Evaluating the extent of cell death in 3D high frequency ultrasound by registration with whole-mount tumor histopathologya)
Flow chart illustrating the main steps of the process: (A) Ultrasound data collection; (B) histological sections of a whole tumor mounted on a slide of ; (C) outlining of cell death on a histological section at a higher magnification of 20×; (D) reconstruction of a histological volume by aligning consecutive slides; (E) rigid registration of histological and ultrasound images and delineating a tumor on ultrasound and histological images; (F) contours conversion to a binary mask; and (G) conversion of a mask file to a finite element model.
Representative ultrasound images of a mouse tumor before and 24 h after radiotherapy presenting regions with increased echogeneity after radiotherapy. The white arrow on the lateral side of each tumor represents the location of the transducer focal point. Scale bars are 2 mm.
Representation of cell death in high frequency ultrasound and histological images: (A) Ultrasound image of a C666–1 tumor xenograft at 24 h after treatment with 4 Gy; (B) corresponding TUNEL stained image indicating an area of cell death, the brown-colored area that has a similar shape as the hyperechoic area in the ultrasound image; and (C) higher magnification of a H&E stained image corresponding to the selection from image (B). The left side of the image (C) demarcated by the black line demonstrates the characteristics of cell death. (D) Ultrasound image of a FaDu tumor xenograft at 24 h after treatment with 8 Gy; (B) corresponding H&E stained image indicating an area of cell death of similar shape as the hyperechoic area in the ultrasound image; and (F) higher magnification of the H&E stained image corresponding to the selection from image (E), demonstrating cell death in the upper part of the image demarcated by the black line. Scale bars are 2 mm in images (A), (B), (D), and (E), in image (C), and in image (F).
(A) Ultrasound image of a PC3 tumor xenograft at 24 h after treatment with 8 Gy indicating a hyperechoic area in the middle of the tumor; (B) corresponding H&E stained image indicating an area of cell death of similar location as the hyperechoic area from the ultrasound image; the arrows indicate the marks created by the needles that helped in the alignment of histological slices for this tumor; and (C) different types of cell structural damage in PC3 tumor at 24 h after radiotherapy: The white arrow indicates microscopic edema, the black arrow indicates possible red blood cells escaping from intravascular space, and the gray arrow indicates apoptosis of endothelial cells lining blood microvasculature. Scale bars are 2 mm in images (A) and (B) and in image (C).
Volume differences and volume overlaps of tumor and cell death in ultrasound and histology. (A) Percent differences in the volume of tumor and cell death in ultrasound and histology, before and after correction for tissue shrinkage. (B) Overlap of tumor and cell death. Volumes are relative to the volume of tumor and cell death evaluated from ultrasound images.
(A) Finite element model of a tumor and cell death segmented from ultrasound images with (B) corresponding cross-section ultrasound image illustrating tumor orientation and the position of the transducer focal point (the white arrow on the lateral side of the ultrasound image) during scanning; (C) finite element model of tumor and cell death segmented from histology with (D) corresponding histological cross section, demonstrating an area of cell death outlined in black; finite element models illustrating the overlap of cell death derived from ultrasound and histological images, respectively, demonstrating (E) a good overlap (81%) and (F) a weak overlap (45%). Scale bars are 2 mm for all images.
Tumor and cell death volumes as assessed from ultrasound and histological images. The numbers in brackets from the first column represent the radiotherapy doses.
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