and challenges for MR-guided radio-immunotherapy. MRgRT might especially assist in answering open questions in radio-immunotherapy regarding optimal radiation dose, fractionation, timing of immunotherapy, appropriate irradiation volumes, and response prediction.

Radiation protection to patients in radiology: A review study

The present paper aims at reviewing different shielding methods used for patients in medical imaging and investigating their merits and demerits. These techniques are generally classified into two groups including in-plane and out-of-plane shielding. Bismuth (Bi) shielding is a conventional in-plane shielding method used during CT examinations to protect radiosensitive organs. This method has reduced radiosensitive organs dose by about 34–68% during different CT examinations. However, it causes considerable degrading effects on image quality and for this reason AAPM recommended against its application in 2017. Recently, another in-plane shielding, named Saba shielding, introduced wherein all the shortcomings and deficits of Bi shielding have been resolved or fixed. Saba shielding reduces radiosensitive organs dose by about 50% without degrading image quality. Out-of-plane shields can decrease the patient dose by more than 55%. However, due to the low dose of the scattered radiation received by out-of-plane organs, in the case of applying out-of-plane shields such as gonad or thyroid shields, the risk and benefit of their usage should be evaluated.

DEVELOPMENT OF THE DESIGN OF THE PRECLINICAL TRIALS OF RADIOPHARMACEUTICALS FOR THE RADIONUCLIDE DIOAGNOSTICS AND THERAPY BASED ON THE AMBA PEPTIDE

The use of the bombesin analogues labeled with 68Ga and 177Lu for the radionuclide diagnostics and therapy of the prostate cancer, respectively, is one of the novel and promising approaches of the nuclear medicine. These radiopharmaceuticals are currently on the stage of preclinical and clinical trials in the foreign countries; in the Russian Federation, a preclinical trial is being developed. The aim of the current study was to develop the design of the preclinical study for the radiopharmaceuticals based on AMBA for the assessment of their biodistribution. The study was based on the meta-analysis of the available publications in peer-reviewed journals. The analysis was performed using the full-text archive of biomedical and life sciences journals PubMed Central for the following keywords: radionuclide therapy, nuclear medicine, AMBA, 68Ga и 177Lu. The study included the comparative analysis of the animal and patient samples, methods of data collection and results of the accumulation of radiopharmaceuticals in nodules and radiosensitive organs and tissues. The results of the study allowed proposing the minimal requirements for the animal samples (at least 30 animals for each radiopharmaceutical), data collection (direct radiometry and PET) and time points (not less than 5 measurements in 120-240 minutes for the radiopharmaceuticals labeled with 68Ga and 5 measurements in 336 hours for the radiopharmaceuticals labeled with 177Lu) for the assessment of the biodistribution of the radiopharmaceuticals.

REDUCING ABSORBED DOSE TO THYROID IN NECK CT EXAMINATIONS: THE EFFECTS OF SABA SHIELDING

Bi shielding has been used for the protection of radiosensitive organs during computed tomography (CT) for 20 years. In 2017, American Association of Physicists in Medicine recommended against Bi shielding due to its degrading effects on image quality. Saba shielding introduced recently protecting organs as Bi shielding without degrading image quality. In this study, the Saba shield was modified and primary radiation attenuation values of the shields and entrance skin dose (ESD) on the thyroid were measured with and without shielding. Furthermore, the quality of images obtained using Saba shielding was investigated quantitatively and qualitatively. Saba and Bi shielding reduced the ESD on the thyroid by about 50%. Saba shielding had about 5–7 HU less noise and about 51–65 HU less CT numbers shift in comparison with Bi shielding at a distance of 1 cm from the shields. Saba shielding had no degrading effects on image quality in the patient study.