Parathyroid Imaging With Pertechnetate Plus Perchlorate/MIBI Subtraction Scintigraphy

Abstract

We set up a modified technetium-99m (Tc-99m) pertechnetate/Tc-99m MIBI (Tc-MIBI) subtraction scintigraphy for parathyroid imaging by introducing the use of potassium perchlorate (KCLO4). Initially, the effect of KCLO4 on technetium thyroid wash-out was evaluated in five healthy volunteers: 40-minute dynamic studies of the thyroid were obtained 20 minutes after the injection of technetium 150 MBq (4 mCi), both in baseline conditions and after the oral administration of 400 mg KCLO4. After an average latency time of 10.5 minutes, KCLO4 administration resulted in fast and relevant technetium thyroid wash-out with a mean half-time of 16.2 minutes (the half-time was 142.8 minutes in baseline conditions), and a 40-minute reduction of thyroid activity of 78% (it was 14% in baseline conditions). Based on these findings, a new Tc-MIBI subtraction procedure was established as follows: 1) 150 MBq technetium (4 mCi) injection; 2) 400 mg KCLO4 administered orally; 3) patient neck immobilization; 4) acquisition of a 5-minute technetium thyroid scan; 5) 500 MBq MIBI (13.5 mCi) injection; 6) acquisition of a sequence of seven MIBI images, each lasting 5 minutes; and 7) processing (image realignment when necessary, background subtraction, normalization of MIBI images to the maximum pixel count of the technetium image, and subtraction of the technetium image from the MIBI images). In addition, high-resolution neck ultrasound (US) was performed in all cases on the same day as the scintigraphic evaluation. Eighteen consecutive patients with primary hyperparathyroidism were enrolled in the study. Tc-MIBI scintigraphy revealed a single adenoma in all cases and US showed this finding in 15 of 18 cases (83.3%). Furthermore, in three patients, a thyroid nodule associated with hyperparathyroidism was detected by technetium thyroid scans and neck US. In all patients, the parathyroid adenoma was easily identified on both the 20- to 40-minute MIBI and subtracted (MIBI-Tc) images. Regarding the scintigraphic parameters, no difference was found between parathyroid adenomas located in the region of the thyroid bed or in ectopic sites and in parathyroid adenomas with a retrothyroid location. Surgical findings confirmed the presence of a single parathyroid adenoma in all cases. In the three patients with a concomitant thyroid nodule, thyroid lobectomy was performed. These preliminary data suggest that 1) double-tracer subtraction scintigraphy, combined with neck US, appears to be the preferable preoperative imaging procedure in hyperparathyroidism patients with concomitant thyroid nodular disease, 2) in the Tc-MIBI parathyroid scan, the use of KCLO4 results in a rapid and relevant technetium thyroid clearance, improving the quality of MIBI images and making the visualization of parathyroid adenomas, particularly those located behind the thyroid gland, easier.

Less Invasive Surgery for Primary Hyperparathyroidism Based on Preoperative 99m Tc-hexakis-2-methoxyisobutylisonitrile Imaging Findings

“…18 However, other investigators have reported that this issue can be solved by combining MIBI scintigraphy with 123 I or 99m Tc-pertechnetate, which is a specific tracer for the thyroid node. 19,20 In our study, no falsepositive results due to nodular lesion of the thyroid gland were obtained when combining MIBI scintigraphy with neck US.…”

Role of gamma probes in performing minimally invasive parathyroidectomy in patients with primary hyperparathyroidism: optimization of preoperative and intraoperative procedures

“…For this reason the double-tracer scan is usually preferred in geographic areas with a high prevalence of nodular goiter (21,23). We utilize a double-tracer subtraction scintigraphy using 99m Tc-pertechnetate as a thyroid agent, which is significantly cheaper than 123 I (14). Moreover, a correlative ultrasound imaging is useful to differentiate thyroid from parathyroid enlargements (21,23).…”

“…The preoperative localizing imaging work-up consisted of a double-tracer 99m Tc-pertechnetate/MIBI subtraction scan combined with high-resolution neck ultrasound (14). In cases of congruent scan/ultrasound results (both positive or negative) imaging was terminated, while in some cases of discrepancy (scan-positive and ultrasound-negative) for the presence of an enlarged parathyroid gland in the neck or with planar scintigraphy showing an ectopic parathyroid gland, the imaging protocol was completed by tomographic (single photon emission computed tomography (SPECT)) acquisition (n ¼ 36 patients) in order to better define the depth of the parathyroid enlargement.…”

“…Planar scintigraphy was performed using a technique developed in our center (14) and consisted of the following steps: acquisition -(i) 150 MBq 99m Tc-pertechnetate were injected i.v., (ii) 20 min later, 400 mg potassium perchlorate were orally administered, (iii) immediately after potassium perchlorate administration, the patient's neck was immobilized under the gamma camera and a 5 min thyroid scan was acquired, (iv) 550 MBq MIBI were injected i.v., followed by 30 ml saline with the aim of avoiding radiotracer stagnation, (v) a dynamic acquisition of seven 5 min MIBI scans was obtained; and processing -(vi) background activity was subtracted from 99m Tc-pertechnetate and MIBI scans, (vii) normalization of MIBI scans to the maximum pixel count activity of the 99m Tc-pertechnetate scan was performed, (viii) the 99m Tc-pertechnetate scan was subtracted from the MIBI scan (an interactive software program capable of subtracting incremental fractions of the 99m Tc-pertechnetate activity was utilized).…”

Nuclear medicine and minimally invasive surgery of parathyroid adenomas: a fair marriage

“…Second, the relatively low sensitivity of preoperative imaging observed by Bonjer et al [20] might have been related, at least in part, to the method used for scintigraphic acquisition, namely a dual-phase planar technique. A number of recent studies have demonstrated that the sensitivity of 99m Tc-MIBI scintigraphy in detecting parathyroid adenomas is 90% or higher when a dual-tracer technique or a dual-phase SPET technique is employed [17,21,22,23].…”