Role of respiratory-gated PET/CT for pancreatic tumors: A preliminary result

doi:10.1016/j.ejrad.2012.05.037

European Journal of Radiology

Volume 82, Issue 1, January 2013, Pages 69-74

https://doi.org/10.1016/j.ejrad.2012.05.037 Get rights and content

Abstract

Purpose

The aim of this study is to ascertain role of respiratory-gated PET/CT for accurate diagnosis of pancreatic tumors.

Materials and methods

Prior to clinical study, the phantom study was performed to evaluate the impact of respiratory motion on lesion quantification. Twenty-two patients (mean age 65 years) with pancreatic tumors were enrolled. Pathological diagnoses by surgical specimens consisted of pancreatic cancer (n = 15) and benign intraductal papillary mucinous neoplasm (IPMN, n = 7). Whole-body scan of non-respiratory-gated PET/CT was performed at first, and subsequent respiratory-gated PET/CT for one bed position was performed. All PET/CT studies were performed prior to surgery. The SUV max obtained by non-respiratory-gated PET/CT and respiratory-gated PET/CT, and percent difference in SUVmax (%SUVmax) were compared.

Results

The profile curve of 5 respiratory bin image was most similar to that of static image. The third bin of 5 respiratory bin image showed highest FWHM (24.0 mm) and FWTM (32.7 mm). The mean SUVmax of pancreatic cancer was similar to that of benign IPMN on non-respiratory-gated PET/CT (p = 0.05), whereas significant difference was found between two groups on respiratory-gated PET/CT (p = 0.016). The mean %SUV of pancreatic cancer was greater than that of benign IPMN (p < 0.0001). Identification of the primary tumor in pancreatic head (n = 13, 59%) was improved by using respiratory-gated PET/CT because of minimal affection of physiological accumulation in duodenum.

Conclusion

Respiratory-gated PET/CT is a feasible technique for evaluation of pancreatic tumors and allows more accurate identification of pancreatic tumors compared with non-respiratory-gated PET/CT.

Introduction

Technique of image fusion has become widely spread for diagnosing and staging malignancies of abdomen. The integration of computed tomography (CT) and positron emission tomography (PET) is effective because CT provides high spatial resolution along with short acquisition times, while PET is capable of functional and molecular imaging. Positron emission tomography/computed tomography (PET/CT) is an effective method for detecting cancer and differentiating between benign versus malignant abdominal tumor.

For instance, integrated PET/CT is a more accurate imaging modality than contrast-enhanced CT for assessing preoperative or recurrent pancreatic cancer [1], [2], [3]. However, ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) uptake within well-differentiated hepatocellular carcinoma (HCC) is similar to that of the surrounding normal liver tissue, making the detection of focus difficult [4]. Organs’ motion can produce inaccurate information about the size, shape and volume of the anatomical region under examination on CT.

Respiratory motion causes inaccurate PET and CT image co-registration especially in the thorax and upper abdominal region and leads to inaccurate attenuation correction, underestimation of lesion's standardized uptake value (SUV) and lesion volume overestimation, consequently leading to inaccurate PET data quantification. Recent studies reported breath-hold PET/CT improved respiratory misregistration [5], [6], [7], [8]. Some investigators have reported that four-dimensional (4D) PET/CT improved characterization of malignant pulmonary lesions compared with the standard PET/CT, because of its higher sensitivity. On the other hand, Hubert et al. have reported utility of respiratory-gated PET/CT of abdomen with spatial improvement of z-axis in 16 ¹⁸F-FDG-avid tumors [9]. When we evaluate tumors of thorax and upper abdomen on PET/CT, the physiological uptake of the surrounding structure under voluntary respiration affects accurate assessment of the primary lesion [1], [2], [3], [4]. However clinical relevance of respiratory-gated PET/CT for assessment of pancreatic tumors has not been fully elucidated. The aim of the current study was to ascertain role of respiratory-gated PET/CT acquisition for more accurate diagnosis of pancreatic tumors.

Section snippets

Patients

Twenty-two patients (17 men, 5 women, mean age 65 years; range 58–73) with pancreatic tumors were enrolled from April 2006 to March 2008. Of these cases, pathologically confirmed diagnoses consisted of pancreatic cancer (n = 15) and benign intraductal papillary mucinous neoplasm (IPMN, n = 7). Patients were clinically evaluated based on general physical examination and laboratory findings: complete blood count, biochemical data, and tumor markers. The inclusion criteria for the performance status

Results

Compared with static phantom, FWHM and FWTM of dynamic phantom increase 10 and 30%, respectively. We confirmed that blurring was particularly noticeable along the z-axis on PET images. Four types of images including 3 respiratory bin image, 5 respiratory bin image, dynamic image, and static image were precisely obtained. When we compare the conducted profile curves of each type, the profile curve of 5 respiratory bin image was most similar to that of static image (Table 1, Fig. 2). The third

Discussion

Differential diagnosis between malignant and benign pancreatic tumors has been investigated by various imaging modalities including US, CT, MRI, and ¹⁸F-FDG PET [10], [11]. ¹⁸F-FDG PET/CT is considered as a feasible diagnostic modality to differentiate pancreatic carcinoma and benign pancreatic tumors [12], [13], [14]. However, due to respiratory movement, fused images of PET and CT have blurring and mislegistration of the tumor is often encountered. When we consider tumors of pancreas, the

Acknowledgments

No potential conflicts of interest were disclosed.

This study was partly funded by a Grant-in-Aid for Scientific Research from the Japan Society for the Promotion of Science (No. 17209041 and No. 21390342) and the 21st Century COE Program (Medical Science). This study was partly supported by working group of Japanese Society of Nuclear Medicine: Investigation of therapeutic effects in malignant tumors using standardized PET/CT procedure established in October 2011. This study started before

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Systematic review of the utility of 18-FDG PET in the preoperative evaluation of IPMNs and cystic lesions of the pancreas
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Citation Excerpt :
The PubMed search yielded a total of 23 articles.12–34 All 23 abstracts12–34 were analyzed and 10 eligible studies12,15,23–25,28,29,31–33 that fulfilled our inclusion criteria were included in this systematic review. As a result of the PubMed search, we found that 3 studies12,13,34 were from the same institution.
The aim of this systematic review is to assess the role of 18-fluorodeoxyglucose positron emission tomography in the preoperative evaluation of intraductal papillary mucinous neoplasms and cystic lesions of the pancreas.
A computerized PubMed search was conducted according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines to identify studies evaluating positron emission tomography in the preoperative evaluation of pancreatic cystic lesions.
A total of 14 studies evaluated the role of 18-fluorodeoxyglucose positron emission tomography/positron emission tomography-computed tomography, 9 of which evaluated only intraductal papillary mucinous neoplasms and 5 evaluated all pancreatic cystic lesions, including intraductal papillary mucinous neoplasms. Pooled analysis was carried out for studies evaluating intraductal papillary mucinous neoplasms only and studies evaluating all cystic lesions. Imaging with 18-fluorodeoxyblucose positron emission tomography had a positive predictive value, negative predictive value, sensitivity, specificity, and accuracy of 90%, 91%, 85%, 95%, and 91% in identifying malignancy (defined as either invasive and/or high-grade dysplasia) in intraductal papillary mucinous neoplasms and a positive predictive value, negative predictive value, sensitivity, specificity, and accuracy of 85%, 81%, 79%, 86%, and 88% in identifying malignancy in other cystic lesions. Pooled analysis reported the positive predictive value, negative predictive value, sensitivity, specificity, and accuracy of Sendai consensus guidelines (SCG) criteria as 69%, 69%, 68%, 55%, and 58%. The Fukuoka consensus guidelines (FCG) only had sensitivity, specificity, and accuracy reported as 61%, 52%, and 52%, respectively.
The 18-fluorodeoxyblucose positron emission tomography had a high degree of accuracy of detecting malignancy in intraductal papillary mucinous neoplasm and cystic lesion of the pancreas. Comparison of the utility of positron emission tomography with the Fukuoka consensus guidelines and the Sendai consensus guidelines suggest that positron emission tomography is superior to present guidelines in detecting malignant intraductal papillary mucinous neoplasm and cystic lesion of the pancreas. Further studies in larger patient cohorts may be required to corroborate these findings and to determine the place of positron emission tomography in the management of intraductal papillary mucinous neoplasm and cystic lesions of the pancreas.
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To our knowledge, this is also the first report concerning the respiratory motion of pancreatic cancer analysed by 4D-PET. The effect of 4D-PET in the diagnostic imaging of pancreatic tumours, including pancreatic cancer, was reported by a few authors [25,26]. Yukutake et al. evaluated 36 patients with pancreatic cancer and found that 4D-PET reduced respiratory motion artefacts and allowed a significantly higher SUVmax.
The purpose of this study was to evaluate the usefulness of respiratory-gated positron emission tomography (4D-PET) in pancreatic cancer radiotherapy treatment planning (RTTP).
Fourteen patients with 18F-fluorodeoxyglucose (FDG)-avid pancreatic tumours were evaluated between December 2013 and March 2015. Two sets of volumes were contoured for the pancreatic tumour of each patient. The biological target volume in three-dimensional RTTP (BTV3D) was contoured using conventional respiratory un-gated PET. The BTV3D was then expanded using population-based margins to generate a series of internal target volume 3D (ITV3D) values. The ITV 4D (ITV4D) was contoured using 4D-PET. Each of the five phases of 4D-PET was used for 4D contouring, and the ITV4D was constructed by summing the volumes defined on the five individual 4D-PET images. The relative volumes and normalized volumetric overlap were computed between ITV3D and ITV4D.
On average, the FDG-avid tumour volumes were 1.6 (range: 0.8–2.3) fold greater in the ITV4D than in the BTV3D. On average, the ITV3D values were 2.0 (range: 1.1–3.4) fold larger than the corresponding ITV4D values.
The ITV generated from 4D-PET can be used to improve the accuracy or reduce normal tissue irradiation compared with conventional un-gated PET-based ITV.
Respiratory-gated 18F-FDG PET/CT for the diagnosis of liver metastasis
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Citation Excerpt :
Technical strategies for acquiring the respiratory signal, such as the use of pressure sensors or optical/infrared video-based methods, have been described [4]. The diagnostic usefulness of respiratory gated PET/CT has also been assessed in the thorax [5–9], but its clinical diagnostic impact for upper abdominal organs has not been fully assessed [10–12]. When evaluating tumors of the thorax and upper abdomen by PET/CT, the physiological uptake in surrounding structures under voluntary respiration affects accurate assessment of the target lesion.
To ascertain the role of respiratory-gated PET/CT with ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) for accurate diagnosis of liver metastasis.
Forty patients with suspected liver metastasis underwent conventional whole-body PET/CT scan initially, followed by respiratory-gated PET/CT scan covering the liver. Visual detectability (using a 5-point confidence scale), maximum standardized uptake value (SUVmax) and metabolic tumor volume (MTV) of hepatic metastatic lesions were assessed for three data sets including ordinary whole-body (WB) scan, and non-respiratory-gated (nRG) and respiratory-gated (RG) scans. Results of enhanced CT and/or MRI, or clinical and radiological follow-up were used for reference.
Sixteen of the patients were found to have 53 metastatic lesions in the liver. Patient-based accuracy of WB, nRG, and RG was 92.5%, 95.0%, and 97.5%, respectively, with a lesion-based detection rate of 67.9%, 73.6%, and 73.6%, respectively. The average SUVmax of 34 liver metastatic lesions for WB, nRG, and RG was 6.60 ± 2.34, 7.19 ± 2.66, and 8.08 ± 3.24, respectively. SUVmax for RG was significantly higher than that for WB (p = 0.0069). The average MTV of these 40 lesions for the three protocols was 5.32 ± 4.78 cm³, 5.07 ± 4.73 cm³, and 4.73 ± 4.67 cm³, respectively. Among the three protocols, RG showed the best visual and quantitative evaluation for diagnosis of liver metastasis.
Respiratory-gated PET/CT allows more accurate identification of liver metastases than non-respiratory-gated PET/CT.
Respiratory-gated PET/CT examination: Wishful thinking or clinical reality?
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Les mouvements respiratoires en tomographie par émission de positons/tomodensitométrie (TEP/TDM) peuvent être source d’erreurs dans les images TEP, mais également dans les images TDM. Cela induit des erreurs de correspondance entre les images anatomiques et fonctionnelles et donc des biais pour la correction d’atténuation conduisant à des standardized uptake values (SUV) erronées. Cet article a pour but de présenter les méthodes de synchronisation respiratoire applicables en clinique ainsi que les évolutions à venir.
La plupart des appareils actuels sont équipés d’un système de synchronisation respiratoire des acquisitions TEP. Cependant, les logiciels proposés par les constructeurs ne sont pas satisfaisants, notamment de par le fait que plusieurs images TEP, correspondant à différentes positions des tissus durant le cycle respiratoire, sont générées avec la même carte d’atténuation. Certaines équipes ont proposé des alternatives assurant une image TEP correspondant parfaitement à son image TDM associée. Ces dernières méthodes sont utilisables en routine et ont déjà montré, dans différents essais cliniques, leur intérêt. Toutefois, les méthodes de compensation nécessitent un allongement du temps d’examen TEP par la réalisation d’une acquisition supplémentaire.
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The respiratory motion in positron emission tomography/computed tomography (PET/CT) can be a source of errors in PET and images. This induces mismatches between anatomical and functional images thus bias for attenuation correction leading to “standardized uptake values” (SUV) errors. This article aims to present various methods dealing with respiratory motion. Some of them are applicable in clinical routine and others are still under investigation.
Most current devices are equipped with a respiratory gating system, at least for PET acquisitions. However, softwares provided by manufacturers are not satisfactory, notably because multiple PET images, corresponding to different tissue positions during the respiratory cycle, are generated with the same attenuation map. Some groups have proposed other solutions providing a single PET image corresponding exactly to the associated CT. These latter methods can be easily used routinely and have shown already their interest in various clinical trials. However, compensation methods require an extension of examination duration because of additional PET acquisition.
The new trend seeks to develop methods for correcting motion directly by integrating the motion information in the data (acquisition) or in the reconstruction algorithm. These methods have the advantage of using all the acquired data to reconstruct the image, thereby reducing the duration of the gated examination. However, these methods are not transferable in clinical yet. Indeed, the determination of tissue deformations is still problematic, as well as attenuation correction.
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Role of respiratory-gated PET/CT for pancreatic tumors: A preliminary result

Abstract

Purpose

Materials and methods

Results

Conclusion

Introduction

Section snippets

Patients

Results

Discussion

Acknowledgments

The American Journal of Gastroenterology

Gastrointestinal Endoscopy

International Journal of Radiation Oncology, Biology, Physics

Value of contrast-enhanced 18F-fluorodeoxyglucose positron emission tomography/computed tomography in detection and presurgical assessment of pancreatic cancer: a prospective study

Journal of Gastroenterology and Hepatology

Contrast-enhanced 18F-FDG PET/CT: 1-stop-shop imaging for assessing the resectability of pancreatic cancer

Journal of Nuclear Medicine

Performance of integrated FDG-PET/contrast-enhanced CT in the diagnosis of recurrent pancreatic cancer: comparison with integrated FDG-PET/non-contrast-enhanced CT and enhanced CT

Molecular Imaging and Biology

Value of 4-dimensional 18F-FDG PET/CT in the classification of pulmonary lesions

Journal of Nuclear Medicine Technology

Value of contrast-enhanced ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography in detection and presurgical assessment of pancreatic cancer: a prospective study