Endocrine scintigraphy with hybrid SPECT/CT

Integration of molecular imaging in the personalized approach of patients with adrenal masses

Adrenal masses are a frequent finding in clinical practice. Many of them are incidentally discovered with a prevalence of 4% in patients undergoing abdominal anatomic imaging and require a differential diagnosis. Biochemical tests, evaluating hormonal production of both adrenal cortex and medulla (in particular, mineralocorticoids, glucocorticoids and catecholamines), have a primary importance in distinguishing functional or non-functional lesions. Conventional imaging techniques, in particular computerized tomography (CT) and magnetic resonance imaging (MRI), are required to differentiate between benign and malignant lesions according to their appearance (size stability, contrast enhanced CT and/or chemical shift on MRI). In selected patients, functional imaging is a non-invasive tool able to explore the metabolic pathways involved thus providing additional diagnostic information. Several single photon emission tomography (SPET) and positron emission tomography (PET) radiopharmaceuticals have been developed and are available, each of them suitable for studying specific pathological conditions. In functional masses causing hypersecreting diseases (mainly adrenal hypercortisolism, primary hyperaldosteronism and pheochromocytoma), functional imaging can lateralize the involvement and guide the therapeutic strategy in both unilateral and bilateral lesions. In non-functioning adrenal masses with inconclusive imaging findings at CT/MR, [¹⁸F]-FDG evaluation of tumor metabolism can be helpful to characterize them by distinguishing between benign nodules and primary malignant adrenal disease (mainly adrenocortical carcinoma), thus modulating the surgical approach. In oncologic patients, [¹⁸F]-FDG uptake can differentiate between benign nodule and adrenal metastasis from extra-adrenal primary malignancies.

Impacts of acquisition and reconstruction parameters on the absolute technetium quantification of the cadmium-zinc-telluride-based SPECT/CT system: a phantom study

Background

The digital cadmium–zinc–telluride (CZT)-based SPECT system has many advantages, including better spatial and energy resolution. However, the impacts of different acquisition and reconstruction parameters on CZT SPECT quantification might still need to be validated. This study aimed to evaluate the impacts of acquisition parameters (the main energy window and acquisition time per frame) and reconstruction parameters (the number of iterations, subsets in iterative reconstruction, post-filter, and image correction methods) on the technetium quantification of CZT SPECT/CT.

Methods

A phantom (PET NEMA/IEC image quality, USA) was filled with four target-to-background (T/B) ratios (32:1, 16:1, 8:1, and 4:1) of technetium. Mean uptake values (the calculated mean concentrations for spheres) were measured to evaluate the recovery coefficient (RC) changes under different acquisition and reconstruction parameters. The corresponding standard deviations of mean uptake values were also measured to evaluate the quantification error. Image quality was evaluated using the National Electrical Manufacturers Association (NEMA) NU 2–2012 standard.

Results

For all T/B ratios, significant correlations were found between iterations and RCs (r = 0.62–0.96 for 1–35 iterations, r = 0.94–0.99 for 35–90 iterations) as well as between the full width at half maximum (FWHM) of the Gaussian filter and RCs (r = − 0.86 to − 1.00, all P values < 0.05). The regression coefficients of 1–35 iterations were higher than those of 35–90 iterations (0.51–1.60 vs. 0.02–0.19). RCs calculated with AC (attenuation correction) + SC (scatter correction) + RR (resolution recovery correction) combination were more accurate (53.82–106.70%) than those calculated with other combinations (all P values < 0.05). No significant statistical differences (all P values > 0.05) were found between the 15% and 20% energy windows except for the 32:1 T/B ratio (P value = 0.023) or between the 10 s/frame and 120 s/frame acquisition times except for the 4:1 T/B ratio (P value = 0.015) in terms of RCs.

Conclusions

CZT-SPECT/CT of technetium resulted in good quantification accuracy. The favourable acquisition parameters might be a 15% energy window and 40 s/frame of acquisition time. The favourable reconstruction parameters might be 35 iterations, 20 subsets, the AC + SC + RR correction combination, and no filter.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40658-021-00412-4.

A Clinical Challenge: Endocrine and Imaging Investigations of Adrenal Masses

Incidentalomas are reported in 3%-4% of patients who undergo abdominal anatomic imaging, making adrenal mass evaluation a common occurrence. An adrenal mass can be caused by a variety of pathologies, such as benign cortical and medullary tumors, malignant tumors (primary or secondary), cysts, hyperplasia, hemorrhage, or more rarely infection/inflammation processes. Functioning tumors usually have increased hormonal production but they are less common. Regardless of their functional status, some tumors have the potential to behave aggressively. Anatomic and functional imaging together with biologic evaluation play a vital role in adrenal pathology subtyping. Most patients are initially evaluated by CT or MRI, which allows for tumor characterization (to a certain extent) and can rule out malignant behavior based on the absence of tumor growth during longitudinal follow-up. In the remaining patients for whom CT or MRI fail to characterize the pathogenesis of adrenal tumors, the use of specialized molecular imaging techniques should be performed after hormonal screening. This review emphasizes well-established and emerging nuclear medicine imaging modalities and describes their use across various clinical scenarios.

Deep learning enables automated localization of the metastatic lymph node for thyroid cancer on 131I post-ablation whole-body planar scans

The accurate detection of radioactive iodine-avid lymph node (LN) metastasis on 131I post-ablation whole-body planar scans (RxWBSs) is important in tracking the progression of the metastatic lymph nodes (mLNs) of patients with papillary thyroid cancer (PTC). However, severe noise artifacts and the indiscernible location of the mLN from adjacent tissues with similar gray-scale values make clinical decisions extremely challenging. This study aims (i) to develop a multilayer fully connected deep network (MFDN) for the automatic recognition of mLNs from thyroid remnant tissue by utilizing the dataset of RxWBSs and (ii) to evaluate its diagnostic performance using post-ablation single-photon emission computed tomography. Image patches focused on the mLN and remnant tissues along with their variations of probability of pixel positions were fed as inputs to the network. With this efficient automatic approach, we achieved a high F1-score and outperformed the physician score (P < 0.001) in detecting mLNs. Competitive segmentation networks on RxWBS displayed moderate performance for the mLN but remained robust for the remnant tissue. Our results demonstrated that the generalization performance with the multiple layers by replicating signal transmission overcome the constraint of local minimum optimization, it can be suitable to localize the unstable location of mLN region on RxWBS and therefore MFDN can be useful in clinical decision-making to track mLN progression for PTC.

Utility of surgeon-performed pre-operative ultrasound in the localisation of parathyroid adenomas

Background

Primary hyperparathyroidism arising from parathyroid adenoma is one of the most common endocrine disorders treated by endocrine surgeons. The adenoma is commonly identified by imaging techniques. The present study evaluated the performance of a portable ultrasound machine (Sonosite MicroMaxx) operated by a surgeon, departmental ultrasound and ^99mTc-sestamibi-SPECT/CT by a radiologist in the identification of parathyroid adenomas.

Methods

Patient case notes were retrieved from medical records and imaging from picture archiving and communication system over the period from 2006 to 2012. ^99mTc-sestamibi-SPECT/CT and departmental ultrasound images were reported by a nuclear radiologist. The ability of each imaging technique in localising parathyroid adenomas was referenced against the actual adenomas identified from parathyroidectomy.

Results

With reference to the actual site of the lesion, surgeon-performed ultrasound accurately localised the site of the lesion in 30/33 (90.1%) of cases with a sensitivity of 86.7%, departmental ultrasound accurately localised the site of the lesion in 21/26 (80.1%) of cases with a sensitivity of 79.2%. In 6/75 patients where ^99mTc-sestamibi-SPECT/CT did not localise the lesion, departmental ultrasound did not localise any lesions correctly, while surgeon-performed ultrasound successfully located the adenoma in three (50%) of these six patients. Patients whose parathyroid adenomas identified by the surgeon were more likely to have shorter length of stay in hospital: odds ratio = 0.53 (95% confidence interval = 0.30-0.92, p = 0.025).

Conclusions

Surgeon-performed ultrasound for immediately pre-operative localisation improves identification of parathyroid adenomas and reduces length of stay in hospital, lending support for the use of this technique by endocrine surgeons.

Surgical outcomes of patients with primary aldosteronism lateralized with I-131-6 β-iodomethyl-norcholesterol single photon emission/computed tomography without discontinuation or modification of antihypertensive medications

Objectives

Adrenocortical scintigraphy for patients with primary aldosteronism (PA) without discontinuation or modification of antihypertensive medications is of concern because of drug interference with the renin-angiotensin-aldosterone system. We report the surgical outcomes of patients with PA lateralized with adrenocortical scintigraphy without drug discontinuation or modification.

Materials and Methods

We retrospectively reviewed 34 patients with PA with computed tomography (CT)-documented adrenal tumors who had undergoing subsequent I-131-6 β-iodomethyl-norcholesterol (NP-59) single photon emission CT (SPECT)/CT followed by unilateral adrenalectomy according to the results of NP-59 uptake between May 2005 and December 2014. All enrolled patients underwent standard confirmatory tests and lateralization with NP-59 SPECT/CT without discontinuation of existing antihypertensive medications, including spironolactone. The pathological findings, hypertension outcomes, and biochemical changes were reported. The accuracy of NP-59 SPECT/CT without drug discontinuation or modification was also evaluated.

Results

None of the 34 enrolled patients (M:F = 16:18) had complications such as a hypertensive crisis, life-threatening hypokalemic event, or cardiac arrhythmia. Pathology disclosed 31 (91%) adenomas and three cases of hyperplasia. Hypertension cure and improvement were observed in 12 (35%) and 18 (53%) patients, respectively. All of the 30 patients (100%) without postoperative use of beta-blockers and with an available postoperative aldosterone/renin ratio achieved a biochemical cure. The positive predictive values of NP-59 SPECT/CT were 91%, 88%, and 100% for the pathological findings, hypertension outcomes, and biochemical changes, respectively.

Conclusion

Noninvasive NP-59 SPECT/CT without discontinuation or modification of antihypertensive medications not only provided accurate lateralization and safety but also resulted in a high improvement rate for PA-associated hypertension.

Hybrid-fusion SPECT/CT systems in parathyroid adenoma: Technological improvements and added clinical diagnostic value

Nuclear medicine traditionally employs planar and single photon emission computed tomography (SPECT) imaging techniques to depict the biodistribution of radiotracers for the diagnostic investigation of a range of disorders of endocrine gland function. The usefulness of combining functional information with anatomy derived from computed tomography (CT), magnetic resonance imaging (MRI), and high resolution ultrasound (US), has long been appreciated, either using visual side-by-side correlation, or software-based co-registration. The emergence of hybrid SPECT/CT camera technology now allows the simultaneous acquisition of combined multi-modality imaging, with seamless fusion of 3D volume datasets. Thus, it is not surprising that there is growing literature describing the many advantages that contemporary SPECT/CT technology brings to radionuclide investigation of endocrine disorders, showing potential advantages for the pre-operative locating of the parathyroid adenoma using a minimally invasive surgical approach, especially in the presence of ectopic glands and in multiglandular disease. In conclusion, hybrid SPECT/CT imaging has become an essential tool to ensure the most accurate diagnostic in the management of patients with hyperparathyroidism.

Endocrine radionuclide scintigraphy with fusion single photon emission computed tomography/computed tomography

AIM: To review the benefits of single photon emission computed tomography (SPECT)/computed tomography (CT) hybrid imaging for diagnosis of various endocrine disorders.

METHODS: We performed MEDLINE and PubMed searches using the terms: “SPECT/CT”; “functional anatomic mapping”; “transmission emission tomography”; “parathyroid adenoma”; “thyroid cancer”; “neuroendocrine tumor”; “adrenal”; “pheochromocytoma”; “paraganglioma”; in order to identify relevant articles published in English during the years 2003 to 2015. Reference lists from the articles were reviewed to identify additional pertinent articles. Retrieved manuscripts (case reports, reviews, meta-analyses and abstracts) concerning the application of SPECT/CT to endocrine imaging were analyzed to provide a descriptive synthesis of the utility of this technology.

RESULTS: The emergence of hybrid SPECT/CT camera technology now allows simultaneous acquisition of combined multi-modality imaging, with seamless fusion of three-dimensional volume datasets. The usefulness of combining functional information to depict the bio-distribution of radiotracers that map cellular processes of the endocrine system and tumors of endocrine origin, with anatomy derived from CT, has improved the diagnostic capability of scintigraphy for a range of disorders of endocrine gland function. The literature describes benefits of SPECT/CT for ^99mTc-sestamibi parathyroid scintigraphy and ^99mTc-pertechnetate thyroid scintigraphy, ¹²³I- or ¹³¹I-radioiodine for staging of differentiated thyroid carcinoma, ¹¹¹In- and ^99mTc- labeled somatostatin receptor analogues for detection of neuroendocrine tumors, ¹³¹I-norcholesterol (NP-59) scans for assessment of adrenal cortical hyperfunction, and ¹²³I- or ¹³¹I-metaiodobenzylguanidine imaging for evaluation of pheochromocytoma and paraganglioma.

CONCLUSION: SPECT/CT exploits the synergism between the functional information from radiopharmaceutical imaging and anatomy from CT, translating to improved diagnostic accuracy and meaningful impact on patient care.