Ultrasound Guided Optoacoustic Tomography in Assessment of Tumor Margins for Lumpectomies

Abstract

PURPOSE: To determine the accuracy of a handheld ultrasound-guided optoacoustic tomography (US-OT) probe developed for human deep-tissue imaging in ex vivo assessment of tumor margins postlumpectomy. METHODS: A custom-built two-dimensional (2D) US-OT–handheld probe was used to scan 15 lumpectomy breast specimens. Optoacoustic signals acquired at multiple wavelengths between 700 and 1100 nm were reconstructed using model linear algorithm, followed by spectral unmixing for lipid and deoxyhemoglobin (Hb). Distribution maps of lipid and Hb on the anterior, posterior, superior, inferior, medial, and lateral margins of the specimens were inspected for margin involvement, and results were correlated with histopathologic findings. The agreement in tumor margin assessment between US-OT and histopathology was determined using the Bland–Altman plot. Accuracy, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of margin assessment using US-OT were calculated. RESULTS: Ninety margins (6 × 15 specimens) were assessed. The US-OT probe resolved blood vessels and lipid up to a depth of 6 mm. Negative and positive margins were discriminated by marked differences in the distribution patterns of lipid and Hb. US-OT assessments were concordant with histopathologic findings in 87 of 89 margins assessed (one margin was uninterpretable and excluded), with diagnostic accuracy of 97.9% (kappa = 0.79). The sensitivity, specificity, PPV, and NPV were 100% (4/4), 97.6% (83/85), 66.7% (4/6), and 100% (83/83), respectively. CONCLUSION: US-OT was capable of providing distribution maps of lipid and Hb in lumpectomy specimens that predicted tumor margins with high sensitivity and specificity, making it a potential tool for intraoperative tumor margin assessment.

Przegląd metod śródoperacyjnej oceny marginesów w chirurgicznym leczeniu oszczędzającym gruczoł piersiowy

“…Another hybrid approach is a device combining photoacoustic tomography with ultrasonography. The study on a small group of patients showed very high (100%) sensitivity and high specificity in margin assessment [45].…”

“…Mammography confirms the removal of a neoplastic lesion with high accuracy, while a spectroscopy assesses whether the margins of a resected specimen are free of cancer cells. The combination of these two assessments reduces the need for reoperation by up to 50% [45,46]. Another hybrid approach is a device combining photoacoustic tomography with ultrasonography.…”

Biophotonic technologies for assessment of breast tumor surgical margins—A review

“…In a pilot study, Goh et al [28] used the first optical window from 700 to 1100 nm to capture the contrast from hemoglobin and lipid in 25 fresh lumpectomy specimens that were a mix of invasive lobular carcinomas (ILCs), IDCs and DCIS using a customized handheld photoacoustic probe consisting of 2D array of 256 transducers arranged along an arc angle of 125 and center frequency of 5 MHz that helped achieve biochemical information up to 7 mm from the surface. The probe fitted to PAT system, MSOT inVision 512-echo (iThera Medical GmbH) was moved over the sample ( Figure 1A) using a computer controlled stage and covered a volume of 200 cm 3 in 20 minutes [29].…”

“…Specimens with negative margins appeared to have uninterrupted lipid signals in the surface while those with positive margins appeared to lipid signals disrupted by deoxyhemoglobin signals in the blood vessels ( Figure 1B-G) [29]. Based on these classification criteria, the authors analyzed 90 margins (from 15 specimens) that resulted in a sensitivity of 100% and specificity of 97.6% [28]. The authors also proposed unmixing PA spectra for collagen to identify the collagen rich fibroglandular tissue which at the moment appears to have lipid signals of reduced intensity and may be confused with tumors.…”

“…(Reprinted and modified from refs. [28] and [29] following the terms of Creative Commons CC‐BY‐NC‐ND license)…”