Disaster Medical Science Division
Radiological Disasters and Medical Science Lab

Concurrent: Graduate School of Medicine
Research Subject(s)
The Fukushima Nuclear Power Plant accident generated strong public interest in radiation and radioactive material. Nevertheless, many members of the public have misconceptions regarding the effects of radiation on humans.
Our laboratory evaluates radiation doses and radiation effects in humans, analyzes the management of radiation exposure from nuclear hazards and medical procedures, and develops diagnostic-imaging systems for use in disasters. Our research includes studies addressing radiation issues related to both disasters and medicine. One of the main fields in the investigation of the effects of low radiation doses on people is that of medical radiation exposure.
Key Words
Radiation safety and risk management / Evaluation/measurement of radiation doses and radiation effects in humans / Development of diagnostic-imaging systems for use in disasters / Optimization of radiation protection / Methods for reducing radiation
Research Activities

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.)

Selected Works

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.

Selected Memberships
  • Japanese Society of Radiological Technology
  • Japan Radiological Society
  • Japan Society of Medical Physics
  • Japanese Radiation Research Society
  • Japan Radioisotope Association
Selected Awards
  • Radiation Effects Association Award (2010)
  • RSNA (Radiological Society of North America) Exhibit Award "Certificate of Merit"