Diagnostic and procedural intraoperative ultrasound: technique, tips and tricks for optimizing results

Abstract

Intraoperative ultrasound (IOUS) is a valuable adjunctive tool that can provide real-time diagnostic information in surgery that has the potential to alter patient management and decrease complications. Lesion localization, characterization and staging can be performed, as well as surveying for additional lesions and metastatic disease. IOUS is commonly used in the liver for hepatic metastatic disease and hepatocellular carcinoma, in the pancreas for neuroendocrine tumors, and in the kidney for renal cell carcinoma. IOUS allows real-time evaluation of vascular patency and perfusion in organ transplantation and allows for early intervention for anastomotic complications. It can also be used to guide intraoperative procedures such as biopsy, fiducial placement, radiation, or ablation. A variety of adjuncts including microbubble contrast and elastography may provide additional information at IOUS. It is important for the radiologist to be familiar with the available equipment, common clinical indications, technique, relevant anatomy and intraoperative imaging appearance to optimize performance of this valuable imaging modality.

Figure 1.

Sampling of intraoperative probes including a laparoscopic probe (a, b) with long shaft, small face (inset), flexible end and directional controls (arrow, b), small low profile T probe (c), and robotic drop in probe (d) with curved face and ridge for grasping with laparoscopic tools (arrow, inset).

Figure 2.

MRI and corresponding IOUS images of a spectrum of liver lesions. Mucinous CRC metastatic lesion on hepatobiliary phase MRI (a) demonstrates fine calcifications and a hyperechoic appearance at IOUS (b), while a different 88-year-old male with multifocal CRC on hepatobiliary phase MRI (c) demonstrates a lobulated ill-defined hypoechoic lesion at IOUS (d). A heterogeneously enhancing lesion on arterial phase MRI imaging (e) found to be metastatic NET in a 57-year-old female was hyperechoic at IOUS (f). A left lobe lesion that demonstrated arterial enhancement with portal venous washout (arrows, (g) in a 67-year-old male without known liver disease was found to be hepatocellular carcinoma at biopsy. This appeared targetoid with a hypoechoic rim at IOUS (h). CRC, colorectal cancer; IOUS, intraoperative ultrasound; NET, neuroendocrine tumor.

Figure 3.

48-year-old male with pancreas cancer undergoing Whipple with IOUS found to have indeterminate liver lesion (a) underwent intraoperative biopsy which demonstrated metastatic disease (b, arrow, needle). It was challenging to obtain the desired angle of approach through the surgical incision, so a percutaneous puncture site away from the incision was selected for optimal targeting. IOUS, intraoperative ultrasound.

Figure 4.

55-year-old male with metastatic RCC to the pancreas (a, c yellow arrow) and liver (a–c, blue arrows). IOUS image from open approach shows the mass in the pancreas (d, yellow arrow) and hyperechoic caudate liver lesion (e, blue arrow). Patient underwent pancreaticoduodenectomy, wedge resection of hepatic metastatic in segment 4b (not shown) and 6 and intraoperative microwave ablation of hepatic lesions in segment 4a (not shown), caudate, and segments 6/7 for clearance of all metastatic disease. IOUS image demonstrates advancement of a microwave ablation applicator (e, green arrow) into the caudate liver lesion with subsequent ablation and gas cloud with posterior acoustic shadowing encompassing the lesion (f, circle). Due to the small transducer face, it is difficult to lay the needle out along its full length. After this treatment, the patient remains disease free 1 year later. IOUS, intraoperative ultrasound; RCC, renal cellcarcinoma

Figure 5.

42-year-old female with complex cystic lesion of the right kidney (arrows, a, b) identified on pre-operative T₂W (a) and T₁W with contrast (b). Patient underwent robotic partial nephrectomy (c), which utilizes the drop in probe and grasper tool to apply the probe to the lesion (arrow, d) and an ultrasound machine connected to the robot control panel (e). Intraoperative ultrasound images (f) demonstrate a predominantly solid, vascular mass and delineated the proximity of the mass to the renal hilum and major vessels in real time. Surgical pathology demonstrated clear cell RCC. RCC, renalcell carcinoma

Figure 6.

Pre-operative CT (a) in a 23-year-old female demonstrates a mass in the pancreatic head (yellow arrow). EUS biopsy showed solid pseudopapillary neoplasm. At IOUS (b, c), note the small cystic spaces with the lesion identifiable at high resolution but not well seen from a percutaneous approach. The pancreatic duct (blue arrows) is also localized leading up to the mass to aid in operative approach. EUS, enhancedultrasound; IOUS, intraoperative ultrasound

Figure 7.

CEUS in a living donor split liver transplant patient demonstrating a patent hepatic artery (arrow) in the porta that was challenging to see on grayscale ultrasound. The artery was challenging to separate from the adjacent portal vein and CEUS allowed for real-time separation. CEUS, contrast-enhanced ultrasound.

Figure 8.

Ultrasound images obtained immediately post-pancreas transplant (a) demonstrate markedly elevated resistive indices and reversal of diastolic flow in the pancreatic graft. Based on these findings, the patient was taken back to the operating room and extensive graft venous thrombosis was identified on grayscale (b) and color Doppler (c) IOUS images (arrows). Vein graft thrombosis is the most common cause of pancreatic graft loss. IOUS, intraoperative ultrasound

Figure 9.

68-year-old female with heterogeneous endometrial thickening (arrow, a, sagittal CT) and abnormal uterine bleeding. Intraoperative ultrasound guidance for dilation, curettage and endometrial sampling was performed from an anterior percutaneous transabdominal approach. Note the curette within the endometrial cavity (b, arrow). IOUS helps ensure a robust sample but prevents pushing the curette through the uterine fundus. Surgical pathology demonstrated endometrial cancer and sufficient material was obtained for additional pathologic and genetic testing. IOUS, intraoperative ultrasound