Radioguided Parathyroidectomy with Portable Mini Gamma-Camera for the Treatment of Primary Hyperparathyroidism

Seracam: characterisation of a new small field of view hybrid gamma camera for nuclear medicine

BACKGROUND

Portable gamma cameras are being developed for nuclear medicine procedures such as thyroid scintigraphy. This article introduces Seracam® - a new technology that combines small field of view gamma imaging with optical imaging - and reports its performance and suitability for small organ imaging.

METHODS

The count rate capability, uniformity, spatial resolution, and sensitivity for 99mTc are reported for four integrated pinhole collimators of nominal sizes of 1 mm, 2 mm, 3 mm and 5 mm. Characterisation methodology is based on NEMA guidelines, with some adjustments necessitated by camera design. Two diagnostic scenarios - thyroid scintigraphy and gastric emptying - are simulated using clinically relevant activities and geometries to investigate application-specific performance. A qualitative assessment of the potential benefits and disadvantages of Seracam is also provided.

RESULTS

Seracam's performance across the measured characteristics is appropriate for small field of view applications in nuclear medicine. At an imaging distance of 50 mm, corresponding to a field of view of 77.6 mm × 77.6 mm, spatial resolution ranged from 4.6 mm to 26 mm and sensitivity from 3.6 cps/MBq to 52.2 cps/MBq, depending on the collimator chosen. Results from the clinical simulations were particularly promising despite the challenging scenarios investigated. The optimal collimator choice was strongly application dependent, with gastric emptying relying on the higher sensitivity of the 5 mm pinhole whereas thyroid imaging benefitted from the enhanced spatial resolution of the 1 mm pinhole. Signal to noise ratio in images was improved by pixel binning. Seracam has lower measured sensitivity when compared to a traditional large field of view gamma camera, for the simulated applications this is balanced by advantages such as high spatial resolution, portability, ease of use and real time gamma-optical image fusion and display.

CONCLUSION

The results show that Seracam has appropriate performance for small organ 99mTc imaging. The results also show that the performance of small field of view systems must be considered holistically and in clinically appropriate scenarios.

Intraoperative Gamma Cameras: A Review of Development in the Last Decade and Future Outlook

Portable gamma cameras suitable for intraoperative imaging are in active development and testing. These cameras utilise a range of collimation, detection, and readout architectures, each of which can have significant and interacting impacts on the performance of the system as a whole. In this review, we provide an analysis of intraoperative gamma camera development over the past decade. The designs and performance of 17 imaging systems are compared in depth. We discuss where recent technological developments have had the greatest impact, identify emerging technological and scientific requirements, and predict future research directions. This is a comprehensive review of the current and emerging state-of-the-art as more devices enter clinical practice.

Radio-guided procedure in minimally invasive surgery for primary hyperparathyroidism

Minimally invasive parathyroidectomy, of choice in most cases of primary hyperparathyroidism, shows a high detection rate, based on precise preoperative localization by MIBI scintigraphy (SPECT/CT) and neck ultrasound. Radioguided minimally invasive parathyroidectomy is an even more effective technique, which shortens surgical times, maintains minimal incision and few complications, allows immediate verification of parathyroid adenoma removal and is especially interesting in patients with ectopic lesions or cervical surgical history. In this paper, the indications, protocols and differences between the two available radioguided parathyroid surgery procedures (MIBI and R.O.L.L.) are exposed.

IS CONFIRMATION OF PARATHYROID TISSUE BY FROZEN SECTION SUPERIOR TO LOCALIZATION OF SOLITARY PARATHYROID ADENOMA USING INTRAOPERATIVE GAMMA PROBE SURVEY? A RETROSPECTIVE COHORT STUDY

Context

In the surgical treatment of primary hyperparathyroidism, intraoperative localization of the diseased glands is an essential issue. We aimed to evaluate the impact of the intraoperative frozen section during radio-guided focused parathyroidectomy and compare its efficiency with intraoperative gamma probe survey and measurement of intraoperative quick parathyroid hormone.

Methods

All consecutive patients underwent radio-guided focused parathyroidectomy for primary hyperparathyroidism due to solitary parathyroid adenoma. The outcomes of parathyroidectomy were evaluated by serum levels of calcium and parathyroid hormone. The primary outcome was the surgical cure diagnosed by normal serum calcium levels in the sixth postoperative month.

Results

A total of 55 patients with a mean age of 54.3±12.2 years were evaluated. The diagnostic accuracy of the preoperative localization tests was calculated as 92.7%. The intraoperative gamma probe survey impacted the operative plans of four patients (7.3%) by localizing the diseased gland in other positions. The accuracy of intraoperative quick parathyroid hormone and frozen section analysis was 100% for both. In all patients, serum calcium and PTH levels dropped to normal in the sixth postoperative month. There were no cases of the persistent or recurrent disease during the follow-up period.

Conclusion

The results of the intraoperative gamma probe survey, intraoperative quick parathyroid hormone, and frozen section were concordant with the final pathology in all cases. In four patients (7.3%), intraoperative gamma probe survey impacted the operative plans. The intraoperative gamma probe survey may be used as the sole intraoperative method to locate the correct position of the solitary parathyroid adenoma.

Utility of intraoperative digital scintigraphy in radioguided parathyroidectomy

BACKGROUND

Intraoperative scintigraphy (IoS) has been proposed as a tool for real-time intraoperative decision-making regarding parathyroid adenoma localization and confirmation of excision.

METHODS

Retrospective review of patients who underwent minimally invasive parathyroidectomies with scintigraphy performed intraoperatively. Preoperative neck ultrasound, 4D computed tomography, as well as intraoperative parathyroid hormone (IOPTH) and gamma probe measurements were conducted per standard practice. IoS images were obtained prior to and following parathyroid excision. Cases were reviewed to determine accuracy of IoS for localizing parathyroid pathology and confirming successful excision.

RESULTS

Fifty-six cases met the inclusion criteria. Twenty-nine patients (51.8%) showed confirmation of excision of an abnormal gland on post-excision IoS. There were no significant differences in IOPTH reduction and postoperative laboratory values between patients with IoS-identified resolution and those without IoS-identified resolution.

CONCLUSIONS

With low accuracy in correctly localizing abnormal glands and confirming their excision, there is no appreciable benefit of IoS at this time.

Radioguided surgery in primary hyperparathyroidism: a review of the different available techniques

Parathyroidectomy has evolved over the years from bilateral neck exploration to a single gland approach using minimally invasive surgery. The precise presurgical localization of the problem gland, using functional techniques, such as double-phase scintigraphy with [^99mTc] Tc-MIBI including SPECT-CT and PET-CT with [¹⁸F]-Choline and morphological ones, such as ultrasound have played a crucial role in this paradigm's shift. Radioguided surgery techniques have also adapted and grown with new contributions known for their indication in other fields. Thus, we currently have a wide range of techniques that have been added to the minimally invasive radioguided parathyroidectomy with [^99mTc] Tc-MIBI, which was the first on the stage and for which more experience exists. Among them, in this update, we will discuss parathyroidectomy using ultrasound-guided ROLL technique as well as with the use of ¹²⁵I seeds and finally, hybrid techniques that use radiotracer and fluorescence.

λ-Eye: a high-sensitivity γ imaging probe for axillary sentinel lymph node mapping

OBJECTIVE

The aim of this study is the construction and performance evaluation of 'λ-eye', a γ imaging probe, optimized in terms of sensitivity for sentinel lymph node mapping. The optimization of the probe is based on theoretical models and simulation results that were presented in a previous study of our group. In this work, the construction of the probe, the experimental confirmation of the simulation results, and the evaluation of its performance with phantoms and lymph node imaging in small animals are presented.

METHODS

The system's spatial and energy resolution, sensitivity, and count rate performance were measured using phantoms. The values of the integral and differential uniformity in the useful field-of-view and in the central field-of-view were also calculated. Finally, a proof-of-concept animal experiment was conducted for the imaging of the lymph nodes of normal mice.

RESULTS

The system's energy resolution was measured as 36±2% and the spatial resolution was 2.2 mm at 2 mm source-collimator distance. The values of the integral uniformity and differential uniformity in the useful field-of-view and in the central field-of-view were found to be 5.2, 2.1, 1.7, and 0.75%, respectively. Finally, the lymph nodes of normal mice were clearly imaged with a 10 s acquisition time.

CONCLUSION

The 'λ-eye', used for sentinel lymph node mapping, provides a combination of high sensitivity (∼1.5 counts/s/kBq) and good spatial resolution (∼6 mm full-width of the half-maximum at 20 mm and ∼10 mm full-width of the half-maximum at 50 mm distance). Its compact size (40 mm×40 mm×70 mm) allows its use during surgery and/or for the detailed scan of a suspicious region.