The structure of the final product of the DiveScope with a superb resolution to visualize sub-micron organelles
In the final version of the DiveScope, the surgery microscope collection, and processing system consists of the mainframe of an imaging system, a camera readout, a microscope, a distal hood, a power cord, a monitor, and an LED light source (Fig. 2A). The optical components of the camera readout include a Complementary Metal-Oxide-Semiconductor (CMOS) camera, a C-Mount, a fluorescence cube, a relay lens, and a miniature objective. The camera system is generally composed of an image-processing host and a camera. The working principle of the camera system is to connect the lens body through the optical interface, convert the optical signals collected by the lens body into digital signals, input them to the image processing host, and then output them to the display after being processed by the image processing host. The image processing host is the control center of the whole camera system that is used to process surgical videos and images captured from the camera. In our device, a cold light bulb is a bulb that uses a similar light source principle to an LED. The working principle of the cold light source is that the power module supplies power to each functional module, and the program is integrated into the control board module. The control panel module includes three parts: the Medium Attachment Unit (MAU) module, the LED driver module, and the dimming module.
With superb resolution, the DiveScope visualized the resolution test chart and sub-micron organelles, such as nuclei, nucleoli, and cytosol, in vitro imaging (FIG. 2B, C).
Performance of the DiveScope in experimental animals
To preliminarily assess the performance of the DiveScope, we dissected 3 experimental pigs’ brains and observed them under the DiveScope (Fig. 3A). The outline of the neurons’ nuclei in the gray matter can be identified (Fig. 3B), which is much larger compared to the nuclei of glial cells in the white matter (Fig. 3C). These images showed the excellent performance of the DiveScope in distinguishing neurons from the gliocytes. After the surgery, we did not observe evident side effects on all experimental pigs.
Performance of the handheld microscope in clinical application
The patient demographic and clinical variables were abstracted via chart reviews (Table 1). In all the patients, the fluorescent tissues at the margin of the resection cavity were all detected by the DiveScope after the completed microscopic resection. In normal brain tissue, all the neurons are in a sparse and regular cell distribution, with only one large and round nucleus plus a long axon and multiple dendrites (Fig. 4A). In tumorous tissue, no matter what pathologic type it is, tumor cells have been found to have the common features of high density, disordered distribution, a low degree of differentiation, and variation in size. Other than patients included in the statistics who were confirmed to be glioma patients, we also observed DiveScope pictures of one metastatic tumor in order to preliminarily study the performance of DS in other diseases (Fig. 4B). In a patient with an initial diagnosis of “cerebral infarction” from the emergency room, we found a similar manifestation under DiveScope. Such a manifestation can easily be misdiagnosed as a brain tumor. It was considered to be a cerebral abscess with merely large lymphocyte and neutrophil infiltration according to the postoperative pathology (Fig. 4B).
Diagnostic accuracy of the DiveScope in resection margins
First, the blinded pathologist analysis of the hematoxylin and eosin (HE)-stained research biopsies, which were derived from the same tissue observed under the DiveScope previously, served as the gold standard for final comparison with the results observed through the DiveScope. As was shown in Table 2, the consistency of the DiveScope and HE-staining pathology is acceptable, with only 3 cases of FN and the Kappa value of 0.68. Meanwhile, the 2×2 contingency table of the frozen section pathology and the HE-staining pathology was also listed, with the Kappa value of 0.84 (Table 3).
Table 2
Performance of DiveScope to differentiate tumorous from normal tissue in 32 specimens
DiveScope | HE-staining Pathologic Results | Total |
Tumorous Tissue | Normal Tissue |
Positive | 25 | 0 | 25 |
Negative | 3 | 4 | 7 |
Total | 28 | 4 | 32 |
HE = hematoxylin and eosin. |
Table 3
Performance of the frozen sections to differentiate tumorous from normal tissue in 32 specimens
Frozen Sections | HE-staining Pathologic Results | Total |
Tumorous Tissue | Normal Tissue |
Positive | 25 | 0 | 25 |
Negative | 4 | 3 | 7 |
Total | 29 | 3 | 32 |
HE = hematoxylin and eosin. |
Next, we directly compared the interpretation from the DiveScope and the frozen sections. The diagnostic measures of accuracy were calculated to evaluate the ability of the DiveScope as a novel intraoperative miniaturized histopathologic device (Table 4). As a result, 32 samples collected from 18 patients were classified as tumorous or normal tissue by the DiveScope. Regarding HE-stained sections as the gold standard, the sensitivity and the specificity of the DiveScope were 88.29% (95% CI: 70.8% − 97.6%) and 100% (95% CI: 39.8% − 100.0%), respectively, implying its strong ability to identify the positive margin and rule out the negative margin. In contrast, the sensitivity and specificity of the frozen sections were 100% (95% CI: 87.7% − 100%) and 75% (95% CI: 19.4% − 99.4%), respectively. Moreover, the positive likelihood ratio (PLR) of the DiveScope was imponderable because of no false positive case in DiveScope, while in contrast, the negative likelihood ratio (NLR) was 0.11 (95% CI: 0.037–0.31). In the aspect of the ROC curve, the AUC of the DiveScope and the frozen sections were 0.946 and 0.875, respectively (Fig. 5). These results proved the high diagnostic value of the DiveScope as a novel intraoperative miniaturized histopathologic device compared to conventional frozen sections.
Table 4
Comparison between DiveScope and frozen sections to differentiate tumorous from normal tissue in 32 specimens
DiveScope | Frozen Section Pathologic Results | Total |
Tumorous Tissue | Normal Tissue |
Positive | 25 | 0 | 25 |
Negative | 4 | 3 | 7 |
Total | 29 | 3 | 32 |
Time consumption
To prove the superiority of the DiveScope in rapid intraoperative pathologic diagnosis, we divided the samples into two groups according to the median diameter of all the tumorous samples (0.8 cm) and analyzed the time consumption for DiveScope or frozen sections, respectively (Fig. 6A, B). In tumorous samples with ≥ 0.8 cm in diameter, Divescope cost 10.7 minutes on average while frozen pathology cost 41.9 minutes (p < 0.0001). In tumorous samples with < 0.8 cm in diameter, DiveScope cost 10.7 minutes on average while frozen pathology cost 50.1 minutes (p < 0.01). In short, the time consumption for tissue identification for the DiveScope is significantly much faster than for the frozen sections no matter what size the sample is.
A typical clinical case
In this section, we report a typical operation that utilized the DiveScope (Fig. 7). A 49-year-old man presented with severe headache and nausea without vomiting or dizziness for two weeks. Magnetic resonance imaging (MRI) revealed a mass in the right frontal lobe which was considered to be high-grade glioma with intratumoral hemorrhage. During the surgery, we utilized the anterior, posterior, interior, and lateral borders of the tumorous tissue for observation with the DiveScope and frozen sections at the same time (Fig. 7A). After gross tumor resection with the help of intraoperative frozen sections and the DiveScope (Fig. 7B), we did not find a residual contrast-enhancing tumor on the early postoperative MRI (Fig. 7C), and this preliminarily proved the effectiveness of the DiveScope for the clinical determination of surgical margins.