Detection of bone metastases in breast cancer by 18FDG PET: differing metabolic activity in osteoblastic and osteolytic lesions.

PURPOSE: 99mTechnetium methylene diphosphonate (99mTc MDP) bone scintigraphy is currently the method of choice for the detection of bone metastases, but 18F-fluoro-deoxy-D-glucose positron emission tomography (18FDG PET) offers superior spatial resolution and improved sensitivity. We have compared 18FDG PET with 99mTc MDP bone scintigraphy in patients with skeletal metastases from breast cancer and have analyzed the data in subgroups based on radiographic characteristics of lesions. PATIENTS AND METHODS: Twenty-three women with breast cancer and confirmed bone metastases were studied with both 99mTC MDP bone scintigraphy and 18FDG PET, and the number of lesions detected and the quantitation of uptake (standardized uptake values [SUVs]) of 18FDG in osteolytic and osteoblastic metastases were compared. Survival was compared for both lytic and blastic bone metastases and for patients with high and low accumulation of 18FDG. RESULTS: 18FDG PET detected more lesions than 99mTc MDP scintigraphy (mean, 14.1 and 7.8 lesions, respectively; P < .01). However, 18FDG detected fewer bone metastases compared with 99mTc MDP scintigraphy in a subgroup of patients with osteoblastic disease (P < .05). Higher SUVs were observed for osteolytic than osteoblastic disease (mean, 6.77 and 0.95, respectively; P < .01). Survival was lower in patients with osteolytic disease compared with the remainder (P=.01). A difference in survival was not found for those patients with high SUVs (> 3.6; P=.4). CONCLUSION: 18FDG PET is superior to bone scintigraphy in the detection of osteolytic breast cancer metastases, which led to a poorer prognosis. In contrast, osteoblastic metastases show lower metabolic activity and are frequently undetectable by PET. The biologic explanation for this observation remains to be elucidated.

Influence of anatomic correction for transposition of the great arteries on myocardial perfusion: radionuclide imaging with technetium-99m 2-methoxy isobutyl isonitrile.

OBJECTIVES: We sought to determine the incidence of late perfusion defects attributable to coronary artery mobilization in patients undergoing anatomic correction for complete transposition of the great arteries. BACKGROUND: Anatomic correction (arterial switch procedure) is currently the surgical treatment of choice for complete transposition. From its conception, there has been concern about the impact on myocardial perfusion of the coronary artery mobilization and reimplantation involved in the correction. Previous studies have demonstrated myocardial perfusion defects in patients after correction, although a causal relation between coronary mobilization, and perfusion abnormality has not been established. METHODS: In a case-comparison study designed to test this hypothesis, 29 children underwent imaging with technetium-99m 2-methoxy isobutyl isonitrile (technetium-99m mibi). Ten had undergone anatomic correction (arterial switch group; interval from operation 6.9 +/- 1.42 years [range 4.9 to 9.1]); 9 had required noncoronary open heart surgery for other cardiac lesions (post-bypass group; interval from operation 5.6 +/- 3.6 years [range 1.0 to 13.25]); and 10 had had no surgical procedure (control group). The latter group comprised children with atrial or ventricular septal defects who required a radionuclide study for shunt calculation. Planar studies were performed in all 29 children, and additional tomographic acquisition was achieved in 25. To assess reversibility of perfusion defects both an exercise and a rest planar study were performed in the arterial switch group. RESULTS: Perfusion abnormalities were observed in seven of the nine children in the postbypass group and in all 10 children in the arterial switch group. The frequency of perfusion defects in these two groups was similar, with at least 25% of the tomographic segments reported being abnormal. The control group had significantly fewer defects than the other two groups (p = 0.02), with only 8% of the tomographic segments judged to be abnormal. In all except one patient in the arterial switch group, the segments reported as abnormal on the planar exercise study were either abnormal or equivocal on the rest study, indicating a fixed abnormality. CONCLUSIONS: Although the precise etiology of these perfusion abnormalities cannot be defined from this study, these data suggest that their origin is related more to the insult of open heart surgery itself than to the coronary manipulation involved in the arterial switch procedure. The functional importance requires further study.

Double-outlet right ventricle: morphologic demonstration using nuclear magnetic resonance imaging.

Sixteen patients with double-outlet right ventricle, aged 1 week to 29 years (median 5 months), were studied with a 1.5 tesla nuclear magnetic resonance (NMR) imaging scanner. Two-dimensional echocardiography was performed in all patients. Thirteen patients underwent angiography, including nine who underwent subsequent surgical correction. Three patients underwent postmortem examination. Small children and infants were scanned inside a 32 cm diameter proton head coil. Multiple 5 mm thick sections separated by 0.5 mm and gated to the patient's electrocardiogram were acquired with a spin-echo sequence and an echo time of 30 ms. A combination of standard and oblique imaging planes was used. Imaging times were less than 90 min. The NMR images were technically unsuitable in one patient because of excessive motion artifact. In the remaining patients, the diagnosis of double outlet right ventricle was confirmed and correlated with surgical and postmortem findings. The NMR images were particularly valuable in demonstrating the interrelations between the great arteries and the anatomy of the outlet septum and the spatial relations between the ventricular septal defect and the great arteries. Although the atrioventricular (AV) valves were not consistently demonstrated, NMR imaging in two patients identified abnormalities of the mitral valve that were not seen with two-dimensional echocardiography. In one patient who had a superoinferior arrangement of the ventricles, NMR imaging was the most useful imaging technique for demonstrating the anatomy. In patients with double-outlet right ventricle, NMR imaging can provide clinically relevant and accurate morphologic information that may contribute to future improvement in patient management.

A quantitative evaluation of aortic regurgitation after anatomic correction of transposition of the great arteries.

Twenty patients who had undergone anatomic correction of transposition of the great arteries were assessed by Doppler echocardiography or cardiac catheterization, or both, to identify the presence of aortic regurgitation. The severity of aortic regurgitation was evaluated by radionuclide angiographic measurement of the stroke volume index a mean of 47.1 months postoperatively. The stroke volume index was defined as the ratio of the stroke counts between the left and right ventricles. A value greater than 1.8 was considered to indicate significant left ventricular volume overload. Eight patients (40%) were shown to have various degrees of aortic regurgitation by Doppler echocardiography or cardiac catheterization, or both. The mean (+/- SD) stroke volume index was 1.03 +/- 0.15 in these patients and 1.01 +/- 0.21 in the 12 patients without aortic regurgitation (p = NS). The stroke volume index was not above the normal range in any patient, indicating that the degree of aortic regurgitation present was trivial. This medium-term study indicates that trivial or mild aortic regurgitation is a frequent finding after anatomic correction of transposition of the great arteries. However, it rarely results in an audible cardiac murmur or significant left ventricular volume overload. Long-term evaluation is required to determine its importance.

A study of the effects of sumatriptan on myocardial perfusion in healthy female migraineurs using 13NH3 positron emission tomography.

Sumatriptan, a 5-HT1D receptor agonist, is believed to alleviate migraine attacks by extracerebral vasoconstriction. Chest pain associated with myocardial ischemia may occur after sumatriptan administration. We investigated the effect of a single 6-mg subcutaneous dose of sumatriptan on myocardial perfusion (MP) as measured by 13NH3 positron emission tomography (PET) in a randomized, double-blind, placebo-controlled, crossover trial at the Clinical PET Centre, Guy's and St. Thomas' Hospitals, London. Nineteen volunteer female migraineurs, age range 33 to 62 years, at low risk for ischemic heart disease were included. All bad undergone previous treatment with oral or intravenous sumatriptan. Patients were recruited by advertisement and referral from local neurology specialists. Each volunteer underwent two scanning sessions. On each occasion, a baseline dynamic 13NH3 PET scan was acquired followed by a 13NH3 PET scan 10 minutes after subcutaneous injection of placebo or 6 mg of sumatriptan. Regional MP was measured in five myocardial regions using the Patlak system of image analysis. The mean % change from baseline (+/-SD) in global MP after placebo was +9.5% +/- 18.0 and after sumatriptan was +6.6% +/- 18.8 (repeated measures ANOVA for treatment effect p = 0.56). There were no significant differences in MP changes from baseline observed in any of the five myocardial regions (treatment p = 0.32 to 0.84). These data suggest that in healthy female migraineurs, a single 6-mg subcutaneous dose of sumatriptan does not cause a significant change in regional or global myocardial perfusion.

Significance of interictal bilateral temporal hypometabolism in temporal lobe epilepsy.

OBJECTIVE: To assess the clinical implications and the pathophysiologic determinants of interictal bitemporal hypometabolism (BTH) in temporal lobe epilepsy (TLE) not associated with bilateral MRI abnormalities or intracranial space-occupying lesions. METHODS: The authors compared the clinical, interictal, and ictal EEG, Wada test, and neuropsychology data of 15 patients with intractable complex partial seizures of temporal lobe origin and BTH with those of 13 consecutive patients with unilateral TLE associated with unilateral temporal hypometabolism (UTH) who remained seizure free for more than 3 years after anterior temporal lobectomy. 18F-fluorodeoxyglucose PET scans were analyzed visually and semiquantitatively, and ratios of counts in individual temporal areas to the rest of the cerebrum were compared with the corresponding values from 11 normal control subjects and with the nonepileptogenic hemisphere of the 13 patients with UTH. BTH was defined as more than 2.5 SDs below control values for two or more temporal areas on each side irrespective of any asymmetry. RESULTS: BTH reflected bilateral independent seizure onset in eight patients (53%). The topography of the metabolic depression was not a reliable predictor of epileptogenicity, but involvement of the inferior temporal gyrus was related specifically to ipsilateral seizure onset (70% sensitivity, 100% specificity). In patients with unilateral TLE, contralateral hypometabolism was associated with longer disease duration and worst memory performance during the Wada test, which amounted to global amnesia after ipsilateral injection in three patients, precluding surgical treatment. Contralateral seizure spread in the ictal EEG was significantly faster in patients with BTH. CONCLUSIONS: In TLE, symmetric or asymmetric BTH may signal bilateral independent seizure onset in approximately half the patients, especially when involving the inferior temporal gyrus. Alternatively, it may reflect an advanced stage of the disease process, characterized by a breakdown of the inhibitory mechanisms in the contralateral hemisphere, and secondary memory deficit associated with higher risk of postoperative memory decline. Patients with TLE and BTH but without bilateral MRI changes may still be operated on successfully, but surgical suitability should be proved by comprehensive intracranial EEG studies and Wada test.

Skeletal muscle uptake of fluorine-18-FDG: effect of oral diazepam.

UNLABELLED: We have observed a pattern of symmetrically increased uptake of [18F]fluorodeoxyglucose (FDG) in the neck and thoracic paravertebral regions of several patients referred for whole-body PET. The distribution is suggestive of uptake in contracting skeletal muscle in tense patients. METHODS: To test this hypothesis, six successive patients who exhibited this pattern of uptake underwent rescanning using an identical imaging protocol but with oral diazepam before injection of FDG. RESULTS: The increased neck and paravertebral uptake was significantly reduced or abolished with diazepam, confirming the supposition that this increased neck and paravertebral uptake represents a normal variant of muscle uptake. CONCLUSION: Oral diazepam, given before the uptake period can be helpful in such patients to exclude the masking of potential abnormalities by this characteristic pattern of FDG uptake.

Fluorine-18-FDG PET in Paget's disease of bone.

UNLABELLED: Paget's disease of bone is common in the elderly and is associated with increased osteoblastic and osteoclastic activity at affected sites in the skeleton. It is not known whether this high metabolic activity is associated with increased glycolysis and, hence, uptake of [18F]FDG. The appearances of Paget's disease with [18F]FDG PET have not been described and it is not known whether Paget's may cause false-positive studies in those undergoing oncological staging or whether [18F]FDG PET can reliably differentiate benign pagetic change from osteosarcoma that may complicate Paget's disease. We reviewed [18F]FDG PET scans in patients with uncomplicated Paget's disease and documented its appearances. METHODS: Eighteen patients with established Paget's disease and typical radiological features had 99mTc-MDP bone scans and [18F]FDG PET scans performed. Serum alkaline phosphatase (ALP) was also measured. RESULTS: All patients showed high uptake of MDP in affected bones. Of the 18 patients only six showed any uptake of [18F]FDG. This occurred in some but not all bones shown to be involved on MDP bone scans. Three patients demonstrated low-grade uptake and three showed marked accumulation of [18F]FDG. The [18F]FDG-positive group had higher serum ALP levels than the [18F]FDG-negative patients (p < 0.05). CONCLUSION: Paget's disease of bone is not associated with abnormal [18F]FDG uptake in the majority of patients and, therefore, there is potential for discriminating between benign Paget's disease and associated Paget's sarcoma. However, low-grade uptake may be seen in patients with more active disease as measured by ALP. Rarely, marked uptake of [18F]FDG may be seen and Paget's disease should be included as a possible cause of false-positive scans in elderly patients who are being assessed for metastatic disease.

Pentavalent [99mTc]DMSA, [131I]MIBG, and [99mTc]MDP--an evaluation of three imaging techniques in patients with medullary carcinoma of the thyroid.

Nine patients with histologically proven medullary carcinoma of the thyroid (MCT) were imaged using pentavalent [99mTc]dimercaptosuccinic acid [(V)DMSA], [131I] metaiodobenzylguanidine (MIBG) and [99mTc]methylene diphosphonate (MDP). Technetium-99m (V)DMSA demonstrated most of the tumor sites in eight patients with proven metastases, with an overall sensitivity of 95% in lesion detection. Iodine-131 MIBG showed definite uptake in some of the tumor sites in three of the nine patients imaged, with equivocal uptake seen in a further one patient, with sensitivity of only 11% for lesion detection. Technetium-99m MDP demonstrated bony metastases only, in four of the patients imaged yielding a sensitivity of 61%. Technetium-99m (V)DMSA has been demonstrated in this study to be a useful imaging agent in patients with MCT, showing uptake in significantly more lesions and with better imaging qualities than [131I]MIBG, and with the ability to detect soft tissue as well as bony metastases.

Dynamic renal transplant imaging with Tc-99m DTPA (Sn) supplemented by a transplant perfusion index in the management of renal transplants.

We have performed 955 studies on 152 patients with 167 renal transplants. Images were recorded following bolus injection of 12-15 mCi Tc-99m DTPA (Sn). The data were stored on a computer and analyzed by generation of region-of-interest curves from (a) the iliac artery distal to the transplant, (b) the kidney, and (c) a background area. A perfusion index was adopted: formula see text. In 276 studies the patient clearly had acute tubular necrosis (ATN), rejection, or a normal kidney on retrospective analysis. The normal perfusion index has a value below 150, and it increases with falling perfusion, such as is seen in rejection and in renal-artery stenosis. The use of this index in addition to sequential images and changes in the region-of-interest curves usually allows separation of rejection from ATN and, particularly, rejection from normals. When serial studies are performed, the separation of rejecting from nonrejecting transplants is excellent, although renal-artery stenosis may cause similar changes in perfusion.

Visual and semiquantitative analysis of cortical FDG-PET scans in childhood epileptic encephalopathies.

UNLABELLED: The optimal method for analyzing PET scans in children being considered for epilepsy surgery is unresolved: Fully quantified methods are invasive, and the required controls are generally unavailable. We sought to compare visual inspection with semiquantitative analysis for the detection of cortical metabolic defects. METHODS: Thirty-two children with cryptogenic epileptic encephalopathies were studied prospectively with 18F-fluorodeoxyglucose (FDG) PET. Visual inspection was performed on separate occasions by independent observers. Four-millimeter circular regions of interest were used to sample radiotracer uptake in selected cortical regions. Asymmetry between homologous regions were calculated to detect focal abnormalities. Bilateral and diffuse abnormalities were assessed by comparing the ratio of cortical-to-cerebellar uptake in patients with historical age-matched controls. The sensitivity and specificity of visual inspection was compared with that of semiquantitative analysis for the detection of focal, bilateral and diffuse cortical metabolic abnormalities. RESULTS: Visual inspection revealed full inter-rater agreement for the presence of major focal abnormalities. The sensitivity and specificity for visual inspection compared to semiquantitative analysis were 77% and 92%, respectively, with semiquantitative analysis often revealing abnormalities to be more extensive than had been suspected visually. Compared with semiquantitative analysis, visual inspection had a low sensitivity but high specificity for the detection of bilateral and diffuse hypometabolism. CONCLUSION: Semiquantitative analysis gives clinically useful information additional to that obtained from visual inspection.

Scintigraphy and treatment of medullary carcinoma of the thyroid with iodine-131 metaiodobenzylguanidine.

We report our experience using [131I]metaiodobenzylguanidine (MIBG) to image nine patients with proven medullary carcinoma of the thyroid (MCT). Positive uptake was seen in four patients, equivocal uptake in one patient, and no uptake in four patients. Data is presented to demonstrate the pharmacokinetics of [131I]MIBG in three of the patients studied. Two patients, with diarrhea and severe pain from known bone metastases and positive uptake on [131I]MIBG diagnostic scanning, subsequently received therapeutic doses of [131I]MIBG, with marked improvement in both pain and diarrhea, but no evidence of significant biochemical response. Iodine-131 MIBG uptake in patients with MCT is variable, and gives a higher false-negative rate than is found when using [131I]MIBG to image other neuroectodermally derived tumors. The therapeutic potential of [131I]MIBG in patients with MCT warrants further evaluation, in view of the symptomatic relief experienced following therapy doses in two patients with extensive disease.

Technetium-99m (v) dimercaptosuccinic acid uptake in patients with head and neck squamous carcinoma: experience in imaging.

A recently developed imaging agent, technetium-99m (v) dimercaptosuccinic acid (99mTc (v) DMSA), has been used to assess head and neck squamous carcinoma (SCC). We have prospectively studied 62 patients of whom 53 had a histologically proven head and neck SCC. The remaining nine had benign lesions. The results of planar imaging in patients with primary disease yielded an 85% sensitivity and 78% specificity. Planar imaging in patients with cervical lymphadenopathy revealed a 59% sensitivity. Nineteen patients also had single photon emission computed tomography imaging which improved the image quality, spatial resolution and sensitivity of the investigation. Twenty-seven patients were scanned before and after radiotherapy and, of these, 96% showed positive uptake in the salivary glands with no evidence of tumor recurrence. This study has shown 99mTc (v) DMSA imaging provides a cheap and rapid method of investigating head and neck SCC and further studies are necessary to evaluate its role in the management of patients with this disease.

Speech-related visualization of laryngeal muscles with fluorine-18-FDG.

UNLABELLED: This study describes the physiological uptake of 18F-fluoro-2-deoxyglucose (FDG) by the laryngeal muscles secondary to activation of the patient's vocal folds and related laryngeal muscles during speech. METHODS: Twenty-four patients undergoing routine PET scans were randomized into two groups to ascertain the relationship between FDG uptake in the laryngeal region and speech. One group was assigned to talk and the other group remained silent during the injection and uptake period of FDG. RESULTS: FDG uptake in the laryngeal muscles in the scans was correlated with speech. Patients who spoke continually during the uptake period had high-grade FDG uptake, those who spoke intermittently had low-grade uptake and those who remained silent had no detectable increase in FDG uptake in the region of the larynx. CONCLUSION: The relationship between the degree of laryngeal muscle uptake and speech provides useful information to allow differentiation of physiological from pathological uptake in the neck.

The pharmacokinetics and biodistribution of technetium-99m(V)dimercaptosuccinic acid in an animal tumor model.

This study used an established rabbit tumor model with squamous carcinoma to evaluate the pharmacokinetics and biodistribution of technetium-99m-(V)dimercaptosuccinic acid. A total of 54 rabbits were studied (25 with no tumor; 29 with tumor). Technetium-99m(V)dimercaptosuccinic acid had a bi-exponential blood clearance in rabbits with no tumors (28 and 325 min) and in rabbits with tumors (27 and 352 min). There was no significant difference (p greater than 0.05) in mean clearance times between the two groups and clearance appeared unaffected by tumor mass. Technetium-99m(V)dimercaptosuccinic acid had a bi-exponential cumulative urine excretion with no apparent difference in half-times between non-tumor and tumor rabbit groups (200 and 240 min, respectively). Technetium-99m(V)dimercaptosuccinic acid had a major organ biodistribution in rabbits which included bone, kidneys, bladder and the blood pool. The major route of excretion was via the urine. There was no significant difference (p greater than 0.05) in organ biodistribution between rabbits with no tumors and rabbits with tumors and there was no evidence of active uptake of technetium-99m(V)dimercaptosuccinic acid by either squamous carcinoma or inflammatory tissue.

Planar imaging techniques used with technetium-99m sestamibi to evaluate chronic myocardial ischemia.

The results of published and some unpublished studies comparing planar imaging performed with 2 radionuclides, thallium-201 (T1-201) and technetium-99m (Tc-99m) sestamibi, are reviewed. The average sensitivity for the detection of coronary artery disease (CAD) in studies involving 594 patients was 85% (range 73 to 96%). The average sensitivity for individual vessels was 65% (range 60 to 70%). The average segmental concordance between T1-201 and Tc-99m sestamibi was 89%. End-diastolic gated perfusion images improved the concordance between Tc-99m sestamibi and angiography in 22 patients from 83.4 to 87%. Semiquantitative analysis increased the concordance between T1-201 and Tc-99m sestamibi from 89 to 91%. Ventricular function derived from gated Tc-99m sestamibi perfusion images showed a significant correlation with echocardiography (n = 62, r = 0.85); with angiography (n = 70, r = 0.91); and with equilibrium radionuclide ventriculography (n = 18, r = 0.86). The ratio of lung to left ventricle uptake and the ratio of right ventricle to left ventricle uptake was assessed. Eight of 52 patients had an abnormally elevated lung index (greater than 42%) and these patients had the most severe CAD. Six of the 52 patients had an abnormally elevated right ventricular index (greater than 56%) and these patients had more severe CAD.

Radionuclide measurement of right ventricular function in atrial septal defect, ventricular septal defect and complete transposition of the great arteries.

Right ventricular (RV) function was assessed in 80 patients with congenital heart disease by first-pass and gated equilibrium radionuclide angiography. In 30 patients with a ventricular septal defect (VSD) the mean RV ejection fraction (+/- standard deviation) was 64 +/- 7%. In 30 patients with a secundum atrial septal defect it was 61 +/- 9% and in 20 patients with surgically corrected complete transposition of the great arteries it was 49 +/- 13%. These values are in close agreement with values established with cineangiography for similar groups of patients. The mean ejection fraction in the group with transposition of the great arteries was significantly less than in the group with VSD (p less than 0.001). Phase analysis of the equilibrium studies showed that there was delayed RV contraction in many patients in the absence of conduction abnormalities. This delay was significantly greater in patients with atrial septal defect than in those with VSD (p less than 0.05). There was a strong correlation between size of left-to-right shunt and phase delay in patients with VSD (r = -0.72). Thus, first-pass gated radionuclide angiography provides a valid measurement of RV ejection fraction, and delayed RV contraction on phase analysis may be a sensitive index of early RV dysfunction.

Normal physiological and benign pathological variants of 18-fluoro-2-deoxyglucose positron-emission tomography scanning: potential for error in interpretation.

The use of positron-emission tomography in clinical practice is increasing, particularly with the use of 18-fluoro-2-deoxyglucose (FDG) for oncological studies. As in other imaging modalities, it is important to be aware of normal variants and benign diseases that may mimic more serious pathology. Uptake of FDG in a number of sites may be variable. Uptake of FDG may be seen normally in the skeletal muscle after exercise or under tension, in the myocardium, in parts of the gastrointestinal tract, especially the stomach and cecum, and in the urinary tract. Some causes of increased physiological uptake are avoidable, and measures can be taken to minimize accumulation, thus aiding study interpretation. Inflammatory lesions may cause an increase in FDG uptake, but not usually to the same degree as malignancy. Benign disease such as Paget's disease of bone, sarcoidosis, and tuberculosis may cause uptake that occasionally mimics that of malignancy. Typical examples of a number of physiological and benign variants are described and illustrated.

Positron emission tomography in lung cancer.

Carcinoma of the lung is one of the most frequent malignancies and a major cause of mortality. The use of positron emission tomography (PET) has been extensively investigated in patients with carcinoma of the lung and has established clinical utility and cost-effectiveness in characterization of solitary pulmonary nodules and preoperative staging of carcinoma of the lung. Evolving applications in carcinoma of the lung include detection of recurrence, assessment of treatment response, radiotherapy planning, and prognosis. In addition, there is developing interest in combined anatomic/metabolic imaging and new tracer techniques, in particular gene expression imaging. This review aims to present existing data supporting the use of PET in carcinoma of the lung and to explore the evolving indications and future prospects of PET and lung cancer.

[11C]Methionine positron emission tomography for patients with persistent or recurrent hyperparathyroidism after surgery.

OBJECTIVE: Reoperation in patients with recurrent hyperparathyroidism usually requires localisation of abnormal glands. Current imaging techniques are not always successful in this group of patients. An evaluation of [11C]methionine positron emission tomography (PET) has been made to assess the ability of the technique to localise abnormal glands in patients with hyperparathyroidism after previous surgery. SUBJECTS AND METHODS: Eight patients (five with primary, and three with tertiary hyperparathyroidism) who had undergone one to three previous surgical explorations were studied. [11C]methionine PET scans of the neck and mediastinum were performed in all patients. All had recent technetium-99m (99mTc)-labelled sestamibi (n = 7) or thallium-201 (201Tl)/99mTc subtraction (n = 1) parathyroid scans available for comparison. Subsequent surgical correlation was available in all cases. RESULTS: [11C]methionine PET correctly located an abnormal site of uptake in all five patients with primary hyperparathyroidism compared with only one when conventional nuclear medicine methods were used. In the patients with tertiary hyperparathyroidism, [11C]methionine PET correctly located one, confirmed the absence of cervical or mediastinal abnormality in a patient with an autotransplanted forearm autonomous gland, and failed to demonstrate an abnormality in a third. 99mTc-labelled sestamibi scans were negative in all three patients. CONCLUSION: [11C]methionine PET correctly locates abnormal parathyroid glands in the majority of patients with persistent or recurrent hyperparathyroidism after surgery in whom conventional non-invasive nuclear medicine imaging has failed.