Sonography in the diagnosis of peri-implant bone defects: An in vitro study on native human mandibles.

AIM: The aim of this study on native human cadavers was to compare clinical, sonographic, and radiological measurements of fenestrations, dehiscences, and 3-wall bone defects on implants. MATERIALS AND METHODS: The examination was carried out on five human mandibles. After the insertion of 27 implants, dehiscences (n = 14), fenestrations (n = 7) and 3-wall bone defects (n = 6) were prepared in a standardized manner. The direct measurement of the bone defects was carried out with a periodontal probe and the radiological examination was carried out using digital volume tomography (DVT). The ultrasound examination (US) was performed using a clinical 24-MHz US imaging probe. Means and standard deviations of the direct, US, and DVT measurements were calculated. Measurements were statistically compared using the Pearson correlation coefficient and Bland-Altman analysis. RESULTS: Bone defects were on average 3.22 ± 1.58 mm per direct measurement, 2.90 ± 1.47 mm using US, and 2.99 ± 1.52 mm per DVT assessment. Pairwise correlations of these measurements were R = .94 (p < .0001) between direct and US, R = .95 (p < .0001) between DVT and US, and R = .96 (p < .0001) between direct and DVT. The mean differences of the measurements (and 95% CI) between direct and US was 0.41 (-0.47 to 1.29), US and DVT 0.33 (-0.30 to 0.97), and direct and DVT 0.28 (-0.50 to 1.07). CONCLUSION: All peri-implant bone defects could be identified and sonographically measured. US measurements showed a strong correlation with direct and DVT measurements. The sonographic measurement accuracy was highest for dehiscences, followed by fenestrations and 3-wall bone defects.

Ultrasonography-Derived Elasticity Estimation of Live Porcine Oral Mucosa.

OBJECTIVES: To investigate the biomechanical properties of porcine oral tissues with in vivo ultrasonography and to compare the difference between oral alveolar mucosa and gingival tissue concerning compressional and tensile mechanical strain. MATERIALS AND METHODS: Sinclair minipigs (6 females and 4 males, 6 to 18 months of age) were anesthetized for ultrasonography. In vivo high-frequency tissue harmonic ultrasound (12/24 MHz) cine-loops were obtained while inducing mechanical tissue stress (0 to 1 N). Post-processing strain analysis was performed in a cardiac speckle tracking software (EchoInsight®). Region of interest (ROI) was placed for gingival and alveolar mucosa tissues for longitudinal (compressional) and tensile strain analyses. A calibrated gel pad was employed to determine the absolute force (pressure) for the measured tissue strain response function. The resulting elasticity data was statistically analyzed using custom Matlab scripts. RESULTS: In total, 38 sonography cine-loops around the third premolars were included in the investigation. The longitudinal strain of alveolar mucosa ε AM L was found to be significantly (P < .05) larger than that of gingiva ε G L . Across the measured force range, ε AM L ~ 1.7 × Îµ G L . Significant differences between alveolar mucosa and gingiva tissues were found for all forces. The tensile strain of the alveolar mucosa ε AM T was found to be ~2 × Îµ G T (on the epithelial surface of the gingiva). Both were statistically significantly different for forces exceeding ~0.08 N. At depth, that is, 500 and 1000 µm below the epithelial surface, the gingiva was found to have less ability to stretch contrary to the alveolar mucosa. Gingival tissue at 500 µm depth has significantly less tensile strain than at its surface and more than at 1000 µm depth. In contrast, the tensile strain of alveolar mucosa is largely independent of depth. CONCLUSION: Ultrasonography can reveal significant differences in oral alveolar mucosal and gingival elastic properties, such as compressional and tensile strain. Under minute forces equivalent to 10 to 40 g, these differences can be observed. As dental ultrasound is a chairside, and noninvasive modality, obtaining real-time images might soon find clinical utility as a new diagnostic tool for the objective and quantitative assessment of periodontal and peri-implant soft tissues in clinical and research realms. As ultrasound is a safe modality with no known bioeffects, longitudinal monitoring of areas of concern would be particularly attractive.

Doppler ultrasonographic evaluation of tissue revascularization following connective tissue graft at implant sites.

AIM: To assess the Doppler ultrasonographic tissue perfusion at dental implant sites augmented with connective tissue graft (CTG) using coronally advanced flap (CAF) or tunnel technique (TUN). MATERIALS AND METHODS: Twenty-eight patients presenting with isolated healthy peri-implant soft-tissue dehiscence (PSTD) were included in this randomized clinical trial. PSTDs were treated with either CAF + CTG or TUN + CTG. Ultrasound scans were taken at baseline, 1 week, 1 month, 6 months and 12 months. Tissue perfusion at the mid-facial, mesial and distal aspects of the implant sites was assessed by colour Doppler velocity (CDV) and power Doppler imaging (PDI). Early vascularization of the graft and the flap at 1 week and at 1 month were evaluated via dynamic tissue perfusion measurements (DTPMs), including flow intensity (FI), mean perfusion relief intensity (pRI) and mean perfused area (pA). RESULTS: Regression analysis did not reveal significant differences in terms of mid-facial CDV and PDI changes between CAF and TUN over 12 months (p > .05), while significant differences between the two groups were observed at the interproximal areas (p < .001 for both CDV and PDI changes). Higher early DTPMs were observed at the TUN-treated sites in terms of mean FI of the graft (p = .027) and mean FI (p = .024) and pRI of the flap (p = .031) compared with CAF-treated sites at 1 week. Assessment of the FI direction showed that CTG perfusion at 1 week and at 1 month mainly occurred from the flap towards the implant/bone. Early tissue perfusion outcomes were found to be associated with the 12-month mean PSTD coverage and mucosal thickness gain. CONCLUSIONS: Doppler ultrasonography shows tissue perfusion changes occurring at implant sites augmented with CTG. The main differences in tissue perfusion between CAF and TUN were observed at the interproximal sites, with early perfusion associated with clinical and volumetric outcomes at 12 months.

Coronally advanced flap versus tunnel technique for the treatment of peri-implant soft tissue dehiscences with the connective tissue graft: A randomized, controlled clinical trial.

AIM: To evaluate the efficacy of coronally advanced flap (CAF) versus tunnel technique (TUN) in covering isolated mid-facial peri-implant soft tissue dehiscences (PSTDs). MATERIALS AND METHODS: Twenty-eight participants presenting with isolated non-molar implants exhibiting PSTDs were enrolled and randomized to receive either CAF or TUN, both with a connective tissue graft (CTG). The primary outcome of the study was the percentage of mean PSTD coverage at 12 months. Secondary endpoints included the frequency of complete PSTD coverage, changes in keratinized mucosa width (KMW) and horizontal mucosal thickness (MT), as assessed with transgingival probing, 3D optical scanning and ultrasonography, professional aesthetic evaluation and patient-reported outcome measures (PROMs). RESULTS: At 12 months, the mean PSTD coverage of the CAF and TUN groups was 90.23% and 59.76%, respectively (p = .03). CAF-treated sites showed a substantially higher frequency of complete PSTD coverage (p = .07), together with significantly greater gain of KMW (p = .01), increase in MT (p = .02), volumetric gain (p < .01) and professional aesthetic outcomes (p = .01). Both interventions showed an improvement in patient-reported aesthetics and a reduction of the anxiety related to the appearance of the implant compared to baseline, with the CAF group obtaining significantly higher scores (p = .03 for both PROMs). CONCLUSIONS: CAF + CTG resulted in superior PSTD coverage outcomes, greater gain in KMW and MT, and better PROMs than TUN + CTG for the treatment of isolated PSTDs (ClinicalTrials.gov NCT03498911).

Preliminary Experience in Transducer Preparation for Intraoral Imaging.

Intraoral scanning must meet a stringent infection control standard because of contact with the oral mucosa. A preparation protocol is thus presented for increased inquiries about intraoral scanning requirements. Materials required for such a preparation include: a single-use bubble-free gel packet, a gel standoff pad, and a transducer probe cover. Postscan reprocessing of the ultrasound transducer requires high-level disinfection. Examples for proper and improper use are provided as well as limitations of this preparation protocol and recommendations for future development. This guidance meets the current infection control standard and may guide the user to obtain consistent ultrasound image quality.

Recombinant human platelet-derived growth factor improves root coverage of a collagen matrix for multiple adjacent gingival recessions: A triple-blinded, randomized, placebo-controlled trial.

AIM: To evaluate the efficacy of recombinant human platelet-derived growth factor (rhPDGF)-BB combined with a cross-linked collagen matrix (CCM) for the treatment of multiple adjacent gingival recession type 1 defects (MAGRs) in combination with the coronally advanced flap (CAF). MATERIALS AND METHODS: Thirty patients were enrolled in this triple-blind, randomized, placebo-controlled trial and treated with either CAF + CCM + rhPDGF, or CAF + CCM + saline. The primary outcome was mean root coverage (mRC) at 6 months. Complete root coverage, gain in gingival thickness (GT), keratinized tissue width, volumetric and ultrasonographic changes, and patient-reported outcome measures were also assessed. Mixed-modelling regression analyses were used for statistical comparisons. RESULTS: At 6 months, the mRC of the CCM + rhPDGF and CCM alone groups were 88.25% and 77.72%, respectively (p = .02). A significant gain in GT was consistently observed for both treatment arms, and more so for the patients receiving the matrix containing rhPDGF through time (0.51 vs. 0.80 mm, on average, p = .01). The rhPDGF + CCM treated patients presented greater volume gain, higher soft tissue thickness, and a superior aesthetic score. CONCLUSION: rhPDGF enhances the clinical, volumetric, and aesthetic outcomes of MAGRs above the results achieved with CAF + CCM alone (ClinicalTrials.gov NCT04462237).

Umbilical Vein Pulse Wave Spectral Analysis: A Possible Method for Placental Assessment Through Evaluation of Maternal and Fetal Flow Components.

OBJECTIVES: Placental blood flow analysis is complicated by having both maternal and fetal flow components. Using the Fast Fourier Transform (FFT) of the umbilical venous pulse wave spectra (PW) envelope, we could simultaneously assess maternal/fetal blood flow in the placenta and investigate if normal and intrauterine growth restriction (IUGR)/pre-eclamptic pregnancies could be distinguished. METHODS: This retrospective study included normal gestations (N = 11) and gestations with IUGR, pre-eclampsia, or both (N = 13). Umbilical vein PW were acquired and spectral envelopes were identified as a function of time and analyzed by FFT. Base-10 logarithms of the ratios of the maternal/fetal spectral peaks (LRSP) were compared in normal and IUGR/pre-eclamptic populations (two-tailed t-test). Body mass index (BMI), gestational age at scan time, placental position, and weight-normalized umbilical vein blood volume flow (two-tailed t-test, analysis of variance [ANOVA] analysis) were tested. P < .05 was considered significant. RESULTS: The LRSP for normal and IUGR/pre-eclamptic pregnancies were 0.141 ± 0.180 and -0.072 ± 0.262 (mean ± standard deviation), respectively (P = .033). We detected differences between normal gestations and combinations of LRSP and weight-normalized umbilical venous blood flows. Placental effects based on LRSPs and blood flow may act synergistically in cases with both pre-eclampsia and IUGR (P = .014). No other significant associations were seen. CONCLUSIONS: In this preliminary study, we showed that umbilical venous flow contains markers related to placental maternal/fetal blood flow, which can be used to assess IUGR and pre-eclampsia. When coupled with umbilical cord blood flow, this new marker may potentially identify the primary causes of the two conditions.

Ultrasonographic tissue perfusion analysis at implant and palatal donor sites following soft tissue augmentation: A clinical pilot study.

AIM: To describe the application of power Doppler Ultrasonography (US) for evaluating blood flow at implant and palatal donor sites following soft tissue augmentation with the connective tissue graft (CTG). MATERIALS AND METHODS: Five patients exhibiting a peri-implant soft tissue dehiscence received treatment with a coronally advanced flap and corresponding CTG. Power Doppler US was used for assessing blood volume at baseline, 1 week, 1 month, 6 months and 12 months post-surgery for assessing blood-flow dynamics at the implant and palatal donor sites. The speed-weighted and power-weighted colour pixel density (CPPD) were computed from colour velocity (CV) and colour power (CP), respectively. RESULTS: A mean increase in CV of 199.25% was observed at the midfacial region of the implant sites after 1 week compared to baseline. CV and CP were increased in all sites at 1 week and 1 month. At 6 and 12 months, the mean CV appeared lower than baseline at the implant sites. CCPD was increased at the palatal donor sites and at the great palatine foramen areas at the 1-week and 1-month post-operative evaluations. CONCLUSIONS: Power Doppler US is a non-invasive and valuable tool for estimating tissue perfusion and CPPD variation during different phases of intra-oral soft tissue graft healing.

Comprehensive peri-implant tissue evaluation with ultrasonography and cone-beam computed tomography: A pilot study.

OBJECTIVES: The aim of the present study was to explore the feasibility of ultrasonography (US) for clinical imaging of peri-implant tissues. MATERIAL AND METHODS: Patients with ≥1 implant, a cone-beam computed tomography (CBCT) scan, an US scan, and clinical photographs taken during the surgery were included. The crestal bone thickness (CBT) and facial bone level (FBL) were measured on both US and CBCT modalities, and direct FBL measurements were also made on clinical images. US measurements were compared with CBCT and direct readings. RESULTS: A total of eight implants from four patients were included. For FBL measurements, US and direct (r2 = 0.95) as well as US and CBCT (r2 = 0.85) were highly correlated, whereas CBCT correlated satisfactorily with the direct reading (r2 = 0.75). In one implant without facial bone, CBCT was not able to measure CBT and FBL accurately. The estimated bias for CBT readings was 0.17 ± 0.23 mm (p = .10) between US and CBCT. US blood flow imaging was successfully recorded and showed a wide dynamic range among patients with different degrees of clinical inflammation. CONCLUSION: US is a feasible method to evaluate peri-implant facial crestal bone dimensions. Additional US features, for example, functional blood flow imaging, may be useful to estimate the extent and severity of inflammation.

Comparison of Variations Between Spectral Doppler and Gaussian Surface Integration Methods for Umbilical Vein Blood Volume Flow.

OBJECTIVES: We are studying a new method for estimating blood volume flow that uses 3-dimensional ultrasound to measure the total integrated flux through an ultrasound-generated Gaussian surface that intersects the umbilical cord. This method makes none of the assumptions typically required with standard 1-dimensional spectral Doppler volume flow estimates. We compared the variations in volume flow estimates between techniques in the umbilical vein. METHODS: The study was Institutional Review Board approved, and all 12 patients gave informed consent. Because we had no reference standard for the true umbilical vein volume flow, we compared the variations of the measurements for the flow measurement techniques. At least 3 separate spectral Doppler and 3 separate Gaussian surface measurements were made along the umbilical vein. Means, standard deviations, and coefficients of variation (standard deviation/mean) for the flow estimation techniques were calculated for each patient. P < .05 was considered significant. RESULTS: The ranges of the mean volume flow estimates were 174 to 577 mL/min for the spectral Doppler method and 100 to 341 mL/min for the Gaussian surface integration (GSI) method. The mean standard deviations (mean ± SD) were 161 ± 95 and 45 ± 48 mL/min for the spectral Doppler and GSI methods, respectively (P < .003). The mean coefficients of variation were 0.46 ± 0.17 and 0.18 ± 0.14 for the spectral Doppler and GSI methods respectively (P < 0.002). CONCLUSIONS: The new volume flow estimation method using 3-dimensional ultrasound appears to have significantly less variation in estimates than the standard 1-dimensional spectral Doppler method.

Three-dimensional US for Quantification of Volumetric Blood Flow: Multisite Multisystem Results from within the Quantitative Imaging Biomarkers Alliance.

Background Quantitative blood flow (QBF) measurements that use pulsed-wave US rely on difficult-to-meet conditions. Imaging biomarkers need to be quantitative and user and machine independent. Surrogate markers (eg, resistive index) fail to quantify actual volumetric flow. Standardization is possible, but relies on collaboration between users, manufacturers, and the U.S. Food and Drug Administration. Purpose To evaluate a Quantitative Imaging Biomarkers Alliance-supported, user- and machine-independent US method for quantitatively measuring QBF. Materials and Methods In this prospective study (March 2017 to March 2019), three different clinical US scanners were used to benchmark QBF in a calibrated flow phantom at three different laboratories each. Testing conditions involved changes in flow rate (1-12 mL/sec), imaging depth (2.5-7 cm), color flow gain (0%-100%), and flow past a stenosis. Each condition was performed under constant and pulsatile flow at 60 beats per minute, thus yielding eight distinct testing conditions. QBF was computed from three-dimensional color flow velocity, power, and scan geometry by using Gauss theorem. Statistical analysis was performed between systems and between laboratories. Systems and laboratories were anonymized when reporting results. Results For systems 1, 2, and 3, flow rate for constant and pulsatile flow was measured, respectively, with biases of 3.5% and 24.9%, 3.0% and 2.1%, and -22.1% and -10.9%. Coefficients of variation were 6.9% and 7.7%, 3.3% and 8.2%, and 9.6% and 17.3%, respectively. For changes in imaging depth, biases were 3.7% and 27.2%, -2.0% and -0.9%, and -22.8% and -5.9%, respectively. Respective coefficients of variation were 10.0% and 9.2%, 4.6% and 6.9%, and 10.1% and 11.6%. For changes in color flow gain, biases after filling the lumen with color pixels were 6.3% and 18.5%, 8.5% and 9.0%, and 16.6% and 6.2%, respectively. Respective coefficients of variation were 10.8% and 4.3%, 7.3% and 6.7%, and 6.7% and 5.3%. Poststenotic flow biases were 1.8% and 31.2%, 5.7% and -3.1%, and -18.3% and -18.2%, respectively. Conclusion Interlaboratory bias and variation of US-derived quantitative blood flow indicated its potential to become a clinical biomarker for the blood supply to end organs. © RSNA, 2020 Online supplemental material is available for this article. See also the editorial by Forsberg in this issue.

Spatiotemporal control of micromechanics and microstructure in acoustically-responsive scaffolds using acoustic droplet vaporization.

Acoustically-responsive scaffolds (ARSs), which are composite fibrin hydrogels, have been used to deliver regenerative molecules. ARSs respond to ultrasound in an on-demand, spatiotemporally-controlled manner via a mechanism termed acoustic droplet vaporization (ADV). Here, we study the ADV-induced, time-dependent micromechanical and microstructural changes to the fibrin matrix in ARSs using confocal fluorescence microscopy as well as atomic force microscopy. ARSs, containing phase-shift double emulsion (PSDE, mean diameter: 6.3 µm), were exposed to focused ultrasound to generate ADV - the phase transitioning of the PSDE into gas bubbles. As a result of ADV-induced mechanical strain, localized restructuring of fibrin occurred at the bubble-fibrin interface, leading to formation of locally denser regions. ADV-generated bubbles significantly reduced fibrin pore size and quantity within the ARS. Two types of ADV-generated bubble responses were observed in ARSs: super-shelled spherical bubbles, with a growth rate of 31 µm per day in diameter, as well as fluid-filled macropores, possibly as a result of acoustically-driven microjetting. Due to the strain stiffening behavior of fibrin, ADV induced a 4-fold increase in stiffness in regions of the ARS proximal to the ADV-generated bubble versus distal regions. These results highlight that the mechanical and structural microenvironment within an ARS can be spatiotemporally modulated using ultrasound, which could be used to control cellular processes and further the understanding of ADV-triggered drug delivery for regenerative applications.

Ultrasonographic characterization of lingual structures pertinent to oral, periodontal, and implant surgery.

OBJECTIVES: Increased applications of ridge augmentation in the lingual posterior mandible call for an urgent need to study its anatomy. Therefore, our first aim was to validate ultrasound in measuring the mandibular lingual structures in human cadavers. Secondarily, to test its feasibility in imaging the lingual nerve in live humans. MATERIALS AND METHODS: Nine fresh un-embalmed fully/partially edentulous cadaver heads were utilized for aim 1. Three areas in the lingual mandible were imaged (mandibular premolar, molar, and retromolar). Immediately after, biopsies were harvested from each site. The thickness of the mucosa, mylohyoid muscle, and lingual nerve diameter was measured via ultrasound and statistically compared to histology. Similarly, the lingual nerve in live humans was also imaged. RESULTS: None of the differences between the ultrasound and histology measurements reached statistical significance (p > .05). The mean mucosal thickness via ultrasound and histology was 1.45 ± 0.49 and 1.39 ± 0.50 mm, 5 mm lingual to the mylohyoid muscle attachment. At 10 mm beyond the attachment, the ultrasound and histologic values were 1.54 ± 0.48 and 1.37 ± 0.49, respectively. The mean muscle thickness measured via ultrasound and histology was 2.31 ± 0.56 and 2.25 ± 0.47 mm, at the 5 mm distance. At the 10 mm distance, the measurements were 2.46 ± 0.56 and 2.36 ± 0.5 mm, respectively. The mean ultrasonic lingual nerve diameter was 2.38 ± 0.44 mm, versus 2.43 ± 0.42 mm, with histology. The lingual nerve diameter on 19 live humans averaged to 2.01 ± 0.35 mm (1.4-3.1 mm). CONCLUSIONS: Within its limitations, ultrasound accurately measured mandibular lingual soft tissue structures on cadavers, and the lingual nerve on live humans.

Three-dimensional US Fractional Moving Blood Volume: Validation of Renal Perfusion Quantification.

Background Three-dimensional (3D) fractional moving blood volume (FMBV) derived from 3D power Doppler US has been proposed for noninvasive approximation of perfusion. However, 3D FMBV has never been applied in animals against a ground truth. Purpose To determine the correlation between 3D FMBV and the reference standard of fluorescent microspheres (FMS) for measurement of renal perfusion in a porcine model. Materials and Methods From February 2017 to September 2017, adult pigs were administered FMS before and after measurement of renal 3D FMBV at baseline (100%) and approximately 75%, 50%, and 25% flow levels by using US machines from two different vendors. The 3D power Doppler US volumes were converted and segmented, and correlations between FMS and 3D FMBV were made with simple linear regression (r2). Similarity and reproducibility of manual segmentation were determined with the Dice similarity coefficient and 3D FMBV reproducibility (intraclass correlation coefficient [ICC]). Results Thirteen pigs were studied with 33 flow measurements. Kidney volume (mean Dice similarity coefficient ± standard deviation, 0.89 ± 0.01) and renal segmentation (coefficient of variation = 12.6%; ICC = 0.86) were consistent. The 3D FMBV calculations had high reproducibility (ICC = 0.97; 95% confidence interval: 0.96, 0.98). The 3D FMBV per-pig correlation showed excellent correlation for US machines from both vendors (mean r2 = 0.96 [range, 0.92-1.0] and 0.93 [range, 0.78-1.0], respectively). The correlation between 3D FMBV and perfusion measured with microspheres was high for both US machines (r2 = 0.80 [P < .001] and 0.70 [P < .001], respectively). Conclusion The strong correlation between three-dimensional (3D) fractional moving blood volume (FMBV) and fluorescent microspheres indicates that 3D FMBV shows excellent correlation to perfusion and good reproducibility. © RSNA, 2019 Online supplemental material is available for this article. See also the editorial by Morrell et al in this issue.

Ultrasonography for noninvasive and real-time evaluation of peri-implant tissue dimensions.

AIM: Existing methods for evaluating marginal bone loss and tissue biotype around dental implants present with many limitations. The aim of this study was to examine the accuracy of high-resolution, 3-dimensional ultrasound to measure peri-implant tissue dimensions. MATERIAL AND METHODS: A 25-MHz ultrasound probe prototype was used to scan peri-implant tissues of 17 implants from seven fresh human cadavers. Four ultrasonic measurements were made as follows: the marginal bone level/thickness, and mucosal level/thickness. The readings were statistically compared to cone beam computed tomography (CBCT) and/or open bone measurements. RESULTS: The correlations (r) between the ultrasound and direct/CBCT readings of the four parameters ranged from 0.85 to 0.98 (p < 0.0001). The mean absolute difference in the four parameters between ultrasound-direct and ultrasound-CBCT ranged from 0.033 to 0.24 mm. CONCLUSION: Encouraging evidence is shown that ultrasound can accurately measure peri-implant tissue dimensions. Following clinical trial validations, ultrasound offers potential as a valuable tool to evaluate long-term peri-implant tissue stability without concerns of ionizing radiation and image artefacts around implants.

Evaluation of Umbilical Vein Blood Volume Flow in Preeclampsia by Angle-Independent 3D Sonography.

OBJECTIVES: To investigate the association between umbilical vein blood volume flow and the condition of preeclampsia in an at-risk maternal patient cohort. Umbilical vein volume flow was quantified by a 3-dimensional (3D) sonographic technique that overcomes several limitations of standard sonographic flow measurement methods. METHODS: A total of 35 patients, each with a singleton pregnancy, were recruited to provide 5 patients with preeclampsia, derived as a subset from a 26-patient at-risk group, and 9 patients with normal pregnancies. An ultrasound system equipped with a 2.0-8.0-MHz transducer was used to acquire multivolume 3D color flow and power mode data sets to compute the mean umbilical vein volume flow in patients with normal pregnancies and preeclampsia. RESULTS: The gestational ages of the pregnancies ranged from 29.7 to 34.3 weeks in the patients with preeclampsia and from 25.9 to 34.7 weeks in the patients with normal pregnancies. Comparisons between patients with normal pregnancies and those with preeclampsia showed weight-normalized flow with a moderately high separation between groups (P = .11) and depth-corrected, weight-normalized flow with a statistically significant difference between groups (P = .035). Umbilical vein volume flow measurements were highly reproducible in the mean estimate, with an intrapatient relative SE of 12.1% ± 5.9% and an intrameasurement relative SE of 5.6% ± 1.9 %. In patients who developed pregnancy-induced hypertension or severe pregnancy-induced hypertension, umbilical vein volume flow suggested gestational hypertensive disorder before clinical diagnosis. CONCLUSIONS: Results indicate that mean depth-corrected, weight-normalized umbilical vein volume flow is reduced in pregnancies complicated by preeclampsia and that volume flow may indicate hypertensive disorder earlier in gestation. Volume flow measurements are highly reproducible, and further study in a larger clinical population is encouraged to determine whether 3D volume flow can complement the management of preeclampsia and, in general, at-risk pregnancy.

Non-ionizing real-time ultrasonography in implant and oral surgery: A feasibility study.

PURPOSE: Ultrasound imaging has potential to complement radiographic imaging modalities in implant and oral surgery given that it is non-ionizing and provides instantaneous images of anatomical structures. For application in oral and dental imaging, its qualities are dependent on its ability to accurately capture these complex structures. Therefore, the aim of this feasibility study was to investigate ultrasound to image soft tissue, hard tissue surface topography and specific vital structures. MATERIAL AND METHODS: A clinical ultrasound scanner, paired with two 14-MHz transducers of different sizes (one for extraoral and the other for intraoral scans), was used to scan the following structures on a fresh cadaver: (i) the facial bone surface and soft tissue of maxillary anterior teeth, (ii) the greater palatine foramen; (iii) the mental foramen and (iv) the lingual nerve. Multiple measurements relevant to these structures were made on the ultrasound images and compared to those on cone-beam computed tomography (CBCT) scans and/or direct measurements. RESULTS: Ultrasound imaging could delineate hard tissue surfaces, including enamel, root dentin and bone as well as soft tissue with high resolution (110 µm wavelength). The greater palatine foramen, mental foramen and lingual nerve were clearly shown in ultrasound images. Merging ultrasound and CBCT images demonstrated overall spatial accuracy of ultrasound images, which was corroborated by data gathered from direct measurements. CONCLUSION: For the first time, this study provides proof-of-concept evidence that ultrasound can be a real-time and non-invasive alternative for the evaluation of oral and dental anatomical structures relevant for implant and oral surgery.

Acoustic attenuation imaging of tissue bulk properties with a priori information.

Attenuation of ultrasound waves traversing a medium is not only a result of absorption and scattering within a given tissue, but also of coherent scattering, including diffraction, refraction, and reflection of the acoustic wave at tissue boundaries. This leads to edge enhancement and other artifacts in most reconstruction algorithms, other than 3D wave migration with currently impractical, implementations. The presented approach accounts for energy loss at tissue boundaries by normalizing data based on variable sound speed, and potential density, of the medium using a k-space wave solver. Coupled with a priori knowledge of major sound speed distributions, physical attenuation values within broad ranges, and the assumption of homogeneity within segmented regions, an attenuation image representative of region bulk properties is constructed by solving a penalized weighted least squares optimization problem. This is in contradistinction to absorption or to conventional attenuation coefficient based on overall insertion loss with strong dependence on sound speed and impedance mismatches at tissue boundaries. This imaged property will be referred to as the bulk attenuation coefficient. The algorithm is demonstrated on an opposed array setup, with mean-squared-error improvements from 0.6269 to 0.0424 (dB/cm/MHz)2 for a cylindrical phantom, and 0.1622 to 0.0256 (dB/cm/MHz)2 for a windowed phantom.

Volumetric blood flow in transjugular intrahepatic portosystemic shunt revision using 3-dimensional Doppler sonography.

OBJECTIVES: Three-dimensional (3D)/4-dimensional (4D) sonographic measurement of blood volume flow in transjugular intrahepatic porto systemic shunt revision with the intention of objective assessment of shunt patency. METHODS: A total of 17 patients were recruited (12 male and 5 female; mean age, 55 years; range, 30-69 years). An ultrasound system equipped with a 2.0-5.0-MHz probe was used to acquire multivolume 3D/4D color Doppler data sets to assess prerevision and postrevision shunt volume flow. Volume flow was computed offline based on the principle of surface integration of Doppler-measured velocity vectors in a lateral-elevational c-surface positioned at the color flow focal depth (range, 8.0-11.5 cm). Volume flow was compared to routine measurements of the prerevision and postrevision portosystemic pressure gradient. Prerevision volume flow was compared with the outcome to determine whether a flow threshold for revision could be defined. RESULTS: Linear regression of data from revised transjugular intrahepatic portosystemic shunt cases showed an inverse correlation between the mean-normalized change in prerevision and postrevision shunt volume flow and the mean-normalized change in the prerevision and postrevision portosystemic pressure gradient (r(2) = 0.51; P = .020). Increased shunt blood flow corresponded to a decreased pressure gradient. Comparison of prerevision flows showed preliminary threshold development at 1534 mL/min, below which a shunt revision may be recommended (P = .21; area under the receiver operating characteristic curve = 0.78). CONCLUSIONS: Shunt volume flow measurement with 3D/4D Doppler sonography provides a potential alternative to standard pulsed wave Doppler metrics as an indicator of shunt function and predictor of revision.

Acceleration of ultrasound thermal therapy by patterned acoustic droplet vaporization.

One application of acoustic droplet vaporization (ADV), a method of converting biocompatible microdroplets into microbubbles, is to enhance locally high intensity focused ultrasound (HIFU) therapy. Two objectives are pursued here: (1) the controlled creation of a bubble trench prior to HIFU using ADV and (2) use of the trench for increasing ablation volumes, lowering acoustic powers, and decreasing therapy duration. Thermally responsive phantoms were made with perfluorocarbon emulsion. Compound lesions were formed in a laboratory setting and a clinical magnetic resonance imaging (MRI)-guided HIFU system. Linear and spiral patterned compound lesions were generated in trenches. A larger fraction of the HIFU beam is contained to increase the generation of heat. Using the laboratory system, a 90 mm linear length spiral trench was formed in 30 s with mechanical beam steering. Comparatively, the clinical HIFU system formed a 19.9 mm linear length spiral trench in approximately 1 s with electronic beam steering. Lesions were imaged optically and with MRI. A uniform thermal ablation volume of 3.25 mL was achieved in 55.4 s (4-times faster than standard clinical HIFU and 14-times larger volume versus sum of individual lesions). Single lesions showed a 400% volume increase.