An investigation into positron emission tomography contouring methods across two treatment planning systems.

Positron emission tomography (PET) imaging has been used to provide additional information regarding patient tumor location, size, and staging for radiotherapy treatment planning purposes. This additional information reduces interobserver variability and produces more consistent contouring. It is well recognized that different contouring methodology for PET data results in different contoured volumes. The goal of this study was to compare the difference in PET contouring methods for 2 different treatment planning systems using a phantom dataset and a series of patient datasets. Contouring methodology was compared on the ADAC Pinnacle Treatment Planning System and the CMS XiO Treatment Planning System. Contours were completed on the phantom and patient datasets using a number of PET contouring methods-the standardized uptake value 2.5 method, 30%, 40%, and 50% of the maximum uptake method and the signal to background ratio method. Differences of >15% were observed for PET-contoured volumes between the different treatment planning systems for the same data and the same PET contouring methodology. Contoured volume differences between treatment planning systems were caused by differences in data formatting and display and the different contouring tools available. Differences in treatment planning system as well as contouring methodology should be considered carefully in dose-volume contouring and reporting, especially between centers that may use different treatment planning systems or those that have several different treatment planning systems.

Diagnostic and staging impact of radiotherapy planning FDG-PET-CT in non-small-cell lung cancer.

BACKGROUND AND PURPOSE: To evaluate whether FDG-PET performed for radiotherapy (RT) planning can detect disease progression, compared with staging PET. MATERIALS AND METHODS: Twenty-six patients with newly-diagnosed non-small-cell lung cancer underwent planning PET-CT for curative RT within 8 weeks (mean: 33±14days) of staging PET-CT. Progressive disease (PD) was defined as >25% increase in tumour size (transaxial) or volume, as delineated by SUV threshold of 2.5, or new sites (SUV>2.5). RESULTS: The planning PET detected PD in 16 patients (61%), compared to four patients (15%) by CT component of PET-CT. The mean scan interval was longer in patients with progression: 40±12days, compared to 22±11days without progression. Planning PET detected PD in 13/17 (76%), 12/14 (86%) and 7/7 patients if the interval was ≥4, 5 and 6 weeks, respectively, compared with 3/9 patients if interval <4 weeks. Planning PET detected PD in primary metabolic volume in seven patients, 20 new nodal sites in 12 new nodal stations and nine patients, five extra-nodal sites in five patients. This resulted in upstaging in nine patients (35%): stage IIIA in three, IIIB in three and IV in three. CONCLUSIONS: RT-planning FDG-PET can provide incremental diagnostic information and may impact on staging in a significant number of patients.

The prevalence and clinical significance of (18) F-2-fluoro-2-deoxy-D-glucose (FDG) uptake in the thyroid gland on PET or PET-CT in patients with lymphoma.

F(18) -2-fluoro-2-deoxy-D-glucose (FDG) positron emission tomography (PET) has become a well established tool in staging and assessing therapy response in lymphoma. Incidental thyroid uptake on PET is not uncommon and can pose a diagnostic and management challenge. We retrospectively evaluate the prevalence and clinical significance of incidental FDG uptake in the thyroid gland in patients with lymphoma. 1868 lymphoma patients underwent PET and PET-CT between August 2002 and August 2008. 52 patients (2.8%) demonstrated FDG thyroid uptake (M = 17, F = 35; mean age 63 yr). Thyroid uptake was determined as focal or diffuse, maximum standardized uptake values (SUVmax) recorded as well as SUV max ratio compared to background mediastinum activity (SUVR). Corresponding CT findings on PET-CT were evaluated independently. Results were correlated with clinical, histopathological and imaging follow-up. 30 (1.6%) patients had focal thyroid uptake. 16 (53%) had histological confirmation either by surgery (n = 7) or FNA under USS (n = 9). The final diagnosis was benign in 12/30 patients and malignant in 9/30. The malignancy risk for focal thyroid uptake was 30%. Five patients had intercurrent thyroid cancer (four papillary, one microinvasive follicular) and four had lymphomatous involvement. There was no significant difference between the mean sizes of benign (23.7 mm, range 12-34) and malignant nodules (23.6 mm, range 8-48). The mean SUVmax of malignant and benign nodules was 4.4 (range 1.8-10.1) and 3.2 (range 1.8-6.9) respectively with no statistically significant difference. 22 (1.2%) patients had diffuse FDG uptake in thyroid and benign aetiology was found in all with adequate follow-up (15/22). Focal FDG thyroid uptake on PET or PET-CT in lymphoma patients warrants further investigations. The malignancy risk is 30% either due to intercurrent thyroid cancer or lymphomatous involvement. SUVmax, SUVR and CT attenuation characteristics are not helpful in distinguishing between benign and malignant aetiologies. Diffuse thyroid uptake has a benign aetiology.

NEMA NU 2-2001 performance testing of a Philips Gemini GXL PET/CT scanner.

Post installation acceptance testing is vital to demonstrate that the equipment meets the vendor's specification and is suitable for clinical studies. The test procedures described in the NEMA NU 2-2001 document form the basis of vendor performance specifications of PET scanners and hence are also appropriate for acceptance testing. Initial installation performance tests of the Philips Gemini GXL PET/CT scanner installed at Liverpool Hospital revealed that the peak noise equivalent count rate (NECR) measurement of 57.5 kcps was substantially lower than the specification of 70 kcps and the scatter fraction of 38.5% was 10% higher than the specification of

Voxel-based morphometry in the detection of dysplasia and neoplasia in childhood epilepsy: limitations of grey matter analysis.

The purpose of this exploratory investigation was to evaluate voxel-based morphometry (VBM) in detecting lesions underlying childhood epilepsy, and to establish the optimal image processing and statistical parameters in this context. The patients were 16 children (10 boys) aged 5.9 to 15.2 years (mean 11.3 years) with epilepsy and focal cortical dysplasia (FCD) or neoplasia. The control group comprised 24 normal children (12 boys), age matched to the patients. MRI volumes were spatially normalised to a custom template and segmented into grey matter (GM) and white matter. Using statistical parametric mapping, the GM segment from each patient was then contrasted with the mean GM segment of the control group utilising different VBM post-processing methods. Maps showing increased/decreased areas of GM concentration or volume were generated and compared with visually identified lesions. The results indicated that conservative VBM parameters of linear normalisation with no modulation produced the highest rates of lesion detection, which were identical for FCD and neoplasia at 5/8 lesions. These preliminary data suggest that VBM analysis of GM using conservative parameters can usually detect FCD and neoplasia in the MRI of children with epilepsy, but sensitivity may be inadequate for routine clinical application. Further refinement of the technique may be necessary.

Voxel-based morphometry in the detection of dysplasia and neoplasia in childhood epilepsy: combined grey/white matter analysis augments detection.

PURPOSE: Analysis of grey matter on MRI utilising voxel-based morphometry (VBM) may have insufficient sensitivity for routine clinical application. The aim of this exploratory study was to evaluate combined analysis of grey and white matter using VBM for detecting focal lesions underlying childhood epilepsy, and to establish the optimal statistical parameters in this context. METHODS: The patients were 16 children (10 boys) aged 5.9-15.2 years (11.3+/-2.8 years; mean+/-S.D.) with epilepsy and focal cortical dysplasia (FCD) or neoplasia. The control group comprised 24 normal children (12 boys), age matched to the patients. VBM was used to spatially normalise MRI volumes to a custom template and segment them into grey matter (GM) and white matter (WM). The combined GM/WM segments from each patient were contrasted with the control group. Three different VBM post-processing techniques of combined GM/WM were evaluated along with GM-only analysis. Maps showing increased/decreased GM or GM/WM concentration were generated and compared with visually identified lesions. Rates of detection and true/false positives voxels were calculated. RESULTS: The GM-only lesion detection rate was equal for FCD and neoplasia at 5/8, whereas the best combined GM/WM technique detected 8/8 FCD and 6/8 neoplasia. The combined technique also produced a higher overall rate of true positives (87%) than GM-only (44%) with a similar low rate of false positives. CONCLUSIONS: These preliminary data suggest that VBM is ineffective for precise delineation of lesion margins, but could potentially be used to detect subtle dysplasia in MRI negative and equivocal cases.

Application of statistical parametric mapping to SPET in the assessment of intractable childhood epilepsy.

Statistical parametric mapping (SPM) quantification and analysis has been successfully applied to functional imaging studies of partial epilepsy syndromes in adults. The present study evaluated whether localisation of the epileptogenic zone (determined by SPM) improves upon visually examined single-photon emission tomography (SPET) imaging in presurgical assessment of children with temporal lobe epilepsy (TLE) and frontal lobe epilepsy (FLE). The patient sample consisted of 24 children (15 males) aged 2.1-17.8 years (9.8+/-4.3 years; mean+/-SD) with intractable TLE or FLE. SPET imaging was acquired routinely in presurgical evaluation. All patient images were transformed into the standard stereotactic space of the adult SPM SPET template prior to SPM statistical analysis. Individual patient images were contrasted with an adult control group of 22 healthy adult females. Resultant statistical parametric maps were rendered over the SPM canonical magnetic resonance imaging (MRI). Two corresponding sets of ictal and interictal SPM and SPET images were then generated for each patient. Experienced clinicians independently reviewed the image sets, blinded to clinical details. Concordance of the reports between SPM and SPET images, syndrome classification and MRI abnormality was studied. A fair level of inter-rater reliability (kappa=0.73) was evident for SPM localisation. SPM was concordant with SPET in 71% of all patients, the majority of the discordance being from the FLE group. SPM and SPET localisation were concordant with epilepsy syndrome in 80% of the TLE cases. Concordant localisation to syndrome was worse for both SPM (33%) and SPET (44%) in the FLE group. Data from a small sample of patients with varied focal structural pathologies suggested that SPM performed poorly relative to SPET in these cases. Concordance of SPM and SPET with syndrome was lower in patients younger than 6 years than in those aged 6 years and above. SPM is effective in localising the potential epileptogenic zone but does not provide additional benefit beyond SPET in presurgical assessment of children with intractable epilepsy. The impact of different pathologies on the efficacy of SPM warrants further study.