Assessment of tumour size in PET/CT lung cancer studies: PET- and CT-based methods compared to pathology

BACKGROUND: Positron emission tomography (PET) may be useful for defining the gross tumour volume for radiation treatment planning and for response monitoring of non-small cell lung cancer (NSCLC) patients. The purpose of this study was to compare tumour sizes obtained from CT- and various more commonly available PET-based tumour delineation methods to pathology findings. METHODS: Retrospective non-respiratory gated whole body [(18)F]-fluoro-2-deoxy-D-glucose PET/CT studies from 19 NSCLC patients were used. Several (semi-)automatic PET-based tumour delineation methods and manual CT-based delineation were used to assess the maximum tumour diameter. RESULTS: 50%, adaptive 41% threshold-based and contrast-oriented delineation methods showed good agreement with pathology after removing two outliers (R(2)=0.82). An absolute SUV threshold of 2.5 also showed a good agreement with pathology after the removal of 5 outliers (R(2): 0.79), but showed a significant overestimation in the maximum diameter (19.8 mm, p<0.05). Adaptive 50%, relative threshold level and gradient-based methods did not show any outliers, provided only small, non-significant differences in maximum tumour diameter (<4.7 mm, p>0.10), and showed fair correlation (R(2)>0.62) with pathology. Although adaptive 70% threshold-based methods showed underestimation compared to pathology (36%), it provided the best precision (SD: 14%) together with good correlation (R(2)=0.81). Good correlation between CT delineation and pathology was observed (R(2)=0.77). However, CT delineation showed a significant overestimation compared with pathology (3.8 mm, p<0.05). CONCLUSIONS: PET-based tumour delineation methods provided tumour sizes in agreement with pathology and may therefore be useful to define the (metabolically most) active part of the tumour for radiotherapy and response monitoring purposes

Semi-automatic analysis of standard uptake values in serial PET/CT studies in patients with lung cancer and lymphoma

BACKGROUND: Changes in maximum standardised uptake values (SUV(max)) between serial PET/CT studies are used to determine disease progression or regression in oncologic patients. To measure these changes manually can be time consuming in a clinical routine. A semi-automatic method for calculation of SUV(max )in serial PET/CT studies was developed and compared to a conventional manual method. The semi-automatic method first aligns the serial PET/CT studies based on the CT images. Thereafter, the reader selects an abnormal lesion in one of the PET studies. After this manual step, the program automatically detects the corresponding lesion in the other PET study, segments the two lesions and calculates the SUV(max )in both studies as well as the difference between the SUV(max )values. The results of the semi-automatic analysis were compared to that of a manual SUV(max )analysis using a Philips PET/CT workstation. Three readers did the SUV(max )readings in both methods. Sixteen patients with lung cancer or lymphoma who had undergone two PET/CT studies were included. There were a total of 26 lesions. RESULTS: Linear regression analysis of changes in SUV(max )show that intercepts and slopes are close to the line of identity for all readers (reader 1: intercept = 1.02, R(2 )= 0.96; reader 2: intercept = 0.97, R(2 )= 0.98; reader 3: intercept = 0.99, R(2 )= 0.98). Manual and semi-automatic method agreed in all cases whether SUV(max )had increased or decreased between the serial studies. The average time to measure SUV(max )changes in two serial PET/CT examinations was four to five times longer for the manual method compared to the semi-automatic method for all readers (reader 1: 53.7 vs. 10.5 s; reader 2: 27.3 vs. 6.9 s; reader 3: 47.5 vs. 9.5 s; p < 0.001 for all). CONCLUSIONS: Good agreement was shown in assessment of SUV(max )changes between manual and semi-automatic method. The semi-automatic analysis was four to five times faster to perform than the manual analysis. These findings show the feasibility of using semi-automatic methods for calculation of SUV(max )in clinical routine and encourage further development of programs using this type of methods

Dual-Phase PET-CT to Differentiate [F-18]Fluoromethylcholine Uptake in Reactive and Malignant Lymph Nodes in Patients with Prostate Cancer

PURPOSE: To investigate whether time-trends of enhanced [(18)F]Fluoromethylcholine ([(18)F]FCH) in lymph nodes (LN) of prostate cancer (PCa) patients can help to discriminate reactive from malignant ones, and whether single time point standardized uptake value (SUV) measurements also suffice. PROCEDURES: 25 PCa patients with inguinal (presumed benign) and enlarged pelvic LN (presumed malignant) showing enhanced [(18)F]FCH uptake at dual-phase PET-CT were analyzed. Associations between LN status (benign versus malignant) and SUV(max) and SUV(meanA50), determined at 2 min (early) and 30 min (late) post injection, were assessed. We considered two time-trends of [(18)F]FCH uptake: type A (SUV early &gt; SUV late) and type B (SUV late ≥ SUV early). Histopathology and/or follow-up were used to confirm the assumption that LN with type A pattern are benign, and LN with type B pattern malignant. RESULTS: Analysis of 54 nodes showed that LN status, time-trends, and 'late' (30 min p.i.) SUV(max) and SUV(meanA50) parameters were strongly associated (P&lt;0.0001). SUV(max) relative difference was the best LN status predictor. All but one inguinal LN showed a decreasing [(18)F]FCH uptake over time (pattern A), while 95% of the pelvic nodes presented a stable or increasing uptake (pattern B) type. CONCLUSIONS: Time-trends of enhanced [(18)F]FCH uptake can help to characterize lymph nodes in prostate cancer patients. Single time-point SUV measurements, 30 min p.i., may be a reasonable alternative for predicting benign versus malignant status of lymph nodes, but this remains to be validated in non-enlarged pelvic lymph nodes