Radioguided Surgery of Primary Hyperparathyroidism Using the Low-Dose 99mTc-Sestamibi Protocol: Multiinstitutional Experience from the Italian Study Group on Radioguided Surgery and Immunoscintigraphy (GISCRIS)

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FIGURE 1.
Distribution of patients according to main factors affecting choice of surgical approach. BNE = bilateral neck exploration; T = thyroid; PT = parathyroid; MIBI = ^99mTc-sestamibi.

TABLE 1

Preoperative Imaging Modalities Used on 384 Patients with Primary Hyperparathyroidism

Modality	Patients
Modality		n	%
Double-tracer ^99mTc-pertechnetate/^99mTc-sestamibi subtraction scanning (planar) and ultrasonography	240	62.5
Double-tracer ^99mTc-pertechnetate/^99mTc-sestamibi subtraction scanning (planar + SPECT) and ultrasonography	53	13.8
Total double-tracer subtraction scanning and ultrasonography	293	76.3
Single-tracer ^99mTc-sestamibi dual-phase scanning (planar) and ultrasonography	37	9.6
Single-tracer ^99mTc-sestamibi dual-phase scanning (planar + SPECT) and ultrasonography	54	14.1
Total single-tracer dual-phase scanning and ultrasonography*	91	23.7
CT^†	36	9.3
MRI^†	53	13.8

↵* All patients imaged by dual-phase ^99mTc-sestamibi scintigraphy also underwent ^99mTc-pertechnetate scanning for evaluation of possible concomitant thyroid nodule disease.
↵^† CT and MRI were performed after scintigraphic and ultrasound examination, mainly on patients with ectopic PAs or previous neck surgery.
Selective venous blood sampling for assay of parathyroid hormone levels was performed on only 1 patient; arteriography, on none.

TABLE 2

MIRS Protocol of the Present Study

Step	Description
A	Antecubital venous blood sampling both before surgery and 10 min after PA removal, for IQPTH.
B	Intravenous injection of ^99mTc-sestamibi (37–110 MBq, or 1–3 mCi: 37 MBq in 79% of patients, 74 MBq in 13%, and 110 MBq in 8%) in operating theater 10–30 min before surgery.
C	Before surgical incision, external γ-probe scanning to identify area with maximum count activity (cutaneous projection of PA).
D	Surgical access either in midline of neck (approximately 1 cm above sternal notch) or in lateral neck (anterior border of sternocleidomastoid muscle), depending on each surgeon’s experience and convenience.
E	Repeated insertion of γ-probe through a 2- to 2.5-cm skin incision, guiding surgeon to area with maximum count activity, corresponding to PA (ligature of middle thyroid vein and inferior thyroid artery was necessary in some patients with PA deep in neck).
F	γ-Probe measurement of radioactivity count rate on PA, thyroid gland, and background.
G	γ-Probe measurement of radioactivity count rate on ex vivo PA to evaluate success of parathyroid tissue removal.
H	γ-Probe scanning of surgical bed to evaluate completeness of parathyroid tissue removal.
I	Calculation of γ-probe count-rate ratios for various tissues.