Ultrasound-guided intervention: expanding horizons

Ultrasound-guided percutaneous coil and thrombin embolization of a left gastric artery pseudoaneurysm

Pseudoaneurysms are a commonly encountered pathology, though pseudoaneurysms of the visceral arteries are a less frequent, but potentially deadly entity. Transarterial embolization is the typical treatment of visceral pseudoaneurysms, but success is dependent on anatomy that is conducive to selecting the supplying vessel. Abdominal ultrasound is a viable method to effectively treat visceral pseudoaneurysms when transarterial embolization is not possible. It is also an excellent example of the growing utilization of ultrasound guidance in various interventional radiologic procedures. The usefulness of ultrasound is demonstrated in this case report, where a left gastric artery pseudoaneurysm was embolized through ultrasound guidance.

Medical instrument detection in ultrasound: a review

Medical instrument detection is essential for computer-assisted interventions, since it facilitates clinicians to find instruments efficiently with a better interpretation, thereby improving clinical outcomes. This article reviews image-based medical instrument detection methods for ultrasound-guided (US-guided) operations. Literature is selected based on an exhaustive search in different sources, including Google Scholar, PubMed, and Scopus. We first discuss the key clinical applications of medical instrument detection in the US, including delivering regional anesthesia, biopsy taking, prostate brachytherapy, and catheterization. Then, we present a comprehensive review of instrument detection methodologies, including non-machine-learning and machine-learning methods. The conventional non-machine-learning methods were extensively studied before the era of machine learning methods. The principal issues and potential research directions for future studies are summarized for the computer-assisted intervention community. In conclusion, although promising results have been obtained by the current (non-) machine learning methods for different clinical applications, thorough clinical validations are still required.

Training deep neural networks with noisy clinical labels: toward accurate detection of prostate cancer in US data

PURPOSE

Ultrasound is the standard-of-care to guide the systematic biopsy of the prostate. During the biopsy procedure, up to 12 biopsy cores are randomly sampled from six zones within the prostate, where the histopathology of those cores is used to determine the presence and grade of the cancer. Histopathology reports only provide statistical information on the presence of cancer and do not normally contain fine-grain information of cancer distribution within each core. This limitation hinders the development of machine learning models to detect the presence of cancer in ultrasound so that biopsy can be more targeted to highly suspicious prostate regions.

METHODS

In this paper, we tackle this challenge in the form of training with noisy labels derived from histopathology. Noisy labels often result in the model overfitting to the training data, hence limiting its generalizability. To avoid overfitting, we focus on the generalization of the features of the model and present an iterative data label refinement algorithm to amend the labels gradually. We simultaneously train two classifiers, with the same structure, and automatically stop the training when we observe any sign of overfitting. Then, we use a confident learning approach to clean the data labels and continue with the training. This process is iteratively applied to the training data and labels until convergence.

RESULTS

We illustrate the performance of the proposed method by classifying prostate cancer using a dataset of ultrasound images from 353 biopsy cores obtained from 90 patients. We achieve area under the curve, sensitivity, specificity, and accuracy of 0.73, 0.80, 0.63, and 0.69, respectively.

CONCLUSION

Our approach is able to provide clinicians with a visualization of regions that likely contain cancerous tissue to obtain more accurate biopsy samples. The results demonstrate that our proposed method produces superior accuracy compared to the state-of-the-art methods.

Ultrasound-guided drainage vs surgical drainage of deep neck space abscesses: A randomized controlled trial

INTRODUCTION

The most common cause of deep neck infections is dental infection. They are diagnosed with physical examination, imaging studies, ultrasound, or computed tomography. Surgical drainage of collections should always be performed early in a classical or percutaneous way, depending on the case. The aim of the study was to compare ultrasound-guided percutaneous drainage techniques vs. surgical drainage in deep cervical abscesses of odontogenic origin in a controlled and randomized trial.

METHODS

A randomized controlled clinical trial was performed from January 2015 to December 2019. Hospital stay was evaluated as an efficiency variable. Epidemiological and secondary variable data (tumour, trismus, fever, pain), leukocytosis, cosmetic result comparing both techniques were analysed. Statistical analysis was carried out with STATA v 14.0.

RESULTS

128 patients were analysed, 51 women and 77 men. Average age 27.3 (SD = 10.13). The percutaneous group had a mean hospital stay of 3.03 (SD = 2.86) days and the surgical group 5.46 (SD = 2.96). The p-value was <.001. Cosmetic results showed differences favouring the percutaneous drainage group. None of the other variables showed statistically significant results.

DISCUSSION

Surgical treatment (cervicotomy and debridement) should be undertaken early with evidence of extensive collection in deep spaces. Minimally invasive image-guided procedures are an alternative. These can be performed in well-located, unilocular collections, without compromising of the patient's airway. Percutaneous drainage and suction techniques if necessary, serially, or drainage placement may be performed.

CONCLUSIONS

Ultrasound-guided and serially guided percutaneous drainage is the best therapeutic option in patients with mild and/or moderate dental infections.

Urgent ultrasound-guided interventional procedures

Interventional radiology procedures have become a fundamental part of radiology, resulting in faster diagnoses and in safer, more effective, and more precise treatments, all of which are important, and even more so when referring to urgent situations, where time is of the essence. In this context, the use of ultrasound to guide interventional procedures enables real-time viewing in multiple planes that can be done at the patient's bedside, which is a great advantage in critical patients. We review the indications and technical aspects of the most common procedures related with radiological care of urgent patients.

Calculation of left ventricular diastolic time constant (Tau) in dogs with aortic regurgitation using continuous-wave Doppler spectra

OBJECTIVE

To investigate a new noninvasive method for calculating left ventricular diastolic time constant (Tau) through a continuous-wave aortic regurgitation Doppler spectrum.

METHODS

According to ultrasound guidance, twenty-four animal models (beagles) of aortic regurgitation and acute ischemic left ventricular diastolic dysfunction were created. The left ventricular diastolic function was manipulated with dobutamine or esmolol and fifty-nine hemodynamic stages were achieved. Raw audio signals of the continuous-wave Doppler spectra were collected, and new aortic regurgitation Doppler spectra were built after reprocessing by a personal computer. The updating time of the spectral line was 0.3 ms. The new Doppler spectra contour line was automated using MATLAB (MATrix LABoratory, MathWorks, Natick, MA, USA), and two time intervals, (t2-t1) and (t3-t1) were measured on the ascending branch of the aortic regurgitation Doppler spectrum. Then, the two time intervals were substituted into Bai's equations, and Doppler-derived Tau (Tau-D) was resolved and compared with catheter-derived Tau (Tau-c).

RESULTS

There is no significant difference between Tau-D and Tau-c (45.95 ± 16.90 ms and 46.81 ± 17.31 ms, respectively; P > 0.05). Correlation analysis between Tau-c and Tau-D suggested a strong positive relationship ( r = 0.97, P = 0.000). A Bland-Altman plot of Tau-c and Tau-D revealed fair agreement.

CONCLUSIONS

This new calculation method is simple, convenient, and shows a strong positive relationship and fair agreement with the catheter method.

Evaluation of 3D ultrasound for image guidance

PURPOSE

In this paper we compared two different 3D ultrasound (US) modes (3D free-hand mode and 3D wobbler mode) to see which is more suitable to perform the 3D-US/3D-US registration for clinical guidance applications. The typical errors with respect to their impact on the final localization error were evaluated step by step.

METHODS

Multi-point target and Hand-eye calibration methods were used for 3D US calibration together with a newly designed multi-cone phantom. Pointer based and image based methods were used for 2D US calibration. The calibration target error was computed by using a different multi-cone phantom. An egg-shaped phantom was used as ground truth to compare distortions for both 3D modes along with the measurements of the volume. Finally, we compared 3D ultrasound images acquired by 3D wobbler mode and 3D free-hand mode with respect to their 3D-US/3D-US registration accuracy using both, phantom and patient data. A theoretical step by step error analysis was performed and compared to empirical data.

RESULTS

Target registration errors based on the calibration with the 3D Multi-point and 2D pointer/image method have been found to be comparable (∼1mm). They both outperformed the 3D Hand-eye method (error >2mm). Volume measurements with the 3D free-hand mode were closest to the ground truth (around 6% error compared to 9% with the 3D wobbler mode). Additional scans on phantoms showed a 3D-US/3D-US registration error below 1 mm for both, the 3D free-hand mode and the 3D wobbler mode, respectively. Results with patient data showed greater error with the 3D free-hand mode (6.50mm - 13.37mm) than with the 3D wobbler mode (2.99 ± 1.54 mm). All the measured errors were found to be in accordance to their theoretical upper bounds.

CONCLUSION

While both 3D volume methods showed comparable results with respect to 3D-US/3D-US registration for phantom images, for patient data registrations the 3D wobbler mode is superior to the 3D free-hand mode. The effect of all error sources could be estimated by theoretical derivations.

Devices for image-guided lung interventions: State-of-the-art review

Lung cancer is the leading cause of cancer-related death. According to the American Cancer Society, there were an estimated 222,500 new cases of lung cancer and 155,870 deaths from lung cancer in the United States in 2017. Accurate localization in lung interventions is one of the keys to reducing the death rate from lung cancer. In this study, a total of 217 publications from 2006 to 2017 about designs of medical devices for localization in lung interventions were screened, shortlisted, and categorized by localization principle and reviewed for functionality. Each study was analyzed for engineering characteristics and clinical significance. Research regarding interventional imaging equipment, navigation systems, and surgical devices was reviewed, and both research prototypes and commercial products were discussed. Finally, the future directions and existing challenges were summarized, including real-time intra-procedure guidance, accuracy of localization, clinical application, clinical adoptability, and clinical regulatory issues.

Ultrasound-guided genitourinary interventions: principles and techniques

Ultrasound (US) is often used to guide various interventional procedures in the genitourinary (GU) tract because it can provide real-time imaging without any radiation hazard. Moreover, US can clearly visualize the pathway of an aspiration or biopsy needle to ensure the safety of the intervention. US guidance also helps clinicians to access lesions via the transabdominal, transhepatic, transvaginal, transrectal, and transperineal routes. Hence, US-guided procedures are useful for radiologists who wish to perform GU interventions. However, US-guided procedures and interventions are difficult for beginners because they involve a steep initial learning curve. The purpose of this review is to describe the basic principles and techniques of US-guided GU interventions.

Is Ultrasound Fusion a Reasonable Replacement for Computed Tomography in Guiding Abdominal Interventions?

OBJECTIVES

To compare the diagnostic yield, complication rate, and procedure length of ultrasound fusion-guided liver biopsy to the diagnostic yield, complication rate, and procedure length of computed tomography (CT)-guided liver biopsy; to measure the average ionizing radiation dose that patients are exposed to during a typical CT-guided liver biopsy procedure; and to present relevant and interesting cases of ultrasound fusion-guided abdominal interventions to describe the efficacious use of the technology.

METHODS

A retrospective analysis of 63 patients who had image-guided liver biopsies performed at our institution was completed. Patient records were divided into 2 groups according to the type of image guidance used during the procedure (ultrasound fusion versus CT), and data were compared by the χ(2) test, Student t test, and Mann-Whitney U test.

RESULTS

The diagnostic yields and complication rates were not statistically significantly different between the modalities. The average procedure durations were significantly different: ultrasound fusion-guided biopsy, 31.63 minutes; compared to CT-guided biopsy, 61.67 minutes (P = .003).

CONCLUSIONS

Diagnostic yields and complication rates were comparable for ultrasound fusion and CT. However, the average procedure duration for an ultrasound fusion-guided liver biopsy was approximately half that of CT-guided liver biopsy, likely increasing both cost-effectiveness and patient satisfaction.

Interventional radiology neck procedures

Ultrasonography has become extremely useful in the evaluation of masses in the head and neck. It enables us to determine the anatomic location of the masses as well as the characteristics of the tissues that compose them, thus making it possible to orient the differential diagnosis toward inflammatory, neoplastic, congenital, traumatic, or vascular lesions, although it is necessary to use computed tomography or magnetic resonance imaging to determine the complete extension of certain lesions. The growing range of interventional procedures, mostly guided by ultrasonography, now includes biopsies, drainages, infiltrations, sclerosing treatments, and tumor ablation.

[US-guided interventional procedures: what a radiologist needs to know]

US has important advantages in guiding interventional procedures: it is economical and widely available, it does not use ionizing radiation, and it requires less time than other techniques. US guidance can be provided using devices adapted to probes or using the freehand technique (holding the needle in one hand and the probe in the other). US-guided procedures require careful planning, adequate hemostasis or a directly compressible puncture site, the patient's informed consent, and appropriate measures to ensure asepsis and anesthesia. The technique involves introducing the needle or catheter through the plane of the US slice. The advance of the needle is controlled in real time. High resolution linear probes are ideal for interventional procedures in superficial tissues, but 3.5 MHz probes are required for procedures in deep tissues. The most common procedures include biopsies, drainages, and percutaneous injections. Biopsies can be carried out using fine needles to obtain material for cytological study (fine-needle aspiration cytology) or using large needles to obtain specimens for histologic study (core biopsy). Core biopsy is more sensitive and more specific, and it has a low rate of complications. Drainage almost always involves placing a catheter in a fluid collection; it can be done using the Seldinger techniques, trocars, or pleural catheters. US-guided percutaneous injections can be used to inject substances into infectious lesions, tumors, or nerve plexuses, and they are especially useful in musculoskeletal disease.

MRI-guided abdominal biopsy in a 0.23-T open-configuration MRI system

The purpose of this study was to test the hypothesis that when ultrasound (US) guidance is not feasible, abdominal biopsies can be performed safely and accurately under magnetic resonance imaging (MRI) guidance in a low-field environment. MRI-guided abdominal biopsy was performed on 31 consecutive patients, in whom US-guided abdominal biopsy was not possible because the lesion was not visualized in US (n=27) or an US-guided procedure was not considered safe (n=4). The locations of the lesions were liver (n=14), pancreas (n=6), lymph node (n=4), retroperitoneal mass (n=3), adrenal gland (n=3) and spleen (n=1). The average size of the lesion was 2.2 cm (range 1-4 cm) in maximum diameter. All procedures were done by using a 0.23-T open-configuration C-arm-shaped MRI scanner with interventional optical tracking equipment and software. Fine-needle aspiration (FNA) biopsy was performed on all 31 patients; 18 patients underwent both FNA biopsy and cutting needle core biopsy. Procedures were evaluated for diagnostic sensitivity, specificity and accuracy as well as procedure time and complications. The FNA biopsy specimens were adequate for interpretation in 27 (87%) of 31 cases. Two of these proved to be false-negative findings during follow-up or subsequent biopsy. The final diagnosis was malignant in 15 and benign in 16 patients. The sensitivity, specificity and accuracy of FNA biopsy were 71, 100 and 81%, respectively. Of the 18 core-needle biopsies, one was determined false-negative owing to nonrepresentativeness. The sensitivity, specificity and accuracy of histological samples were 90, 100 and 94%, respectively. The needle time was 19 min on average and the mean room time was 1 h 48 min. No immediate or late complications occurred. MRI-guided abdominal biopsy can be performed safely and accurately in a low-field environment in patients for whom an US-guided procedure is not feasible.

Ultrasound-Guided Biopsies: Tricks, Needle Tips, and Other Fine Points

Ultrasound (US)-guided biopsy of thyroid nodules, abdominal masses, liver masses, random core liver biopsies, as well as aspiration of abdominal or pleural fluid is now routine practice. The ability of US to guide biopsy of abnormalities seen on cross-sectional imaging studies is well recognized as an efficient and effective means of achieving a tissue diagnosis. Its use requires basic knowledge of US image analysis, but clinically useful intuitive and nonintuitive methods can enhance its strengths. The purpose of this review is to provide a practical guide to some of these tricks that may be useful in everyday clinical practice.

Is your interventional radiology service ready for SARS?: The Singapore experience

The recent epidemic of severe acute respiratory syndrome caught many by surprise. Hitherto, infection control has not been in the forefront of radiological practice. Many interventional radiology (IR) services are therefore not equipped to deal with such a disease. In this review, we share our experience from the interventional radiologist’s perspective, report on the acute measures instituted within our departments and explore the long-term effects of such a disease on the practice of IR.

Endoscopic ultrasound-guided biopsy for the diagnosis of focal lesions of the spleen

OBJECTIVES

Needle biopsy of splenic lesions using computed tomography (CT) or ultrasound (US) is difficult if the size of the lesion is small. It may be dangerous if the lesion is adjacent to the splenic hilum or located peripherally. We used endoscopic ultrasound-guided fine needle aspiration (EUS-FNA) to elucidate the tissue diagnosis of splenic abnormalities.

METHODS

EUS-FNA was performed in 12 patients when US- or CT-guided biopsy was inconclusive (n = 5), was not attempted because of small tumor size (0.9-1.4 cm; N = 4), or was considered dangerous (n = 3). A linear echo-endoscope and 22-gauge needles were used for cytology and bacteriology.

RESULTS

The age of the patients was 19-68 yr (median 32 yr). Seven patients were male and five female. The size of the lesions was 0.8-4.2 cm (median 1.4 cm). Cytology was inadequate in one patient. Bacteriology was positive for Staphylococcus aureus and Serratia in one patient each, and cultures were positive for Mycobacterium tuberculosis in two patients. A positive diagnosis was made in 10 of 12 patients (83%). Final diagnoses were tuberculosis in two patients, Hodgkin's disease in two, sarcoidosis in two, abscesses in two, metastatic colon cancer in one, and infarction in one. Suspected recurrence of non-Hodgkin's lymphoma was not confirmed in one case. One patient experienced pain after puncture, but no hematoma was demonstrated on subsequent US examination.

CONCLUSIONS

EUS-FNA cytodiagnosis in patients with unknown splenic lesions seems feasible, even in very small foci, when CT- or US-guided biopsy fails. Additional material for bacteriology may show benign treatable diseases such as abscesses or tuberculosis.

[Ultrasonography in urology]

After its introduction more than twenty years ago, ultrasound has continually increased in importance in urology diagnostics and is currently one of the most frequent exploratory techniques used. It corresponds to one out of every four imaging techniques carried out in medicine. The possibility of intervention under echographic control, for either diagnostic or therapeutic purposes, has been studied ever since ultrasound first appeared. Nowadays, interventionist echography is a commonly used technique in urology and is applied in a wide range of procedures carried out on the prostate gland, bladder and kidney that require echography-guided puncture techniques. Timely modifications of ultrasound for control and monitoring of treatments such as shock wave extracorporeal lithotripsy or transperineal brachitherapy has increased even more its day-to-day use by urologists. New technologies currently under development such as high-energy ultrasound in the management of kidney and prostate cancer, 3-dimensional ultrasound, Doppler-energy and contrast ultrasound have also increased the importance of this procedure in urology.