Quantification of tumor vascularity with contrast-enhanced sonography: correlation with magnetic resonance imaging and fluorodeoxyglucose autoradiography in an implanted tumor

Detection of Mice Colorectal Tumors by Endoluminal Ultrasound Biomicroscopic Images and Quantification of Image Augmented Gray Values Following Injection of VEGFR-2 Targeted Contrast Agent

RATIONALE AND OBJECTIVES

Ultrasound biomicroscopy (UBM) is a noninvasive imaging technique that can be applied in detecting colonic tumors and, once associated with an ultrasound contrast agent (UCA), can identify the molecular expression of cancer-related biomarkers, such as the vascular endothelial growth factor receptor 2 (VEGFR-2). The present work aimed to detect colonic tumors and quantify augmented gray values of endoluminal UBM (eUBM) images from colonic tumors following the injection of VEGFR-2 targeted UCA (VEGFR2-UCA) into a mouse model of colorectal cancer.

MATERIAL AND METHODS

A 40 MHz miniprobe catheter inserted through the biopsy channel of a pediatric flexible bronchofiberscope was used to obtain colonoscopic and B-mode eUBM images simultaneously. Seventeen tumor-bearing mice had their colons inspected and six of them were subjected to a VEGFR2-UCA injection to predict VEGFR-2 expression.

RESULTS

All animals developed distal colon tumors and eUBM was able to detect all of them and also to characterize the tumors, with 71.4% being in situ lesions and 28.6% being tumors invading the mucosa + muscularis mucosae + submucosa layers, as confirmed by histopathology. After VEGFR2-UCA injection, gray values from the eUBM tumoral images increased significantly (p < 0.01). Tumor sites with increased eUBM image gray values corresponded to areas with increased VEGFR-2 expression, as confirmed by immunohistochemistry.

CONCLUSION

The results confirm eUBM as a powerful noninvasive and real-time tool for detecting colon tumor and its invasiveness and once associated with VEGFR2-UCA may become a tool for the detection of VEGFR-2 expression in colonic tumors.

The Continuing Evolution of Molecular Functional Imaging in Clinical Oncology: The Road to Precision Medicine and Radiogenomics (Part II)

The present era of precision medicine sees "cancer" as a consequence of molecular derangements occurring at the commencement of the disease process, with morphological changes happening much later in the process of tumourigenesis. Conventional imaging techniques, such as computed tomography (CT), ultrasound (US) and magnetic resonance imaging (MRI) play an integral role in the detection of disease at the macroscopic level. However, molecular functional imaging (MFI) techniques entail the visualisation and quantification of biochemical and physiological processes occurring during tumourigenesis. MFI has the potential to play a key role in heralding the transition from the concept of "one-size-fits-all" treatment to "precision medicine". Integration of MFI with other fields of tumour biology such as genomics has spawned a novel concept called "radiogenomics", which could serve as an indispensable tool in translational cancer research. With recent advances in medical image processing, such as texture analysis, deep learning and artificial intelligence, the future seems promising; however, their clinical utility remains unproven at present. Despite the emergence of novel imaging biomarkers, the majority of these require validation before clinical translation is possible. In this two part review, we discuss the systematic collaboration across structural, anatomical and molecular imaging techniques that constitute MFI. Part I reviews positron emission tomography, radiogenomics, AI, and optical imaging, while part II reviews MRI, CT and ultrasound, their current status, and recent advances in the field of precision oncology.

Color Doppler sonography in obstetrics and gynecology

This review aims to provide the reader with an overview of the present and future clinical applications in color Doppler sonography for the evaluation of vascularity and blood flow within the uterus (both gravid and nongravid), ovaries, fetus and placenta. The clinical use of color Doppler sonography has been demonstrated within many organ systems. Color Doppler sonography has become an integral part of cardiovascular imaging. Significant improvements have recently occurred, improving the visualization and evaluation of intra-organ vascularity, resulting from enhancements in delineation of tissue detail through electronic compounding and harmonics, as well as enhancements in signal processing of frequency- and/or amplitude-based color Doppler sonography. Spatial representation of vascularity can be improved by utilizing 3D and 4D (live 3D) processing. Greater sensitivity of color Doppler sonography to macro- and microvascular flow has provided improved anatomic and physiologic assessment throughout pregnancy and for pelvic organs. The potential use of contrast enhancement is also mentioned as a means to further differentiate benign from malignant ovarian lesions. The rapid development of these new sonographic techniques will continue to enlarge the scope of clinical applications in a variety of obstetric and gynecologic disorders.

Fractal analysis in radiological and nuclear medicine perfusion imaging: a systematic review

OBJECTIVES

To provide an overview of recent research in fractal analysis of tissue perfusion imaging, using standard radiological and nuclear medicine imaging techniques including computed tomography (CT), magnetic resonance imaging (MRI), ultrasound, positron emission tomography (PET) and single-photon emission computed tomography (SPECT) and to discuss implications for different fields of application.

METHODS

A systematic review of fractal analysis for tissue perfusion imaging was performed by searching the databases MEDLINE (via PubMed), EMBASE (via Ovid) and ISI Web of Science.

RESULTS

Thirty-seven eligible studies were identified. Fractal analysis was performed on perfusion imaging of tumours, lung, myocardium, kidney, skeletal muscle and cerebral diseases. Clinically, different aspects of tumour perfusion and cerebral diseases were successfully evaluated including detection and classification. In physiological settings, it was shown that perfusion under different conditions and in various organs can be properly described using fractal analysis.

CONCLUSIONS

Fractal analysis is a suitable method for quantifying heterogeneity from radiological and nuclear medicine perfusion images under a variety of conditions and in different organs. Further research is required to exploit physiologically proven fractal behaviour in the clinical setting.

KEY POINTS

• Fractal analysis of perfusion images can be successfully performed. • Tumour, pulmonary, myocardial, renal, skeletal muscle and cerebral perfusion have already been examined. • Clinical applications of fractal analysis include tumour and brain perfusion assessment. • Fractal analysis is a suitable method for quantifying perfusion heterogeneity. • Fractal analysis requires further research concerning the development of clinical applications.

[The impact of ultrasound in urology]

Ultrasound is of great importance in the diagnosis of acute and chronic diseases in urology, such as kidney colic, testicular torsion, low-grade kidney trauma or for follow-up of vesicoureteral reflux, evaluation of infertility, measurement of residual urinary volume and the detection of cancer. An ultrasound examination is time and cost-effective without exposure to ionizing radiation and is routinely performed by practitioners as well as in the clinical daily routine. With technical innovations, such as contrast-enhanced ultrasound or real time elastography, it would for instance be possible to extend the application field of ultrasound. However, in some fields of investigation ultrasound still lacks accuracy and despite its many advantages the validity of ultrasound findings sometimes has to be verified with computed tomography (CT) or magnetic resonance imaging (MRI).

Power Doppler sonography in the diagnosis of hemophilic synovitis--a promising tool

BACKGROUND

Recurrent hemarthroses in hemophilia results in synovitis and joint arthropathy. Primary prophylaxis when universally instituted at current doses can prevent joint deterioration but is expensive. Alternatively, the selective implementation of prophylaxis would require a more sensitive tool for detecting synovitis than possible with clinical surveillance or plain radiographs. Magnetic resonance imaging (MRI) is such a tool and is utilized for the evaluation of hemophilic joint disease (HJD). However, it is expensive, and requires sedation in younger children precluding its utility for monitoring of synovitis. Ultrasonography (USG) with power Doppler (USG-PDS) has been utilized to detect and quantitate synovial vascularity in other arthritides and could provide an equally effective but less costly tool for HJD, particularly in children who would not require sedation.

OBJECTIVES

To determine whether USG-PDS is comparable to MRI in the evaluation of hemophilic synovitis.

PATIENTS

A prospective cohort of 31 subjects including 33 joints (knees, elbows, ankles) underwent dynamic contrast enhanced (DCE)-MRI and USG-PDS.

RESULTS

USG-PDS measurements of synovial thickness(r = 0.70, P < 0.0001) and synovial vascularity (r = 0.73, P < 0.0001) correlated strongly with those obtained with DCE-MRI. A cutoff of PDS intensity of 1.3 decibels (dB) per mm(2) was found to yield a sensitivity of 100% and a specificity of 94.1% in 17 joints with/without a history of hemarthroses. Pettersson radiographic scores correlated significantly with synovial thickness in adults but not children.

CONCLUSIONS

Our data suggest that USG-PDS may be an inexpensive and easily implemented imaging tool for detecting hemophilic synovitis and could be useful in tailoring effective prophylaxis.

Circulating and imaging markers for angiogenesis

Abundant preclinical and indirect clinical data have for several decades convincingly supported the notion that anti-angiogenesis is an effective strategy for the inhibition of tumor growth. The recent success achieved in patients with metastatic colon carcinoma using a neutralizing antibody directed against vascular endothelial growth factor (VEGF) has translated preclinical optimism into a clinical reality.With this transformation in the field of angiogenesis has come a need for reliable surrogate markers. A surrogate marker by definition serves as a substitute for the underlying process in question, and in the case of angiogenesis, microvessel density (usually in so-called "hot-spots") has until now been the most widely used parameter. However, this parameter is more akin to a static "snap-shot" and does not lend itself either to the dynamic in situ assessment of the status of the tumor microvasculature or to the molecular factors that regulate its growth and involution. This has led to an acute need for developing circulating and imaging markers of angiogenesis that can be monitored in vivo at repeated intervals in large number of patients with a variety of tumors in a non-invasive manner. Such markers of angiogenesis are the subject of this review.

Relationship between retention of a vascular endothelial growth factor receptor 2 (VEGFR2)-targeted ultrasonographic contrast agent and the level of VEGFR2 expression in an in vivo breast cancer model

OBJECTIVE

The aim of this study was to characterize the relationship between retention of a vascular endothelial growth factor receptor 2 (VEGFR2)-targeted ultrasonographic contrast agent (UCA) and VEGFR2 expression in tumor vasculature of breast cancer.

METHODS

67NR breast cancer tumors implanted in mice were evaluated in vivo with both VEGFR2-targeted and nontargeted UCAs, and a high-frequency ultrasound system. A bolus of the UCA was injected and allowed to circulate for 4 minutes to allow binding of targeted microbubbles. After that, 2 sets of images before and after a high-power ultrasonic destruction sequence were acquired. The average video intensity of predestruction and postdestruction images was measured and used as a relative measure of retention of the UCA in the tumor. Levels of VEGFR2 expression and tumor vascular density were quantified by immunohistochemical staining and compared with retention of the VEGFR2-targeted UCA.

RESULTS

Retention of VEGFR2-targeted microbubbles in tumors was significantly higher than retention of nontargeted microbubbles (mean +/- SD, 47.75+/-9.85 versus 18.5+/-5.46 dB; P< .001). Retention of the VEGFR2-targeted UCA was found to correlate with the level of VEGFR2 expression in the studied tumors (r(2)=0.41). In contrast, retention of the nontargeted UCA was not correlated with the level of VEGFR2 expression (r(2)=0.08). Furthermore, retention of the VEGFR2-targeted UCA was not correlated with the level of tumor vascularity.

CONCLUSIONS

The magnitude of the molecular ultrasonographic signal from a VEGFR2-targeted UCA retained by tissue correlates with VEGFR2 expression. These results validate the use of molecular ultrasonography for in vivo detection and quantification of VEGFR2 expression in this breast cancer model.

Dose-response relationship of ultrasound contrast agent in an in vivo murine melanoma model

Many factors affect the sensitivity and reliability of tumor vasculature assessment at the small doses of contrast agent necessary for imaging mice. In this study we investigate the dose-response relationship of ultrasound contrast agent for a minimal exposure power Doppler technique (minexPD) in a murine melanoma model. K1735 murine melanomas grown in 25 C3H/HeN mice were imaged by power Doppler ultrasound using different doses of contrast agents, Optison(R) and Definity(R). Six mice were treated with an antivascular agent, combretastatin A4-phosphate (CA4P), and imaged before and after treatment. The color-weighted fractional area (CWFA) of the peak-enhanced image was measured to assess tumor perfusion on a relative scale of 0 to 100. CWFA increased logarithmically with dose (R(2)=0.97). Treatment with CA4P resulted in pronounced reduction in tumor perfusion 2 h after contrast injection, but perfusion recovered in the tumor periphery after 2 days. CWFA was significantly different between pre- and post-treatment for all doses at 2 h and 2 days (p < 0.05, respectively). There was no significant difference detectable between the two contrast agents, Optison(R) and Definity(R) (p = 0.46). In vivo tumor enhancement in mice increases as logarithmic function with dose. Although the extent of enhancement is dose dependent, the difference between pre- and post-therapy enhancement is relatively unchanged and uniform at varying doses. The two contrast agents tested in this study performed equally well. These results suggest that quantitative contrast-enhanced power Doppler imaging is an effective method for monitoring therapy response of tumors in mice.

Measuring tumor perfusion in control and treated murine tumors: correlation of microbubble contrast-enhanced sonography to dynamic contrast-enhanced magnetic resonance imaging and fluorodeoxyglucose positron emission tomography

OBJECTIVE

The purpose of this study was to evaluate the ability of dynamic microbubble contrast-enhanced sonography (MCES), in comparison with dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and fluorodeoxyglucose positron emission tomography (FDG-PET), to quantitatively characterize tumor perfusion in implanted murine tumors before and after treatment with a variety of regimens.

METHODS

Seventeen mice with Lewis lung carcinoma implants were categorized to control, radiation therapy alone, antiangiogenic chemotherapy alone, and combined chemoradiation. On day 0 of each treatment regimen, MCES and DCE-MRI of each tumor were performed. On day 5 of treatment, dynamic FDG-PET, MCES, and DCE-MRI were performed.

RESULTS

Microbubble contrast-enhanced sonography showed that intratumoral perfusion, blood volume, and blood velocity were highest in the untreated control group and successively lower in each of the treatment groups: radiation therapy alone resulted in a two-thirds reduction of perfusion; antiangiogenic chemotherapy resulted in a relatively larger reduction; and combined chemoradiotherapy resulted in the largest reduction. Microbubble contrast-enhanced sonography revealed longitudinal decreases in tumor perfusion, blood volume, and microvascular velocity over the 5-day course of chemoradiotherapy (all P < .01); conversely, these values rose significantly for the untreated control tumors (P < .01). Dynamic contrast-enhanced MRI showed a smaller and statistically insignificant average decrease in relative tumor perfusion for treated tumors. Dynamic PET revealed delayed uptake of FDG in the tumors that underwent chemoradiotherapy.

CONCLUSIONS

Microbubble contrast-enhanced sonography is an effective tool in the noninvasive, quantitative, longitudinal characterization of neovascularization in murine tumor models and is correlative with DCE-MRI and FDG-PET. Microbubble contrast-enhanced sonography has considerable potential in the clinical assessment of tumor neovascularization and in the assessment of the response to treatment.

Noninvasive assessment of tumor vasculature response to radiation-mediated, vasculature-targeted therapy using quantified power Doppler sonography: implications for improvement of therapy schedules

OBJECTIVE

Stereotactic radiotherapy (ablative radiation) is a modality that holds considerable promise for effective treatment of intracranial and extracranial malignancies. Although tumor vasculature is relatively resistant to small fractionated doses of ionizing radiation, large ablative doses of ionizing radiation lead to effective demise of the tumor vasculature. The purpose of this study was (1) to noninvasively monitor and compare tumor physiologic parameters in response to ablative radiation treatments and (2) to use these noninvasive parameters to optimize the schedule of administration of radiation therapy.

METHODS

Lewis lung carcinoma tumors were implanted into C57BL/6 mice and treated with ablative radiation. The kinetics of change in physiologic parameters of a response to single-dose 20-Gy treatments was measured. Parameters studied included tumor blood flow, apoptosis, and proliferation rates. Serial tumor sections were stained to correlate noninvasive Doppler assessment of tumor blood flow with microvasculature histologic findings.

RESULTS

A single administration of 20 Gy led to an incomplete tumor vascular response, with subsequent recovery of tumor blood flow within 4 days after treatment. Sustained reduction of tumor blood flow by administering the successive ablative radiation treatment before tumor blood flow recovery led to a 3-fold tumor growth delay. The difference in tumor volumes at each measurement time point (every 2 days) was statistically significant (P=.016).

CONCLUSIONS

This study suggests a rational design of schedule optimization for radiation-mediated, vasculature-directed treatments guided by noninvasive assessment of tumor blood flow levels to ultimately improve the tumor response.

Changes in vascularity and blood volume as a result of photodynamic therapy can be assessed with power Doppler ultrasonography

BACKGROUND AND OBJECTIVES

One principal mechanism of photodynamic therapy (PDT) in tumors is destruction of tumor-associated vasculature. In the present study, the vascular effects of PDT in tumors were investigated with power Doppler ultrasonography.

MATERIALS AND METHODS

Seven cutaneous squamous cell carcinomas in cats were treated. Tumors were examined via power Doppler ultrasonography before, 5 minutes, 1 hour, and 24 hours after PDT. Images were digitized for computer-aided assessment of vascularity and blood volume.

RESULTS

Mean baseline tumor vascularity and blood volume were moderate. During PDT, a significant decrease in vascularity and blood volume was noted. Lowest values were found 24 hours after PDT.

CONCLUSIONS

Power Doppler ultrasonography represents a non-invasive modality to successfully monitor the vascular effects and thus, treatment efficacy, of PDT.

Recent advances in the sonographic assessment of vascularity and blood flow in gynecologic conditions

OBJECTIVE

This overview presents recent advances in sonographic depiction of vascularity and blood flow in the uterus, ovaries, and breasts. Enhanced sonographic visualization and evaluation of intraorgan vascularity has resulted from improved image processing and display. Future advances, such as the use of contrast enhancement, are also mentioned in this overview as one of many topics for future investigation.

STUDY DESIGN

This is an overview of the topic based on review of the literature and the authors' experience.

RESULTS

Specifically, the sensitivity of color Doppler sonography has been enhanced with the use of amplitude or power Doppler techniques. Spatial depiction of vascularity has improved because of 3-dimensional and "live 3-dimensional" processing.

CONCLUSION

The combination of more sensitive color Doppler sonography and 3-dimensional imaging provides both anatomic and physiologic assessment of the vascularity and blood flow of the ovary, uterus, and breast.

Contrast-enhanced power Doppler sonography of malignant ovarian tumors using harmonic flash-echo imaging: preliminary experience

To investigate the potential usefulness of contrast-enhanced intermittent harmonic sonography in the diagnosis of ovarian cancer, we evaluated 4 patients with complex adnexal masses suspected of malignancy using intermittent harmonic sonography after injection of a contrast agent. Tumor and/or mural nodule tissue enhancement was detected in all cases of ovarian malignancy. Contrast-enhanced, intermittent harmonic sonography provides a satisfactory visualization of blood flow in the solid portion of the tumor tissue and may support a diagnosis of ovarian malignancy. Depiction of blood vessels using low MI techniques may be possible with other vascular ultrasonographic contrast agents.

Sonographic depiction of microvessel perfusion: principles and potential

OBJECTIVE

To provide an overview of the technical aspects and potential clinical applications of microvessel perfusion as depicted by microbubble-enhanced sonography.

METHODS

Sonographic depiction of microvessel perfusion was obtained by microbubble-enhanced sonography. This technique was used for imaging in vivo murine tumors and was correlated with magnetic resonance and fluorodeoxyglucose autoradiography. Sonographic estimation of microvessel perfusion used parameters derived from time-activity curves.

RESULTS

Preliminary data indicate that accurate and reproducible quantification of microvessel perfusion is possible with the use of microbubble-enhanced sonography.

CONCLUSIONS

Microbubble-enhanced sonography can depict microvessel perfusion. This technique has several potential clinical applications, including assessment of tumor blood flow and changes that occur with treatment.