The “Dose Index Tracker”: An Automated Database of Patient Radiation Dose Records for Quality Monitoring
 
Authors:
Shanshan Wang, Arizona State University; William Pavlicek, PhD; Catherine C. Roberts, MD; Steven G. Langer, PhD; Beth A. Schueler, PhD; Richard L. Morin, PhD; Mary B. Peter, MS; Teresa Wu, PhD; Muhong Zhang, PhD
 
Background:
Quality assurance monitoring of ionizing radiation is required by state regulatory bodies and The Joint Commission during certain examinations and procedures. While radiologists and cardiologists arguably constitute the larger users of ionizing radiation, the requirement is enterprise-wide as hospital surgeons, urologists, GI physicians, and others are credentialed users of ionizing producing equipment, and also fall under these requirements. The prescriptive use of medical radiation is an important public health issue as the number of procedures has increased. This has prompted a hospital quality oversight program to direct greater oversight of radiation use. Required monitoring includes identifying an episode of care that may be excessive with respect to prescription of ionizing radiation, as well as identifying other patients who have received multiple examinations within weeks or even months of one another. At a national level, The Joint Commission lists peak skin dose exposure above 15 Gy as a sentinel event (The Joint Commission Sentinel Event Policy and Procedures, 2007), while at a regional level, many states require the maintenance of dose records for all patients undergoing fluoroscopy and active management of patients who receive high x-ray doses. At the health provider level, the Quality Assurance Committee attempts to review and monitor radiation of potentially repeating exams, such as CT, that may be given to an individual patient. At this time, such records of administered radiation dose are commonly documented (hand recorded) into paper logbooks typically at the operators scanner console. This method has the well known limitations of paper records.

There is a compelling need to develop national standards for the appropriate collection, recording, and monitoring of the use of ionizing radiation as occurs with x-ray diagnostic imaging. One precursor of standardization is the integration of historical radiation exposure data (obtained from Digital Imaging and Communications in Medicine [DICOM] images), with a specific patient (health records). Electronically capturing radiation dose related parameters is the goal of DICOM Structured Dose Reporting. However, to our knowledge no tools exist for centralizing the documented administration of ionizing radiation episodes of care into a form for routine use by quality assurance monitoring staff. A collaboration between Mayo Clinic and Arizona State University aims to create a radiation dose information system to provide: a patient centric; integrated, radiation dose index history; monitoring tools to address existing Joint Commission and state requirements and accreditation standards; and medical Quality Assurance Committee directives for routine monitoring.
 
Evaluation:
“Dose Index Tracker” (DIT) was designed and implemented to integrate into a DICOM compliant infrastructure to fully capture and maintain longitudinal patient specific dose indices for all diagnostic and procedural uses of ionizing radiation. This information system consists of: a knowledge base of known devices (i.e., modalities), a patient episode dose tracking database, dosimetry analyzer tools, a configurable web reporter, and an alert and auto reporting mechanism. The system architecture of DIT, including the composite modules and the connection with other software are shown in Figure 1. The implementation and evaluation of each is summarized as following.

Figure 1
Figure 1

Knowledge Base: DICOM is a continuously evolving standard, and not all modalities are equally far along in their adoption as new standards are defined. The base standard provides extensive information about the patient, the medical examination process, and the imaging modality acquisition settings. DICOM-compliant image files contain modality technical attributes (kvp, mAs, field of view, S#, fluoroscopic dose rate, body part, etc). This detail of dose-related information often varies by vendor, modality, and software version; information may also be provided in an image file (DICOM Secondary Capture). This information is harvested from the DICOM tags (images are not saved) by our application. Because of the variation in supplied tags, our knowledge base includes schema that describes known scanner software versions, including standard and proprietary dose related data elements. Those data, in turn, drive proper algorithm selection for calculating a dose approximation. New “unknown” software versions are converted to “known” following manual inspection of DICOM elements. We have tested the robustness of the knowledge base and currently have CT, Interventional Radiology, Cardiac Catheterization, Nuclear, PET, CR, and Mammography from more than 25 different devices having multiple software versions at the Mayo Clinic Arizona and Rochester.

DIT Database: The database is designed to separate the dose index information from other Patient Healthcare information to avoid redundancy, to balance storage efficiency, and to improve data access efficiency. The resultant schema contains three parts: exam information, image information, and vendor modality specific dose information. To evaluate the schema of the database, we populated data elements from varied scanners into the database: if a scanner’s software version is known, its dose-related tags will be harvested for subsequent searches; if a scanner version is unknown by the knowledge base, the database will automatically alert the database manager(s) (i.e., medical physicist) of the need to specify DICOM dose-related fields for computational use.

Dosimetry Analyzer: For each ionizing radiation modality (i.e., CT, radiography, PET, etc.), the computation of a patient specific radiation dose is required in order to develop the dose associated with an individual episode of care. Extracted information in the DIT includes information such as examination type, gender, age, projection angle, exposure rate, exposure number, etc. Such scan specific information can be used to assess or estimate a dose particular to a specific exam. At a minimum, if the systems used do not support any tags that would help compute the dose, a record of the number of specific examinations, by modality, can be identified for each patient.

Web Reporter: For Quality Assurance purposes, we developed a web reporting tool that shows: the patients having multiple scans, the patients younger than 16 years old by type of examination, the equipment used in conducting the exams, S# that exceeds a predetermined value, etc.

Alert Mechanism: An instant message alert system serves two purposes. The first is to maintain the robustness of the system. Images sent by an unknown scanner, for example generate a message to support staff for a review of the data record. The second purpose is for quality assurance as defined by administrative or QA staff.

 
Discussion:
As stated by Sodickson, et al. (2009), “ultimately, longitudinal dose monitoring efforts will benefit most from improved patient-specific dose estimates for each exam, archived in the DICOM header information or another institutional database.” Implementing an enterprise dose tracker information system offers potential to
  • provide quantitative data hints to reduce radiation exposure;
  • enable monitoring for Quality Assurance purposes (e.g., monitoring by patients, by imaging modality, by physicians, by types of equipment);
  • automatically identify patients at increased risk for adverse radiation effects and identify the best practices with respect to radiation; and
  • provide an enterprise solution for state and federal radiation regulatory compliance.
Conclusion:
Requirements from national, regional, and individual healthcare providers regarding radiation exposure can be addressed using DIT. More experiments are needed to test the robustness and scalability of the system. Continuing advances with dosimetry analysis is needed to accurately capture the dose index history appropriate for a modality. Software provided by vendors that provide DICOM Structured Dose Reporting must be more widely implemented.
 
References:
1. “Scans save lives, but cost a lot, increase radiation exposure”, available at http://www.wral.com/lifestyles/healthteam/story/4699680/, March 9, 2009.

2. Amis ES Jr, Butler PF, Applegate KE, et al. American College of Radiology white paper on radiation dose in medicine. J. Am Coll Radiol 2007;4:272-284.

3. Brenner DJ, Hall EJ, “Computed tomography: An increasing source of radiation exposure.” N Engl J Med; 2007;357:2277-2284.

4. Broder J, Bowen J, Lohr J, Babcock A, Yoon J. Cumulative CT exposures in emergency department patients evaluated for suspected renal colic. J Emerg Med 2007;33:161-168.

5. Einstein AJ, Henzlova MJ, Rajagopalan S. Estimating risk of cancer associated with radiation exposure from 64-slice computed tomography cornoary angiography. JAMA 2007;298:317-323.

6. Huda W, Ravenel JG, Scalzetti EM. How do radiographic techniques affect image quality and patient doses in CT? Semin Ultrasound CT MR. 2002;23:411-422.

7. Huda W, Vance A. Patient radiation doses from adult and pediatric CT. AJR Am J Roentgenol. 2007;188:540-546.

8. Huda W. Radiation doses and risks in chest computer tomography examinations. Proc Am Thorac Soc. 2007;4:316-320.

9. Jaffe TA, Gaca AM, Delaney S, et al. Radiation doses from small-bowel follow-through and abdominopelvic MDCT in Crohn’s disease. AJR Am J Roentgenol. 2007;189:1015-1022.

10. Katz SI, Saluja S, Brink JA, Forman HP. Radiation dose associated with unenhanced CT for suspected renal colic: impact of repetitive studies. AJR Am J Roentgenol. 2006;186:1120-1124.

11. Martin CJ. Effective dose: how should it be applied to medical exposure? Br J Radiol. 2007;80:639-647.

12. Mettler FA Jr, Thomadsen BR, Bhargavan M, et al. Medical radiation exposure in the U.S., in 2006: preliminary results. Health Phys. 2008;95:502-507.

13. Sodickson A, Baeyens PF, Andriole KP, et al. “Recurrent CT, Cumulative Radiation Exposure, and Associated Radiation-induced Cancer Risks from CT of Adults.” Radiology, April 2009;Vol.251:1:175-184.

14. The Joint Commission Sentinel Event Policy and Procedures. The Joint Commission, Oakbrook Terrace, IL. July 2007.