Double-phase parathyroid 99mTc-Sestamibi scintigraphy in chronic haemodialysis patients: correlation with biochemical markers of parathyroid function

99mTc-MIBI Uptake in a Benign Thymic Cyst

A 34-year-old man with end-stage renal failure status post rejection of a deceased donor kidney transplant presented with bone pain in the setting of elevated serum parathyroid hormone and calcium levels. A Tc-MIBI SPECT/CT was performed before planned subtotal parathyroidectomy. SPECT/CT imaging revealed a 1.9-cm anterior mediastinal lesion with radiotracer uptake on both the immediate and delayed images. Surgical pathology of the lesion showed a benign thymic cyst with no parathyroid component.

Advantages of pinhole collimator double-phase scintigraphy with 99mTc-MIBI in secondary hyperparathyroidism

PURPOSE

The aim of the study was to determine if pinhole collimator-acquired images can improve the detection of hyperfunctioning parathyroid glands in patients with secondary hyperparathyroidism.

METHODS

Forty-two patients being treated with cinacalcet for secondary hyperparathyroidism were studied prospectively. Patients were divided into 2 groups according to their levels of parathyroid hormone (PTH), the hormone that defines response to treatment: "responders" (PTH <300 pg/mL) and "nonresponders" (PTH ≥ 300 pg/mL). Double-phase scintigraphy using 888 MBq of (99m)Tc-MIBI was used to acquire early and late parallel-hole and pinhole collimator images. Neck ultrasonography was performed on all patients to identify intrathyroid nodules. All focal uptake in any of the acquired scintigraphic images was considered positive.

RESULTS

The responder group included 24 patients, whereas 18 patients were considered as nonresponders. At least 1 parathyroid gland with (99m)Tc-MIBI uptake was detected in 33 of 42 patients, with a total of 50 parathyroid glands located. We found significant differences between the detection rates of late pinhole collimator and the late parallel-hole images (74% vs 48%, P = 0.0036). This detection rate was highest with late parallel-hole images in the nonresponder group (89%).

CONCLUSIONS

The late pinhole collimator acquisition showed the highest detection rate of hyperfunctioning parathyroid glands using (99m)Tc-MIBI scintigraphy in secondary hyperparathyroidism patients treated with cinacalcet.

Dual-phase 99mTc-MIBI scintigraphy to assess calcimimetic effect in patients on haemodialysis with secondary hyperparathyroidism

OBJECTIVE

To evaluate the effect of calcimimetics with 99mTc-methoxy-isobutyl-isonitrile (MIBI) parathyroid scintigraphy in secondary hyperparathyroidism.

METHODS

This prospective study included 30 consecutive haemodialysis patients with inadequately controlled secondary hyperparathyroidism despite standard medical treatment. Patients were given a single daily oral dose of 30 mg of cinacalcet. A baseline and 1-year follow-up dual-phase 99mTc-MIBI scintigraphy were performed. 99mTc-MIBI uptake in each parathyroid gland was graded on a semiquantitative scale (scoring 0-3).

RESULTS

Twenty-one of the 30 patients responded to cinacalcet (70%). Abnormal positive glands were identified by 99mTc-MIBI scintigraphy in 27 out of 30 patients (53 glands). The sensitivity and specificity of 99mTc-MIBI in detecting cinacalcet response were 90 and 89%, respectively. The mean baseline and posttreatment grades of 99mTc-MIBI uptake were 2.9 ± 1.8 and 1.1 ± 1.2 (P < 0.0001) in the responder group and 3.1 ± 2.1 and 3.9 ± 2.2 (P = ns) in the nonresponder group.

CONCLUSION

99mTc-MIBI scintigraphy is useful in monitoring the response to calcimimetics in secondary hyperparathyroidism.

Determinants of Tc-99m sestamibi SPECT scan sensitivity in primary hyperparathyroidism

BACKGROUND

The aim of this study was to evaluate the influence of patient and adenoma characteristics on (99m)Tc-methoxy isobutyl isonitrile (MIBI) scan performance in individuals diagnosed with primary hyperparathyroidism (PHP).

METHODS

Records of patients undergoing parathyroidectomy for PHP over 6 years at a single center were reviewed.

RESULTS

The overall true-positive (TP) rate for (99m)Tc-MIBI scans was 56%. Adenomas sized 1.9 to 3.5 cm were more likely to have TP scans than 0.3-cm to 1.8-cm adenomas (74% vs 40%, P < .001). Preoperative ionized calcium levels between 1.49 and 1.72 mmol/L were more likely to have TPs than levels between 1.27 and 1.48 mmol/L (65% vs 47%, P < .05). No single class of medication was shown to significantly effect TP rates. A decrease in TP rate was observed for larger adenomas in patients on >or=1 medication (74% vs 65%, P = .05).

CONCLUSIONS

In PHP, (99m)Tc-MIBI scan positivity is most related to adenoma size and preoperative ionized calcium level.

Failed Switching off in the MIBI-Parathyroid Scintigraphy in a Dialyzed Patient with Secondary Hyperparathyroidism Responsive to Cinacalcet Therapy

The aims of your case report is to show the predictivity of (99m)Tc-sestamibi (MIBI) scintigraphy and doppler ultrasound imaging on secondary hyperparathyroidism (SHPT) in a patient responsive to calcimimetic treatment. Moreover, it has been reported that calcimimetic has great potential in reducing the volume of the parathyroid gland. On the other hand, the MIBI scintigraphy is considered a crucial diagnostic procedure to monitor the response to therapy in terms of turnover and cellular metabolism; whereas, ultrasound to monitor the volume variation in response to treatment. It is described the case of a 73-year-old man on hemodialysis from 1995 for ESRD. Within 2 years the patient gradually developed SHPT with progressively increased iPTH up to 1,000 rhog/ml. The ultrasound, highlighted the presence of two parathyroid hyperplasia, confirmed by scintigraphy, showing focal increase uptake of sestamibi in the same anatomical areas. As a result of the patient's refusal to perform a parathyroidectomy, cinacalcet, was administered (65 mg overage daily dose). After a year of treatment, there was a striking decrease of iPTH (from 1300 to 57 rhog/ml, -95%); but, on the contrary to expectations, this positive metabolic outcome, was not followed by parathyroid changes in ultrasound and scintigraphic findings.

Dobutamine modulated Tc-99m MIBI scintigraphy in secondary hyperparathyroidism in uremic patients

The aim of this study was to determine if low-dose dobutamine infusion can enhance Tc-99m methoxy isobutyl isonitrile (MIBI) uptake of hyperfunctioning parathyroid glands of patients with secondary hyperparathyroidism (SHP). We studied 24 patients with chronic renal failure and SHP. Median age of the sample was 47.5 years. A single-tracer, double-phase technique was performed, acquiring planar images of the neck and thorax after the injection of 740 to 1110 MBq (20-30 mCi) of Tc-99m MIBI. After 2 to 7 days, the study was repeated after the infusion of low-dose dobutamine of 2.0 microg . kg . min for 60 minutes. The scan was considered positive for hyperfunctioning parathyroid tissue when an area of increased uptake that persisted on late imaging was found. Parathyroid-to-thyroid count rates (PT/T) were calculated for each abnormal focus. Hyperplasic parathyroid tissue was confirmed in 12 of 24 patients who underwent neck surgery whereas the remaining group had persistent or worsening disease, verified by clinical follow-up between 6 and 25 months after the nuclear studies (median: 12 months). An MIBI baseline study was positive in 21 of 24 patients (87%), whereas the dobutamine study was positive in all patients. Thirty-five abnormal foci were seen on baseline MIBI studies and 43 on dobutamine scans (1.46 +/- 1.02 vs. 1.79 +/- 0.88, mean +/- SD, respectively, P = 0.043). Dobutamine PT/T ratios were significantly higher than those from the baseline study (1.49 +/- 0.30 vs. 1.38 +/- 0.28, mean +/- SD, respectively, P = 0.0002, n = 43). We concluded that low-dose dobutamine Tc-99m MIBI scintigraphy has the potential of enhancing tracer uptake and retention in patients with SHP.

11C-methionine PET/CT in 99mTc-sestamibi-negative hyperparathyroidism in patients with renal failure on chronic haemodialysis

PURPOSE

Scintigraphic localisation of parathyroid glands is often unsuccessful in patients with renal failure on chronic haemodialysis who have secondary hyperparathyroidism (HPT). The purpose of this study was to investigate the use of (11)C-methionine PET/CT to detect hyperfunctioning parathyroid glands in patients with renal failure on chronic haemodialysis who had (99m)Tc-sestamibi-negative HPT.

METHODS

(11)C-methionine PET/CT was performed in 18 patients (11 women and 7 men, aged 42-79 years; mean age 57.8 years) on haemodialysis for renal failure (2-14 years' duration), with normo-, hypo- or hypercalcaemia and HPT not localised by either dual-tracer (99m)Tc-pertechnetate/(99m)Tc-sestamibi subtraction scans or dual-phase (99m)Tc-sestamibi scans.

RESULTS

In three of ten patients with normo- or hypocalcaemic HPT there was increased (11)C-methionine accumulation in one gland. Seven of eight patients with hypercalcaemic HPT showed increased uptake: in five of these patients increased (11)C-methionine accumulation was present in one gland, while in two it was demonstrated in two glands. All patients also had high-resolution ultrasound of the neck and were treated with subtotal parathyroidectomy, leaving a remnant of the smallest of the four glands. Regardless of their size, all glands with abnormal (11)C-methionine parathyroid uptake were removed, and all demonstrated parathyroid hyperplasia. All patients developed post-parathyroidectomy hypoparathyroidism and one patient with normocalcaemic HPT relapsed 8 months after surgery.

CONCLUSION

These data suggest that (11)C-methionine PET/CT may be used to identify hyperfunctioning parathyroid glands in non-primary HPT, and especially hypercalcaemic HPT, when conventional (99m)Tc-sestamibi imaging is non-localising.

Role of pre-operative imaging using 99mTc-MIBI and neck ultrasound in patients with secondary hyperparathyroidism who are candidates for subtotal parathyroidectomy

PURPOSE

The purpose of this study was to assess whether pre-operative (99m)Tc-methoxyisobutylisonitrile (MIBI) scintigraphy and neck ultrasound (US) are of value in improving the outcome of subtotal parathyroidectomy in patients with secondary hyperparathyroidism.

METHODS

Forty-eight consecutive haemodialysis patients with severe secondary hyperparathyroidism prospectively underwent "blinded" subtotal parathyroid surgery, with 1-year follow-up to establish cure or relapse of their secondary hyperparathyroidism. Double-phase (99m)Tc-MIBI scintigraphy and neck US were performed pre-operatively in all patients. When the preserved gland showed (99m)Tc-MIBI uptake or an abnormal size on US, it was considered that "(99m)Tc-MIBI advice" and "US advice", respectively, had not been followed. Pre-operative and follow-up parathyroid hormone (PTH) levels were obtained in all patients. All data were evaluated on a patient by patient basis.

RESULTS

Four parathyroid glands were identified in each patient at primary surgery, resulting in an operative success rate of 100%. Their weight ranged from 15 to 7,300 mg (mean 1,120+/-900 mg). Nine of the 48 patients (19%) showed a recurrence of their secondary hyperparathyroidism. The recurrence rate was 2% (1/48) and 10% (5/48), respectively, when (99m)Tc-MIBI and US advice was followed. The sensitivity, specificity, NPV and PPV for pre-operative imaging were 72%, 95%, 97% and 80% respectively for (99m)Tc-MIBI, and 55%, 67%, 87% and 28% for US.

CONCLUSION

(99m)Tc-MIBI scintigraphy is a reliable non-invasive exploratory tool and its preoperative use results in a significant reduction in the number of recurrences in haemodialysis patients with secondary hyperparathyroidism who are candidates for subtotal parathyroidectomy. The use of neck US did not significantly improve the results obtained with (99m)Tc-MIBI alone.

Biological factors influencing parathyroid localization

The major factor influencing scintigraphic detection of abnormal parathyroid glands seems to be their size. However, false-negative results have been reported in large glands while some very small adenomas have been identified. Other factors can influence 99mTc-MIBI and 99mTc-Tetrofosmin uptake and therefore the accurate detection of hyperfunctioning glands depends also on these. Increases in both perfusion and functional activity and targeting of abundant mitochondria-rich oxyphil cells seem to be relevant mechanisms of uptake. A relationship has been observed between the intensity of focal uptake in the parathyroid glands and the cell cycle phases for patients with secondary hyperparathyroidism. Higher uptake grades correlated with the active growing phase, showing that scintigraphy accurately reflects the functional status of the hyperplastic parathyroid glands. Serum calcium levels may modify radiotracer kinetics by influencing the membrane potential. In addition, P-glycoprotein or multidrug resistance (MDR) associated protein expression may play an important role in the false-negative results of parathyroid scintigraphy. If the lipophilic cationic radiotracers used in parathyroid scintigraphy are transported by the same mechanism as the anticancer drugs, they will be quickly eliminated from the parathyroid glands containing P-glycoprotein or MDR-related protein expression and the uptake in images will be negative. In parathyroid glands with no P-glycoprotein or MDR-related protein expression, the radiotracers remain in the cells, making it easier to detect them by scintigraphy.