In vivo feasibility of real-time MR-US fusion imaging lumbar facet joint injections

OBJECTIVES

Traditionally, facet joint injections (FJI) are performed under fluoroscopic or computed tomography (CT) guidance, mainly due to the deep anatomical location and the presence of bony landmarks. Fusion imaging technology, which couples the ultrasound scan with the corresponding CT or magnetic resonance (MR) image obtained from the diagnostic examination and reformatted in real time according to the ultrasound scanning plane, allows to combine the panoramic view and the elevated anatomical detail of MR or CT with the ease of use of ultrasound without patient exposure to ionizing radiation.

METHODS

Thirty eight patients (24 females; mean age ± SD: 64 ± 9 years) received MR fusion-assisted ultrasound-guided FJI of 1 ml of a mixture of local anaesthetic and corticosteroid using a ultrasound machine (Logiq E9, GE Healthcare) equipped with a GPS-enhanced fusion imaging technology which couples real-time B-mode images with those of the previous recent diagnostic MR examination. Low-dose CT needle positioning confirmation was performed in the first 28 patients. Patients' pain was recorded using a visual analogue scale (VAS), at baseline and at 2, 4 and 8 weeks.

RESULTS

All fusion imaging-guided injections were performed successfully. Out of 112, 96 FJI had optimal intra-articular needle positioning (accuracy: 85.7%). Patients VAS significantly decreases after the procedure with no differences among who received CT needle positioning control and who did not receive it. No major complications were observed.

CONCLUSIONS

Ultrasound needle guidance with MR fusion assistance allows for safe and effective injection of degenerative facet joint disease.

Influence of Scan Duration on Pulmonary Capillary Hemorrhage Induced by Diagnostic Ultrasound

Diagnostic ultrasound can induce pulmonary capillary hemorrhage (PCH) in rats and display this as "comet tail" artifacts (CTAs) after a time delay. To test the hypothesis that no PCH occurs for brief scans, anesthetized rats were scanned using a 6-MHz linear array for different durations. PCH was characterized by ultrasound CTAs, micro-computed tomography (μCT), and measurements of fixed lung tissue. The μCT images revealed regions of PCH, sometimes penetrating the entire depth of a lobe, which were reflected in the fixed tissue measurements. At -3 dB of power, PCH was substantial for 300-s scans, but not significant for 25-s scans. At 0 dB, PCH was not strongly dependent on scan durations of 300 to 10 s. Contrary to the hypothesis, CTAs were not evident during most 10-s scans (p > 0.05), but PCH was significant (p = 0.02), indicating that PCH could occur without evidence of the injury in the images.

A proposal to reduce the risk of transmission of human papilloma virus via transvaginal ultrasound

Three steps must be followed to prevent the transmission of infection via a contaminated transvaginal ultrasound probe: cleaning the probe after every use, high-level disinfection, and covering the probe with a single-use barrier during the examination. There may be critical flaws in at least 2 of these steps as they are currently practiced. First, 2 widely used disinfectants, glutaraldehyde and orthophthalaldehyde, have recently been found to be ineffective at neutralizing human papilloma virus type 16 and type 18. Second, commercial ultrasound probe covers have an unacceptable rate of leakage (8-81%) compared to condoms (0.9-2%). We recommend the use of a sonicated hydrogen peroxide disinfectant system rather than aldehyde-type disinfectants. We recommend that the probe be covered with a condom rather than a commercial probe cover during transvaginal ultrasound examination. Combined with probe cleaning, these 2 steps are estimated to result in an 800 million- to 250 billion-fold reduction in human papilloma virus viral load, which should translate to greatly enhanced patient safety.

Pain experience during saline-contrast sonohysterography differs between premenopausal and postmenopausal women

PURPOSE

To evaluate whether the pain experienced during and after Saline-contrast sonohysterography (SCSH) differs between premenopausal and postmenopausal women.

METHODS

Sonohysterography was performed on 133 consecutive women because of suspected endometrial pathology. Of these, 34 women were excluded for the following reasons: they had cervical stenosis; they did not complete or return a questionnaire; or tenaculum or cervical dilatators were used during the procedure. All women were asked to fill out a questionnaire to characterize their pain and mark their pain experience on a 100-mm pain visual analog scale.

RESULTS

Data from the 99 patients included were used for statistical analysis. It showed that sonohysterography was well tolerated overall: 41% of the women did not feel any pain. Postmenopausal women experienced pain during SCSH more often than premenopausal women did: 71% (17/24) compared with 32% (24/75) experienced pain; p < 0.002; the median tolerance on the 100-mm visual analog scale was 43. The character of the pain differed between the two groups of women: postmenopausal women more often felt sharp pain (42%; 10/24), whereas premenopausal women more often felt gnawing and/or crampy pain (21%; 16/75) (p < 0.13).

CONCLUSIONS

Postmenopausal women were twice as likely to experience pain during SCSH as premenopausal women were. Therefore, postmenopausal women might benefit from analgesia induced prior to the procedure. © 2015 Wiley Periodicals, Inc. J Clin Ultrasound 44:267-271, 2016.

Brain Surface Heating After Exposure to Ultrasound: An Analysis Using Thermography

Ultrasound is the imaging modality of choice to monitor brain pathologies in neonates after complicated deliveries. Animal studies have indicated that ultrasound may cause heating of brain tissues. To date, no study has explored brain surface heating by ultrasound during clinically relevant exposure. Hence, we investigated heating effects of B-mode and pulsed Doppler (PD) mode on ex vivo lamb brains using thermography. Five brains were scanned for 5 min in B-mode or for 3 min, 1 min, 30 s or 15 s in PD mode. Brain surface temperature was measured pre- and post-exposure using thermography. The highest mean temperature increase was recorded by B-mode (3.82 ± 0.43°C). All five PD exposure protocols were associated with surface temperature increases of 2.1-2.7°C. These outcomes highlight for the first time that B-mode ultrasound can contribute to brain surface heating during a routine cranial scan. Scan duration should be minimised whenever possible.

The Influence of Dexmedetomidine on Ultrasound-induced Pulmonary Capillary Hemorrhage in Rats

The use of xylazine, a veterinary sedative, with ketamine for rat anesthesia has been shown to enhance the pulmonary capillary hemorrhage (PCH) effect of diagnostic ultrasound. This study was undertaken to assess whether the sedative/analgesic dexmedetomidine, commonly used in the intensive care unit, can also enhance ultrasound-induced PCH. Female Sprague Dawley rats were anesthetized with various combinations of ketamine plus xylazine or dexmedetomidine. The dosage of dexmedetomidine was reduced for some groups to doses relevant to human clinical usage. The right thorax of all rats was shaved and depilated for ultrasound transmission and the rats were scanned with diagnostic ultrasound using a 7.6-MHz linear array in a 38°C de-gassed water bath. There was no significant difference in PCH results for the recommended anesthetic dosages of ketamine plus xylazine and ketamine plus 500 μg/kg dexmedetomidine. The varied doses of dexmedetomidine enhanced the PCH, even for the lowest dose of 4 μg/kg, equivalent to a low human dose of 0.64 μg/kg. There was no significant difference in PCH for 500 μg/kg dexmedetomidine with or without ketamine. Further research is needed to identify and characterize other factors that may modify the patient risk from ultrasound-induced PCH.

Consensus guidelines for the use of ultrasound for diving research

The International Meeting on Ultrasound for Diving Research produced expert consensus recommendations for ultrasound detection of vascular gas bubbles and the analysis, interpretation and reporting of such data. Recommendations for standardization of techniques to allow comparison between studies included bubble monitoring site selection, frequency and duration of monitoring, and use of the Spencer, Kisman-Masurel or Eftedal-Brubakk scales. Recommendations for reporting of results included description of subject posture and provocation manoeuvres during monitoring, reporting of untransformed data and the appropriate use of statistics. These guidelines are available from www.dhmjournal.com.

Do Anesthetic Techniques Influence the Threshold for Glomerular Capillary Hemorrhage Induced in Rats by Contrast-Enhanced Diagnostic Ultrasound?

OBJECTIVES

Glomerular capillary hemorrhage can be induced by ultrasonic cavitation during contrast-enhanced diagnostic ultrasound (US) exposure, an important nonthermal US bioeffect. Recent studies of pulmonary US exposure have shown that thresholds for another nonthermal bioeffect of US, pulmonary capillary hemorrhage, is strongly influenced by whether xylazine is included in the specific anesthetic technique. The objective of this study was to determine the influence of xylazine on contrast-enhanced diagnostic US-induced glomerular capillary hemorrhage.

METHODS

In this study, anesthesia with ketamine only was compared to ketamine plus xylazine for induction of glomerular capillary hemorrhage in rats by 1.6-MHz intermittent diagnostic US with a microsphere contrast agent (similar to Definity; Lantheus Medical Imaging, Inc, North Billerica, MA). Glomerular capillary hemorrhage was measured as a percentage of glomeruli with hemorrhage found in histologic sections for groups of rats scanned at different peak rarefactional pressure amplitudes.

RESULTS

There was a significant difference between the magnitude of the glomerular capillary hemorrhage between the anesthetics at 2.3 MPa, with 45.6% hemorrhage for ketamine only, increasing to 63.2% hemorrhage for ketamine plus xylazine (P < .001). However, the thresholds for the two anesthetic methods were virtually identical at 1.0 MPa, based on linear regression of the exposure response data.

CONCLUSIONS

Thresholds for contrast-enhanced diagnostic US-induced injury of the microvasculature appear to be minimally affected by anesthetic methods.

Comparison of Thermal Safety Practice Guidelines for Diagnostic Ultrasound Exposures

This article examines the historical evolution of various practice guidelines designed to minimize the possibility of thermal injury during a diagnostic ultrasound examination, including those published by the American Institute of Ultrasound in Medicine, British Medical Ultrasound Society and Health Canada. The guidelines for prenatal/neonatal examinations are in general agreement, but significant differences were found for postnatal exposures. We propose sets of thermal index versus exposure time for these examination categories below which there is reasonable assurance that an examination can be conducted without risk of producing an adverse thermal effect under any scanning conditions. If it is necessary to exceed these guidelines, the occurrence of an adverse thermal event is still unlikely in most situations because of mitigating factors such as transducer movement and perfusion, but the general principle of "as low as reasonably achievable" should be followed. Some limitations of the biological effects studies underpinning the guidelines also are discussed briefly.

Randomized, controlled, double-blind trial of topical lidocaine gel and intrauterine lidocaine infusion for pain relief during saline contrast sonohysterography

OBJECTIVES

To evaluate the efficacy of topical lidocaine gel and intrauterine lidocaine infusion administered prior to saline contrast sonohysterography (SCSH) in reducing pain level during the procedure.

METHODS

This was a randomized, double-blind, placebo controlled trial. We recruited 120 women scheduled to undergo SCSH and randomized them into one of three groups according to administration of gel and intrauterine infusion immediately prior to the procedure: (1) the 'lidocaine gel' group received 3 mL 2% lidocaine gel applied to the cervix and intrauterine infusion, using an infant feeding tube without balloon, of 5 mL normal saline; (2) the 'lidocaine infusion' group received 3 mL gel lubricant applied to the cervix and intrauterine infusion of 5 mL 2% lidocaine; (3) the placebo group received 3 mL gel lubricant applied to the cervix and intrauterine infusion of 5 mL normal saline. The tube was left in place for the SCSH procedure. The primary outcome measure was the overall pain level (on a scale of 0-100) reported by the women during the SCSH procedure. Women also rated their pain levels at various other time points and an observer assessed visible signs of the women's discomfort during the procedure, producing a distress score.

RESULTS

There were no significant differences among the three groups in baseline characteristics, volume of saline solution infused, tenaculum use and duration and difficulty level of the SCSH procedure. The median (range) pain scores during normal saline infusion for the SCSH procedure were 0 (0-65) in the placebo group, 2.5 (0-80) in the lidocaine gel group, and 0 (0-70) in the lidocaine infusion group. The pain scores at other time points, the overall pain score and the distress score were also comparable for the three groups. No significant adverse events were reported.

CONCLUSIONS

SCSH performed with an infant feeding tube without balloon is associated with very low pain levels. Topical lidocaine gel application and intrauterine lidocaine infusion do not further reduce pain levels during SCSH.

Thyroid Echography-induced Thyroid Storm and Exacerbation of Acute Heart Failure

Hyperthyroidism and thyroid storm affect cardiac circulation in some conditions. Several factors including trauma can induce thyroid storms. We herein describe the case of a 57-year-old woman who experienced a thyroid storm and exacerbation of acute heart failure on thyroid echography. She initially demonstrated a good clinical course after medical rate control for atrial fibrillation; however, thyroid echography for evaluating hyperthyroidism led to a thyroid storm and she collapsed. A multidisciplinary approach stabilized her thyroid hormone levels and hemodynamics. Thus, the medical staff should be prepared for a deterioration in the patient's condition during thyroid echography in heart failure patients with hyperthyroidism.

[Comparing Onset Times and Vascular Punctures in axillary Blocks with Nerve Stimulation or Ultrasound: Randomised Trial]

The use of ultrasound (US) guidance in regional anaesthesia has evolved in the last then years and has even been considered the fatest and safest way to identify peripheral nerves and vascular structures thus eliminating the risk of injuring them. Prior to US guidance, peripheral nerve stimulation (PNS) was the gold standard procedure of the last twenty years, still being used in the present alone or alongside US guidance. However, sometimes -especially in vessel rich areas such as the axillary plexus- it is hard to avoid injuring vascular structures with blind techniques such as PNS. The study's hypothesis was that out-of-plane US guided peri-neural axillary plexus block has a better success rate, faster onset and less intravascular punctures than the PNS method.

Pulmonary Capillary Hemorrhage Induced by Fixed-Beam Pulsed Ultrasound

The induction of pulmonary capillary hemorrhage (PCH) by pulsed ultrasound was discovered 25 y ago, but early research used fixed-beam systems rather than actual diagnostic ultrasound machines. In this study, results of exposure of rats to fixed-beam focused ultrasound for 5 min at 1.5 and 7.5 MHz were compared with recent research on diagnostic ultrasound. One exposure condition at each frequency used 10-μs pulses delivered at 25-ms intervals. Three conditions involved Gaussian modulation of the pulse amplitudes at 25-ms intervals to simulate diagnostic scanning: 7.5 MHz with 0.3- and 1.5-μs pulses at 100- and 500-μs pulse repetition periods, respectively, and 1.5 MHz with 1.7-μs pulses at 500-μs repetition periods. Four groups were tested for each condition to assess PCH areas at different exposure levels and to determine occurrence thresholds. The conditions with identical pulse timing resulted in smaller PCH areas for the smaller 7.5-MHz beam, but both had thresholds of 0.69-0.75 MPa in situ peak rarefactional pressure amplitude. The Gaussian modulation conditions for both 7.5 MHz with 0.3-μs pulses and 1.5 MHz with 1.7-μs pulses had thresholds of 1.12-1.20 MPa peak rarefactional pressure amplitude, although the relatively long 1.5-μs pulses at 7.5 MHz yielded a threshold of 0.75 MPa. The fixed-beam pulsed ultrasound exposures produced lower thresholds than diagnostic ultrasound. There was no clear tendency for thresholds to increase with increasing ultrasonic frequency when pulse timing conditions were similar.

Anesthetic techniques influence the induction of pulmonary capillary hemorrhage during diagnostic ultrasound scanning in rats

OBJECTIVES

Pulmonary capillary hemorrhage can be induced by diagnostic ultrasound (US) during direct pulmonary US scanning in rats. The influence of specific anesthetic techniques on this bioeffect was examined.

METHODS

Ketamine plus xylazine has been used previously. In this study, the influence of intraperitoneal injections of ketamine and pentobarbital, inhalational isoflurane, and the supplemental use of xylazine with ketamine and isoflurane was tested. A diagnostic US machine with a 7.6-MHz linear array was used to image the right lung of anesthetized rats in a warmed water bath at different mechanical index (MI) settings. Pulmonary capillary hemorrhage was assessed by measuring comet tail artifacts in the image and by morphometry of the hemorrhagic areas on excised lungs.

RESULTS

Pulmonary capillary hemorrhage was greatest for pentobarbital, lower for inhalational isoflurane, and lowest for ketamine anesthesia, with occurrence thresholds at MIs of about 0.44, 0.8, and 0.8, respectively. Addition of xylazine produced a substantial increase in hemorrhage and a significant proportion of hemorrhage occurrence for ketamine at an MI of 0.7 (P < .01) and for isoflurane at an MI of 0.52 (P < .01).

CONCLUSIONS

Ketamine plus xylazine and pentobarbital yield lower thresholds than ketamine or isoflurane alone by nearly a factor of 2 in MI. These results suggest that the choice of the anesthetic agent substantially modifies the relative risks of pulmonary capillary hemorrhage from pulmonary US.

Ultrasound bio-effects and safety considerations

The responsibility for safe ultrasound applications has been devolved to the user with the introduction of displayed safety indices on the scanner screen. It is therefore essential that the mechanisms of interaction of the ultrasound beam with the tissue being interrogated are properly understood and that the potential biological effects are determined.

[Morphological changes in the fatty tissue after a single exposure to the ultrasound]

The morphological changes in the fatty tissue of the posterior surface of knee joint were studied in rats (n = 96) using the method of light microscopy 1, 2, 3, 4 and 5 days after a single ultrasonic exposure of various duration (5, 10, 20 min)) in a diagnostic mode. This exposure resulted in hyperemia, lymphostasis and increase of vascular permeability. The degree of changes was found to increase in proportion to the duration of exposure. All the changes detected were reversible, and the majority of them disappeared within 1-2 days. During the practical application, it is necessary to take into account the possibility the induction of cell and tissue damage during the ultrasonographic examinations. Development and application of the measures directed to decrease the edema and to stabilize the vascular wall both during the ultrasonography and immediately after it are expedient. Ultrasonography should be performed only when there are significant medical indications, and to receive the required diagnostic information, the lowest power of the device should be used.

Renal retention of lipid microbubbles: a potential mechanism for flank discomfort during ultrasound contrast administration

BACKGROUND

The etiology of flank pain sometimes experienced during the administration of ultrasound contrast agents is unknown. The aim of this study was to investigate whether microbubble ultrasound contrast agents are retained within the renal microcirculation, which could lead to either flow disturbance or local release of vasoactive and pain mediators downstream from complement activation.

METHODS

Retention of lipid-shelled microbubbles in the renal microcirculation of mice was assessed by confocal fluorescent microscopy and contrast-enhanced ultrasound imaging with dose-escalating intravenous injection. Studies were performed with size-segregated microbubbles to investigate physical entrapment, after glycocalyx degradation and in wild-type and C3-deficient mice to investigate complement-mediated retention. Urinary bradykinin was measured before and after microbubble administrations. Renal contrast-enhanced ultrasound in human subjects (n = 13) was performed 7 to 10 min after the completion of lipid microbubble administration.

RESULTS

In both mice and humans, microbubble retention was detected in the renal cortex by persistent contrast-enhanced ultrasound signal enhancement. Microbubble retention in mice was linearly related to dose and occurred almost exclusively in cortical glomerular microvessels. Microbubble retention did not affect microsphere-derived renal blood flow. Microbubble retention was not influenced by glycocalyx degradation or by microbubble size, thereby excluding lodging, but was reduced by 90% (P < .01) in C3-deficient mice. Urinary bradykinin increased by 65% 5 min after microbubble injection.

CONCLUSIONS

Lipid-shelled microbubbles are retained in the renal cortex because of complement-mediated interactions with glomerular microvascular endothelium. Microbubble retention does not adversely affect renal perfusion but does generate complement-related intermediates that are known to mediate nociception and could be responsible for flank pain.

Efficacy and safety of daily repeated sonographically guided high-intensity focused ultrasound treatment of uterine fibroids: preliminary study

OBJECTIVES

To evaluate the efficacy and safety of repeated low-dose sonographically guided high-intensity focused ultrasound (HIFU) treatment of uterine fibroids.

METHODS

Between April and December 2010, 24 consecutive premenopausal women with symptomatic uterine fibroids were enrolled in this study. The treatment was performed with an HIFU unit without anesthesia or sedative administration and Foley catheter insertion. The treatment was performed 40 to 70 min/d according to the tumor volume. The entire treatment was finished after 4 to 6 days of treatment. We assessed the differences in the symptom severity score, tumor volume, and contrast-enhanced volume at baseline and 1 and 3 months after treatment. The clinical success rates according to tumor volume and contrast-enhanced volume reductions and echogenicity and vascular flow changes were analyzed. The clinical success rates according to the baseline characteristics of fibroids were analyzed. We assessed adverse events during and after treatment.

RESULTS

The symptom severity score, tumor volume, and contrast-enhanced volume decreased significantly after repeated low-dose HIFU treatment (P < .05). There were significant correlations between tumor volume and contrast-enhanced volume reduction and the decrease in the symptom severity score. The clinical success rates were significantly different according to the tumor vascularity on color Doppler sonography and the degree of enhancement on magnetic resonance imaging. Skin burns and other serious adverse events did not develop.

CONCLUSIONS

Although this preliminary report had several limitations, daily repeated HIFU treatment of uterine fibroids may be a useful and safe method and can be used as a different option for HIFU treatment in patients who prefer treatment without anesthesia or sedation.

Automated three-dimensional coded contrast imaging hysterosalpingo-contrast sonography: feasibility in office tubal patency testing

OBJECTIVE

To evaluate the feasibility of transvaginal hysterosalpingo-contrast sonography (HyCoSy) with new automated three-dimensional coded contrast imaging (3D-CCI) software in the evaluation of tubal patency and visualization of tubal course.

METHODS

Patients undergoing HyCoSy with automated 3D-CCI software were evaluated prospectively. First, to evaluate the feasibility of 3D visualization of tubal course, we performed consecutive volume acquisitions while injecting SonoVue contrast agent. We then performed conventional two-dimensional (2D) real-time HyCoSy to confirm tubal patency status by detection of saline and air bubbles moving through the Fallopian tubes and around the ovaries. We also evaluated visualization with CCI of the contrast agent around the ovaries, side effects and pain during and after the procedure, by visual analog scale (VAS) (ranging from 0 to 10, with 0 corresponding to no pain and 10 corresponding to maximum pain).

RESULTS

A total of 126 patients (252 tubes) underwent 3D-CCI HyCoSy followed by 2D real-time HyCoSy. According to the final 2D real-time evaluation, bilateral tubal patency was observed in 111 patients, bilateral tubal occlusion in four patients and unilateral tubal patency in 11 patients. The concordance rate for tubal patency status between the first 3D volume acquisition and the final 2D real-time evaluation was 84% and that between the second 3D volume acquisition and the final 2D real-time evaluation was 97%. A pain score >5 on VAS was recorded in 58% of patients during the procedure, but a pain score ≤ 5 was recorded in 85.7% of patients immediately after the procedure.

CONCLUSIONS

HyCoSy with automated 3D-CCI technology retains the advantages of conventional 2D HyCoSy while overcoming the disadvantages. 2D HyCoSy is highly observer-dependent and is only accurate in the hands of experienced investigators; by obtaining a volume of the uterus and tubes, automated 3D volume acquisition permits visualization of the tubes in the coronal view and of the tubal course in 3D space, and should allow less experienced operators to evaluate tubal patency status relatively easily.

In-situ spectroscopic investigation of ultrasonic assisted unfolding and aggregation of insulin

It is well-known that fibrillogenesis of proteins can be influenced by diverse external parameters, such as temperature, pressure, agitation or chemical agents. The present preliminary study suggests that ultrasonic excitation at moderate intensities has a significant influence on the unfolding and aggregation behaviour of insulin. Irradiation with an average sound intensity of even as low as 70mW/cm(2) leads to a lowering of the unfolding and aggregation temperature up to 7K. The effect could be explained by an increase of the aggregation kinetics due to ultrasonically induced acoustic micro-streaming in the insulin solution that most probably enhances the aggregation rate. The clear and remarkable effect at relatively low sound intensities offers interesting options for further applications of ultrasound in biophysics and biochemistry. On the other hand, a process that causes a change of kinetics equivalent to 7K also gives a warning signal concerning the safety of those medical ultrasonic devices that work in this intensity range.

Experience improves performance of hysterosalpingo-contrast sonography (HyCoSy): a comprehensive and well-tolerated screening modality for the subfertile patient

PURPOSE

To investigate the clinical observations, provider experience, safety, and tolerance of the hysterosalpingo-contrast sonography (HyCoSy) procedure.

MATERIALS AND METHODS

A retrospective study design in which data was collected from ninety-six subfertile women who underwent the HyCoSy procedure at the University of Louisville over a 16-month interval.

RESULTS

Ninety-six HyCoSy procedures were performed by a single investigator and contained complete records for review. The authors observed significant decreases in the quantities of saline and air utilized per procedure over time (p < 0.0001 and p = 0.0001). Results from the HyCoSy studies were more often non-diagnostic or non-patent in women with a body mass index (BMI) > 30. Reported pain scores did not statistically differ over the course of the study interval. There were no procedure-related complications noted.

CONCLUSION

The HyCoSy procedure is a timely and minimally invasive study that can be implemented in an office setting with minimal prior operator experience that improves over time.

Theoretical microbubble dynamics in a viscoelastic medium at capillary breaching thresholds

In order to predict bioeffects in contrast-enhanced diagnostic and therapeutic ultrasound procedures, the dynamics of cavitation microbubbles in viscoelastic media must be determined. For this theoretical study, measured 1.5 to 7.5 MHz pulse pressure waveforms, which were used in experimental determinations of capillary breaching thresholds for contrast-enhanced diagnostic ultrasound in a rat kidney, were used to calculate cavitation nucleated from contrast agent microbubbles. A numerical model for cavitation in tissue was developed based on the Keller-Miksis equation (a compressible extension of the Rayleigh-Plesset equation for spherical bubble dynamics), with a Kelvin-Voigt constitutive relation. From this model, the bubble dynamics corresponding to the experimentally obtained capillary breaching thresholds were determined. Values of the maximum radius and temperature corresponding to previously determined bioeffect thresholds were computed for a range of ultrasound pulses and bubble sizes for comparison to inertial cavitation threshold criteria. The results were dependent on frequency, the gas contents, and the tissue elastic properties. The bioeffects thresholds were above previously determined inertial cavitation thresholds, even for the tissue models, suggesting the possibility of a more complex dosimetry for capillary injury in tissue.

Induction of pulmonary hemorrhage in rats during diagnostic ultrasound

The induction of pulmonary hemorrhage by pulsed ultrasound was discovered over 20 years ago. This phenomenon may pose a risk of patient lung injury, particularly for point of care pulmonary ultrasound. A diagnostic ultrasound machine (HDI 5000; Philips Healthcare, Andover MA USA) with 7.6 MHz (CL15-7) linear array was used to image the right lung of anesthetized rats in a warmed water bath. The image showed rapid initiation and progression of comet tail artifacts across the lung image for an on-screen mechanical index (MI) of 0.9, which corresponded to a pulmonary hemorrhage in the lung. Groups of rats were scanned at a range of MI settings and a threshold was located at an MI of about 0.44. This finding indicated a greater sensitivity to pulmonary ultrasound than was expected, based on previous results. Further research is needed to understand this phenomenon and to develop safety guidelines for sonographers.