Prospective evaluation of pretreatment and intratreatment FDG PET-CT SUV stability in primary head and neck cancer.

PURPOSE: To evaluate standardized uptake value (SUV) stability on pretreatment and intratreatment 18-fluorodeoxyglucose (FDG) positron emission tomography-computed tomography (PET-CT) in patients undergoing definitive CRT for head and neck cancer (HNC). METHODS: Primary tumor and nodal volumes of interest (VOIs) from HNC patients were contoured on the pretreatment and intratreatment PET-CT by two independent observers. SUV stability was measured with intersection calculations (DICE, overlap fraction, center to center) between the VOIs at threshold levels of 50%, 60%, 70%, 80%, and 90% of the SUV maximum. RESULTS: The mean calculated DICE of the 50%, 60%, 70%, 80%, 90% SUV threshold was 0.53, 0.48, 0.41, 0.28, and 0.12, respectively. The mean calculated overlap fraction was 0.71, 0.65, 0.58, 0.43, and 0.2, respectively. Center-center difference demonstrates spatial variability of 7.8, 8.2, 8.6, 9.5, and 11.2 mm for these SUV subvolumes of interest. CONCLUSIONS: HNC subvolumes defined by SUV thresholding technique in FDG PET-CT imaging do not remain physically stable during (chemo)RT. HIGHLIGHTS: All pretreatment and intratreatment SUV thresholds (50%-90%) overlap indexes are low during the course of (chemo)radiation. Pretreatment and intratreatment center to center variation further corroborates that all FDG threshold volumes do not remain stable during treatment. No difference in SUV threshold stability was seen between p16 positive and negative tumors.

Differentiating between visual hallucination-free dementia with Lewy bodies and corticobasal syndrome on the basis of neuropsychology and perfusion single-photon emission computed tomography.

INTRODUCTION: Dementia with Lewy bodies (DLB) and Corticobasal Syndrome (CBS) are atypical parkinsonian disorders with fronto-subcortical and posterior cognitive dysfunction as common features. While visual hallucinations are a good predictor of Lewy body pathology and are rare in CBS, they are not exhibited in all cases of DLB. Given the clinical overlap between these disorders, neuropsychological and imaging markers may aid in distinguishing these entities. METHODS: Prospectively recruited case-control cohorts of CBS (n =31) and visual hallucination-free DLB (n =30), completed neuropsychological and neuropsychiatric measures as well as brain perfusion single-photon emission computed tomography and structural magnetic resonance imaging (MRI). Perfusion data were available for forty-two controls. Behavioural, perfusion, and cortical volume and thickness measures were compared between the groups to identify features that serve to differentiate them. RESULTS: The Lewy body with no hallucinations group performed more poorly on measures of episodic memory compared to the corticobasal group, including the delayed and cued recall portions of the California Verbal Learning Test (F (1, 42) =23.1, P <0.001 and F (1, 42) =14.0, P =0.001 respectively) and the delayed visual reproduction of the Wechsler Memory Scale-Revised (F (1, 36) =9.7, P =0.004). The Lewy body group also demonstrated reduced perfusion in the left occipital pole compared to the corticobasal group (F (1,57) =7.4, P =0.009). At autopsy, the Lewy body cases all demonstrated mixed dementia with Lewy bodies, Alzheimer's disease and small vessel arteriosclerosis, while the corticobasal cases demonstrated classical corticobasal degeneration in five, dementia with agyrophilic grains + corticobasal degeneration + cerebral amyloid angiopathy in one, Progressive Supranuclear Palsy in two, and Frontotemporal Lobar Degeneration-Ubiquitin/TAR DNA-binding protein 43 proteinopathy in one. MRI measures were not significantly different between the patient groups. CONCLUSIONS: Reduced perfusion in the left occipital region and worse episodic memory performance may help to distinguish between DLB cases who have never manifested with visual hallucinations and CBS at earlier stages of the disease. Development of reliable neuropsychological and imaging markers that improve diagnostic accuracy will become increasingly important as disease modifying therapies become available.

Dose equivalent rate constants and barrier transmission data for nuclear medicine facility dose calculations and shielding design.

A primary goal of nuclear medicine facility design is to keep public and worker radiation doses As Low As Reasonably Achievable (ALARA). To estimate dose and shielding requirements, one needs to know both the dose equivalent rate constants for soft tissue and barrier transmission factors (TFs) for all radionuclides of interest. Dose equivalent rate constants are most commonly calculated using published air kerma or exposure rate constants, while transmission factors are most commonly calculated using published tenth-value layers (TVLs). Values can be calculated more accurately using the radionuclide's photon emission spectrum and the physical properties of lead, concrete, and/or tissue at these energies. These calculations may be non-trivial due to the polyenergetic nature of the radionuclides used in nuclear medicine. In this paper, the effects of dose equivalent rate constant and transmission factor on nuclear medicine dose and shielding calculations are investigated, and new values based on up-to-date nuclear data and thresholds specific to nuclear medicine are proposed. To facilitate practical use, transmission curves were fitted to the three-parameter Archer equation. Finally, the results of this work were applied to the design of a sample nuclear medicine facility and compared to doses calculated using common methods to investigate the effects of these values on dose estimates and shielding decisions. Dose equivalent rate constants generally agreed well with those derived from the literature with the exception of those from NCRP 124. Depending on the situation, Archer fit TFs could be significantly more accurate than TVL-based TFs. These results were reflected in the sample shielding problem, with unshielded dose estimates agreeing well, with the exception of those based on NCRP 124, and Archer fit TFs providing a more accurate alternative to TVL TFs and a simpler alternative to full spectral-based calculations. The data provided by this paper should assist in improving the accuracy and tractability of dose and shielding calculations for nuclear medicine facility design.

Phase I trial of intraoperative detection of tumor margins in patients with HER2-positive carcinoma of the breast following administration of 111In-DTPA-trastuzumab Fab fragments.

INTRODUCTION: Our aim was to conduct a Phase I clinical trial to determine the feasibility of intraoperative detection of tumor margins in HER2 positive breast carcinoma using a hand-held γ-probe following administration of (111)In-DTPA-trastuzumab Fab fragments. Accurate delineation of tumor margins is important for preventing local recurrence. METHODS: Six patients with HER2-positive in situ or invasive ductal carcinoma were administered 74MBq (0.5mg) of (111)In-DTPA-trastuzumab Fab fragments and counts in the tumor, surgical cavity wall and en face margins were measured intraoperatively at 72h post-injection using the Navigator or C-Trak γ-probes. Margins were evaluated histologically. Quantitative whole body planar imaging was performed to estimate radiation absorbed doses using OLINDA/EXM software. SPECT imaging of the thorax was performed to evaluate tumor uptake. The pharmacokinetics of elimination from the blood and plasma were determined over 72h. RESULTS: There were no acute adverse reactions from (111)In-DTPA-trastuzumab Fab fragments and no changes in hematological or biochemical indices were found over a 3month period. (111)In-DTPA-trastuzumab Fab fragments exhibited a biphasic elimination from the blood and plasma with t1/2α=11.9h and 7.5h, respectively, and t1/2ß=26.6 and 20.7h, respectively. The radiopharmaceutical accumulated in the liver, spleen and kidneys. SPECT imaging did not reveal tumor in any patient. The mean effective dose was 0.146mSv/MBq (10.8mSv for 74MBq). Counts in excised tumors were low but were higher than in margins. Margins in two patients harboured tumor but this was not correlated with counts obtained using the γ-probes. Surgical cavity counts were high and likely due to detection of γ-photons outside the surgical field. CONCLUSION: We conclude that it was not feasible, at least at the administered amount of radioactivity used in this study, to reliably detect the margins of disease in patients with in situ or invasive ductal carcinoma intraoperatively using a hand-held γ-probe and (111)In-DTPA-trastuzumab Fab fragments due to low uptake in the tumor and involved margins.

Feasibility evaluation of radioimmunoguided surgery of breast cancer.

Breast-conserving surgery involves completely excising the tumour while limiting the amount of normal tissue removed, which is technically challenging to achieve, especially given the limited intraoperative guidance available to the surgeon. This study evaluates the feasibility of radioimmunoguided surgery (RIGS) to guide the detection and delineation of tumours intraoperatively. The 3D point-response function of a commercial gamma-ray-detecting probe (GDP) was determined as a function of radionuclide ((131)I, (111)In,( 99m)Tc), energy-window threshold, and collimator length (0.0-3.0-cm). This function was used to calculate the minimum detectable tumour volumes (MDTVs) and the minimum tumour-to-background activity concentration ratio (T:B) for effective delineation of a breast tumour model. The GDP had larger MDTVs and a higher minimum required T:B for tumour delineation with (131)I than with (111)In or (99m)Tc. It was shown that for (111)In there was a benefit to using a collimator length of 0.5-cm. For the model used, the minimum required T:B required for effective tumour delineation was 5.2 ± 0.4. RIGS has the potential to significantly improve the accuracy of breast-conserving surgery; however, before these benefits can be realized, novel radiopharmaceuticals need to be developed that have a higher specificity for cancerous tissue in vivo than what is currently available.

Visual attention deficits in Alzheimer's disease: relationship to HMPAO SPECT cortical hypoperfusion.

Patients with Alzheimer's disease (AD) display a multiplicity of cognitive deficits in domains such as memory, language, and attention, all of which can be clearly linked to the underlying neuropathological alterations. The typical degenerative changes occur early on in the disease in the temporal-parietal lobes, with other brain regions, such as the frontal cortex, becoming more affected as the disease progresses. In light of the importance of the parietal cortex in mediating visuospatial attentional processing, in the present study, we investigated a deficit in covert orienting of visual attention and its relationship to cortical hypoperfusion in AD. We characterized the visual attentional profile of 21 AD patients, relative to that of 26 matched normal individuals, and then assessed the correspondence between behavior and hypoperfusion, as measured by regional cerebral blood flow using SPECT. Relative to controls, the AD group demonstrated a unilateral attentional deficit, with disproportionate slowing in reorienting attention to targets in the left compared to the right hemispace, especially following an invalid peripheral cue. Furthermore, even in the presence of bilateral pathology typical of AD, there was a positive correlation between this unilateral attentional disorder and the magnitude of the right superior parietal lobe hypoperfusion. The association of the altered attentional processing profile (i.e., greater difficulty disengaging attention from right-sided stimuli) with right-hemisphere-predominant hypoperfusion not only confirms the critical role of the right parietal lobe in covert attentional orienting but, more importantly, identifies a potential locus of the behavioral alterations in visuospatial processing in AD.

Design and construction of a quality control phantom for SPECT and PET imaging.

In this article, the authors present a method for quickly and easily constructing test phantoms for PET and SPECT quality assurance. As a demonstration, they constructed a complex prototype test phantom, showing the strengths of the construction method. Images taken using a PET/CT and a SPECT scanner are presented, along with a qualitative evaluation of PET/CT using the test phantom. The construction technique provides a quick, easy, and cost effective means of constructing a phantom for use in nuclear medicine imaging.

Experimental evaluation of an online gamma-camera imaging of permanent seed implantation (OGIPSI) prototype for partial breast irradiation.

Previously, our team used Monte Carlo simulation to demonstrate that a gamma camera could potentially be used as an online image guidance device to visualize seeds during permanent breast seed implant procedures. This could allow for intraoperative correction if seeds have been misplaced. The objective of this study is to describe an experimental evaluation of an online gamma-camera imaging of permanent seed implantation (OGIPSI) prototype. The OGIPSI device is intended to be able to detect a seed misplacement of 5 mm or more within an imaging time of 2 min or less. The device was constructed by fitting a custom built brass collimator (16 mm height, 0.65 mm hole pitch, 0.15 mm septal thickness) on a 64 pixel linear array CZT detector (eValuator-2000, eV Products, Saxonburg, PA). Two-dimensional projection images of seed distributions were acquired by the use of a digitally controlled translation stage. Spatial resolution and noise characteristics of the detector were measured. The ability and time needed for the OGIPSI device to image the seeds and to detect cold spots was tested using an anthropomorphic breast phantom. Mimicking a real treatment plan, a total of 52 103Pd seeds of 65.8 MBq each were placed on three different layers at appropriate depths within the phantom. The seeds were reliably detected within 30 s with a median error in localization of 1 mm. In conclusion, an OGIPSI device can potentially be used for image guidance of permanent brachytherapy applications in the breast and, possibly, other sites.

Online gamma-camera imaging of 103Pd seeds (OGIPS) for permanent breast seed implantation.

Permanent brachytherapy seed implantation is being investigated as a mode of accelerated partial breast irradiation for early stage breast cancer patients. Currently, the seeds are poorly visualized during the procedure making it difficult to perform a real-time correction of the implantation if required. The objective was to determine if a customized gamma-camera can accurately localize the seeds during implantation. Monte Carlo simulations of a CZT based gamma-camera were used to assess whether images of suitable quality could be derived by detecting the 21 keV photons emitted from 74 MBq (103)Pd brachytherapy seeds. A hexagonal parallel hole collimator with a hole length of 38 mm, hole diameter of 1.2 mm and 0.2 mm septa, was modeled. The design of the gamma-camera was evaluated on a realistic model of the breast and three layers of the seed distribution (55 seeds) based on a pre-implantation CT treatment plan. The Monte Carlo simulations showed that the gamma-camera was able to localize the seeds with a maximum error of 2.0 mm, using only two views and 20 s of imaging. A gamma-camera can potentially be used as an intra-procedural image guidance system for quality assurance for permanent breast seed implantation.

Comparison of manual and semi-automated delineation of regions of interest for radioligand PET imaging analysis.

BACKGROUND: As imaging centers produce higher resolution research scans, the number of man-hours required to process regional data has become a major concern. Comparison of automated vs. manual methodology has not been reported for functional imaging. We explored validation of using automation to delineate regions of interest on positron emission tomography (PET) scans. The purpose of this study was to ascertain improvements in image processing time and reproducibility of a semi-automated brain region extraction (SABRE) method over manual delineation of regions of interest (ROIs). METHODS: We compared 2 sets of partial volume corrected serotonin 1a receptor binding potentials (BPs) resulting from manual vs. semi-automated methods. BPs were obtained from subjects meeting consensus criteria for frontotemporal degeneration and from age- and gender-matched healthy controls. Two trained raters provided each set of data to conduct comparisons of inter-rater mean image processing time, rank order of BPs for 9 PET scans, intra- and inter-rater intraclass correlation coefficients (ICC), repeatability coefficients (RC), percentages of the average parameter value (RM%), and effect sizes of either method. RESULTS: SABRE saved approximately 3 hours of processing time per PET subject over manual delineation (p < .001). Quality of the SABRE BP results was preserved relative to the rank order of subjects by manual methods. Intra- and inter-rater ICC were high (>0.8) for both methods. RC and RM% were lower for the manual method across all ROIs, indicating less intra-rater variance across PET subjects' BPs. CONCLUSION: SABRE demonstrated significant time savings and no significant difference in reproducibility over manual methods, justifying the use of SABRE in serotonin 1a receptor radioligand PET imaging analysis. This implies that semi-automated ROI delineation is a valid methodology for future PET imaging analysis.

Medial temporal hypoperfusion and aggression in Alzheimer disease.

BACKGROUND: It is not understood why some patients with Alzheimer disease (AD) display aggression and others do not. OBJECTIVE: To examine the relation between regional brain perfusion and aggression in AD. DESIGN: Single-photon emission computed tomographic scans were coregistered to a standardized template in Talairach space, generating mean ratios of uptake referenced to the cerebellum. PARTICIPANTS: Forty-nine outpatients (25 men and 24 women; mean +/- SD age, 74 +/- 11 years) with probable AD (Mini-Mental State Examination score, 17.7 +/- 5.0; 30 aggressive and 19 nonaggressive), comparable in age, sex, and severity of cognitive impairment. MAIN OUTCOME MEASURES: Regional perfusion ratios were determined for 5 bilateral regions of interest: orbitofrontal, middle medial temporal, inferior medial temporal, hypothalamus/thalamus, and anterior cingulate. RESULTS: Compared with nonaggressive patients, aggressive ones displayed hypoperfusion in the right and left middle medial temporal regions of interest (P = .02 for both), but not the others (all (t tests, unpaired, 2-tailed). On regression analyses, right middle temporal hypoperfusion (P = .001), younger age (P = .002), greater activity disturbances (P = .004), and higher Mini-Mental State Examination scores (P = .04) independently predicted aggression, accounting for 44% of the total variance (F = 8.7; P<.001). Statistical parametric mapping analyses supported right middle medial temporal hypoperfusion in the aggressive group (P = .008). CONCLUSION: In this sample of patients with AD, the right middle medial temporal region emerged as an important neural correlate of aggression.

The influence of sex on limbic volume and perfusion in AD.

The goal of the current study was to determine whether Alzheimer's disease (AD) pathology affects the limbic system of men and women differently as measured by in vivo neuroimaging. Magnetic resonance imaging (MRI) and coregistered single photon emission computed tomography (SPECT) were used to examine the limbic system in 20 men and 20 women with probable AD compared to 40 age- and education-matched normal controls (20 men, 20 women). Limbic volumes and relative perfusion values were obtained from the MR images and coregistered SPECT scans, respectively. No significant differences were found between sexes in limbic volumes or relative perfusion values in the normal controls. Many limbic regions were significantly affected in both men and women with AD compared to normal controls. However, only the men with AD displayed atrophy in the orbitofrontal cortex, middle and posterior cingulate cortices, hypothalamus, and mamillary bodies, and relative hypoperfusion in the anterior and middle cingulate cortices. Women with AD exclusively showed anterior thalamic atrophy. Separating men and women did not substantially improve diagnostic classification.

Can PET provide the 3D extent of tumor motion for individualized internal target volumes? A phantom study of the limitations of CT and the promise of PET.

PURPOSE: To characterize the limitations of fast, spiral computed tomography (CT) when imaging a moving object and to investigate whether positron emission tomography (PET) can predict the internal target volume (ITV) and ultimately improve the planning target volume (PTV) for moving tumors. METHODS AND MATERIALS: To mimic tumors, three fillable spheres were imaged while both stationary and during periodic motion using spiral CT and PET. CT- and PET-imaged volumes were defined quantitatively using voxel values. Ideal PTVs for each scenario were calculated. CT-based PTVs were generated using margins of 7.5, 10, and 15 mm to account for both organ motion and setup uncertainties. PET-based PTVs were derived with the assumption that motion was captured in the PET images and only a margin (7.5 mm) for setup errors was necessary. Comparisons between CT-based and PET-based PTVs with ideal PTVs were performed. RESULTS: CT imaging of moving spheres resulted in significant distortions in the three-dimensional (3D) image-based representations, and did not, in general, result in images well representative of either moving or stationary spheres. PET images were similar to the ideal capsular shape encompassing the sphere and its motion. In all cases, CT-imaged volumes were larger than that for the stationary sphere (range of excess volume from 0.4 to 29 cm(3) for stationary volumes of 2.14 to 172 cm(3)), but smaller than that for the true motion volume. PET-imaged volumes were larger than the true motion volume (difference from ideal ranged from 3 to 94 cm(3) for motion volumes of 1.2 to 243 cm(3)) and much larger than the stationary volume. Using CT data, geographic miss of some part of the ideal PTV occurred for 0 of 24 cases, 11 of 24 cases, and 18 of 24 cases using a 15-mm, 10-mm, and 7.5-mm margin, respectively. Geographic miss did not occur in any case for the PET-based PTV. The amount of "normal tissue" included in CT-based PTVs was dramatically greater than that included in PET-based PTVs. CONCLUSION: Fast CT imaging of a moving tumor can result in poor representation of the time-averaged position and shape of the tumor. PET imaging can provide a more accurate representation of the 3D volume encompassing motion of model tumors and has potential to provide patient-specific motion volumes for an individualized ITV.

Multimodality imaging for precise localization of craniofacial osteomyelitis.

Functional imaging identifies areas of abnormal bone turnover, providing a useful adjunct in the treatment of osteomyelitis and bone tumors. The low resolution and lack of anatomical detail limit the application of bone scans in craniofacial surgery, however. Multimodality image registration addresses this problem by fusing functional images (single photon emission computed tomography [SPECT]) to high-resolution structural images (computed tomography [CT]) for precise anatomical delineation of bone activity. This article describes a technique for spatial registration of CT and SPECT images to provide precise anatomical delineation of abnormal bone turnover, thereby guiding the extent of resection in the management of craniofacial osteomyelitis. Standard CT and SPECT imaging protocols were used in imaging the skull from the vertex to the mentum. Image data were imported into Analyze (Biomedical Imaging Resource; Mayo Foundation, Rochester, MN) on a dedicated Windows NT (Microsoft Corporation, Redmond, WA) workstation. Using the CT data, the craniofacial skeleton, osteotomy segments, and bone grafts were interactively mapped out. Consecutive axial slices were then reconstructed to form a three-dimensional volume of interest. The CT-derived volume of interest was registered to the technetium Tc 99m-methylene diphosphonate SPECT scan using the Analyze program to provide a fused multimodality image. The imaging technique was used to localize osteomyelitis in a complex craniofacial reconstruction. The fused images guided the extent of resection during surgery, and postoperative microbiological and histological testing confirmed the diagnosis. Multimodality image registration provides a readily available method to relate facial skeletal anatomy and physiology. This technique is valuable in planning and monitoring therapeutic interventions in clinical conditions in which bone turnover is abnormal.

Utility of simultaneous brain, CSF and hyperintensity quantification in dementia.

Improved methods of quantifying MRI are needed to study brain-behavior relationships in dementia. Rating scales are variable; lesion-tracing approaches can be subjective and ignore atrophy; segmentation of MRI hyperintensities is complicated by partial volume effects; and hyperintense lesions in different anatomical areas may have different effects. The goal of this study was to extend existing segmentation approaches to include hyperintensities and to demonstrate the utility of simultaneously assessing atrophy and lesion compartments in dementia. A semi-automated method was applied to quantify brain and cerebrospinal fluid (CSF) compartments and to subclassify hyperintensities into periventricular, deep white matter, thalamic and basal ganglia compartments. Twenty MR scans from participants in an ongoing dementia study were used to generate intra- and inter-rater reliability estimates. High intra- and inter-class correlation coefficients (0.83-0.99) were obtained for all measures and the semi-automated measurements were highly correlated with traced volumes. Brain, CSF and specific lesion volumes were significantly correlated with neuropsychological functions. In models using only total hyperintensity volumes, the effects of lesion compartments (such as thalamic) were masked. Simultaneous quantification of atrophy and anatomically distinct hyperintensities is important for understanding cognitive impairments in dementia.

Limbic system perfusion in Alzheimer's disease measured by MRI-coregistered HMPAO SPET.

The goal of this study was to perform a systematic, semi-quantitative analysis of limbic perfusion in patients with Alzheimer's disease (AD) using coregistered single-photon emission tomography (SPET) images aligned to magnetic resonance (MR) images. Limbic perfusion in 40 patients with mild to moderate AD was compared with that of 17 age-, sex-, and education-matched normal controls (NC). HMPAO SPET scans and 3D T1-weighted MR images were acquired for each subject. Structures of the limbic system (i.e. hippocampus, amygdala, anterior thalamus, hypothalamus, mamillary bodies, basal forebrain, septal area and cingulate, orbitofrontal and parahippocampal cortices) were traced on the MR images and transferred to the coregistered SPET scans. Perfusion ratios for all limbic regions were calculated relative to cerebellar perfusion. General linear model multivariate analysis revealed that, overall, limbic structures showed significant hypoperfusion (F=7.802, P<0.00001, eta (2)=0.695 ) in AD patients compared with NC. Greatest differences (d > or = 0.8) were found in the hippocampus, as well as all areas of the cingulate cortex. Significant relative hypoperfusion was also apparent in the parahippocampal cortex, amygdala/entorhinal cortex, septal area and anterior thalamus, all of which showed medium to large effect sizes (d=0.6-0.8). No significant relative perfusion differences were detected in the basal forebrain, hypothalamus, mamillary bodies or orbitofrontal cortex. Logistic regression indicated that posterior cingulate cortex perfusion was able to discriminate AD patients from NC with 93% accuracy (95% sensitivity, 88% specificity). The current results suggest that most, but not all, limbic structures show significant relative hypoperfusion in AD. These findings validate previous post-mortem studies and could be useful in improving diagnostic accuracy, monitoring disease progression and evaluating potential treatment strategies in AD.

The impact of (18)FDG-PET on target and critical organs in CT-based treatment planning of patients with poorly defined non-small-cell lung carcinoma: a prospective study.

PURPOSE: To prospectively study the impact of coregistering (18)F-fluoro-deoxy-2-glucose hybrid positron emission tomographic (FDG-PET) images with CT images on the planning target volume (PTV), target coverage, and critical organ dose in radiation therapy planning of non-small-cell lung carcinoma. METHODS AND MATERIALS: Thirty patients with poorly defined tumors on CT, referred for radical radiation therapy, underwent both FDG-PET and CT simulation procedures on the same day, in radiation treatment position. Image sets were coregistered using external fiducial markers. Three radiation oncologists independently defined the gross tumor volumes, using first CT data alone and then coregistered CT and FDG-PET data. Standard margins were applied to each gross tumor volume to generate a PTV, and standardized treatment plans were designed and calculated for each PTV. Dose-volume histograms were used to evaluate the relative effect of FDG information on target coverage and on normal tissue dose. RESULTS: In 7 of 30 (23%) cases, FDG-PET information changed management strategy from radical to palliative. In 5 of the remaining 23 (22%) cases, new FDG-avid nodes were found within 5 cm of the primary tumor and were included in the PTV. The PTV defined using coregistered CT and FDG-PET would have been poorly covered by the CT-based treatment plan in 17--29% of cases, depending on the physician, implying a geographic miss had only CT information been available. The effect of FDG-PET on target definition varied with the physician, leading to a reduction in PTV in 24-70% of cases and an increase in 30-76% of cases. The relative change in PTV ranged from 0.40 to 1.86. On average, FDG-PET information led to a reduction in spinal cord dose but not in total lung dose, although large differences in dose to the lung were seen for a few individuals. CONCLUSION: The coregistration of planning CT and FDG-PET images made significant alterations to patient management and to the PTV. Ultimately, changes to the PTV resulted in changes to the radiation treatment plans for the majority of cases. Where possible, we would recommend that FDG-PET data be integrated into treatment planning of non-small-cell lung carcinoma, particularly for three-dimensional conformal techniques.