First Experiences with Navigated Radio-Guided Surgery Using Freehand SPECT

PET- and SPECT-based navigation strategies to advance procedural accuracy in interventional radiology and image-guided surgery

INTRODUCTION

Nuclear medicine has a crucial role in interventional strategies where a combination between the increasing use of targeted radiotracers and intraprocedural detection modalities enable novel, but often complex, targeted procedures in both the fields of interventional radiology and surgery. 3D navigation approaches could assist the interventional radiologist or surgeon in such complex procedures.

EVIDENCE ACQUISITION

This review aimed to provide a comprehensive overview of the current application of computer-assisted navigation strategies based on nuclear imaging to assist in interventional radiology and image-guided surgery. This work starts with a brief overview of the typical navigation workflow from a technical perspective, which is followed by the different clinical applications organized based on their anatomical organ of interest.

EVIDENCE SYNTHESIS

Although many studies have proven the feasibility of PET- and SPECT-based navigation strategies for various clinical applications in both interventional radiology and surgery, the strategies are spread widely in both navigation workflows and clinical indications, evaluated in small patient groups. Hence, no golden standard has yet been established.

CONCLUSIONS

Despite that the clinical outcome is yet to be determined in large patient cohorts, navigation seems to be a promising technology to translate nuclear medicine findings, provided by PET- and SPECT-based molecular imaging, to the intervention and operating room. Interventional Nuclear Medicine (iNM) has an exciting future to come using both PET- and SPECT-based navigation.

Intraoperative sentinel node imaging versus SPECT/CT in oral cancer - A blinded comparison

INTRODUCTION

Sentinel node biopsy (SNB) is gaining popularity as a staging tool in oral cancer. Protocol mandates radiotracer injection and pre-operative imaging (LSG ± SPECT/CT) in the nuclear medicine department. This approach limits application to accessible tumours and to centres with nuclear medicine. New technology, freehand single photon emission computed tomography (fhSPECT), has proved a useful adjunct in intraoperative imaging and localisation of sentinel nodes. This study investigates fhSPECT as an alternative to traditional imaging, an approach that would widen the remit of SNB.

METHODS

Fifty consecutive cT1-T2 N0 oral cancer patients received radiotracer followed by lymphoscintigraphy and SPECT/CT. Surgery was undertaken using fhSPECT by a surgeon blinded to pre-operative imaging. Prior to biopsy completion, results of pre-operative imaging were reviewed and any additional nodes removed. The accuracy of LSG, SPECT/CT and fhSPECT were compared.

RESULTS

Nineteen patients had positive sentinel nodes. Disease free survival for sentinel node positive versus negative was significant (p < 0.005). All modalities missed positive nodes in at least one patient. The false negative rate for lymphoscintigraphy, SPECT/CT and fhSPECT was 26.3%, 15.8% and 5.3% respectively.

DISCUSSION

These data show a surgeon naïve to the results of traditional pre-operative sentinel node imaging can use fhSPECT in the operating theatre to accurately locate sentinel nodes in oral cancer. Freehand SPECT showed excellent sensitivity and a low false negative rate offering the possibility of a streamlined intraoperative sentinel node protocol.

3D scintigraphic imaging and navigation in radioguided surgery: freehand SPECT technology and its clinical applications

Freehand SPECT (fhSPECT) is a technology platform for providing 3-dimensional (3D) navigation for radioguided surgical procedures, such as sentinel lymph node (SLN) biopsy (SLNB). In addition to the information provided by conventional handheld gamma detection probes, fhSPECT allows for direct visualization of the distribution of radioactivity in any given region of interest, allowing for improved navigation to radioactive target lesions and providing accurate lesion depth measurements. Herein, we will review the currently available clinical data on the use of fhSPECT: (i) for SLNB of various malignancies, including difficult-to-detect SLNs, and (ii) for radioguided localization of solid tumors. Moreover, the combination of fhSPECT with other technologies (e.g., small field-of-view gamma cameras, and diagnostic ultrasound) is discussed. These technical advances have the potential to greatly expand the clinical application of radioguided surgery in the future.

Clinical Usefulness of a Novel Freehand 3D Imaging Device for Radio-Guided Intraoperative Sentinel Lymph Node Detection in Malignant Melanoma

INTRODUCTION

Patients with invasive malignant melanoma are commonly referred for sentinel lymph node (SLN) detection. A recently proposed 3D tomographic imaging modality is freehand SPECT (declipseSPECT). This "bedside system" was originally developed to enable minimal-invasive image-guided surgery. The aim of this retrospective analysis was to assess the clinical use of this freehand detector device for image-guided lymphatic mapping in melanoma patients.

MATERIALS AND METHODS

Thirty-nine patients (12 female and 27 male subjects) were included (age, 30-79 years). All of them had at least one location of melanoma with tumoral stage pT1b or greater in 37 and pTx in 2 patients in different sites of the body (abdomen in 4, back in 14, head and neck in 5, lower extremity in 6, and upper extremity in 10 patients). Lymphoscintigraphy was performed with 65 to 127 MBq Tc-nanocolloid. A 2-day protocol was applied with SPECT-CT acquisition (Brightview XCT, Philips) at day 1 and surgery using radio-guided freehand SPECT at day 2. SPECT-CT data were integrated into the 3D navigation system to enable fast and direct localization of the SLN by displaying the depth of the node from the skin surface and lateral margins in relation to the gamma probe.

RESULTS

Comparable preoperative imaging and intraoperative localization was observed in 18 patients. In 14 cases, more lymph nodes were resected than detected by SPECT-CT including 1 patient without evidence of an SLN because this node was located close to the primary right ear tumor. In 10 of these patients, intraoperative freehand SPECT revealed additional sites of lymph nodes. In 7 cases, more findings were detected by SPECT-CT than surgically removed. The procedure was safe and easy to perform, and the time of surgical intervention using freehand SPECT was in the range of 36 to 133 minutes (mean time, 66.56 minutes).

CONCLUSIONS

Freehand SPECT detected more SLN compared with SPECT-CT, and the tracking system provided precise anatomical localization of the radioactive-labeled SLNs.

First experience with image-guided resection of paraganglioma

A 32-year-old male patient showed 2 focal uptakes of I-MIBG next to the left renal vein in a diagnostic scan, corresponding to paragangliomas. An operation was indicated, and to guide resection during surgery we used the freehand SPECT system. In the operating room, using freehand SPECT, both lesions were found. The system was of additional value in planning the operative access to the region of interest and in determining the depth of 1 lesion for precise and more rapid extirpation. Furthermore, it confirmed no residues in the operating field after resection of the tumors.

1D-3D registration for intra-operative nuclear imaging in radio-guided surgery

3D functional nuclear imaging modalities like SPECT or PET provide valuable information, as small structures can be marked with radioactive tracers to be localized before surgery. This positional information is valuable during surgery as well, for example when locating potentially cancerous lymph nodes in the case of breast cancer. However, the volumetric information provided by pre-operative SPECT scans loses validity quickly due to posture changes and manipulation of the soft tissue during surgery. During the intervention, the surgeon has to rely on the acoustic feedback provided by handheld gamma-detectors in order to localize the marked structures. In this paper, we present a method that allows updating the pre-operative image with a very limited number of tracked readings. A previously acquired 3D functional volume serves as prior knowledge and a limited number of new 1D detector readings is used in order to update the prior knowledge. This update is performed by a 1D-3D registration algorithm that registers the volume to the detector readings. This enables the rapid update of the visual guidance provided to the surgeon during a radio-guided surgery without slowing down the surgical workflow. We evaluate the performance of this approach using Monte-Carlo simulations, phantom experiments and patient data, resulting in a positional error of less than 8 mm which is acceptable for surgery. The 1D-3D registration is also compared to a volumetric reconstruction using the tracked detector measurements without taking prior information into account, and achieves a comparable accuracy with significantly less measurements.

Feasibility of preoperative (125)I seed-guided tumoural tracer injection using freehand SPECT for sentinel lymph node mapping in non-palpable breast cancer

Background

This study was designed to explore the feasibility of replacing the conventional peri-/intratumoural ultrasound (US)-guided technetium-99m albumin nanocolloid (^99mTc-nanocolloid) administration by an injection of the same tracer guided by a freehand single-photon emission computed tomography (SPECT) device in patients with non-palpable breast cancer with an iodine-125 (¹²⁵I) seed as tumour marker, who are scheduled for a sentinel lymph node biopsy (SLNB). This approach aimed to decrease the workload of the radiology department, avoiding a second US-guided procedure.

Methods

In ten patients, the implanted ¹²⁵I seed was primarily localised using freehand SPECT and subsequently verified by conventional US in order to inject the ^99mTc-nanocolloid. The following 34 patients were injected using only freehand SPECT localisation. In these patients, additional SPECT/CT was acquired to measure the distance between the ^99mTc-nanocolloid injection depot and the ¹²⁵I seed. In retrospect, a group of 21 patients with US-guided ^99mTc-nanocolloid administrations was included as a control group.

Results

The depth difference measured by US and freehand SPECT in ten patients was 1.6 ± 1.6 mm. In the following 36 ¹²⁵I seeds (34 patients), the average difference between the ¹²⁵I seed and the centre of the ^99mTc-nanocolloid injection depot was 10.9 ± 6.8 mm. In the retrospective study, the average distance between the ¹²⁵I seed and the centre of the ^99mTc-nanocolloid injection depot as measured in SPECT/CT was 9.7 ± 6.5 mm and was not significantly different compared to the freehand SPECT-guided group (two-sample Student's t test, p = 0.52).

Conclusion

We conclude that using freehand SPECT for ^99mTc-nanocolloid administration in patients with non-palpable breast cancer with previously implanted ¹²⁵I seed is feasible. This technique may improve daily clinical logistics, reducing the workload of the radiology department.

Development and characterization of a round hand-held silicon photomultiplier based gamma camera for intraoperative imaging

This paper describes the development of a hand-held gamma camera for intraoperative surgical guidance that is based on silicon photomultiplier (SiPM) technology. The camera incorporates a cerium doped lanthanum bromide (LaBr₃:Ce) plate scintillator, an array of 80 SiPM photodetectors and a two-layer parallel-hole collimator. The field of view is circular with a 60 mm diameter. The disk-shaped camera housing is 75 mm in diameter, approximately 40.5 mm thick and has a mass of only 1.4 kg, permitting either hand-held or arm-mounted use. All camera components are integrated on a mobile cart that allows easy transport. The camera was developed for use in surgical procedures including determination of the location and extent of primary carcinomas, detection of secondary lesions and sentinel lymph node biopsy (SLNB). Here we describe the camera design and its principal operating characteristics, including spatial resolution, energy resolution, sensitivity uniformity, and geometric linearity. The gamma camera has an intrinsic spatial resolution of 4.2 mm FWHM, an energy resolution of 21.1 % FWHM at 140 keV, and a sensitivity of 481 and 73 cps/MBq when using the single- and double-layer collimators, respectively.

Freehand SPECT-guided sentinel lymph node biopsy in early oral squamous cell carcinoma

BACKGROUND

In oral squamous cell carcinoma (OSCC), cervical lymph node status is the most important prognostic factor. Compared to elective neck dissection, reduced morbidity and better quality of life was demonstrated for sentinel lymph node biopsy, which is controversial because of the reduced detection rate of sentinel lymph nodes in close proximity to the injection site (also known as the shine-through phenomenon).

METHODS

We report the case of a 44-year-old woman with a biopsy-proven early OSCC of the anterior floor of the mouth, who received SLNB guided with freehand single-photon emission CT (fhSPECT), a system for the 3D visualization of radioactivity in the body.

RESULTS

One level III sentinel lymph node and 1 level I sentinel lymph node, in close proximity to the injection site, were detected and dissected. The level I sentinel lymph node contained a metastasis.

CONCLUSION

Using fhSPECT, the issue outlined was overcome, and the precise histopathological lymph node status (pN1; 1 of 49) was determined.

Freehand SPECT for sentinel lymph node detection in patients with head and neck cancer: first experiences

CONCLUSION

Feasibility of intraoperative 3D imaging with freehand (fh) SPECT for sentinel lymph node (SLN) biopsy in head and neck cancer (HNC) could be demonstrated. Controlled clinical studies are needed to evaluate its accuracy and impact on patient morbidity.

OBJECTIVES

The clinical N0 neck in HNC needs improvement in management to sufficiently detect occult neck disease but to spare patients from potential morbidity by elective neck dissection. The SLN concept has potential to accurately stage the neck with low morbidity.

METHODS

fhSPECT is a 3D tomographic imaging modality with a gamma probe system combined with an infrared optical tracking system. Five patients with HNC and clinical N0 neck were recruited. Scanning for SLN using fhSPECT was performed before excision and selective neck dissection and specimens were analyzed histopathologically.

RESULTS

Preoperatively, a total of nine SLNs were located in five patients with fhSPECT. SLNs in three patients were positive for metastatic disease; in two patients the SLNs were tumor-free. No residual radioactivity was found in the neck in any of the patients after extirpation of SLNs. fhSPECT acquisitions took 2.6 ± 0.4 min. No metastatic lymph nodes were detected in any other node harvested during subsequent selective neck dissection in any patients.

Bone graft scintigraphy. A new diagnostic tool to assess perfusion during surgery

AIM

To evaluate a scintigraphic tool for intraoperative assessment of vascularized bone graft perfusion before and after transplantation.

PATIENTS, METHODS

This pilot study included three patients scheduled for surgical segmental mandibulectomy followed by reconstruction with a vascularized iliac bone graft. A continuous (99m)Tc-pertechnetate infusion was applied selectively arterial into the blood vessel supplying the respective graft before osteotomy as well as after transplantation. Perfusion was analysed by scintigrams acquired using the intraoperative camera systems declipseSPECT and Sentinella. Results were compared qualitatively.

RESULTS

Before harvesting the graft, intraoperative scintigraphy revealed a clearly delineated area of the iliac crest with a relatively homogenous pertechnetate distribution representing good perfusion. After osteotomy, transplantation to the mandibula and re-anastomosis of the nutrient vessels, scintigraphy in all patients showed a moderately inhomogenous distribution pattern of the pertechnetate indicating an adequate perfusion of the bone transplant through the arterial anastomosis.

CONCLUSION

Intraoperative assessment of bone graft perfusion is possible with the imaging systems Sentinella as well as with declipseSPECT using a continuous intra-arterial infusion of 99mTc-pertechnetate.