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

Caldwell, Curtis; Mah, Kandice; Skinner, Matthew J.; Danjoux, Cyril

doi:10.1016/s0360-3016(02)04609-6

Cited by 158 publications

(101 citation statements)

References 23 publications

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“…CT is the current standard for NSCLC GTV delineation, but despite excellent spatial resolution, substantial variation exists (32)(33)(34). According to the available literature, CT scan-based target volume delineation may over-or underestimate the extent of the GTV.…”

Section: Discussionmentioning

confidence: 99%

Autocontouring and Manual Contouring: Which Is the Better Method for Target Delineation Using ¹⁸F-FDG PET/CT in Non–Small Cell Lung Cancer?

Ung

Hwang

et al. 2010

J Nucl Med

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Previously, we showed that a CT window and level setting of 1,600 and -300 Hounsfield units, respectively, and autocontouring using an 18 F-FDG PET 50% intensity level correlated best with pathologic results. The aim of this study was to compare this autocontouring with manual contouring, to determine which method is better. Methods: Seventeen patients with non-small cell lung cancer underwent 18 F-FDG PET/CT before surgery. The maximum diameter on pathologic examination was determined. Seven sets of gross tumor volumes (GTVs) were defined. The first set (GTV CT ) was contoured manually using only CT information. The second set (GTV Auto ) was autocontoured using a 50% intensity level for 18 F-FDG PET images. The third set (GTV Manual ) was manually contoured using a visual method on PET images. The other 4 sets combined CT and 18 F-FDG PET images fused to one another to become composite volumes: GTV CT1Auto , GTV CT1Manual , GTV CT2Auto , and GTV CT-Manual . To quantitate the degree to which CT and 18 F-FDG PET defined the same region of interest, a matching index was calculated for each case. The maximum diameter of GTV was compared with the maximum diameter on pathologic examination. Results: The median GTV CT , GTV Auto , GTV Manual , GTV CT1Auto , GTV CT1Manual , GTV CT-Auto , and GTV CT-Manual were 6. 96, 2.42, 4.37, 7.46, 10.17, 2.21, and 3.38 cm 3 , respectively. The median matching indexes of GTV CT versus GTV CT1Auto , GTV Auto versus GTV CT1Auto , GTV CT versus GTV CT1Manual , and GTV Manual versus GTV CT1Manual were 0.86, 0.65, 0.88, and 0.81, respectively. Compared with the maximum diameter on pathologic examination, the correlations of GTV CT , GTV Auto , GTV Manual , GTV CT1Auto , and GTV CT1Manual were 0.87, 0.83, 0.93, 0.86, and 0.94, respectively. Conclusion: The matching index was higher for manual contouring than for autocontouring using a 50% intensity level on 18 F-FDG PET images. When using a 50% intensity level to contour the target of non-small cell lung cancer, one should also consider using manual contouring of 18 F-FDG PET to check for any missed disease. It is well established that 18 F-FDG PET plays an important role in the staging of non-small cell lung cancer (NSCLC). Multiple studies have demonstrated the utility of PET for improving staging accuracy. In an overview of the available literature, 18 F-FDG PET was found to have a 79%-100% sensitivity and a 40%-90% specificity in diagnosing primary lung cancer (1).The conventional imaging modality for therapy planning in NSCLC is CT. Targeting of the gross tumor has been facilitated by the use of CT simulation, which allows for more accurate delineation of the tumor. Multimodality imaging combining functional and anatomic information such as PET has allowed for further refinement in the therapy planning process and has a significant impact on the planning target volume. However, much uncertainty exists regarding the most appropriate threshold cutoff that should be used to define a PET target volume in NSCLC therapy planning. There ar...

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Section: Discussionmentioning

confidence: 99%

Autocontouring and Manual Contouring: Which Is the Better Method for Target Delineation Using ¹⁸F-FDG PET/CT in Non–Small Cell Lung Cancer?

Ung

Hwang

et al. 2010

J Nucl Med

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“…Therefore, care must be taken during BH imaging, interpretation of respiratory traces, and creation of treatment‐planning margins based solely upon external markers. Alternatively, if available, an approach other than BH CT such as multiple slow CT scans, (26, 27) positron emission tomography, (28) extended‐time CT, or 4DCT, (29, 30) may more accurately elucidate the true extent of tumor motion during FB and provide more accurate ITVs for treatment planning.…”

Section: Discussionmentioning

confidence: 99%

Comparison of breath‐hold and free‐breathing positions of an external fiducial by analysis of respiratory traces

Hunjan

Starkschall

Rosen

et al. 2008

J Applied Clin Med Phys

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An internal target volume (ITV) accounting for respiratory‐induced tumor motion is best obtained using 4DCT. However, when 4DCT is not available, inspiratory/expiratory breath‐hold false(BHinsp, BHexpfalse) CT images have been suggested as an alternative. In such cases, an external fiducial on the abdomen can be used as a substitute for tumor motion and CT images are acquired when the marker position matches – as judged by the therapist/physicist ‐ its positions at previously determined free‐breathing (FB) respiratory extrema false(FBinsp, FBexpfalse). In this study we retrospectively determined the accuracy of these matches. Free breathing 4DCT images were acquired, followed by BHinsp and BHexp CT images for 25 patients with non‐small‐cell lung cancer. Respiration was monitored using a commercial external fiducial system, which generates positional information while CT studies are conducted. Software was written for statistically analyzing the displacement of the external fiducial during BHinsp and BHexp CT acquisition and comparing these displacements with corresponding mean FB extrema positions false(FBinsp and FBexp, respectivelyfalse) using a Student's t‐test. In 72% of patients, mean positions at BHinsp differed significantly from mean positions at FBinsp false(normalp<0.05: 0.13–1.40 cmfalse). In 92% of patients, mean positions at BHexp differed significantly from mean positions at FBexp false(normalp<0.05: 0.03–0.70 cmfalse), although this difference was smaller than 0.5 cm in many cases false(median=0.34 cmfalse). Our findings indicate that relying solely on abdominal external markers for accurate BH CT imaging in order to accurately estimate FB extrema positions may be subject to significant error.PACS numbers 87.53.bd, 87.57.C‐, 87.59.Fm, 87.55.Gh

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“…Although stationary spheres filled with 18 F-FDG may serve as an adequate model for tumors without significant motion during treatment, Caldwell et al (6) have shown that such spheres are inadequate for modeling tumors throughout respiratory motion. Furthermore, the limitation of a mean SUVof greater than 2 would have excluded half the tumors in our study.…”

Section: Replymentioning

confidence: 99%

Reply: Dynamic Threshold for Radiation Target Volume by PET/CT

Biehl¹,

Bradley²

2007

Journal of Nuclear Medicine

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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

Cited by 158 publications

References 23 publications

Autocontouring and Manual Contouring: Which Is the Better Method for Target Delineation Using ¹⁸F-FDG PET/CT in Non–Small Cell Lung Cancer?

Autocontouring and Manual Contouring: Which Is the Better Method for Target Delineation Using ¹⁸F-FDG PET/CT in Non–Small Cell Lung Cancer?

Comparison of breath‐hold and free‐breathing positions of an external fiducial by analysis of respiratory traces

Reply: Dynamic Threshold for Radiation Target Volume by PET/CT

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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

Cited by 158 publications

References 23 publications

Autocontouring and Manual Contouring: Which Is the Better Method for Target Delineation Using 18F-FDG PET/CT in Non–Small Cell Lung Cancer?

Autocontouring and Manual Contouring: Which Is the Better Method for Target Delineation Using 18F-FDG PET/CT in Non–Small Cell Lung Cancer?

Comparison of breath‐hold and free‐breathing positions of an external fiducial by analysis of respiratory traces

Reply: Dynamic Threshold for Radiation Target Volume by PET/CT

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Autocontouring and Manual Contouring: Which Is the Better Method for Target Delineation Using ¹⁸F-FDG PET/CT in Non–Small Cell Lung Cancer?

Autocontouring and Manual Contouring: Which Is the Better Method for Target Delineation Using ¹⁸F-FDG PET/CT in Non–Small Cell Lung Cancer?