ULTRASOUND DEVICES: TWO-STAGE 510(K) PROCEDURE
This article was originally published in The Gray Sheet
ULTRASOUND DEVICES: TWO-STAGE 510(K) PROCEDURE involves submission of a "preliminary" and a "final" premarket notification document, FDA states in its Feb. 17 "Revised 510(k) Diagnostic Ultrasound Guidance." The agency explains in the guidance, which is effective immediately, that the preliminary submission "should contain all the information normally found in a 510(k) except that it can be based on prototype or design data" and should be submitted "at least 90 days prior to the desired marketing date." The final 510(k) will consist of "final labeling for the device, the acoustic output tables measured on production devices, and the indications for use," FDA notes. FDA says that "a provisional letter will be issued" when there are "no outstanding issues except for submission of final labeling and production device acoustic output measurements." The final 510(k), clearance of which will allow the device to be marketed, is to be submitted "when the device is in final form." FDA says it "will try to respond to these final 510(k) submissions within 30 days." FDA is implementing the two-stage procedure to enable manufacturers to make last-minute changes to devices and to receive market clearance more rapidly once the ultrasound device is finalized and ready for production. The final 510(k) "will satisfy the requirement for the submission of an initial report required" by FDA radiation control regulations, the agency notes. FDA says it "has a Federal Register initiative to revise the initial report system used under the Radiation Control for Health and Safety Act." When this is finalized, FDA "may revise the 510(k)/initial report process for diagnostic ultrasound systems." The guidance document also spells out acoustic output reporting requirements for different types of ultrasound devices. The revised guidance incorporates requirements of a 1992 voluntary standard on output display developed by FDA, the National Electrical Manufacturers Association and the American Institute of Ultrasound in Medicine ("The Gray Sheet" Aug. 31, In Brief). For "Track 3" ultrasound devices -- those that "follow the Output Display Standard or fetal Doppler applications except for fetal heart rate monitors" -- acoustic output evaluation will be "based upon conformance with the output display standard," which "eliminates the application-specific comparison of acoustic output" to preamendment levels, FDA states. Manufacturers of Track 3 devices must "provide certification" that "measurements of acoustic output display indices -- the thermal index (TI) and the mechanical index (MI) -- will be made" in accordance with the voluntary output display standard and that "information supplied in the 510(k) will be for maximum TI and MI values." In the preliminary 510(k) submissions, manufacturers of Track 3 devices must "provide prototype or design acoustic output data or may certify that the acoustic output of a transducer will be below the maximum preamendment levels," the guidance also states. FDA notes that it "is sensitive to the need for a more scientifically based mechanism for evaluating acoustic output levels used for various clinical applications." The agency plans to "collaborate with other professional groups...in efforts to develop such a mechanism (or mechanisms)." For "Track 1" ultrasound systems -- those that do not conform to the output display standard or are not indicated for any fetal Doppler applications except for fetal heart rate monitors -- acoustic output reporting should be "based on application-specific comparisons to preamendment output levels," FDA states. In addition, "intensity measurements for each transducer must be made at the highest output setting available for use." Preliminary 510(k)s for Track 1 devices should "summarize the mode/application possibilities for each system/transducer combination," FDA says. For Track 1 transducers for transcranial applications, FDA specifically asks the manufacturer to "provide an estimate of maximum temperature rise attributable to the use of that transducer for each operating mode" and to "describe the model used to determine this estimation." The agency notes that "an acceptable model for making these estimates can be found" in the output display standard. The guidance also formally adopts the ALARA principle, which requires manufacturers to include labeling instructions to ensure that the amount of ultrasound energy used during diagnostic procedures is as low as reasonably achievable. FDA first signaled its intention to adopt the policy in an Oct. 12, 1990 draft document ("The Gray Sheet" June 18, 1990, p. 9). The policy requires manufacturers to "provide suggestions on how to use" the ultrasound system in order to follow the ALARA principle. Labeling for Track 3 devices also must include "a summary of the ALARA education program for the clinical end-user," FDA states. The education program should include explanations of: "the basic interaction between ultrasound and matter" ** "the possible biological effects" ** "the derivation and meaning of the [acoustic output] indices" ** and "a recommendation to use and the need for following the ALARA principle in all studies." In the guidance, FDA also implements "a mechanism for submission of [Track 1] 'special situation devices.'" These devices, "whose overall acoustic output exceeds application specific limits," will be reviewed by the agency "on a case-by- case basis." Manufacturers should support the high acoustic output levels with "laboratory and clinical data demonstrating the need for higher output" and should "describe what user interactive features are provided to enhance user awareness of acoustic output" such as on screen display, power up default settings and manual override. FDA also indicates in the document that it is terminating use of "Track 2," the interim fetal Doppler track. "The use of this track will cease 90 days after the date of issuance of this guidance," the agency notes. FDA is eliminating the track because its requirements are now included in the Track 3 program.
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