Our division conducts research on managing the radiation dose and quality control/assurance of radiation equipment in radiological examinations, including interventional radiology (IVR).
In particular, our main fields of education and research are as follows:
• Radiation safety and risk management in radiological examinations (patients and staff).
• Quality control and quality assurance of medical X-ray systems and radiographic images.
• Optimization of the radiation dose and X-ray image quality.
• Development of dosimeters and evaluation methods for radiation exposure in radiological examinations.
• Radiation protection for pediatric patients.
• Avoidance of radiation-induced injury (deterministic and stochastic effects) in radiological examinations.
• Optimization of medical radiation exposure and radiation protection.
• Justification of radiological procedures.
Educating radiological technology students and medical physicists is also an important aspect of our division.
We produced a prototype real-time dosimeter that uses nontoxic phosphor for interventional radiology (IR) patients.
Although many patients benefit greatly from IR procedures, radiation-induced injuries have been reported in patients following IR procedures. Therefore, real-time monitoring of individual radiation doses is important to avoid such injuries. However, there is currently no feasible real-time patient dosimeter available for IR.
Although skin dose monitors (SDMs) were previously used for this purpose, SDMs were discontinued because they contained zinc-cadmium phosphor, a toxic substance.
A patient skin dosimeter (PSD) can also accurately measure radiation doses to the skin in real-time. However, the PSD sensor and cable are clearly visible on radiographic images, and thus severely impede the IR procedure.
Therefore, new technologies that enable real-time monitoring of the radiation doses received by IR patients are necessary.
The prototype real-time dosimeter consists of photoluminescence sensors (nontoxic phosphor, maximum four sensors), an optical fiber cable, a photodiode, and a digital display that includes the power supply. Our previous research found that Y2O2S:Eu,Sm is a suitable red-emission phosphor that is nontoxic and exhibits relatively high sensitivity. (Nakamura, Chida, et al. Med Phys 2014, doi: 10.1118/1.4893534.).
Like the SDM, the new dosimeter cable is not radiopaque on fluoroscopic images. The basic characteristics of the prototype real-time dosimeter are comparable to those of the previously used SDM.
The novel real-time dosimeter can be equipped with multichannel sensors (maximum four sensors), whereas the SDM had only a single sensor. The multichannel sensors are one of the major advantages of the novel dosimeter because real-time patient dose measurements are available from four sensors simultaneously, enabling an accurate detection of the maximum radiation skin dose.
Therefore, we suggest that our prototype real-time dosimeter is superior to the SDM for measuring the radiation exposure dose to the skin during IR. (Nakamura, Chida, et al. AJR 2015, doi: 10.2214/AJR.14.13925; Chida, et al. Phys Med 2016, doi: 10.1016/j.ejmp.2016.10.013.)
Kato M, Chida K, Nakamura M, Toyoshima H, Terata K, Abe Y. New real-time patient radiation dosimeter for use in radiofrequency catheter ablation. J Radiat Res. 2019 Mar 1;60(2):215-220. doi: 10.1093/jrr/rry110. PMID: 30624747;
Haga Y, Chida K, Kaga Y, Sota M, Meguro T, Zuguchi M. Occupational eye dose in interventional cardiology procedures. Sci Rep. 2017 Apr 3;7(1):569. doi: 10.1038/s41598-017-00556-3.
Kashimura Y, Chida K. Nuclear Reactor Accident Fallout Artifacts: Unusual Black Spots on Digital Radiographs. AJR Am J Roentgenol. 2015 Dec;205(6):1240-3. doi: 10.2214/AJR.15.14557.
Chida K, Kaga Y, Haga Y, Kataoka N, Kumasaka E, Meguro T, Zuguchi M. Occupational dose in interventional radiology procedures. AJR Am J Roentgenol. 2013 Jan;200(1):138-41. doi: 10.2214/AJR.11.8455.
Chida K, Ohno T, Kakizaki S, Takegawa M, Yuuki H, Nakada M, Takahashi S, Zuguchi M. Radiation dose to the pediatric cardiac catheterization and intervention patient. AJR Am J Roentgenol. 2010 Nov;195(5):1175-9. doi: 10.2214/AJR.10.4466.