SPI study guide
SPI · Work through your exam, one topic at a time.
The Sonography Principles and Instrumentation (SPI) examination is the physics-and-instrumentation exam within the Inteleos/ARDMS certification family. It is aimed at sonographers, vascular technologists, and physicians who need to demonstrate that they understand how ultrasound equipment generates, displays, and measures information - not anatomy or pathology. Content generally centers on the behavior of sound in tissue, transducer construction and selection, beam formation and focusing, signal processing and image display, axial and lateral resolution, artifacts, Doppler principles and hemodynamics, bioeffects, and quality assurance and instrument safety. Because the official exam page could not be retrieved when this material was compiled (the address returned a 404 error page), verifiable logistics such as item count, time limit, fee, passing standard, retake rules, and published domain weights are not stated here; confirm them on the current official Inteleos/ARDMS page before you register. Topics on this exam: Physical Principles and Instrumentation, Doppler and Hemodynamics, and Quality Assurance, Safety and Artifacts. The SPI study guide has 3 sections and about 1,304 words.
01Physical Principles and Instrumentation
Diagnostic ultrasound is a mechanical, longitudinal wave. Average soft-tissue propagation speed is 1540 m/s (1.54 mm/µs). Wavelength λ = c/f and period T = 1/f: higher frequency means shorter wavelength, shorter period, and less penetration. Attenuation in soft tissue is roughly 0.5 dB/cm/MHz, so a 5 MHz beam loses about 2.5 dB per centimeter and 5 MHz reaches roughly half as deep as 2.5 MHz.
317 words, about 2 min02Doppler and Hemodynamics
fd = (2 × f0 × v × cosθ) / c. The factor of 2 accounts for the round trip. Shift is greatest at 0° or 180° and vanishes at 90°, so keep the angle at or below 60°. Common calculation errors: using mean velocity when peak is requested, omitting the cosine term, or entering frequency in kHz.
326 words, about 2 min03Quality Assurance, Safety and Artifacts
QA confirms that a system still performs as it did at acceptance and catches drift before it affects patients. Baseline values are recorded at installation and compared on a schedule (daily, monthly, annual, after transducer replacement or repair). Tests use tissue-equivalent phantoms with known 1540 m/s propagation speed and approximately 0.5 dB/cm/MHz attenuation. Axial resolution is the closest two reflectors along the beam that remain separate and is governed by spatial pulse length.
661 words, about 3 min