Doppler Spectral Analysis Research Articles

Imaging Approach to Suspected Vascular Anomalies in Children

The purpose of this review is to become familiar with the terminology and typical presentation of vascular anomalies in children and to present the imaging approach to these anomalies. Vascular anomalies are the most common cause of soft-tissue masses in children. Many physicians are not familiar with the correct terminology for vascular anomalies which results in errors in diagnosis, prognosis, and treatment. The updated International Society for the Study of Vascular Anomalies classification, based on the original Hamburg classification, divides vascular anomalies into two types: vascular tumours (haemangiomas) and vascular malformations (venous, lymphatic, arteriovenous). Grey-scale and Doppler ultrasound (US) are the initial imaging modalities in suspected vascular anomalies. Grey-scale US is highly nonspecific. Therefore, a diagnostic algorithm based on grey-scale and Doppler signs is proposed. Spectral Doppler analysis reveals the type of vascular flow present within the lesion: high-flow is typical for infantile haemangiomas and arteriovenous malformations, low-flow for venous and noflow for lymphatic malformations. Magnetic resonance imaging with angiography is indicated only when US has not been diagnostic, when the lesion is too big or lies too deeply, and when information about the accurate anatomic location and possible infiltration of surrounding structures is necessary. Digital subtraction angiography is performed when interventional treatment is considered. Conclusion − The new terminology of vascular anomalies should be used in everyday clinical practice to avoid misunderstandings. Grey-scale and Doppler US are the most important imaging modalities for the accurate diagnosis and follow-up of vascular anomalies in children.

Choroidal vasculature imaging with laser Doppler holography.

The choroid is a highly vascularized tissue supplying the retinal pigment epithelium and photoreceptors. Its implication in retinal diseases is gaining increasing interest. However, investigating the anatomy and flow of the choroid remains challenging. Here we show that laser Doppler holography provides high-contrast imaging of choroidal vessels in humans, with a spatial resolution comparable to state-of-the-art indocyanine green angiography and optical coherence tomography. Additionally, laser Doppler holography contributes to sort out choroidal arteries and veins by using a power Doppler spectral analysis. We thus demonstrate the potential of laser Doppler holography to improve our understanding of the anatomy and flow of the choroidal vascular network.

Gray Scale Ultrasound, Color Doppler Ultrasound, and Contrast-Enhanced Ultrasound in Renal Parenchymal Diseases.

Ultrasound (US), which may be combination of gray scale and spectral Doppler US, color and power Doppler US, with or without microbubble contrast agents, is usually the first imaging modality to be used in renal parenchymal diseases. The most typical appearance of diffuse renal parenchymal diseases on gray scale US is an increased renal cortical echogenicity and increased or reduced corticomedullary differentiation. Spectral Doppler analysis of intrarenal flows may reveal an increase in intrarenal resistive index value greater than 0.70 in native kidneys, and greater than 0.8 in renal transplants. Gray scale US and spectral Doppler US do not exhibit high specificity and sensitivity because different renal parenchymal diseases often display the same US appearance, whereas the same renal parenchymal disease may present different appearances on US according to disease stage. Consequently, correlation of the US pattern with patient's history and clinical background is essential for a correct characterization.

The use of fluid dynamics for the assessment of cardiovascular disease

The use of Multifrequency Doppler spectral analysis (MFDSA) combined with ultrafast acquisition times was investigated for wall shear stress measurement in renal arteries. MFDSA relies on the use of the inherent additional frequencies present in a finite ultrasound pulse to provide additional analysis. The development of arterial disease in the renal arteries is of clinical interest as it is associated with increased risk of a number of life threatening conditions. A potential biomechanical marker of this damage is wall shear stress (WSS), which is linked to arterial wall stiffening as well as the formation of atherosclerotic plaques. A key requirement in the assessment of WSS is the accurate mapping of blood velocity close to the arterial wall. Therefore, it is of paramount importance that any technique measuring WSS has a high signal-to-noise ratio (SNR) as well as excellent velocity resolution. MFDSA combined with ultrafast acquisition times has the potential to improve the SNR and velocity resolution for the quantification of blood velocity. A series of anatomically realistic walled arterial flow phantoms (0–50% stenosis) were constructed with a range of wall stiffness values corresponding to different stages of arterial disease. These phantoms were employed for investigating the use of an Aixplorer (Supersonic-Imagine) ultrasound scanner for the measurement of velocity profiles. Inphase and Quadrature (IQ) data was acquired for a range of flow velocities (5–50 cm/s) and processed using custom code (Matlab) to determine the velocity data using Fourier analysis and MFDSA. The preliminary results indicate an average improvement in SNR of up to 27% when using MFDSA compared to standard Fourier analysis. Additional testing to improve the SNR and velocity resolution is planned. MFDSA combined with ultrafast imaging was found to demonstrate a marked improvement to the quality of blood velocity data which will ultimately improve the assessment of WSS.

Validity of Gray Scale Sonography along with Color Doppler Spectral Analysis for the detection of Malignant Breast Tumour

Background: Detection of mass in the breastis very essential for the early treatment.Objective: The purpose of the present study was to validate the Doppler sonography to detect the pathological lesions of breast.Methodology: This cross sectional study was carried out in the Department of Radiology and Imaging in collaboration with the Department of Surgery and Department of Pathology at Banghabandhu Sheikh Mujib Medical University (BSMMU), Dhaka from July 2008 to June 2009 for a period of one (01) year. Clinically suspected women with breast mass who were attended in the OPD or inpatient department were selected purposively as study population. All the patients were examined by 2-D Real-Time B-Mode Ultrasonography by using high frequency (7.5 MHz) linear transducer. Blood flow was studied using Duplex sonography in which Gray scale 2D sonography was combined with Pulsed Doppler. Test of validity was done for color Doppler Sonographic findings in evaluation of benign and malignant breast lesion.Result:A total number of 50 cases were recruited for this study. Out of 50 cases,25 cases true positive, 1 false negative, 2 false positive, 22 true negative confirmed by histopathology. Here sensitivity and specificity of color Doppler ultrasonography are 92.59% and 86.95% respectively. Here accuracy of color Doppler study is 90.0% and the positive predictive value was 89.28% and negative predictive value was 90.9%.Conclusion: Color Doppler Ultrasonography is a useful imaging method in the differentiation between benign and malignant breast masses.Journal of National Institute of Neurosciences Bangladesh, 2017;3(1): 10-13

Toward Exploring the Synergy Between Cloud Radar Polarimetry and Doppler Spectral Analysis in Deep Cold Precipitating Systems in the Arctic

AbstractThe study of Arctic ice and mixed‐phase clouds, which are characterized by a variety of ice particle types in the same cloudy volume, is challenging research. This study illustrates a new approach to qualitative and quantitative analysis of the complexity of ice and mixed‐phase microphysical processes in Arctic deep precipitating systems using the combination of Ka‐band zenith‐pointing radar Doppler spectra and quasi‐vertical profiles of polarimetric radar variables measured by a Ka/W‐band scanning radar. The results illustrate the frequent occurrence of multimodal Doppler spectra in the dendritic/planar growth layer, where locally generated, slower‐falling particle populations are well separated from faster‐falling populations in terms of Doppler velocity. The slower‐falling particle populations contribute to an increase of differential reflectivity (ZDR), while an enhanced specific differential phase (KDP) in this dendritic growth temperature range is caused by both the slower and faster‐falling particle populations. Another area with frequent occurrence of multimodal Doppler spectra is in mixed‐phase layers, where both populations produce ZDR and KDP values close to 0, suggesting the occurrence of a riming process. Joint analysis of the Doppler spectra and the polarimetric radar variables provides important insight into the microphysics of snow formation and allows the separation of the contributions of ice of different habits to the values of reflectivity and ZDR.

Influence of ultrasound contrast agents on spectral Doppler analysis in recipients of liver transplantation.

Background/AimsClinical validation is required to determine whether Doppler measurements are comparable before and after administering ultrasound contrast agent (USCA). The purpose of this study is to explore whether the use of USCA affects spectral Doppler analysis in recipients of liver transplantation (LT).MethodsFor this study, 36 patients were examined using Doppler ultrasonography (US) along with a contrast-enhanced US for surveillance of vascular complications after LT. The following spectral Doppler US parameters were measured before and after administration of USCA: peak systolic velocity, end-diastolic velocity, resistive index, and systolic acceleration time of the graft hepatic artery; peak flow velocity of the graft portal vein; and peak flow velocity and venous pulsatility index of the graft hepatic vein.ResultsThe mean peak systolic and end-diastolic velocities of the hepatic artery and the peak flow velocity of the portal and hepatic veins were increased after intravenously administration of the USCA, ranging from 10% to 13%. However, the changes were not statistically significant (P=0.097, 0.103, 0.128, and 0.190, respectively). There were no significant differences in other measured parameters, including the resistive index (P=0.205) and systolic acceleration time (P=0.489) of the hepatic artery and venous pulsatility index (P=0.494) of the hepatic vein.ConclusionsThe measured velocities of graft hepatic vessels tended to increase after administration of USCA, but without statistical significance. The comparison of serial Doppler parameters with or without injection of USCA is valid during Doppler surveillance in recipients of LT.

Analysis of the Velocity Profile of the Popliteal Artery and Its Relevance During Blood Flow Studies

The mean blood velocity is required to calculate blood flow and to determine the associated shear rate. The maximal blood flow velocity is assumed to have a parabolic velocity profile; therefore, the mean velocity is half of the maximal value. Previous studies have been carried out on vessels such as the brachial and femoral artery, but none have been reported for the popliteal artery. To assess the velocity profile of the popliteal artery, a spectral Doppler analysis was performed on ten healthy patients during varied flow states (resting, distal occlusion, hyperemia). The results were then averaged over the entire cardiac cycle. The flow described in these patients’ popliteal artery had a blunted parabolic flow profile with a TAVmean:TAVmax ratio of 0.68 ± 0.07 at baseline. The baseline measures were compared to a TAVmean:TAV max ratio of 0.68 ± 0.12 during distal occlusion and 0.67 ± 0.16 during reactive hyperemia. These descriptive results may suggest that adjustments may be needed for a blunted parabolic profile, especially when calculating the mean velocity of the popliteal artery.

Determining the presence of Peripheral Arterial Disease in patients with Rheumatoid Arthritis.

Objectives: The aim of the study was to determine the manifestations of PAD in a population of RA participants with no history of cardiovascular events. Methods: A prospective observational non-experimental study was conducted on 100 participants presenting with RA and no history of significant cardiovascular events. Vascular assessment including Doppler spectral waveform analysis and Ankle Brachial Pressure Index was conducted. Results: Triphasic waveforms was found in the Posterior Tibial Artery (PT) in 70% right foot, 66% left foot and Dorsalis Pedis Artery (DP) in both feet in the64% of the patients. Twenty-nine per cent of the participants had biphasic PT right foot and 33% had biphasic PT left foot. Thirty-six per cent had biphasic DP both feet whilst only one participant (1%) had a discontinuous monophasic PT of both feet. The ABPI readings were found to be normal in 96% of participants and mild PAD was found in only 4% of the study population. Conclusions: Results indicate that whilst the ABPI index was normal in the majority of participants, waveform analysis was suboptimal (biphasic) in approximately one-third of the study sample. These findings highlight that the assessment of peripheral arterial perfusion should utilize both modalities to identify patients with early PAD.

Potential role of imaging in assessing harmful effects on spermatogenesis in adult testes with varicocele.

Varicocele is characterized by an abnormal dilatation and retrograde blood flow in the spermatic veins. Varicocele is the leading correctable cause of male infertility. Although it is highly prevalent in infertile men, it is also observed in individuals with normal fertility. Determining which men are negatively affected by varicocele would enable clinicians to better select those men who will benefit from treatment. To assess the functional status of the testes in men with varicocele, color Doppler sonographic parameters were evaluated. Testicular arterial blood flow was significantly reduced in men with varicocele, reflecting an impairment of spermatogenesis. An improvement in the testicular blood supply was found after varicocelectomy on spectral Doppler analysis. Testicular contrast harmonic imaging and elastography might improve our knowledge about the influence of varicocele on intratesticular microcirculation and tissue stiffness, respectively, providing possible information on the early damage of testicular structure by varicocele. Magnetic resonance imaging (MRI), with measurement of apparent diffusion coefficient has been used to assess the degree of testicular dysfunction and to evaluate the effectiveness of varicocele repair. Large prospective studies are needed to validate the possible role of functional sonography and MRI in the assessment of early defects of spermatogenesis in testes with varicocele.

Current capabilities of ultrasound tomography for evaluation of the depth of myometrial invasion and its transfer to the cervix in patients with cancer of the uterus

With the purpose of studying opportunities of modern ultrasound technologies in diagnostics of an endometrial carcinoma we survey 33 patients. It was revealed high information value of ultrasound for definition of depth of uterus cancer invasion. At carrying out of ultrasonic research the complex of the following techniques two-dimensional/three-dimensional ultrasound in the В mode, Color and Power coding, sonoelastography, spectral Doppler analysis was used. Use sonoelastography, ultrasound in a combination to an wide spectrum modern Doppler techniques allows to solve the broad audience of problems in frameworks for intronozologycal diagnostics of an endometrial carcinoma: to determine precise localization of a tumor in a cavity of a uterus; volume of the primary tumoral center; depth invasion in myometrium; transition of tumoral process on cervical canals. Sonoelastography is the modern method for a comparative analysis of the density and compressibility of tissues, and it can be an additional diagnostic test for diagnostic test to define of local prevalence of the tumor. It is very important for surgeons to determine an adequate volume of operation.

Utilização da furosemida em bolus e em infusão contínua em cães e gatos: revisão de literatura

A furosemida é um potente diurético com ação no ramo espesso ascendente da alça de Henle. Em Medicina Veterinária é amplamente utilizada devido à rápida ação na remoção de fluidos intersticiais, média toxicidade e rápida excreção do organismo. É indicada no tratamento da retenção líquida inadequada, aumento da diurese, edema pulmonar, insuficiência cardíaca congestiva, síndrome nefrótica, doenças renais agudas e crônicas, ascites, edemas periféricos e pacientes irresponsivos a outros diuréticos ou anti-hipertensivos. A via de administração da furosemida endovenosa pode ser realizada sob a forma de bolus ou infusão contínua, com diferenças marcantes entre elas. Alterações hemodinâmicas, variações nas concentrações séricas e resistência diurética são desvantagens observadas na forma de bolus. Já sob a forma de infusão contínua, o aumento e a manutenção da diurese são vantagens observadas, mas com desequilíbrios hidroeletrolíticos mais evidenciados comparada à administração em bolus, necessitando de monitoramento constante. Atualmente, poucos são os estudos científicos na Medicina Veterinária que demonstram as diferenças específicas, com as indicações, benefícios ou efeitos deletérios orgânicos da utilização da furosemida intravenosa sob a forma de bolus ou infusão contínua. Assim, este trabalho busca promover uma atualização científica quanto às características farmacológicas, doses e efeitos da furosemida endovenosa nas diferentes formas de administração, visando a auxiliar a conduta terapêutica quando utilizada em cães e gatos.

Sonomorphological, gray scale and color Doppler flow imaging evaluation of ovarian lesions

Background: Ultrasonography (USG) is considered the primary imaging modality for confirmation of the ovarian origin of the mass and characterization of the nature of the mass as benign or malignant. However, when morphologic features alone are applied to the prediction of ovarian malignancy, there is a tendency to over diagnose malignant tumors because of a substantial overlap between malignant and benign-appearing masses. Transvaginal color Doppler imaging with pulsed Doppler spectral analysis improves the characterization of ovarian masses by means of quantitative blood flow measurements obtained from tumor vessels. Color Doppler ultrasound helps identify solid, vascularized components in a mass. Objectives: To evaluate prospectively the relative usefulness of color Doppler, spectral Doppler, and gray scale sonography in differentiating benign from malignant adnexal masses. Materials and Methods: Patients with abdominal lump were screened for sonography. If on sonography patient having ovarian lesion then detailed study was carried out by gray scale, color, power Doppler and by spectral waveform analysis. Morphologic indexing of the adnexal masses was performed using the Sassone score. Flow results were recorded as being absent or present and further characterized as normal or increased, vessel location, and arrangement. Results: A total of 50 patients with 53 adnexal masses were enrolled into the study. Benign lesions were common in premenopausal age (30 [81%]) and malignant lesions (10 [77%]) were more common in the postmenopausal state. 23 out of 49 masses were considered suspicious of malignancy (Sassone score = 9), of which, 18 were malignant (including bilateral ovarian metastasis as a separate lesion) and 8 were benign. The sonomorphologic evaluation following Sassone scoring system had a sensitivity of 90%, specificity 75%, positive predictive value (PPV) 69% and negative predictive value (NPV) 92%. The sensitivity, specificity, PPV, and NPV of gray scale USG alone were 70%, 72.22%, 58.33%, and 81.25% respectively. While for gray scale with combined color and spectral Doppler USG the values were 90%, 91.66%, 85.71%, and 94.28%, respectively. Conclusion: Adding color Doppler to conventional sonography produced a specificity and PPV higher than those of conventional sonography alone and so gray scale USG in combination with Color Doppler and Spectral Doppler is proposed as the first and foremost diagnostic modality in patients with ovarian lesions.

Doppler images of intra-pulmonary shunt within atelectasis in anesthetized children.

BackgroundDoppler images of pulmonary vessels in pulmonary diseases associated with subpleural consolidations have been described. Color Doppler easily identifies such vessels within consolidations while spectral Doppler analysis allows the differentiation between pulmonary and bronchial arteries. Thus, Doppler helps in diagnosing the nature of consolidations. To our knowledge, Doppler analysis of pulmonary vessels within anesthesia-induced atelectasis has never been described before. The aim of this case series is to demonstrate the ability of lung ultrasound to detect the shunting of blood within atelectatic lung areas in anesthetized children.FindingsThree anesthetized and mechanically ventilated children were scanned in the supine position using a high-resolution linear probe of 6–12 MHz. Once subpleural consolidations were detected in the most dependent posterior lung regions, the probe was rotated such that its long axis followed the intercostal space. In this oblique position, color Doppler mapping was performed to detect blood flow within the consolidation. Thereafter, pulsed waved spectral Doppler was applied in the previously identified vessels during a short expiratory pause, which prevented interferences from respiratory motion. Different flow patterns were identified which corresponded to both, pulmonary and bronchial vessels. Finally, a lung recruitment maneuver was performed which leads to the complete resolution of the aforementioned consolidation thereby confirming the pathophysiological entity of anesthesia-induced atelectasis.ConclusionsLung ultrasound is a non-invasive imaging tool that not only enables the diagnosis of anesthesia-induced atelectasis in pediatric patients but also analysis of shunting blood within this consolidation.Electronic supplementary materialThe online version of this article (doi:10.1186/s13089-016-0055-7) contains supplementary material, which is available to authorized users.

Vertebral and internal mammary artery steal syndrome in patients with hemodialysis access.

Increased flow in the subclavian artery feeding a vascular access for hemodialysis can induce steal phenomena in the vertebral (VA) and internal mammary artery (IMA). The aim of this study was to describe the hemodynamic effects of access flow on the VA and IMA in patients with native fistulas and grafts. Peak systolic (PSV) and end diastolic (EDV) velocity measurements of the VA, IMA and carotid arteries, as well as flow volume measurements of the subclavian artery, were performed. Flow measurements at the side of the vascular access were compared with the contralateral side. Fifty-five patients were consecutively included, most with a radio-cephalic fistula on the left arm with a mean shunt volume of 1156 ml/min. Pathologic flow patterns were observed in the ipsilateral VA in four patients (7.3 %); contralateral VA flow was normal in all patients. Peak systolic velocity of the VA was significantly decreased at the side of the shunt arm with a PSV of 42.6 ± 11.8 cm/s compared to 48.4 ± 15.6 cm/s contralateral (p < 0.05). The IMA flow pattern were normal in all patients. The PSV of the IMA was significantly decreased (p < 0.01) at the side of the shunt arm (87.5 ± 29.1 cm/s) compared to the non-shunt arm (95.9 ± 27.4 cm/s). We describe significant hemodynamic effects of fistulas to the vertebral and internal mammary arteries. Doppler spectral analysis of the vertebral and internal mammary arteries should be integrated in ultrasound, especially in patients with cerebrovascular or cardiac symptoms.

Ultrasonography of the scrotum in adults.

Ultrasonography is the ideal noninvasive imaging modality for evaluation of scrotal abnormalities. It is capable of differentiating the most important etiologies of acute scrotal pain and swelling, including epididymitis and testicular torsion, and is the imaging modality of choice in acute scrotal trauma. In patients presenting with palpable abnormality or scrotal swelling, ultrasonography can detect, locate, and characterize both intratesticular and extratesticular masses and other abnormalities. A 12-17 MHz high frequency linear array transducer provides excellent anatomic detail of the testicles and surrounding structures. In addition, vascular perfusion can be easily assessed using color and spectral Doppler analysis. In most cases of scrotal disease, the combination of clinical history, physical examination, and information obtained with ultrasonography is sufficient for diagnostic decision-making. This review covers the normal scrotal anatomy as well as various testicular and scrotal lesions.

Scattering and Doppler Spectral Analysis for a Fast-Moving Target above Time-Varying Lossy Dielectric Sea Surface

A numerical electromagnetic method based on the physical optics with physical optics method (PO-PO) is employed to calculate backscattered returns from a missile-like target above sea surface. Surfaces are time-varying Monte Carlo simulations initialized as realizations of a Pierson–Moskowitz spectrum. The monostatic normalized radar cross section of composite model by the hybrid PO-PO method is calculated and compared with those by the conventional method of moments, as well as the runtime and memory requirements. The results are found to be in good agreement. The runtime shows that the hybrid PO-PO method enables large-scale time-varying Monte Carlo simulations. The numerical simulations of the Doppler spectrum from the fast-moving target above time-varying lossy dielectric sea surface are obtained, and the Doppler spectra of backscattered signals from this model are discussed for different incident angles, speed of flying target, wind speeds, incident frequencies, and target altitudes in detail. Finally, the coupling effects on Doppler spectra are analyzed. All the results are obtained at the incidence of horizontal polarization wave in this study.

Management of Intrauterine Arteriovenous Malformation (AVM) in 14 Patients by Sonographically Guided Tisseel Application.

AVMs are rare tumorous vascular lesions derived from placental tissue that may present with massive post-partum hemorrhage (PPH) causing potentially life-threatening anemic shock. Current treatment options include the embolization of uterine arteries and emergency postpartum hysterectomy. We present a new form of minimally invasive, highly specific sonographically guided treatment in the form of the application of a human fibrin sealant leading to the instant cease of blood loss. A management protocol was established and a case series of 14 patients is presented. Diagnosis by endovaginal color Doppler sonography is followed by the sonographically guided application of biological glue (TISSEEL®), thus allowing for super-selective occlusion of the feeding vessels. The procedure was technically successful in all 14 patients, 3 of whom (21 %) had a repeated procedure after 4 - 7 days. The mean age (yrs.) of the patients was 31 (25 - 40), thegravity was median 2 (1 - 5) and the parity was median 1 (0 - 4), the lowest Hb value was on average 9.35 ± 2.25 (5.2 - 14.2) g/dl, the lowest Ht was on average 30.82 ± 6.02 (18 - 41 %). Spectral Doppler analysis revealed an average of 80.71 ± 11.2 (66 - 115) cm/sec for the maximal detectable PSV. In the period of 4 - 55 months after treatment, 7 patients (50 %) had 8 successful pregnancies and 2 miscarriages. In PPH there is vital interest in timely diagnosis of the underlying cause, thus allowing fertility-sparing, minimally invasive and super-selective emergency treatment. In AVMs causing PPH, a positive impact on perinatal morbidity and mortality may be achieved by sonographically guided application of this biological glue.

Deep bleeder acoustic coagulation (DBAC)-Part I: development and in vitro testing of a research prototype cuff system.

BackgroundBleeding from limb injuries is a leading cause of death on the battlefield, with deep wounds being least accessible. High-intensity focused ultrasound (HIFU) has been shown capable of coagulation of bleeding (cautery). This paper describes the development and refereed in vitro evaluation of an ultrasound (US) research prototype deep bleeder acoustic coagulation (DBAC) cuff system for evaluating the potential of DBAC in the battlefield. The device had to meet quantitative performance metrics on automated operation, therapeutic heating, bleeder detection, targeting accuracy, operational time limits, and cuff weight over a range of limb sizes and bleeder depths. These metrics drove innovative approaches in image segmentation, bleeder detection, therapy transducers, beam targeting, and dose monitoring. A companion (Part II) paper discusses the in vivo performance testing of an animal-specific DBAC system.Materials and methodsThe cuff system employed 3D US imaging probes (“Ix”) for detection and localization (D&L) and targeting, with the bleeders being identified by automated spectral Doppler analysis of flow waveforms. Unique high-element-count therapeutic arrays (“Tx”) were developed, with the final cuff prototype having 21 Tx’s and 6 Ix’s. Spatial registration of Ix’s and Tx’s was done with a combination of image-registration, acoustic time-of-flight measurement, and tracking of the cuff shape via a fiber optic sensor. Acoustic radiation force impulse (ARFI) imaging or thermal strain imaging (TSI) at low-power doses were used to track the HIFU foci in closed-loop targeting. Recurrent neural network (RNN) acoustic thermometry guided closed-loop dosing. The cuff was tested on three phantom “limb” sizes: diameters = 25, 15, and 7.5 cm, with bleeder depths from 3.75 to 12.5 cm. “Integrated Phantoms” (IntP) were used for assessing D&L, closed-loop targeting, and closed-loop dosing. IntPs had surrogate arteries and bleeders, with blood-mimicking fluids moved by a pulsatile pump, and thermocouples (TCs) on the bleeders. Acoustic dosing was developed and tested using “HIFU Phantoms” having precisely located TCs, with end-of-dose target ∆T = 33–58 °C, and skin temperature ∆T ≤ 20 °C, being required.ResultsMost DBAC cuff performance requirements were met, including cuff weight, power delivery, targeting accuracy, skin temperature limit, and autonomous operation. The automated D&L completed in 9 of 15 tests (65 %), detecting the smallest (0.6 mm) bleeders, but it had difficulty with the lowest flow (3 cm/sec) bleeders, and in localizing bleeders in the smallest (7.5 cm) phantoms. D&L did not complete within the 9-min limit (results ranged 10–21 min). Closed-loop targeting converged in 20 of 31 tests (71 %), and closed-loop dosing power shut-off at preset ∆Ts was operational.Summary and conclusionThe main performance objectives of the prototype DBAC cuff were met, however the designs required a number of challenging new technology developments. The novel Tx arrays exhibited high power with significant beam steering and focusing flexibility, while their integrated electronics enabled the required compact, lightweight configurability and simplified driving controls and cable/connector architecture. The compounded 3D imaging, combined with sophisticated software algorithms, enabled automated D&L and initial targeting and closed-loop targeting feedback via TSI. The development of RNN acoustic thermometry made possible feedback-controlled dosing. The lightweight architecture required significant design and fabrication effort to meet mechanical functionalities. Although not all target specifications were met, future engineering solutions addressing these performance deficiencies are proposed. Lastly, the program required very complex limb test phantoms and, while very challenging to develop, they performed well.

Vascular Laboratory Technology that Was Current in the 1970s

Plethysmography and continuous-wave Doppler were the noninvasive testing modalities that predominated in the 1970s diagnostic vascular laboratory. Grayscale ultrasound imaging (with a mechanically guided, pulsed-wave [PW] Doppler) was in its infancy, although PW Doppler-derived mapping had been described in 1971. Pulsed-wave Doppler spectral analysis of the intracranial circulation (transcranial Doppler) was not introduced into the United States until the early 1980s. This article describes the application of directional continuous-wave and PW Doppler, plethysmography (air, strain gauge, and photo) and spectrum analyzers to the diagnosis of peripheral vascular disease in the 1970s decade.