Medical health physics: a review

Twelfth Annual Warren K. Sinclair Keynote Address--the Influence of the NCRP on Radiation Protection in the United States: Guidance and Regulation

The Warren K. Sinclair Keynote Address for the 2015 Annual Meeting of the National Council on Radiation Protection and Measurements (NCRP) describes the Council's influence in the development of radiation protection guidance in the United States since its founding in 1929 as the U.S. Advisory Committee on X-Ray and Radium Protection. The National Bureau of Standards (NBS) was the coordinating agency for the Advisory Committee, and its reports were published as NBS handbooks. In 1946, the Advisory Committee was renamed the National Committee on Radiation Protection and remained so until NCRP was chartered by the U.S. Congress in 1964. In 1931, the U.S. Advisory Committee on X-Ray and Radium Protection proposed the first formal standard for protecting people from radiation sources as NBS Handbook 15 and issued the first handbook on radium protection, NBS Handbook 18. Revised recommendations for external exposure were issued in 1936 and for radium protection in 1938 and remained in force until 1948. Throughout its 86 y history, the Council and its predecessors have functioned as effective advisors to the nation on radiation protection issues and have provided the fundamental guidance and recommendations necessary for the regulatory basis of the control of radiation exposure, radiation-producing devices, and radioactive materials in the United States.

Cervical spine imaging using mini--C-arm fluoroscopy: patient and surgeon exposure to direct and scatter radiation

STUDY DESIGN

Direct and scatter radiation was measured during cadaveric cervical spine imaging with a mini-C-arm fluoroscope.

OBJECTIVE

The purpose of this study was to evaluate radiation exposure to the patient and surgeon when using a mini-C-arm fluoroscope to image the cervical spine.

SUMMARY OF BACKGROUND DATA

Prior studies have quantified radiation exposure using large C-arm fluoroscopy during procedures involving the cervical, thoracic, and lumbar spine. To our knowledge, no studies have quantified radiation exposure during mini-C-arm fluoroscopy of the cervical spine.

METHODS

A calibrated OEC MINI 6800 C-arm was used to image a prepared cadaveric cervical spine specimen, which included the skull. The specimen was suspended on an adjustable polycarbonate platform. Thirteen film badge dosimeters were mounted at various positions and angles to detect direct and scatter radiation. Recorded exposure levels were collected and analyzed.

RESULTS

Surgeon exposures from the mini-C-arm were considerably lower than previously reported with the standard C-arm, but nonetheless concerning. Patient exposures were considerable and not always reduced compared with values from the standard C-arm. The kVp generated by the mini-C-arm was similar to the standard C-arm. Dosimeters mounted in the same plane recorded dissimilar amounts of radiation during the same test, which underscores the influence of shape on the amount of reflected scatter.

CONCLUSIONS

Although using a mini-C-arm unit may reduce exposure levels, substantial exposure to both patient and staff is still achievable. Use of a mini-C-arm for cervical spine imaging reduces exposure to the surgeon more effectively than to the patient. To lower the risk of radiation exposure in the cadaver laboratory, a mini-C-arm should be used in each instance that offers appropriate visualization. In the operating room, all appropriate radiation dose-reducing measures should be strictly enforced by supervising physicians to minimize risk to patients, medical staff, and themselves.

The effects of dialysis on 131I kinetics and dosimetry in thyroid cancer patients--a pharmacokinetic model

Currently, an accepted post-surgical treatment of patients with thyroid carcinoma is administration of an ablative dose of I. This treatment is well established based on extensive experience and modeling. However, for patients with renal disease, reduced iodine removal rates result in controversial thyroid doses and potentially excessive red bone marrow doses. There are differences of opinion regarding I dose recommendations ranging from a reduction in dose to an increase in dose compared with conventional amounts. Determination of suitable doses must take into account varying dialysis protocols and absorbed dose considerations to the thyroid and sensitive tissues such as red bone marrow. The specific aim of this study was to develop a simple yet comprehensive compartmental model for I kinetics in patients with thyroid carcinoma and end stage renal disease, which accounts for dialysis and provides absorbed dose estimates for the thyroid as well as the red bone marrow. STELLA, a compartmental modeling software program, was used to develop a kinetic model that includes the blood pool, thyroid, gastrointestinal tract, kidneys, bladder, and a conventional dialysis machine. Benchmarking was performed to demonstrate the validity of the model with data obtained from ICRP 30 and MIRD Dose Estimate Report No. 5. Iodine kinetics were simulated for normal patients, thyroid cancer patients, and patients with thyroid cancer and renal failure undergoing two standard types of dialysis, hemodialysis and continuous ambulatory peritoneal dialysis (CAPD). Results in this work show that thyroid doses to patients with thyroid cancer and renal failure on hemodialysis or CAPD are slightly higher than doses to patients with thyroid cancer and normal renal function. These results further indicate that red bone marrow doses to patients with thyroid cancer and renal failure on dialysis can be significantly higher than red bone marrow doses to patients with thyroid cancer and normal renal function, and thus these patients could benefit from a reduction in administered activity. Thyroid doses and red bone marrow doses to patients on standard hemodialysis depend on both dialysis frequency and the time interval between administration and first dialysis. The results in this study provide guidelines on how much activity a patient on dialysis should receive based on thyroid and red bone marrow absorbed dose (Gy MBq) considerations. This study should help to clarify some of the contradictory recommendations regarding I dose for thyroid carcinoma patients with renal failure.