Chapter Four · failure evidence
What Ultrasonic Imaging & Characterization got wrong, from 55 dissertations
These records detail experimental and analytical failures across ultrasonic imaging, guided wave testing, and acoustic characterization systems. Reported shortcomings stem from severe media attenuation, interface impedance mismatches, algorithm breakdowns under acoustic speckle, and sensitivity limits relative to alternative diagnostic modalities. These records come from PhD theses at 18 institutions, 2021 to 2026. Each links to its thesis. They were extracted by language models reading the full text, so treat each as a lead to read, not a verdict.
Resolution, sensitivity, and contrast limits compared to baseline modalities
Ultrasound methods struggled to distinguish subtle material phase transitions, tissue steatosis grades, and slow microvascular flows due to limited sensitivity and spatial resolution. Planar acquisitions, uncalibrated three-dimensional sweeps, and guided Lamb wave scans frequently underperformed compared to volumetric imaging, radiography, optical coherence tomography, and conventional C-scans.
Tried and failed
ultrasonic attenuation spectroscopy applied to detecting nanoscale precipitate phase transitions. Outcome: no signal. Reason: attenuation changes between the isothermal phase and parent matrix were too small to detect
Ultrasonic characterization of Ti-5Al-5Mo-5V-3Cr · Iowa State
Tried and failed
ultrasound attenuation measurement applied to grading moderate versus severe tissue steatosis. Outcome: no signal. Reason: insufficient statistical separation between moderate and severe grades of fat infiltration
Lost to a baseline
Ultrasound detected caliber variations in only 42.77% of cases compared to 82.64% detected by MRCP and 98.68% by ERCP
Sonographische Befunde bei Patienten mit primär sklerosierender Cholangitis · Publikationssystem UB Tuebingen
Considered and rejected
Considered and rejected: Rejected relying exclusively on ultrasonic C-scan for post-impact fatigue monitoring due to insensitivity to subsurface growth prior to global boundary breakout.
Lost to a baseline
Radiography showed higher interobserver agreement (Gwet's AC1 0.9215-0.9423) than ultrasound (0.4486).
Ultrasonographic evaluation of sites of osteochondrosis in young Thoroughbred horses · Research Repository UCD
Lost to a baseline
For fetal lens visualization, 2D ultrasound outperformed 3D ultrasound across 12–14 weeks (2D achieved 95% vs 3D at 39%).
A prospective three-dimensional imaging and anatomy screening study · Imperial
Considered and rejected
Considered and rejected: Rejected standard ultrasound imaging for in vivo cranial blast cavitation due to poor axial resolution, skull fusion in adult animals, and acoustic backscatter.
Biological cavitation and protein profiles as unique hallmarks of blast-induced traumatic brain injury · Iowa State
Considered and rejected
Considered and rejected: Rejected intravascular ultrasound (IVUS) imaging in favor of optical coherence tomography (OCT) due to resolution limitations (100-120 microns for IVUS vs 10 microns for OCT).
Lost to a baseline
Conventional ultrasonic C-scan achieves 1 mm x 1 mm spatial resolution, resolving exact crack morphology which Lamb wave scanning cannot.
Ultrasonic guided waves for mechanical defects detection on thin-film solar photovoltaic modules · Georgia Tech
Considered and rejected
Considered and rejected: Freehand 3D ultrasound without position sensors, rejected because lack of positional data yields inadequate volumetric reconstruction quality preventing quantitative measurements
Evaluation of tomographic 3D ultrasound for the assessment of vascular pathology · Imperial
Tried and failed
two-dimensional ultrasound diameter reduction measurement applied to transplant renal artery stenosis diagnosis. Outcome: worse than baseline. Reason: planar measurements yielded low diagnostic accuracy compared to volumetric and magnetic resonance angiography assessments
The evaluation of advanced ultrasonography applications in the assessment of transplanted kidneys · Imperial
Tried and failed
super-resolution ultrasound localization microscopy vessel density estimation applied to in vivo tumor microvasculature quantification. Outcome: no signal. Reason: vessel density measurements did not correlate significantly with histological endothelial staining counts
Tried and failed
conventional colour Doppler ultrasound imaging applied to inter-cord placental vascular anastomoses. Outcome: no signal. Reason: insufficient sensitivity and resolution to detect slow microvascular blood flow between umbilical cords
Placental Vascular imaging and its association with pregnancy outcomes · Imperial
Considered and rejected
Considered and rejected: Rejected measuring tissue thickness using traditional methods (histology, mechanical thickness gauges/calipers, ultrasound, and optical coherence tomography) due to being destructive, having low spatial resolution, offering only focal points, or possessing depth limitations
Towards understanding tricuspid valve mechanics & function in health, disease, and repair · UT Austin
Acoustic attenuation and penetration losses in thick or absorbing media
High acoustic attenuation, material absorption, and guided wave leakage severely degraded signal-to-noise ratios in thick composites, sediment cores, cranial bone, and viscous fluids. Deep acoustic penetration paths caused signal voids and frequency downshifting that obscured shear wave arrivals, blood flow Doppler shifts, and structural defect reflections.
Tried and failed
Ultrasonic pulse transmission for shear-wave arrival detection applied to sediment samples under triaxial loading. Outcome: no signal. Reason: High acoustic attenuation and internal reflections at low effective stress obscured arrival signatures
Tried and failed
ultrasonic guided wave inspection outside optimal frequency-thickness applied to fluid-filled pipes. Outcome: no signal. Reason: frequencies outside 1.0-1.5 MHz-mm caused excessive leaky attenuation of the A0 mode into the fluid
Pipeline health monitoring using helical guided ultrasonic waves · UT Austin
Tried and failed
ultrasonic C-scan non-destructive testing applied to thick filament-wound composite pipes. Outcome: no signal. Reason: severe acoustic attenuation and scattering in thick filament-wound glass-fiber structures prevented acceptable image clarity
Tried and failed
motor oil acoustic couplant applied to high-temperature ultrasonic guided wave testing. Outcome: no signal. Reason: high ultrasonic wave attenuation and absorption at elevated temperatures
Influence of dynamic load and temperature on guided wave ultrasonic damage detection in thin plates · Cranfield
Considered and rejected
Considered and rejected: Rejected relying on ultrasound-range (1-3 MHz) acoustic emission sensors for trans-cranial cavitation detection due to severe attenuation (10-30 dB) across the skull.
Cavitation in Blunt Traumatic Brain Injury · DukeSpace
Considered and rejected
Considered and rejected: Rejected Sylgard-184 for ultrasound flow loops due to high acoustic attenuation coefficent
On the extraction of path-dependent dynamics from recirculating pulsatile flows using optical and ultrasound imaging · Queens University Institutional Repository
Tried and failed
delay-and-sum ultrasonic imaging applied to thick composite impact damage localization. Outcome: no signal. Reason: weak reflection from small defects combined with guided wave mode dispersion in thick media
Structural health monitoring of thick composites using ultrasonic guided waves · Imperial
Tried and failed
sensor-tracked freehand 3D ultrasound reconstruction applied to deep tissue vascular imaging. Outcome: no signal. Reason: excessive acoustic penetration depth degraded image quality beyond reconstruction software thresholds
Evaluation of tomographic 3D ultrasound for the assessment of vascular pathology · Imperial
Tried and failed
high-frequency ultrasound in viscous immersion fluid applied to acoustic reflection resolution enhancement. Outcome: worse than baseline. Reason: Fluid viscous attenuation downshifted the center frequency, eliminating high-frequency spatial resolution advantages.
Considered and rejected
Considered and rejected: Rejected measuring vessel wall diameter in renal/segmental arteries via Doppler ultrasound due to depth attenuation and lack of resolution, relying instead on blood velocity changes.
Exercise in the Heat: Implications on Kidney Function and Acute Kidney Injury · DSpace at SUNY Buffalo
Tried and failed
low-frequency uncontrasted ultrasound Doppler flow measurement applied to in vivo arterial blood flow. Outcome: no signal. Reason: acoustic absorption dominated over blood scattering at frequencies below 15 MHz
Compact modular open platform for low-cost ultrasound imaging · Imperial
Algorithmic failures in image reconstruction, filtering, and segmentation
Advanced filtering and reconstruction techniques degraded image quality by discarding vital phase information, altering speckle textures, or entangling wave aberrations across angles. Segmentation routines and shadow detection heuristics failed because acoustic speckle noise and missing low-frequency spectral components caused boundary discontinuities and vessel underestimation.
Tried and failed
1D scanline intensity summation applied to acoustic shadow detection in ultrasound. Outcome: did not generalise. Reason: Oversensitivity from relying on raw pixel intensities instead of dynamic spatial variations
Computer-assisted intraoperative ultrasound in brain tumour surgery · Imperial
Tried and failed
2D spatial image representation for time-series classification applied to ultrasonic non-destructive testing signal classification. Outcome: worse than baseline. Reason: Synthetic 2D image focusing added computational overhead while yielding poorer classification performance than raw 1D time-domain traces
Machine learning applications in guided wave testing · Imperial
Tried and failed
angular coherence factor on redundant signals applied to ultrasound aberration correction. Outcome: worse than baseline. Reason: local wave aberrations became entangled across angles, lowering contrast compared to standard coherence factor
Tried and failed
sparse wavelet regularization using iterative shrinkage thresholding applied to ultrasound image reconstruction. Reason: Altered natural speckle patterns and improperly thresholded continuous linear intensity gradients.
Ultrasound Imaging: From Physical Modeling to Deep Learning · EPFL
Tried and failed
intensity thresholding and adaptive segmentation algorithms applied to speckle-corrupted ultrasound image segmentation. Reason: acoustic speckle noise caused false vessel wall classifications and contour discontinuities
Forward-Viewing Ultrasound Guidance of a Robotically-Steered Guidewire for Peripheral Interventions · Georgia Tech
Tried and failed
training CNNs on envelope-detected data applied to ultrasound image reconstruction. Outcome: worse than baseline. Reason: envelope detection discards phase information, causing blurred speckle patterns compared to raw RF/IQ representations
Ultrasound Imaging: From Physical Modeling to Deep Learning · EPFL
Tried and failed
Image deconvolution without geometric aberration correction applied to transcranial ultrasound blood flow imaging. Reason: Disabling cranial aberration coordinate remapping caused systematic vessel diameter underestimation
Ultrasound-based Noninvasive Monitoring Methods for Neurocritical Care · MIT
Tried and failed
multipulse harmonic filtering for tissue clutter cancellation applied to row-column array ultrasound imaging. Reason: transducer element elongation and hardware system non-linearities limited suppression to 30-35 dB instead of clinical 50-60 dB
Ultrafast 3-D ultrasound super-resolution imaging with a row-column array · Imperial
Tried and failed
filtered back-projection with ramp filtering applied to plane-wave ultrasound image reconstruction. Outcome: worse than baseline. Reason: missing low-frequency components in transducer Gaussian pulses negated ramp filter benefits
Lost to a baseline
Threshold control, 2-D quadratic filtering, and CWM filtering failed to outperform standard median filtering on the phantom ultrasound data.
Median Filtering and Wavelet Filtering: A Study of Noise Eeduction in Prostate Ultrasound Images · TXST Digital Repository
Acoustic impedance mismatches, couplant defects, and interface boundary artifacts
Severe acoustic impedance mismatches at air voids, dense calcifications, and rigid test containers caused total reflections, acoustic shadowing, or signal distortion. Couplant layers and dry-clamped mechanical transducers suffered from trapped air bubbles, fluid damping of target mechanics, and drastic signal amplitude drops compared to bonded transducers.
Tried and failed
ultrasonic non-destructive testing applied to subsurface biological targets inside internal voids. Outcome: no signal. Reason: acoustic impedance mismatch and signal scattering across air-filled voids prevented target detection
Investigating the infestation : Understanding and communicating Deathwatch beetle activity on HMS Victory · Cranfield
Tried and failed
ultrasonic C-scan inspection applied to impact-induced kissing bond detection in laminates. Outcome: no signal. Reason: weak interface contact without acoustic impedance mismatch produced no detectable ultrasonic reflection
Considered and rejected
Considered and rejected: Rejected glass tubes and acrylic blocks due to acoustic impedance mismatch and non-physiological ultrasound representation.
Entwicklung eines kostengünstigen Phantoms für das Erlernen der Dopplersonografie Development of a low-cost phantom for learning Doppler sonography · open_UMR Marburg DSpace 10.0
Tried and failed
spatial tracking 3D reconstruction from 2D ultrasound applied to calcified vascular lumen volume assessment. Outcome: data insufficient. Reason: acoustic shadowing behind dense calcifications created signal voids that prevented automated volume segmentation
Evaluation of tomographic 3D ultrasound for the assessment of vascular pathology · Imperial
Considered and rejected
Considered and rejected: Rejected glass coverslips for ultrasound imaging due to severe acoustic impedance mismatch (c=5600 m/s, rho=2200 kg/m3) causing total reflection; switched to PDMS coverslips
Ultrasound imaging of cells using gas vesicles and perfluorocarbon nanodroplets · Georgia Tech
Considered and rejected
Considered and rejected: Rejected ultrasonic reflectometry for contact patch measurements due to acoustic transmission across narrow gaps distorting true boundary profiles.
Experimental Evaluation of Wheel-Rail Interaction · Virginia Tech
Considered and rejected
Considered and rejected: Rejected standard high-resolution CT and ultrasound for dynamic diagnosis due to CT's low resolution (333 um)/radiation and ultrasound's requirement for liquid coupling media that dampens middle ear mechanics.
OPTICAL COHERENCE TOMOGRAPHY FOR CLINICAL OTOLOGY · DalSpace
Tried and failed
Viscoelastic couplant for external absorbing boundaries applied to ultrasonic wave absorption. Reason: Large acoustic impedance mismatch and requirement of an unrealistically thin coupling layer.
Ultrasonic methods for assessing fatigue degradation in metals · Imperial
Tried and failed
elastomer adhesive bonding for acoustic coupling applied to ultrasonic acoustic power transfer interfaces. Outcome: worse than baseline. Reason: adhesive layer introduced bonding defects and trapped air bubbles, degrading acoustic transmission efficiency
Acoustic Power Transfer Leveraging Piezoelectricity and Metamaterials · Georgia Tech
Tried and failed
dry-coupled mechanical clamping of piezoelectric transducers applied to ultrasonic guided wave structural monitoring. Outcome: worse than baseline. Reason: produced order of magnitude lower voltage amplitude and significantly worse signal stability than adhesive bonding
The use of circumferential guided waves to monitor axial cracks · Imperial
Transducer electrical matching, aperture geometry, and hardware configuration constraints
Inappropriate transducer geometries, purely resistive electrical matching, and aperture limitations caused severe signal loss, poor echo-receive efficiency, and high noise. Experimental transducers and phased array wave mixing setups suffered from residual noise, damping from surface attachments, and off-frequency components that prevented clean harmonic extraction.
Tried and failed
ultrasonic echo gating using early/late arrivals applied to defect imaging in layered structures. Outcome: no signal. Reason: early echoes lack defect interaction while late echoes suffer from poor signal-to-noise ratio
Ultrasonic guided waves for mechanical defects detection on thin-film solar photovoltaic modules · Georgia Tech
Tried and failed
pulse-based phased array wave mixing applied to nonlinear ultrasound characterization of metals. Outcome: no signal. Reason: off-frequency spectral components and lack of precise polarity control prevented harmonic extraction
Nonlinear ultrasound for the characterization of additively manufactured metals · Georgia Tech
Tried and failed
applying retro-reflective tape for optical detection applied to ultrasonic surface wave measurements. Outcome: worse than baseline. Reason: introduced excessive high-frequency acoustic damping and thickness calibration errors
Texture characterisation in metals using diffuse ultrasound · Imperial
Considered and rejected
Considered and rejected: Single-frequency ultrasound transducers with electronic second-harmonic filtering, rejected due to residual acoustic noise in the signal in favour of pulse inversion / phase-shift harmonic imaging
Evaluation of tomographic 3D ultrasound for the assessment of vascular pathology · Imperial
Tried and failed
ultrasonic guided-wave time-of-flight-shift tracking applied to lithium-ion pouch cells. Outcome: no signal. Reason: low signal amplitude and high noise from the specific transducer geometry configuration
Ultrasonic and vibrational methods to determine changes of state of lithium-ion cells · UT Austin
Tried and failed
purely resistive electrical impedance matching applied to capacitive ultrasound transducer interfaces. Outcome: worse than baseline. Reason: suboptimal acoustic and electrical reflectivity resulted in over 12 dB worse echo-receive efficiency than negative capacitance matching
Integrated Electronics for Wireless Imaging Microsystems with CMUT Arrays · Georgia Tech
Lost to a baseline
Commercial ultrasonic transducers achieved higher SNR (42.4–59.3 dB vs 14.8–31.9 dB) across all PLB lead diameters.
Dual-Use Strain Sensors for Simultaneous Strain Measurement and Acoustic Source Location · Virginia Tech
Environmental, thermal, and contact variations confounding signal stability
Operating conditions such as temperature fluctuations, moisture absorption, and contact surface variations altered acoustic propagation and masked structural damage features. Long-term monitoring and reflectometry suffered from standing wave interferences and sensor drift that confounded true defect identification and contact state classification.
Tried and failed
linear ultrasonic guided wave damage detection applied to crack detection under varying environmental temperatures. Outcome: no signal. Reason: signal changes from temperature drift masked or mimicked damage-induced acoustic feature changes
Baseline-free structural health monitoring in aeronautical structures under in-service conditions · Imperial
Tried and failed
ultrasonic C-scan amplitude mapping applied to incremental moisture-induced bond degradation tracking. Outcome: no signal. Reason: absorbed water altered acoustic sensitivity, obscuring the progressive changes in bond strength
Mechanical degradation of composite structures subjected to environmental effects. · Cranfield
Considered and rejected
Considered and rejected: Rejected relying solely on ultrasonic signal amplitude/intensity for long-term battery monitoring due to vulnerability to transducer deterioration and temperature fluctuations, choosing relative wave attenuation instead.
Ultrasonic monitoring of temperature distributions and degradation in engineering components · Imperial
Considered and rejected
Considered and rejected: Rejected continuous wave ultrasound for multi-angle scattering due to severe acoustic standing wave and reflection interference patterns from the pipe observation section
The characterisation of multicomponent (liquid) flows using scattered ultrasound. · Cranfield
Tried and failed
ultrasonic measurement of interfacial tangential stiffness applied to contact state classification across friction interfaces. Outcome: did not generalise. Reason: Assembly-to-assembly surface variations confounded absolute stiffness values between sticking and sliding regimes
Optical and ultrasound local contact measurements of dry friction interface under vibration · Imperial
Left open by the authors
Problems the authors named and did not get to.
Left open
Investigate why acoustic power transfer improvement is negligible below 39 kHz when piezoelectric transducer reactance is inductive. Blocker: Requires a physical experimental ultrasonic power transfer testbed with specific piezoelectric transducers (FUS-40E)
Acoustic power distribution techniques for wireless sensor networks · Imperial
Left open
Evaluate guided wave ultrasonic testing parameters for breathing cracks in corroded plate regions under varying temperature conditions. Blocker: Requires experimental ultrasonic testing apparatus (PZT transducers, temperature chamber, corroded/cracked specimens) or complex uncalibrated multi-physics modeling.
Influence of dynamic load and temperature on guided wave ultrasonic damage detection in thin plates · Cranfield
Left open
Optimize ultrasonic horn dimensions and cross-sectional geometries using acoustic and structural simulations for reverse osmosis fouling mitigation. Blocker: Lack of specific target performance metrics, objective functions, and constraints
Ultrasonic Fouling Mitigation for Renewable Energy Powered Reverse Osmosis Desalination Systems · YorkSpace
Left open
Investigate guided wave ultrasonic damage detection in thin plates under combined dynamic stress and temperature variations. Blocker: Requires a physical testing apparatus with ultrasonic transducers and thermomechanical loading capabilities
Influence of dynamic load and temperature on guided wave ultrasonic damage detection in thin plates · Cranfield
Left open
Combine ultrasonic backscattering measurements with phase velocity estimates into a unified materials characterisation framework for superalloys. Blocker: Requires ultrasonic physical testing apparatus, transducers, water tank setup, and physical superalloy specimens to perform backscattering measurements.
Phase characterisation of nickel-based superalloys using ultrasound · Imperial
Left open
Develop a method comparing relative ultrasonic guided wave mode amplitudes to characterize defect sizing and orientation. Blocker: Requires ultrasonic phased array hardware, transducer wedges, and experimental defect specimens for validation
Left open
Assess whether the ratio of SH0 to axially propagating S0 wave amplitude and phase remains proportional and stable across hardware variations. Blocker: Requires physical ultrasonic transducers, pipe testing apparatus, and hardware variations to measure wave modes.
The use of circumferential guided waves to monitor axial cracks · Imperial
Left open
Correlate measured nonlinear ultrasound beta parameters with material microstructures for selective damage assessment in additively manufactured metals. Blocker: Requires physical experimental ultrasound hardware, wedge transducers, and AM metal samples for microstructure characterization
Nonlinear ultrasound for the characterization of additively manufactured metals · Georgia Tech
Left open
Identify sources of discrepancy between SRAS and bulk experimental surface acoustic wave velocity measurements in Ti-5Al-5Mo-5V-3Cr samples. Blocker: Requires physical ultrasonic testing equipment, SRAS experimental setup, and specific alloy samples
Ultrasonic characterization of Ti-5Al-5Mo-5V-3Cr · Iowa State
Left open
Test helical guided ultrasonic waves on liquid-filled, pressurized pipes and examine the effects of coatings, pressure, vibrations, and bends. Blocker: Requires specialized physical experimental setup with pressurized liquid-filled pipes, ultrasonic transducers, and structural testbeds
Pipeline health monitoring using helical guided ultrasonic waves · UT Austin
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