Intra-individual comparison of PET/CT with different body weight-adapted FDG dosage regimens

Background

18F-2-fluoro-2-deoxy-D-glucose (FDG) positron emission tomography (PET)/ computed tomography (CT) imaging demands guidelines to safeguard sufficient image quality at low radiation exposure. Various FDG dose regimes have been investigated; however, body weight-adapted dose regimens and related image quality (IQ) have not yet been compared in the same patient.

Purpose

To investigate the relationship between FDG dosage and image quality in PET/CT in the same patient and determine prerequisites for low dosage scanning.

Material and Methods

This study included 61 patients undergoing a clinically indicated PET/CT imaging study and follow-up with a normal (NDS, 5 MBq/kg body weight [BW]) and low dosage scanning protocol (LDS, 4 MBq/kg BW), respectively, using a Discovery VCT64 scanner. Two blinded and independent readers randomly assessed IQ of PET using a 5-point Likert scale and signal-to-noise ratio (SNR) of the liver.

Results

Body mass index (BMI) was significantly lower at LDS (P = 0.021) and represented a significant predictor of SNR at both NDS (P < 0.001) and LDS (P = 0.005). NDS with a mean administered activity of 340 MBq resulted in significantly higher IQ (P < 0.001) and SNR as compared with LDS with a mean of 264 MBq (F-value = 23.5, P < 0.001, mixed model ANOVA adjusted for covariate BMI). Non-diagnostic IQ at LDS was associated with a BMI > 22 kg/m².

Conclusion

FDG dosage significantly predicts IQ and SNR in PET/CT imaging as demonstrated in the same patient with optimal IQ achieved at 5 MBq/kg BM. PET/CT imaging at 4 MBq/kg BW may only be recommended in patients with a BMI ≤ 22 kg/m² to maintain diagnostic IQ.

Spot scanning-based proton therapy for intracranial meningioma: long-term results from the Paul Scherrer Institute

BACKGROUND

To assess the long-term clinical results of spot scanning proton therapy (PT) in the treatment of intracranial meningiomas.

PATIENTS AND METHODS

Thirty-nine patients with meningioma (histologically proven 34/39) were treated with PT between July 1997 and January 2010. Thirty-two (82.1%) patients were treated as primary treatment (exclusive PT, n = 8; postoperative PT, n = 24). Mean age was 48.3 ± 17.9 years and 32 (82.1%) patients had skull base lesions. For patients undergoing surgery, 24 patients had a diagnosis of World Health Organization (WHO) Grade I and 10 of a WHO Grade II/III meningioma, respectively. The female-to-male ratio was 3.3. The median administered dose was 56.0 Gy (relative biologic effectiveness [RBE]) (range, 52.2-66.6) at 1.8-2.0 Gy (RBE) per fraction. Gross tumor volume (GTV) ranged from 0.76 to 546.5 cm(3) (median, 21.5). Late toxicity was assessed according to Common Terminology Criteria for Adverse Events version 3.0. Mean follow-up time was 62.0 months and all patients were followed for >6 months.

RESULTS

Six patients presented with tumor recurrence and 6 patients died during follow-up, of which 4 of tumor progression. Five-year actuarial local control and overall survival rates were 84.8% and 81.8%, respectively, for the entire cohort and 100% for benign histology. Cumulative 5-year Grade ≥3 late toxicity-free survival was 84.5%. On univariate analysis, LC was negatively influenced by WHO grade (p = 0.001), GTV (p = 0.013), and male gender (p = 0.058).

CONCLUSIONS

PT is a safe and effective treatment for patients with untreated, recurrent, or incompletely resected intracranial meningiomas. WHO grade and tumor volume was an adverse prognostic factor for local control.