99mTc-tetrofosmin or 99mTc-sestamibi for double-phase parathyroid scintigraphy?

Parathyroid Imaging

Primary hyperparathyroidism (1° HPT) is a relatively common endocrine disorder usually caused by autonomous secretion of parathormone by one or several parathyroid adenomas. 1° HPT causing hypercalcemia, kidney stones and/or osteoporosis should be treated whenever possible by parathyroidectomy. Accurate preoperative location of parathyroid adenomas is crucial for surgery planning, mostly when performing minimally invasive surgery. Cervical ultrasonography (US) is usually performed to localize parathyroid adenomas as a first intention, followed by 99mTc- sestamibi scintigraphy with SPECT/CT whenever possible. 4D-CT is a possible alternative to 99mTc- sestamibi scintigraphy. Recently, 18F-fluorocholine positron emission tomography/computed tomography (18F-FCH PET/CT) has made its way in the clinics as it is the most sensitive method for parathyroid adenoma detection. It can eventually be combined to 4D-CT to increase its diagnostic performance, although this results in higher dose exposure to the patient. Other forms of hyperparathyroidism consist in secondary (2° HPT) and tertiary hyperparathyroidism (3° HPT). As parathyroidectomy is not usually part of the management of patients with 2° HPT, parathyroid imaging is not routinely performed in these patients. In patients with 3° HPT, total or subtotal parathyroidectomy is often performed. Localization of hyperfunctional glands is an important aid to surgery planning. As 18F-FCH PET/CT is the most sensitive modality in multigland disease, it is the preferred imaging technic in 3° HPT patients, although its cost and availability may limit its widespread use in this setting.

Nuclear Medicine Methods for Evaluation of Abnormal Parathyroid Glands in Patients with Primary and Secondary Hyperparathyroidism

Considered rare disease in the past, primary hyperparathyroidism (PHPT) has dramatically increased in incidence over the past thirty years with the introduction of routine calcium measurements; it is now approximately 42 per 100 000 persons. By far, the most common lesion found in patients with PHPT is the solitary parathyroid adenoma, occurring in 85%-90% of patients, while in the rest 10%- 15% primary hyperplasia of the parathyroid glands is present. Currently, the most widely used surgical approach is minimally invasive parathyroidectomy which is associated with less post-surgery complications and shorter operation time. To be successful this procedure needs to rely on a precise preoperative localization of the abnormal parathyroid glands, hence preoperative parathyroid imaging gained so large importance. The rationale for locating abnormal parathyroid tissue prior to surgery is that the glands can be notoriously unpredictable in their location. There is a general consensus that the best imaging procedure identifying abnormal parathyroid glands is the preoperative scintigraphy with 99mTc-sestamibi or 99mTc-tetrofosmin. It is characterized with high sensitivity and specificity exceeding those of ultrasound, CT or MRI. Combining scintigraphy with the other imaging techniques increases the precision for topic localization.

Primary hyperparathyroidism: imaging to pathology

The aim of this review is to describe the multimodal imaging (ultrasound, magnetic resonance, computed tomography, and nuclear medicine) of primary hyperparathyroidism and its correlation to the pathological findings. In the last decades, imaging science has progressed a great deal. Accurate preoperative localization of the involved glands is essential for surgical success.

Imaging of parathyroid glands

Preoperative imaging studies have an important role in facilitating successful localization of adenomas for surgeons. Their use has increased and parallels the recent growth of minimally invasive parathyroidectomy. Based on findings that scintigraphy is reported to have the highest accuracy for localization of adenomas when compared with anatomic imaging techniques, this article discusses the current role and limitations of imaging, with a focus on scintigraphy, in the evaluation of patients before surgery for hyperparathyroidism.

PET and Parathyroid

In parathyroid disease, classical scintigraphic techniques remain the first choice for localizing hyperfunctional parathyroid glands in primary known hyperparathyroidism and in case of secondary, tertiary, and recurrent hyperparathyroidism. When classical scintigraphic techniques are not diagnostic, however, (11)C-methionine seems to offer a good imaging alternative.

Scintigraphic techniques in primary hyperparathyroidism: from pre-operative localisation to intra-operative imaging

INTRODUCTION

Primary hyperparathyroidism (PHPT) is an increasingly diagnosed disease worldwide. In most cases, PHPT is related to the presence of a solitary parathyroid adenoma (PA). Fifty percent or more of newly diagnosed PHPT patients are asymptomatic, and there is debate among endocrinologists and endocrine surgeons about whether or not such patients should be treated.

LOCALIZATION

Usually, in a PHPT patient with a solitary PA that is well localised pre-operatively, a parathyroidectomy with limited or minimally invasive neck exploration is offered. The diffusion of minimally invasive neck exploration procedures is a consequence of the significant improvement in the accuracy of pre-operative imaging (mainly scintigraphic) techniques; these techniques have changed the surgical strategy to PHPT, from the wide traditional bilateral neck exploration to limited neck exploration.

REVIEW

The present review considers developments during the past 10-15 years with regard to both the accuracy of pre-operative localising imaging techniques and intra-operative minimally invasive procedures in order to provide endocrinologists and endocrine surgeons with further information about the newly available diagnostic and therapeutic tools for use in PHPT patients with a solitary PA.

Parathyroid imaging: how good is it and how should it be done?

Hypersecretion of parathormone in primary hyperparathyroidism is common, occurring in approximately 1 in 500 women and 1 in 2,000 men per year in their fifth to seventh decades of life. This has been suggested from the literature to be primarily the result of a parathyroid adenoma (80-85% of cases), hyperplasia involving more than 1 gland, usually with all 4 glands being involved (10-15% of cases), or the result, albeit rarely, of parathyroid carcinoma (0.5-1% of cases). Surgical removal of the hypersecreting gland is the primary treatment; this procedure is best performed by a skilled surgeon who would normally find the abnormality in 95% of cases. Imaging, however, should be used to identify the site of abnormality, potentially reducing inpatient stay and improving the patient experience. Functional imaging of parathyroid tissue using thallium was introduced in the 1980s but has largely been superceded by the use of (99m)Tc-labeled isonitriles. The optimum techniques have used (99m)Tc-sestamibi with subtraction imaging or washout imaging. A recent systematic review reported the percentage sensitivity (95% confidence intervals) for sestamibi in the identification of solitary adenomas as 88.44 (87.48-89.40), multigland hyperplasia 44.46 (41.13-47.8), double adenomas 29.95 (-2.19 to 62.09), and carcinoma 33 (33). This review does not separate the washout and subtraction techniques. The subtraction technique using (99m)Tc-sestamibi and (123)I is the optimal technique enabling the site to be related to the thyroid tissue when the parathyroid gland is in the neck in a normal position. If there is an equivocal scan then confirmation with high resolution ultrasound should be used. With ectopic glands, the combined use of single-photon emission computed tomography may then provide anatomical information to enable localization of the functional abnormality. In patients who have had surgical exploration by an experienced parathyroid surgeon in a unit with an experienced nuclear medicine team and negative sestamibi imaging, it is reasonable to image the patient with (11)C methionine. It is debatable whether patients with a high likelihood of secondary hyperparathyroidism should be imaged. The only possible justification for this is to exclude an ectopic site. There is no substitute for an experienced surgeon and an experienced imaging unit to provide a parathyroid service.

Nonequivalent Results of Tetrofosmin and Sestamibi Imaging of Parathyroid Tumors

OBJECTIVE

To report the case of a patient with a large parathyroid carcinoma missed by dual-phase technetium Tc 99m tetrofosmin (TETRO) parathyroid scanning.

METHODS

We present the clinical findings, laboratory results, imaging studies, and surgical pathology report in a man with parathyroid carcinoma and review the literature regarding the use of TETRO scintigraphy in patients with hyperparathyroidism.

RESULTS

In an 83-year-old man with hyperparathyroidism, severe hypercalcemia developed in the context of nephrolithiasis. An in-office ultrasonographic evaluation of the neck revealed a partially calcified mass (2.3 by 1.3 by 1.6 cm) at the inferoposterior border of the left thyroid lobe. Technetium Tc 99m sestamibi (MIBI) scanning was requested and reported as "negative." In fact, TETRO scanning had been substituted for MIBI scanning by the management of the nuclear medicine facility. Before neck exploration, performance of dual-phase MIBI parathyroid scintigraphy revealed radionuclide retention in the left lower neck area at 120 minutes, in the same site as the ultrasonographically visualized mass. A limited left inferior parathyroidectomy was performed, and intraoperative parathyroid hormone levels declined from 254 pg/mL to 28 pg/mL 10 minutes after near-complete resection of the mass. Pathology evaluation of the surgical specimen revealed a 2,000-mg parathyroid carcinoma.

CONCLUSION

Although both agents incorporate the same technetium Tc 99m radionuclide, TETRO and MIBI parathyroid scanning are not equivalent in the detection of parathyroid tumors with use of the dual-phase technique. We do not recommend substitution of TETRO for MIBI as a cost-control measure in the evaluation of hyperparathyroidism.

Innovative Diagnostik in der Früherkennung und beim Staging des lokalisierten Prostatakarzinoms

Prostate cancer is the most common malignancy in males. Men aged 50 years and older are recommended to undergo an annual digital rectal examination (DRE) and determination of prostate-specific antigen (PSA) in serum for early detection. Fortunately, disease-specific mortality continues to decline as a result of advances in screening, staging, and patient awareness. However, about 30% of men with a clinically organ-confined disease show evidence of extracapsular extension or seminal vesicle invasion on pathological analysis. Consequently, there is a need for more accurate diagnostic tools for planning tailored treatment. A variety of modern imaging techniques has been implemented in an attempt to obtain more precise staging, thereby allowing for more detailed counseling, and instituting optimum therapy. This review highlights developments in prostate cancer imaging that may improve staging and treatment planning for prostate cancer patients.