Shin-Hwa Yeh

Fluorine-18 fluoromisonidazole tumour to muscle retention ratio for the detection of hypoxia in nasopharyngeal carcinoma

In vivo demonstration of hypoxia is of significance for tumour patient management. Fluorine-18 fluoromisonidazole ([18F]FMISO) is a proven hypoxie imaging agent. We developed an [18F]FMISO tumour to muscle retention ratio (TMRR) for the detection of tumour hypoxia in nasopharyngeal carcinoma (NPC). Data were acquired by positron emission tomography (PET) of the nasopharynx and neck after intravenous injection of 370 MBq of [18F]FMISO. Two imaging protocols were adopted: a long protocol for comprehensive dynamic information and a short protocol for a simple, clinically convenient imaging procedure. Tomograms were reconstructed and evaluated visually. ROI analysis on the basis of time-activity curve evaluation was performed to calculate the TMRR of NPC or cervical nodal metastases (CNMs) in relation to the suboccipital muscles at 2 h. The calculation of the TMRR was exactly the same for both the long and the short protocol as two 30-min composite frames had been created immediately after intravenous injection and 2 h after injection of [18F]FMISO in the long protocol. The normal tissue to muscle retention ratio (NTMRR) was derived similarly from the normal nasopharynx. The data of 12 controls and 24 patients with NPC were analysed. The long protocol was used in 15 patients, and the short protocol in nine. In controls, the mean NTMRR±1 SD was 0.96±0.14. The mean TMRRs for NPC and CNMs were 2.56±1.50 and 1.35±0.51, respectively; these values were significantly higher than the mean NTMRR for normal controls (P<0.005 in each case). At the retention threshold value of 1.24, tumour hypoxia occurred in 100% of the primary lesions of NPC and 58% of CNMs. The TMRR for undifferentiated carcinoma was significantly lower than that for non-keratinized carcinoma (P<0.05). The [18F]FMISO TMRR is a simple and clinically useful index for detecting tumour hypoxia in NPC.

Detection of anaerobic odontogenic infections by fluorine-18 fluoromisonidazole.

Odontogenic infections are a potential risk for patients who receive cervicofacial radiotherapy and should be treated before irradiation. Anaerobic microbial infections are the most common causes. This study assessed the value of the hypoxic imaging agent fluorine-18 fluoromisonidazole (FMISO) in detecting anaerobic odontogenic infections. Positron emission tomography (PET) imaging was performed at 2 h after injection of 370 MBq (10 mCi) of FMISO in 26 nasopharyngeal carcinoma patients and six controls with healthy teeth. Tomograms were interpreted visually to identify hypoxic foci in the jaw. All patients received thorough dental examinations as a pre-radiotherapy work-up. Fifty-one sites of periodontitis, 15 periodontal abscesses, 14 sites of dental caries with root canal infection, 23 sites of dental caries without root canal infection, and seven necrotic pulps were found by dental examination. Anaerobic pathogens were isolated from 12 patients. Increased uptake of FMISO was found at 45 out of 51 sites of periodontitis, all 15 sites of periodontal abscess, all 14 sites of dental caries with root canal infection, all seven sites of necrotic pulp and 15 sites of dental caries without obvious evidence of active root canal infection. No abnormal uptake was seen in the healthy teeth of patients or in the six controls. The diagnostic sensitivity, specificity, positive and negative predictive values, and accuracy of FMISO PET scan in detecting odontogenic infections were 93%, 97%, 84%, 99% and 96%, respectively.18F-fluoride ion bone scan done in three patients showed that18F-fluoride ion plays no role in the demonstration of anaerobic odontogenic infection. FMISO PET scan is a sensitive method for the detection of anaerobic odontogenic infections, and may play a complementary role in the evaluation of the dental condition of patients with head and neck tumours prior to radiation therapy.

1-11C-Acetate Versus 18F-FDG PET in Detection of Meningioma and Monitoring the Effect of γ-Knife Radiosurgery

This study aimed to define the potential of 1-11C-acetate PET, compared with 18F-FDG, in detecting meningiomas and monitoring the effect of γ-knife radiosurgery. Methods: Twenty-two patients with the neuroradiologic diagnosis of meningioma were examined by 1-11C-acetate and 18F-FDG PET on the same day. There were 12 cases of histopathologically proven meningioma (8 grade I, 2 grade II, and 2 grade III), 1 of tuberculous granuloma, and 1 of degenerative tissue. 1-11C-acetate PET scans of fasting patients were obtained 10 min after intravenous administration of 740 MBq of 1-11C-acetate. 18F-FDG PET was performed at 2 h after 1-11C-acetate scanning. The PET images were evaluated by a qualitative method and semiquantitative analysis using standardized uptake value and tumor-to-cortex ratio. Results: The 18F-FDG PET study revealed a hypometabolic focus in 17 meningiomas (8 grade I, 1 grade II, and 8 unknown grade) and hypermetabolism in 1 grade II and 2 grade III meningiomas. High uptake of 1-11C-acetate was observed in all 20 meningiomas, in contrast to the low uptake in surrounding normal brain tissue, allowing a clearer demarcation of the tumor boundary than that provided by 18F-FDG. Dissociation of regional accumulation of 1-11C-acetate and 18F-FDG within the tumor was also noted on the coregistered images. The standardized uptake value for 1-11C-acetate was not different from that for 18F-FDG (mean ± SD, 3.16 ± 1.75 vs. 3.22 ± 1.50, P = 0.601), but the tumor-to-cortex ratio for 1-11C-acetate was higher than that for 18F-FDG (3.46 ± 1.38 vs. 0.93 ± 1.08, P < 0.005). 18F-FDG was able to differentiate grade I from grade II–III meningiomas, whereas 1-11C-acetate was unable to do so. Tuberculous granuloma had a high 1-11C-acetate and 18F-FDG uptake similar to that of grade II/III meningioma. Five patients received 1-11C-acetate and 18F-FDG PET before and after γ-knife surgery. 1-11C-acetate performed better than did 18F-FDG in monitoring the response of tumor metabolism to radiosurgery. Conclusion: 1-11C-acetate was found to be useful for detecting meningiomas and evaluating the extent of meningiomas and potentially useful for monitoring tumor response to radiosurgery. However, 1-11C-acetate was not useful for evaluating the tumor grade. 18F-FDG was found to be less useful than 1-11C-acetate for evaluating the extent of meningiomas and the response to radiosurgical treatment but may be useful for differentiating benign from malignant meningiomas. 18F-FDG and 1-11C-acetate are complementary for assessing diverse cell metabolism of meningioma.

Salivary scintigraphy with vitamin C stimulation: an aid in differentiating unilateral parotitis from Warthin's tumor

Of the nine patients included in this study, five with proven unilateral parotitis initially had diffuse high uptake of99mTc-pertechnetate in the affected glands with adequate washout following vitamin C stimulation. Of four patients with proven Warthins tumor, two had focal high uptake in the parotid masses and two had diffuse high uptake on baseline images. All tumors were clearly delineated after stimulation.99mTc-pertechnetate salivary scintigraphy with vitamin C stimulation may provide a useful tool in differentiating unilateral parotitis from Warthins tumor.

Superscan in patients with nasopharyngeal carcinoma

Bone scintigraphy plays an important role in the early detection of bone metastases in patients with nasopharyngeal carcinoma and serial scans may aid the clinician to assess the therapeutic response. A superscan is a pattern described as abnormal bone scan, indicating extensive bony metastases associated with various neoplastic diseases. Bone scans from 407 patients with nasopharyngeal carcinoma were reviewed retrospectively. Only six superscans (1.5%) were found. The appearance of a superscan is frequently accompanied by an abnormal titer of serological markers IgG-VCA and IgA-VCA, liver metastases, and poor survival. Although a superscan rarely occurs in nasopharyngeal carcinoma, its appearance may represent a poor prognosis in these patients.

Scintigraphic appearance of parosteal osteosarcoma.

Parosteal osteosarcoma is a rare form of bone tumor. The lesion is usually well differentiated and arises from the bone surface. It has a better prognosis than other osteosarcomas. Although the radiographic features of parosteal osteosarcoma have been well documented, the scintigraphic characteristics of this tumor have not been described in the English literature. The authors show the unique and distinctive scintigraphic appearance of this tumor.

Tc-99m phytate bone marrow scintigraphy showing multiple areas of focal hyperactivity in a patient with lung cancer. A case report.

Focal hyperactivity indicative of metastases is a rare finding in bone marrow imaging. In a lung cancer patient with multiple bony metastases, the Tc-99m phytate bone marrow imaging revealed multiple focal areas of increased radioactivity corresponding to the bone scan findings. The findings presented are consistent with a previous animal study, which found that phytate distribution was similar to that of diphosphonate in the skeletal system of rats and rabbits. The authors conclude that Tc-99m phytate should not be used as a bone marrow imaging agent. Further studies of Tc-99m phytate bone marrow scintigraphy on human beings are under way.