Validation of Metal Oxide Semiconductor Field Effect Transistor Technology for Organ Dose Assessment During CT: Comparison with Thermoluminescent Dosimetry

• Published in: American journal of roentgenology (1976) Vol. 188; no. 5; pp. 1332 - 1336
• Main Authors: Yoshizumi, Terry T, Goodman, Philip C, Frush, Donald P, Nguyen, Giao, Toncheva, Greta, Sarder, Maksudur, Barnes, Lottie
• Format: Journal Article
• Language: English
• Published: Leesburg, VA Am Roentgen Ray Soc 01.05.2007; American Roentgen Ray Society
• Subjects: Adult; Applied radiobiology (equipment, dosimetry...); Biological and medical sciences; Biological effects of radiation; Female; Fundamental and applied biological sciences. Psychology; Humans; Medical sciences; Miscellaneous; Phantoms, Imaging; Radiation Dosage; Radiometry - methods; Radiotherapy. Instrumental treatment. Physiotherapy. Reeducation. Rehabilitation, orthophony, crenotherapy. Diet therapy and various other treatments (general aspects); Semiconductors; Thermoluminescent Dosimetry; Tissues, organs and organisms biophysics; Tomography, X-Ray Computed; Transistors, Electronic; Radiobiology; Radiodiagnosis; Medical imagery; Computerized axial tomography; Dosimetry; Dose; Comparative study
• ISSN: 0361-803X; 1546-3141
• DOI: 10.2214/AJR.06.0742

The purposes of this study were to apply near-real-time dose-measurement technology with metal oxide semiconductor field effect transistors (MOSFETs) to the assessment of organ dose during CT and to validate the method in comparison with the thermoluminescent dosimeter (TLD) method. Dosimetry measurements were performed in two ways, one with TLDs and the other with MOSFETs. Twenty organ locations were selected in an adult anthropomorphic female phantom. High-sensitivity MOSFET dosimeters were used. For the reference standard, TLDs were placed in the same organ locations as the MOSFETs. Both MOSFET and TLD detectors were calibrated with an X-ray beam equivalent in quality to that of a commercial CT scanner (half-value layer, approximately 7 mm Al at 120 kVp). Organ dose was determined with a scan protocol for pulmonary embolus studies on a 4-MDCT scanner. Measurements for selected organ doses and the percentage difference for TLDs and MOSFETs, respectively, were as follows: thyroid (0.34 cGy, 0.31 cGy, -8%), middle lobe of lung (2.4 cGy, 3.0 cGy, +26%), bone marrow of thoracic spine (2.2 cGy, 2.5 cGy, +11%), stomach (1.0 cGy, 0.93 cGy, -6%), liver (2.5 cGy, 2.6 cGy, +6%), and left breast (3.0 cGy, 2.9 cGy, -1%). Bland-Altman analysis showed that the MOSFET results agreed with the TLD results (bias, 0.042). We found good agreement between the results with the MOSFET and TLD methods. Near-real-time CT organ dose assessment not previously feasible with TLDs was achieved with MOSFETs. MOSFET technology can be used for protocol development in the rapidly changing MDCT scanner environment, in which organ dose data are extremely limited.