FDG-PET/CT imaging for staging and radiotherapy treatment planning of head and neck carcinoma

<p>Abstract</p> <p>Background</p> <p>Positron emission tomography (PET) has a potential improvement for staging and radiation treatment planning of various tumor sites. We analyzed the use of ¹⁸F-fluorodeoxyglucose (FDG)-PET/computed tomography (CT) images for staging and target volume delineation of patients with head and neck carcinoma candidates for radiotherapy.</p> <p>Methods</p> <p>Twenty-two patients candidates for primary radiotherapy, who did not receive any curative surgery, underwent both CT and PET/CT simulation. Gross Tumor Volume (GTV) was contoured on CT (CT-GTV), PET (PET-GTV), and PET/CT images (PET/CT-GTV). The resulting volumes were analyzed and compared.</p> <p>Results</p> <p>Based on PET/CT, changes in TNM categories and clinical stage occurred in 5/22 cases (22%). The difference between CT-GTV and PET-GTV was not statistically significant (p = 0.2) whereas the difference between the composite volume (PET/CT-GTV) and CT-GTV was statistically significant (p < 0.0001).</p> <p>Conclusion</p> <p>PET/CT fusion images could have a potential impact on both tumor staging and treatment planning.</p

FDG-PET/CT imaging for staging and target volume delineation in conformal radiotherapy of anal carcinoma

Background: FDG-PET/CT imaging has an emerging role in staging and treatment planning of various tumor locations and a number of literature studies show that also the carcinoma of the anal canal may benefit from this diagnostic approach. We analyzed the potential impact of FDG-PET/CT in stage definition and target volume delineation of patients affected by carcinoma of the anal canal and candidates for curative radiotherapy. Methods: Twenty seven patients with biopsy proven anal carcinoma were enrolled. Pathology was squamous cell carcinoma in 20 cases, cloacogenic carcinoma in 3, adenocarcinoma in 2, and basal cell carcinoma in 2. Simulation was performed by PET/CT imaging with patient in treatment position. Gross Tumor Volume (GTV) and Clinical Target Volume (CTV) were drawn on CT and on PET/CT fused images. PET-GTV and PET-CTV were respectively compared to CT-GTV and CT-CTV by Wilcoxon rank test for paired data. Results: PET/CT fused images led to change the stage in 5/27 cases (18.5%): 3 cases from N0 to N2 and 2 from M0 to M1 leading to change the treatment intent from curative to palliative in a case. Based on PET/CT imaging, GTV and CTV contours changed in 15/27 (55.6%) and in 10/27 cases (37.0%) respectively. PET-GTV and PET-CTV resulted significantly smaller than CT-GTV (p = 1.2 7 10-4) and CT-CTV (p = 2.9 7 10-4). PET/CT-GTV and PET/CT-CTV, that were used for clinical purposes, were significantly greater than CT-GTV (p = 6 7 10-5) and CT-CTV (p = 6 7 10-5). Conclusions: FDG-PET/CT has a potential relevant impact in staging and target volume delineation of the carcinoma of the anal canal. Clinical stage variation occurred in 18.5% of cases with change of treatment intent in 3.7%. The GTV and the CTV changed in shape and in size based on PET/CT imaging

Threshold segmentation for PET target volume delineation in radiation treatment planning: the role of target-to-background ratio and target size

A multivariable approach was adopted to study the dependence of the percentage threshold [TH (%)] used to define the boundaries of F 18 -FDG positive tissue on emission scan duration (ESD) and activity at the start of acquisition (Aacq) for different target sizes and target-to-background (T/B) ratios. An anthropomorphic model, at least for counting rate characteristics, was used to study this dependence in conditions resembling the ones that can be encountered in the clinical studies. An annular ring of water bags of 3 cm thickness was fitted over an International Electrotechnical Commission (IEC) phantom in order to obtain counting rates similar to those found in average patients. The scatter fraction of the modified IEC phantom was similar to the mean scatter fraction measured on patients, with a similar scanner. A supplemental set of microhollow spheres was positioned inside the phantom. The NEMA NU 2-2001 scatter phantom was positioned at the end of the IEC phantom to approximate the clinical situation of having activity that extends beyond the scanner field of view. The phantoms were filled with a solution of water and F 18 (12 kBq/mL) and the spheres with various T/B ratios of 22.5, 10.3, and 3.6. Sequential imaging was performed to acquire PET images with varying background activity concentrations of about 12, 9, 6.4, 5.3, and 3.1 kBq/mL. The ESD was set to 60, 120, 180, and 240 s/bed. Data were fitted using two distinct multiple linear regression models for sphere ID 6410 mm and sphere ID>10 mm. The fittings of both models were good with an R2 of 0.86 in both cases. Neither ESD nor Aacq resulted as significant predictors of the TH (%). For sphere ID 6410 mm the target size was the most significant predictor of the TH (%), followed by the T/B ratio, while for sphere ID>10 mm the explanatory power of the target size and T/B ratio were reversed, the T/B ratio being now the most important predictor of the TH (%). Both the target size and T/B ratio play a major role in explaining the variance of the TH (%), throughout the whole range of target sizes and T/B ratios examined. Thus, algorithms aimed at automatic threshold segmentation should incorporate both variables with a relative weight which critically depends on target size. \ua9 2008 American Association of Physicists in Medicine

The Value of Imaging in Standing Position in Preoperative Breast Lymphoscintigraphy

Purpose: Breast lymphoscintigraphy is an accurate technique, but in a minority of cases the sentinel node (SN) visualization cannot be achieved or can be very difficult. We evaluated the potential clinical advantages and limitations of performing imaging in the standing position. The aim was to establish if this examination modality is quicker and helpful in the presence of "hidden" SN, checking also for any influence of SN skin landmarking in the upright position on the correct intraoperative SN identification. The overall objective was to verify if the standing position can be routinely used in breast lymphoscintigraphy. Methods: A total of 144 patients underwent lymphoscintigraphy in both standing and supine positions. In both modalities, a skin landmark was set coincident with the SN orthogonal projections. The acquisition times of 2 groups (each consisting of 45 patients) examined with the standing or supine acquisition modality, were compared. Results: In 6 cases with hidden SN and in 34 cases with difficult or partial visualization in one of the supine views, the standing protocol was effective and led to better and quicker visualization of lymph nodes (median examination time: 25.5 minutes standing, 35.5 minutes supine). Significant differences in skin landmark position between the 2 modalities were present only in overweight patients and in large breasts. This, however, did not have a negative impact on successful intraoperative localization of SN with the gamma probe. Conclusions: Standing acquisition resulted to be a faster, easier, and more accurate examination protocol and can be used as the routine method for SN detection in breast lymphoscintigraphy

Influence of different contributions of scatter and attenuation on the threshold values in contrast-based algorithms for volume segmentation

The aim of this work is to evaluate the role of different amount of attenuation and scatter on FDG-PET image volume segmentation using a contrast-oriented method based on the target-to-background (TB) ratio and target dimensions. A phantom study was designed employing 3 phantom sets, which provided a clinical range of attenuation and scatter conditions, equipped with 6 spheres of different volumes (0.5e26.5 ml). The phantoms were: (1) the Hoffman 3-dimensional brain phantom, (2) a modified International Electro technical Commission (IEC) phantom with an annular ring of water bags of 3 cm thickness fit over the IEC phantom, and (3) a modified IEC phantom with an annular ring of water bags of 9 cm. The phantoms cavities were filled with a solution of FDG at 5.4 kBq/ml activity concentration, and the spheres with activity concentration ratios of about 16, 8, and 4 times the background activity concentration. Images were acquired with a Biograph 16 HI-REZ PET/CT scanner. Thresholds (TS) were determined as a percentage of the maximum intensity in the cross section area of the spheres. To reduce statistical fluctuations a nominal maximum value is calculated as the mean from all voxel >95%. To find the TS value that yielded an area A best matching the true value, the cross section were auto-contoured in the attenuation corrected slices varying TS in step of 1%, until the area so determined differed by less than 10 mm2 versus its known physical value. Multiple regression methods were used to derive an adaptive thresholding algorithm and to test its dependence on different conditions of attenuation and scatter. The errors of scatter and attenuation correction increased with increasing amount of attenuation and scatter in the phantoms. Despite these increasing inaccuracies, PETthreshold segmentation algorithms resulted not influenced by the different condition of attenuation and scatter. The test of the hypothesis of coincident regression lines for the three phantoms used provided no statistical basis for believing that the three lines are not coincident. Calibration curves needed to implement contouring algorithms based on adaptive TS segmentation of PET volumes can be devised in different conditions of attenuation and scatter. This opens the possibility of defining a unified contrast-based method for target delineation in different anatomical districts

Spatial and Temporal Heterogeneity of Regional Myocardial Uptake in Patients Without Heart Disease Under Fasting Conditions on Repeated Whole-Body 18F-FDG PET/CT.

none8Imaging of cardiac F-18-FDG uptake is used in the diagnostic evaluation of residual viable myocardium. Although, originally, hibernating myocardium was identified by a mismatch between perfusion defect and relatively preserved F-18-FDG uptake, at present several studies propose that 18F-FDG distribution can also be used alone for this purpose. Nevertheless, even severe myocardial F-18-FDG uptake defects are frequently observed in cancer patients without any cardiac disease. The aim of this study was to retrospectively analyze global and regional F-18-FDG cardiac images of 49 consecutive cancer patients free of cardiac diseases who submitted to 3 PET scans under fasting conditions. Methods: Images were acquired with a high-resolution PET/CT scanner. Three-dimensional regions of interest drawn on the fused PET/CT images to measure the maxima standardized uptake value of the left ventricular myocardium (SUVMyo) as well as the average SUV of the left ventricular blood (SUVLV) and of the liver (SUVLiver). Analysis of regional myocardial F-18-FDG uptake was performed on a subsample of 26 patients by an automatic recognition of endocardial and epicardial borders and subdividing the left ventricle in 20 segments. Regional F-18-FDG distribution was defined as the percentage of SUVMyo. in each region. Results: SUVMyo as well as SUVLV and SUVLiver did not change on average throughout the studies. This stability was not caused by a persistent pattern of myocardial (18-)FDG distribution. Rather, it was associated with important variations in both directions over time. Regional F-18-FDG distribution was largely heterogeneous in all 3 studies, with a variation coefficient in each patient of 18% +/- 7%, 18% +/- 5%, and 17% +/- 5%, respectively. An F-18-FDG uptake of 10% in 76 and in 116 of 468 segments, respectively. Conclusion: The large spatial and temporal heterogeneity of the myocardial metabolic pattern, in cancer patients free of any disease, suggests a word of caution on the use of F-18-FDG alone as a diagnostic tool for myocardial viability.INGLESE E; LEVA L; MATHEOUD R; SACCHETTI G; SECCO C; GANDOLFO P; BRAMBILLA M; G. SAMBUCETIInglese, E; Leva, L; Matheoud, R; Sacchetti, G; Secco, C; Gandolfo, P; Brambilla, M; Sambuceti, Gianmari