Application of Oral Contrast Media in Coregistered Positron Emission Tomography—CT

Dizendorf, Elena; Treyer, Valérie; Schulthess, Gustav K. von; Hany, Thomas F.

doi:10.2214/ajr.179.2.1790477

Cited by 104 publications

(40 citation statements)

References 19 publications

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“…However, this phenomenon does not seem to have much clinical effect. No significant difference in the distribution of intense FDG uptake in the intestinal regions was shown by DIZENDORF et al [29] in a study of two groups of 30 patients each. To minimise these artefacts, low-density barium appears to be suitable for clinical use [30]; administration of a negative oral contrast agent using mannitol is also promising [31].…”

Section: Value Of Integrated Pet/ct W De Wever Et Almentioning

confidence: 74%

Detection of extrapulmonary lesions with integrated PET/CT in the staging of lung cancer

Wever¹,

Vankan²,

Stroobants³

et al. 2007

European Respiratory Journal

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The aim of the present study was to assess retrospectively the additional value of positron emission tomography (PET)/computed tomography (CT) in the detection of unexpected extrapulmonary lesions in the staging of patients with a malignant pulmonary lesion in comparison with CT and PET used alone.A total of 217 patients with a pathologically proven lung tumour underwent PET/CT. CT, PET and PET/CT were evaluated in the detection of extrapulmonary lesions. These abnormalities were compared with the final diagnosis obtained from the medical records and statistical analysis was carried out.In total, 108 lesions were clinically detected. PET/CT showed a sensitivity, specificity, positive and negative predictive values and accuracy of 100, 81, 71, 100 and 87%, respectively, for the detection of extrapulmonary lesions and 92, 98, 89, 98 and 97%, respectively, for the detection of malignant extrapulmonary lesions. PET/CT was significantly better than CT and PET used alone.Conventional staging work-up has a poor sensitivity in detecting second primary cancers or unexpected metastases. The detection of malignant extrapulmonary lesions is necessary for correct tumour staging. By combining both metabolic and anatomical information, positron emission tomography/computed tomography is able to depict more unexpected extrapulmonary lesions than computed tomography and positron emission tomography used alone, and positron emission tomography/computed tomography provides more additional information of malignancy or benignancy of lesions detected with one of the two imaging modalities alone.KEYWORDS: Extrapulmonary lesion, integrated positron emission tomography/computed tomography, lung cancer L ung cancer is a common disease and is the leading cause of death in many countries. Several imaging techniques are available to detect distant metastases of lung cancer. Computed tomography (CT) is the routine imaging procedure for staging patients with lung cancer in many institutions. Usually, a combination of a CT scan of the brain to exclude brain metastasis, a CT scan of the upper abdomen to exclude liver and adrenal metastasis, and bone scintigraphy to exclude bone metastases are performed [1]. However, the technique of CT is often not able to exclude reliably extrapulmonary metastases, especially occult metastases, and to detect second primary cancers. Many reports suggest that F-fluoro-2-deoxyglucose positron emission tomography (FDG-PET) is more sensitive than CT in the diagnosis of extrapulmonary lesions [2]. FDG-PET can detect unsuspected occult metastases and second primary cancers.In the study by STROOBANTS et al. [3], an additional detection of distant malignant lesions was found in 5% of patients. According to STROOBANTS et al. [3], the most important contribution of FDG-PET was its ability to exclude malignancy in the most distant lesions using equivocal CT.Recently, integrated PET/CT has been introduced more routinely into clinical situations [4]. Integrated PET/CT enables the direct correlation of FDG-accumula...

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Section: Value Of Integrated Pet/ct W De Wever Et Almentioning

confidence: 74%

Detection of extrapulmonary lesions with integrated PET/CT in the staging of lung cancer

Wever¹,

Vankan²,

Stroobants³

et al. 2007

European Respiratory Journal

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“…Several other investigators have recently confirmed the feasibility of using intravenous contrast in various types of modified injection protocols allowing combined diagnostic CT with PET (10-12). Oral contrast may affect the CT-based attenuation (2,13,14). The resulting attenuation-corrected PET activity can be overestimated by as much as 20%, but with an average of 4.4% with standard dilutions of positive oral contrast (13,15).…”

Section: Discussionmentioning

confidence: 99%

Limitations of CT During PET/CT

Gollub¹,

Hong²,

Sarasohn³

et al. 2007

Journal of Nuclear Medicine

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Our aim was to determine the diagnostic limitations of low-dose, unenhanced CT scans performed for anatomic reference and attenuation correction during PET/CT. Methods: The Radiology Information System at our oncologic hospital was queried during the 9-mo period from July 2002 to April 2003 for patients with PET/CT scans and diagnostic enhanced CT within 2 wk of each other. One radiologist interpreted the CT portion of the PET/CT (CT p ) unaware of the PET results and the associated enhanced diagnostic CT (CT d ). A medical student compared this interpretation with the official report of the CT d and listed all discrepancies between reports. A separate radiologist compared CT p and CT d images and classified true discrepant findings as due to lack of intravenous contrast, arm-position artifact, lack of enteric contrast, low milliamperage (mA), and quality of lung images. Results: Among 100 patients, the most common malignancies were lymphoma (n 5 37), cancer of the colorectum (n 5 31), and esophageal cancer (n 5 15). Among 194 true discrepancies in which findings were missed at CT p , causes were as follows: (a) lack of intravenous contrast (128/194, 66%), (b) armdown artifact (17/194, 9%), (c) quality of lung images (26/194, 13%), (d) lack of enteric contrast (15/194, 8%), and (e) low mA (8/194, 4%). Discrepancies were seen most commonly in detecting lymphadenopathy and visceral metastases. Conclusion: Most missed findings on the unenhanced CT portion of the PET/CT scans were due to technical factors that could be altered. Discrepant findings would have led to altered management in only 2 patients, suggesting a role for limited repeat imaging to reduce radiation and use of valuable resources. Di agnostic CT scanning has been the mainstay of oncologic imaging over the past 25 y. By the end of the 1990s, 18 F-FDG PET/CT was developed, offering the first opportunity to combine metabolic and anatomic information leading to a powerful new combined-modality imaging examination.Methodologic and technical differences between the CT performed for anatomic localization and attenuation correction (CT p ) and a typical diagnostic CT scan (CT d ) include arm position (frequently down for CT p ), suspended respiration (vs. quiet breathing for CT p ), use of enteric contrast (variable in CT p ) and intravenous contrast materials (not typically used in CT p ), and levels of microamperageÁseconds (mAÁs) of radiation (much lower in CT p ).The limitations of the CT p are partly intuitive, based on the increased accuracy of CT using oral and intravenous contrast agents noted early on in the development of CT protocols (1). The functional information provided by PETwhen correlated with the CT anatomic information, in some clinical scenarios, served to overcome expected limitations incurred with the absence of intravenous or oral contrast. This has been most obvious in patients with lymphoma, where nodal disease status is not well predicted by size or morphology on CT as much as by metabolic activity on 18 F-FDG PET; thus, diagnosti...

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“…In oncologic PET/CT, the use of intravenous enhanced CT data for attenuation correction has been found to produce image artifacts when the bolus injection results in high concentrations of contrast agent (11,12). However, other studies suggest that for tumor staging, this biased quantification usually does not change the diagnostic decision (13)(14)(15)(16)(17), especially if non-attenuationcorrected images are read alongside. This type of artifact can also be observed in cardiac PET/CT, especially in the region of the superior and inferior cava veins (3), and is likely to be more pronounced because CT coronary angiography requires data acquisition during an early arterial phase when the concentration of contrast agent in the blood is high, whereas oncologic CT is often acquired during the venous phase, when blood concentrations are lower.…”

Section: Discussionmentioning

confidence: 99%

Effective Methods to Correct Contrast Agent-Induced Errors in PET Quantification in Cardiac PET/CT

Büther

Stegger²,

Dawood³

et al. 2007

Journal of Nuclear Medicine

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In combined PET/CT studies, x-ray attenuation information from the CT scan is generally used for PET attenuation correction. Iodine-containing contrast agents may induce artifacts in the CT-generated attenuation map and lead to an erroneous radioactivity distribution on the corrected PET images. This study evaluated 2 methods of thresholding the CT data to correct these contrast agent-related artifacts. Methods: PET emission and attenuation data (acquired with and without a contrast agent) were simulated using a cardiac torso software phantom and were obtained from patients. Seven patients with known coronary artery disease underwent 2 electrocardiography-gated CT scans of the heart, the first without a contrast agent and the second with intravenous injection of an iodine-containing contrast agent. A 20-min PET scan (single bed position) covering the same axial range as the CT scans was then obtained 1 h after intravenous injection of 18 F-FDG. For both the simulated data and the patient data, the unenhanced and contrast-enhanced attenuation datasets were used for attenuation correction of the PET data. Additionally, 2 threshold methods (one requiring user interaction) aimed at compensating for the effect of the contrast agent were applied to the contrast-enhanced attenuation data before PET attenuation correction. All PET images were compared by quantitative analysis. Results: Regional radioactivity values in the heart were overestimated when the contrast-enhanced data were used for attenuation correction. For patients, the mean decrease in the left ventricular wall was 23%. Use of either of the proposed compensation methods reduced the quantification error to less than 5%. The required time for postprocessing was minimal for the user-independent method. Conclusion: The use of contrast-enhanced CT images for attenuation correction in cardiac PET/CT significantly impairs PET quantification of tracer uptake. The proposed CT correction methods markedly reduced these artifacts; additionally, the user-independent method was time-efficient. Bot h PET and CT can provide valuable diagnostic and prognostic information noninvasively to guide the management of patients with heart disease. Molecular and functional PET can be used, for example, to assess myocardial perfusion, perfusion reserve, metabolism, and innervation. With morphologic CT, calcification of coronary arteries may be detected and quantified, and modern equipment even allows for the noninvasive visualization of the vessel lumen (coronary angiography). The main advantage of combined PET/CT devices over stand-alone PET and CT lies in the acquisition of both molecular and morphologic data with spatial and temporal coregistration in a single session, making data interpretation easier and quicker. It is self-evident that the PET/CT protocol has to be tailored to each patient to minimize radiation exposure and scanning time. Unnecessary scans have to be avoided. Unlike stand-alone PET scanners, attenuation correction of the PET data in PET/CT studies is usually n...

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Application of Oral Contrast Media in Coregistered Positron Emission Tomography—CT

Abstract: An oral contrast agent can be used for coregistered PET-CT without the introduction of artifacts in PET.

Cited by 104 publications

References 19 publications

Detection of extrapulmonary lesions with integrated PET/CT in the staging of lung cancer

Detection of extrapulmonary lesions with integrated PET/CT in the staging of lung cancer

Limitations of CT During PET/CT

Effective Methods to Correct Contrast Agent-Induced Errors in PET Quantification in Cardiac PET/CT

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