PATIENTS AND METHODS

Patients

Nine consecutive patients with TA who were admitted to the rheumatology outpatient clinic of Barzilai Medical Centre, Ashkelon, Israel between 1999 and 2000 were included in the study. All the patients fulfilled the American College of Rheumatology criteria for TA.¹

Exclusion criteria included any other known or clinically evident inflammatory or granulomatous disease which might enhance ⁶⁷Ga uptake in the temporal area, or known allergic reaction to gallium citrate.

Controls

The control group comprised six patients who underwent ⁶⁷Ga scintigraphy in the nuclear medicine department of Barzilai Medical Centre in the same period for febrile disease.

⁶⁷Ga SPECT scan

All the patients underwent a ⁶⁷Ga SPECT scan, which was performed on a dual head helix gamma camera two days after intravenous injection of 8–10 mCi of gallium citrate. Data were collected on 64×64 matrices with acquisition time 20–25 sec per frame. An Mz-type filter was used for reconstruction of the acquisition data. The ⁶⁷Ga uptake ratio—temporal bone region/bone out of temporal area (TR/bone)—was estimated on transaxial and coronary slices after SPECT scan reconstruction. For each patient and control, calculations of both temporal areas were made.

Statistical analysis

Results are presented as mean and SD. The mean quantitative values for the groups were compared using the two tailed Student’s t test. A value p<0.01 was considered significant.

RESULTS

Fifteen patients participated in the study—nine with TA and six controls. The patients diagnosed as TA showed typical clinical features of this disease such as new onset headache in the temporal area, temporal artery tenderness on palpation—unilateral in six and bilateral in three, and an erythrocyte sedimentation rate above 50 mm/1st h. Four patients had jaw claudication, while six were found to have polymyalgia rheumatica. One patient was admitted to the hospital with sudden blindness in one eye as the presenting symptom of TA. Six of the nine patients underwent temporal artery biopsy—five after a ⁶⁷Ga scan and one before. In this latter patient the ⁶⁷Ga uptake ratio of the biopsied side was not calculated (patient No 2) in order to avoid false results. Only one patient showed positive results on biopsy, and in the five other patients the results of biopsy were negative, probably because of prednisolone treatment which was given 4–5 days before biopsy. Prednisolone treatment was introduced before performing a ⁶⁷Ga scan in seven patients. Table 1 presents the clinical data of the patients.

The group of controls comprised six patients who underwent ⁶⁷Ga scanning because of febrile disease. The mean (SD) age of these patients was 64.4 (25.7), and their mean (SD) erythrocyte sedimentation rate was 45 (13.3) mm/1st h. None of the control patients had headache in temporal areas, none had shoulder pain.

All the nine patients showed an increased uptake in both temporal areas of the skull in comparison with control patients. The calculated ⁶⁷Ga uptake ratio in the patients was 1.47 (0.16) in the coronary view and 1.31 (0.14) in the transaxial view. In control patients the calculated ⁶⁷Ga uptake ratios were 1.11 (0.06) and 1.04 (0.09), respectively. The results showed a significant difference (p<0.001). Figures 1 and 2 show examples of increased ⁶⁷Ga uptake in the temporal area.

DISCUSSION

The diagnosis of TA is mainly based on clinical criteria and although temporal artery biopsy may confirm the diagnosis, it is not instructive in many cases. There is a genuine need for a non-invasive procedure which may contribute to the diagnosis and follow up of patients with TA. Scintigraphy is a non-invasive diagnostic procedure that may eventually help the clinician to diagnose and localise the vasculitic process.

⁶⁷Ga is a commonly used agent for the imaging of inflammation because of its ability to accumulate non-specifically in inflamed areas as a metal-transferrin complex, followed by further binding to transferrin receptors.

⁶⁷Ga scintigraphy has been performed in patients with polyarteritis nodosa, Wegener’s granulomatosis, and Kawasaki disease.^11–13 Interestingly, in Takayasu’s arteritis, which is a large vessel vasculitis, ⁶⁷Ga scintigraphy has been widely used. Hahn et al reviewed 31 patients with Takayasu’s arteritis over a 15 year period. A ⁶⁷Ga SPECT study was done in 16 of them and found positive in 12.¹⁴ Moreover, ⁶⁷Ga scintigraphy was a helpful tool in assessing disease activity during the treatment.¹⁵

In recent years, PET has been introduced for the imaging of vasculitic processes. Blockmans et al performed fluorodeoxy-glucose PET (FDG-PET) in patients with polymyalgia rheumatica/TA. They found increased FDG uptake in the tibial arteries and thoracic large vessels in 19/25 (76%) patients. However, high uptake of FDG in the brain and the relatively small diameter of temporal arteries prevented direct investigation of these arteries.⁵

We have demonstrated significantly increased ⁶⁷Ga uptake in the temporal area of the skull in patients with TA in comparison with control patients. Moreover, all patients showed increased ⁶⁷Ga uptake in both temporal areas, despite the clinical picture of unilateral process in some patients.

SPECT is a method that offers the advantage of cross sectional imaging as compared with conventional planar imaging. Further, computer aided, three dimensional reconstruction of SPECT data helps to make measurements directly in the zone of interest, to obtain a higher image contrast and a clear cut signal of the investigated area. Therefore, the anatomical description of the process is better. In our work after the performance of skull SPECT and further three dimensional reconstruction of the data, we chose for calculation the particular slice of temporal artery anatomical area. It helped us to localise the vasculitic process and contributed to the accuracy of measurements.

Despite treatment with prednisolone before ⁶⁷Ga scintigraphy in eight of nine patients, all our patients had positive uptake suggestive of active TA.

Therefore, we suggest that the 48 hours lag time which is needed for realisation of a gallium scan does not interfere with prednisolone treatment and if TA is strongly suspected on clinical grounds, the treatment should be started immediately.

In conclusion, ⁶⁷Ga skull SPECT seems to be a useful non-invasive technique in the investigation of patients with TA. We are aware of the limitations of our study, which included a small number of patients. It may be argued that the low incidence of histological findings typical of TA does not allow an appreciation of the accuracy of this method. However, this is the first study which aimed at clarifing the contribution of ⁶⁷Ga SPECT scan to the diagnosis of TA. These preliminary results are encouraging and suggest a role of ⁶⁷Ga SPECT scan in the evaluation of patients with TA.

Further studies in larger groups of patients are needed to confirm these data.