Perspectives: MRI of angiogenesis

Updated criteria for the approval of subsequent pregnancy after cesarean section with a transverse uterine fundal incision based on 17 years of experience

In the case of placenta previa-accreta when the placenta covers the entire anterior uterine wall, it is difficult to avoid transecting the placenta by traditional low-transverse cesarean section (CS), resulting in catastrophic hemorrhage and fetal anemia. To prevent this critical risk, we developed the CS with transverse uterine fundal incision (TUFI) and this technique has been widely used as a beneficial surgical method in clinical practice owing to its safety advantages for the mother and neonate since our first report. However, the risk of uterine rupture during a subsequent pregnancy remains unclear. Based on our 17 years of experience, patients who require TUFI do not need to avoid this beneficial operative method simply because of their desire to conceive again, as long as certain conditions can be met. To approve a post-TUFI pregnancy, an appropriate suture method, delay in conception for at least 12 months with evaluation of the TUFI scar, and cautious postoperative management are at a minimum essential. In this article, we showed our recommendation for operative procedure and discuss the current status of the management of post-TUFI pregnancies based on the evaluation of the TUFI wound scar and experience with postoperative pregnancies.

Evaluation of incision healing status after transverse uterine fundal incision for cesarean delivery and postoperative pregnancy: a ten-year single-center retrospective study

BACKGROUND

Transverse uterine fundal incision (TUFI) is a beneficial procedure for mothers and babies at risk due to placenta previa-accreta, and has been implemented worldwide. However, the risk of uterine rupture during a subsequent pregnancy remains unclear. We therefore evaluated the TUFI wound scar to determine the approval criteria for pregnancy after this surgery.

METHODS

Between April 2012 and August 2022, we performed TUFI on 150 women. Among 132 of the 150 women whose uteruses were preserved after TUFI, 84 women wished to conceive again. The wound healing status, scar thickness, and resumption of blood flow were evaluated in these women by magnetic resonance imaging (MRI) and sonohysterogram at 12 months postoperatively. Furthermore, TUFI scars were directly observed during the Cesarean sections in women who subsequently conceived.

RESULTS

Twelve women were lost to follow-up and one conceived before the evaluation, therefore 71 cases were analyzed. MRI scans revealed that the "scar thickness", the thinnest part of the scar compared with the normal surrounding area, was ≥ 50% in all cases. The TUFI scars were enhanced in dynamic contrast-enhanced MRI except for four women. However, the scar thickness in these four patients was greater than 80%. Twenty-three of the 71 women conceived after TUFI and delivered live babies without notable problems until August 2022. Their MRI scans before pregnancy revealed scar thicknesses of 50-69% in two cases and ≥ 70% in the remaining 21 cases. And resumption of blood flow was confirmed in all patients except two cases whose scar thickness ≥ 90%. No evidence of scar healing failure was detected at subsequent Cesarean sections, but partial thinning was found in two patients whose scar thicknesses were 50-69%. In one woman who conceived seven months after TUFI and before the evaluation, uterine rupture occurred at 26 weeks of gestation.

CONCLUSIONS

Certain criteria, including an appropriate suture method, delayed conception for at least 12 months, evaluation of the TUFI scar at 12 months postoperatively, and cautious postoperative management, must all be met in order to approve a post-TUFI pregnancy. Possible scar condition criteria for permitting a subsequent pregnancy could include the scar thickness being ≥ 70% of the surrounding area on MRI scans, at least partially resumed blood flow, and no abnormalities on the sonohysterogram.

TRIAL REGISTRATION

Retrospectively registered.

Diagnostic performance of contrast-enhanced ultrasound in breast lesions: what diagnostic models could be used for lesions of different sizes?

Background

Previous studies show the size of lesions could affect the diagnostic accuracy of contrast-enhanced ultrasound (CEUS). It is unclear whether CEUS has good diagnostic performance for lesions ≤2.0 and ≤1.0 cm. It is beneficial for the early diagnosis to explore the application of CEUS in breast lesions of different sizes. This study aims to analyze the diagnostic performance of CEUS and explore diagnostic models better suited to breast lesions of different sizes.

Methods

A total of 1,059 lesions (656 benign and 403 malignant) examined by ultrasound and CEUS with definite pathological results were included in this retrospective study and divided into training (n=847) and validation (n=212) sets. All lesions were divided into three groups according to size. Diagnostic models (M0: all lesions; M1: ≤1.0 cm, M2: >1.0-2.0 cm, and M3: >2.0 cm) were developed through logistic regression analyses of CEUS features from the training set. Diagnostic performance was evaluated using the area under the receiver operating characteristic curve (AUC) and validated in the validation set.

Results

The median age of patients was 45±11 years (range, 18-80 years). The AUC values of M0 combined with the Breast Imaging Reporting and Data System (BI-RADS) in the training and validation sets were 0.921 and 0.922, respectively (P=0.893). The AUC values of M0 combined with BI-RADS in the three groups were 0.844, 0.936 and 0.928 respectively. M0 was less effective in diagnosing lesions ≤1.0 cm (0.844 vs. 0.921, P=0.029). The AUC of M1 combined with BI-RADS for lesions ≤1.0 cm was higher than that of M0 (0.893 vs. 0.844, P=0.047), and M2 and M3 had no statistical difference in diagnostic performance when compared with M0 (P=0.243; P=0.246).

Conclusions

The diagnostic performance of CEUS was closely related to lesion size. Establishing a new diagnostic model for lesions ≤1.0 cm can improve the CEUS diagnostic performance for breast lesions ≤1.0 cm.

Neovascularization, vascular mimicry and molecular exchange: The imaging of tumorous tissue aggressiveness based on tissue perfusion

Angiogenesis in healthy tissue and within malignant tumors differs on many levels, which may partly be explained by vascular mimicry formation resulting in altered contrast material or different radiopharmaceuticals distributions. Failed remodulation results in changes in the molecular exchange through the capillary wall and those consequences affect the behavior of contrast agents and radiopharmaceuticals. One of the most indicative signs of malignant tissue is the increased permeability and the faster molecular exchange that occurs between the extracellular and intravascular spaces. Dynamic imaging can help to assess the changed microenvironment. The fast-distribution of molecules reflects newly developed conditions in blood-flow redistribution inside a tumor and within the affected organ during the early stages of tumor formation. Tumor development, as well as aggressiveness, can be assessed based on the change to the vascular bed development, the level of molecular exchange within the tissue, and/or indicative distribution within the organ. The study of the vascular network organization and its impact on the distribution of molecules is important to our understanding of the image pattern in several imaging methods, which in turn influences our interpretation of the findings. A hybrid imaging approach (including PET/MRI) allows the quantification of vascularization and/or its pathophysiological impressions in structural and metabolic images. It might optimize the evaluation of the pretreatment imaging, as well as help assess the effect of therapy targeting neovascularization; antiVEGF drugs and embolization-based therapies, for example.

An optoacoustic imaging feature set to characterise blood vessels surrounding benign and malignant breast lesions

Combining optoacoustic (OA) imaging with ultrasound (US) enables visualisation of functional blood vasculature in breast lesions by OA to be overlaid with the morphological information of US. Here, we develop a simple OA feature set to differentiate benign and malignant breast lesions. 94 female patients with benign, indeterminate or suspicious lesions were recruited and underwent OA-US. An OA-US imaging feature set was developed using images from the first 38 patients, which contained 14 malignant and 8 benign solid lesions. Two independent radiologists blindly scored the OA-US images of a further 56 patients, which included 31 malignant and 13 benign solid lesions, with a sensitivity of 96.8% and specificity of 84.6%. Our findings indicate that OA-US can reveal vascular patterns of breast lesions that indicate malignancy using a simple feature set based on single wavelength OA data, which is therefore amenable to application in low resource settings for breast cancer management.

Assessment of Microvessel Permeability in Murine Atherosclerotic Vein Grafts Using Two-Photon Intravital Microscopy

Plaque angiogenesis and plaque hemorrhage are major players in the destabilization and rupture of atherosclerotic lesions. As these are dynamic processes, imaging of plaque angiogenesis, especially the integrity or leakiness of angiogenic vessels, can be an extremely useful tool in the studies on atherosclerosis pathophysiology. Visualizing plaque microvessels in 3D would enable us to study the architecture and permeability of adventitial and intimal plaque microvessels in advanced atherosclerotic lesions. We hypothesized that a comparison of the vascular permeability between healthy continuous and fenestrated as well as diseased leaky microvessels, would allow us to evaluate plaque microvessel leakiness. We developed and validated a two photon intravital microscopy (2P-IVM) method to assess the leakiness of plaque microvessels in murine atherosclerosis-prone ApoE3*Leiden vein grafts based on the quantification of fluorescent-dextrans extravasation in real-time. We describe a novel 2P-IVM set up to study vessels in the neck region of living mice. We show that microvessels in vein graft lesions are in their pathological state more permeable in comparison with healthy continuous and fenestrated microvessels. This 2P-IVM method is a promising approach to assess plaque angiogenesis and leakiness. Moreover, this method is an important advancement to validate therapeutic angiogenic interventions in preclinical atherosclerosis models.

Preclinical Applications of Magnetic Resonance Imaging in Oncology

The evolving possibilities of molecular imaging (MI) are fundamentally changing the way we look at cancer, with imaging paradigms now shifting away from basic morphological measures toward the longitudinal assessment of functional, metabolic, cellular, and molecular information in vivo. Recent developments of imaging methodology and probe molecules utilizing the vast number of novel animal models of human cancers have enhanced our ability to non-invasively characterize neoplastic tissue and follow anticancer treatments. While preclinical molecular imaging offers a whole palette of excellent methodology to choose from, we will focus on magnetic resonance imaging (MRI) techniques, since they provide excellent molecular imaging capabilities and bear high potential for clinical translation. Prerequisites and consequences of using animal models as surrogates of human cancers in preclinical molecular imaging are outlined. We present physical principles, values, and limitations of MRI as molecular imaging modality and comment on its high potential to non-invasively assess information on metabolism, hypoxia, angiogenesis, and cell trafficking in preclinical cancer research.