Intraoperative radio-guided localization of parathyroid adenomas using 3D freehand SPECT technology

Parathyroidectomy for primary hyperparathyroidism (PHPT) could have poor outcomes, even with accurate preoperative localization of the adenomas, because their intraoperative localization can be challenging. Freehand single photon emission computed tomography (fhSPECT) is a new technique for radio-guided intraoperative navigation. Its use during parathyroidectomy could be useful and such data are limited. We herein present our experience on the feasibility of fhSPECT for intraoperative detection of abnormal parathyroid glands. We retrospectively reviewed the clinical data of 55 patients (30-77 years old) with PHPT due to parathyroid adenomas, that were subjected to parathyroidectomy from 12/2017 to 7/2022. In average, 111 ± 74 MBq of Tc-99 m Sestamibi were injected intravenously, approximately 2 h before the operation and fhSPECT was used to generate 3D images during parathyroidectomy. Measurements of PTH and calcium levels were performed preoperatively, postoperatively and 4-6 months after the procedure. FhSPECT successfully identified the parathyroid adenoma in all the patients. It took 3 min (median time) for fhSPECT to detect at least one radioactive spot in all patients. The mean duration of the operation was 66.6 ± 7.3 min. Forty-nine patients out of 55 had solitary and 6/55 had multiple adenomas, whereas 6/55 had ectopic abnormal parathyroid glands. None of the patients had persistent hyperparathyroidism during follow-up. To the best of our knowledge, this is the largest series of patients with PHPT that underwent fhSPECT assisted parathyroidectomy. Our data suggest that this navigation system is helpful in identifying parathyroid adenomas intraoperatively.

Concordance between freehand SPECT and conventional scintigraphy for sentinel lymph node detection in breast cancer

INTRODUCTION

Freehand SPECT can be a useful imaging technique for preoperative planning of sentinel lymph node biopsy (SLNB) as it allows localization of the sentinel node by 3D and real-time tomographic imaging and determines its depth after a few minutes of scanning. The aim of the study was to evaluate the correlation between the number of detected SNs between freehand SPECT images and lymphoscintigraphy (LS).

MATERIALS AND METHODS

100 patients with a diagnosis of invasive breast cancer and no clinical evidence of lymph node involvement prospectively underwent SLNB. The preoperative study included freehand SPECT imaging at 15min after injection and LS imaging at 25 and 60-90min after injection (early and late). The observed agreement was analyzed and a concordance study was performed between the number of SNs detected with freehand SPECT and LS.

RESULTS

The observed agreement in the detection of SNs between freehand SPECT and early LS was 72%; between freehand SPECT and late LS was 85%; and between early and late LS was 87%. In the concordance study, there was moderate concordance between freehand SPECT and early LS (kappa coefficient: 0.42); moderate-high concordance between freehand SPECT and late LS (kappa coefficient: 0.60); and moderate-high concordance between early and late LS (kappa coefficient: 0.70), with no significant differences between them (p-value=0.16).

CONCLUSION

Freehand SPECT showed a moderate-high concordance with conventional imaging studies and could be a valid alternative for the presurgical study of SLNB in breast cancer.

Intraoperative freehand SPECT as an alternative imaging technique for use in radioguided parathyroidectomy

Freehand single photon emission computed tomography (fhSPECT) is a technique that is used to monitor body's radioactivity intraoperatively. Accordingly, in this study, the feasibility of using fhSPECT for intraoperative 3D mapping in radioguided parathyroidectomy has been assessed. Patients, who were diagnosed with primary hyperparathyroidism consecutively, were scanned intraoperatively using fhSPECT to locate parathyroid adenomas before surgical procedure. The fhSPECT images were acquired intraoperatively using a declipse^®SPECT device (SurgicEye^TM). The fhSPECT protocol could not be completed due to the technical problems in one patient. Parathyroid adenoma was located in the first patient with no lateral deviation. Nevertheless, a deviation of 8 mm was detected in the depth of the parathyroid adenoma, which is the distance of parathyroid adenoma from the skin. A 20 mm lateral deviation and a 10 mm deviation in depth were detected in the second patient. In the third patient, as was the case in the first patient, parathyroid adenoma was located with no lateral deviation. However, there was a 15 mm deviation in the depth of the parathyroid adenoma. A 5 mm lateral deviation was detected in the fourth patient yet with no deviation in the depth of parathyroid adenoma. Finally, neither lateral nor vertical deviation was detected in fifth patient. Based on the findings of this study, it was concluded that the fhSPECT technology can be helpful to a certain degree in locating the parathyroid adenoma. However, further studies are needed to support the findings of this preliminary study.

Evaluation of camera-based freehand SPECT in preoperative sentinel lymph node mapping for melanoma patients

BACKGROUND

Assessment of lymphatic status via sentinel lymph node (SLN) biopsy is an integral and crucial part of melanoma surgical oncology. The most common technique for sentinel node mapping is preoperative planar scintigraphy of an injected gamma-emitting lymphatic tracer followed by intraoperative node localization using a non-imaging gamma probe with auditory feedback. In recent years, intraoperative visualization of SLNs in 3D has become possible by coupling the probe to an external system capable of tracking its location and orientation as it is read out, thereby enabling computation of the 3D distribution of the tracer (freehand SPECT). In this project, the non-imaging probe of the fhSPECT system was replaced by a unique handheld gamma camera containing an array of sodium iodide crystals optically coupled to an array of silicon photomultipliers (SiPMs). A feasibility study was performed in which preoperative SLN mapping was performed using camera fhSPECT and the number of detected nodes was compared to that visualized by lymphoscintigraphy, probe fhSPECT, and to the number ultimately excised under non-imaging probe guidance.

RESULTS

Among five subjects, SLNs were detected in nine lymphatic basins, with one to five SLNs detected per basin. A basin-by-basin comparison showed that the number of SLNs detected using camera fhSPECT exceeded that using lymphoscintigraphy and probe fhSPECT in seven of nine basins and five of five basins, respectively. (Probe fhSPECT scans were not performed for four basins.) It exceeded the number excised under non-imaging probe guidance for seven of nine basins and equaled the number excised for the other two basins.

CONCLUSIONS

Freehand SPECT using a prototype SiPM-based gamma camera demonstrates high sensitivity for detection of SLNs in a preoperative setting. Camera fhSPECT is a potential means for efficiently obtaining real-time 3D activity distribution maps in applications such as image-guided percutaneous biopsy, and surgical SLN biopsy or radioguided tumor excision.

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.

Fusion of freehand SPECT and ultrasound: First experience in preoperative localization of sentinel lymph nodes

PURPOSE

Radioguided sentinel lymph node biopsy (SLNB) is the standard of care in breast cancer and melanoma. Additional preoperative Single-photon emission computed tomography (SPECT/CT) for improved anatomical co-registration of the SLNs causes additional radiation exposure and is time-consuming and expensive. The aim of this prospective study was to evaluate a novel approach involving real-time fusion of freehand SPECT (fhSPECT) and ultrasound (US) for anatomical co-registration of SLNs.

METHODS

From February 2015 to February 2016, 153 patients were included in this prospective study. All patients underwent lymphoscintigraphy according to practical guidelines and 151 (118 cases of breast cancer, 30 cutaneous malignancies, and three cases of vulvar cancer) of the 153 patients were additionally investigated with fhSPECT-US. FhSPECT connected to a hand-held gamma detector generates three-dimensional images of the radioactivity distribution in the scanned area. For co-registration and real-time fusion of fhSPECT and subsequently performed US, an infrared stereo tracking system was used.

RESULTS

In all patients an SLN was found on lymphoscintigraphy, and the fhSPECT detected corresponding hotspots in all but one patient. In 72 % of patients and 73 % of lymph node basins, real-time anatomical co-registration with US was feasible. The rate of success in achieving good co-registration increased from 60 to 75 % after training by a radiologist specialized in breast imaging. A higher co-registration rate (78 %) was observed in patients with only one SLN than in those with two SLNs (68 %) or three or more SLNs (0 %).

CONCLUSIONS

Real-time fusion of fhSPECT and US for preoperative anatomical co-registration of SLNs is feasible. However, before this approach can completely replace preoperative lymphatic imaging, further technical developments are needed.

[Initial experience in intraoperative radiolocalization of the parathyroid adenoma with freehand SPECT and comparative assessment with portable gamma-camera]

Initial experience is presented by using freehand SPECT in the intraoperative radiolocalization of a parathyroid adenoma in 2 patients, one which was mediastinal. There is only one previous publication including 3 patients with parathyroid adenomas in usual parathyroid localizations. We also report for the first time a comparative assessment of results with portable gammacamera during the same surgery. In the operating room, we obtained images with portable gamma-camera and 3 D reconstruction with freehand SPECT from 15 min after iv injection of 5 mCi of (99m)Tc-MIBI. Both devices enabled the 2 adenomas to be detected intraoperatively, as well as checking activity of the excised gland and absence of significant uptake in surgical bed, with confirmation by intraoperative pre-postsurgical PTH levels, pathology and clinical follow-up for 10 months. Both devices accurately located the parathyroid adenomas intraoperatively, as well as confirmation of their extirpation, but freehand SPECT provided additional information of adenoma depth (mm) from the skin border, very useful for minimally invasive radio-guided surgery.

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.

First Experiences with Navigated Radio-Guided Surgery Using Freehand SPECT

Background

Sentinel lymph node biopsy (SLNB) in melanoma using one-dimensional gamma probes is a standard of care worldwide. Reports on the performance are claimed by most groups to successfully detect the SLNs during the surgical procedure in almost 100% of the patients. In clinical practice, however, several issues remain which are usually not addressed: the difficulty of intraoperative detection of deeply located nodes, SLN detection in obese patients or in the groin and the impossibility to make a scan of the entire wound after SLN resection to avoid false negative testing for eventually remaining SLNs.

Materials and Methods

The concept behind freehand SPECT is to combine a gamma probe as used for conventional radio-guided surgery with a tracking system as used in neurosurgical navigation. From this combination and a proper algorithm framework the 3D reconstruction of radioactivity distributions and displaying these intraoperatively is possible.

Conclusion

In summary, the feasibility of freehand SPECT could be shown and provides an image-guided SLNB and a truly minimally invasive and optimized surgical procedure.