Is hybridic positron emission tomography/computerized tomography the only option? The future of nuclear medicine and molecular imaging

As we all know, Nuclear Medicine is the medical science using nuclear radiation for diagnosis, treatment and research. Nuclear Medicine, in contrast to Radiology, makes use of unsealed sources of radiation. Nuclear Medicine a few years ago has partly offered Nuclear Cardiology, the most lucrative of all Nuclear Medicine "children" at that time, to Cardiology. Radiology, has succeeded in being recognized by the European Union Authorities as Clinical Radiology. The word "clinical" offers greater independence to Clinical Radiology and makes it difficult for such a specialty to relinquish any of its equipment i.e. the diagnostic CT scan or the newly developed fast angiography CT, to other specialties. Contrary to Clinical Radiology, Nuclear Medicine being a laboratory specialty in most countries seems to have no right to deny offering, after some period of "proper certified education", its PET camera to Clinical Radiologists. Nuclear Medicine by virtue of its unique diagnostic techniques and treatments, is and should be recognized as a "Clinical Specialty" The interference of other specialties in the fields of Nuclear Medicine is also indicated by the fact that in vitro techniques of Nuclear Medicine are often used by Endocrinologists and Oncologists in their own laboratories. Also in some hospitals the Director of the Radiology Department acts as the Director of Nuclear Medicine Laboratory. Finally at present, Radiologists wish after "proper certified education", to be on equal terms in charge of the new hybridic equipment, the PET/CT scanner. If that is followed to happen, Nuclear Medicine will be in a difficult position losing at least part of PET and consequently should ask for help from its "Overlords and Protectors" i.e. the National and the European Societies of Nuclear Medicine and the Society of Nuclear Medicine of the United States of America. Radiology as a specialty participating om equal terms with the PET camera will then include the study of: a) "open sources of radiation" b) nuclear radiation and c) molecular nuclear medicine. The "European Journal of Nuclear Medicine and Molecular Imaging" shall have to erase the three last words of its title and be renamed. As Professor Abass Alavi et al (2007), have mentioned: "Is PET/CT the only option?" In favor of PET/CT are the following: Attenuation correction (AC) and better anatomical localization of lesions visualized with PET. Also PET/CT can be used as a diagnostic CT scanner (dCT). Against using the PET/CT scanners are the following arguments: a) This equipment is not necessary because we can always ask the Radiologists for a dCT scan. Many patients have already done a dCT scan at the time they are referred for a PET scan to the Nuclear Medicine Department. b) The absolute clinical indications for PET/CT with the use of a contrast agent, are under investigation. c) Although there is at present a list of indications suggested for the PET/CT scanner, there are studies disputing some of these indications, as for example in metastatic colon cancer where a high diagnostic accuracy for PET study alone, has been reported. d) The option of AC performed by the PET/CT scanner has also been questioned. Artifacts may be up to 84%. e) The PET/CT is expensive, time consuming, space occupying, and needs additional medical and technical personnel. f) Not to mention the extra radiation dose to the patients. g) Shall we inform those young medical students who wish to become nuclear medicine physicians, to hold their decision till the content of future Nuclear Medicine is clarified? We may suggest that: Our specialty could be renamed as: "Clinical Nuclear Medicine" and include additional "proper certified education" on the PET/CT equipment. The PET/CT scanner should remain in the Nuclear Medicine Department where Radiologists could act as advisors.     

Reducing radiation dose in rest-stress cardiac PET/CT by single poststress cine CT for attenuation correction: quantitative validation.

Cardiac PET/CT is optimized by cine CT with dedicated shift software for manual correction of attenuation-emission misregistration. Separate rest and stress CT scans incur greater radiation dose to patients than does standard helical PET/CT or "pure" PET using rotating rod attenuation sources. To reduce radiation dose, we tested quantitative accuracy of using a single poststress cine CT attenuation scan for reconstructing rest perfusion images to eliminate resting CT attenuation scans. METHODS: A total of 250 consecutive patients underwent diagnostic rest-dipyridamole myocardial perfusion PET/CT with (82)Rb and a 16-slice PET/CT scanner using averaged cine CT attenuation data during breathing at rest and stress. After correcting for any attenuation-emission misregistration, we quantitatively compared resting perfusion images reconstructed using rest cine CT attenuation data with the same resting emission data reconstructed with poststress cine CT attenuation data. Automated software quantifying average regional quadrant activity, severity, size, and combined size and severity of perfusion defects was used for this comparison. RESULTS: Resting perfusion images reconstructed using rest cine CT attenuation data were quantitatively comparable to resting images reconstructed with poststress cine CT attenuation data with no clinically significant differences. Twenty-five (10%) of 250 cases required shifting of stress cine CT attenuation data to achieve optimal attenuation-emission coregistration with resting perfusion data. Eliminating rest CT attenuation scans reduced CT radiation dose by 50% below rest-plus-stress cine CT protocols. CONCLUSION: Resting perfusion images reconstructed using poststress cine CT attenuation data are quantitatively comparable to resting images reconstructed with resting cine CT attenuation data. Eliminating the rest CT scan reduces CT radiation dose by 50%.     

PET/CT——功能与解剖结构的同机图像融合

PET/CT为近几年出现的一种新技术,将PET与CT安装在同一机架上,一次扫描可获得PET与CT的融合图像,对定位诊断肿瘤、指导肿瘤放疗计划、选择活检部位及监测疗效等具有重要价值,同时,CT提供了一种PET衰减校正的方法。本文简要介绍PET/CT的结构设计与性能、优势及目前尚存在的技术问题。     

Clinical evaluation of CT radiation dose in whole-body 18F-FDG PET/CT in relation to scout imaging direction and arm position

Annals of Nuclear Medicine - Radiation exposure in CT is modulated by automatic exposure control (AEC) mainly based on scout images. We evaluated CT radiation dose in whole-body PET/CT in relation...     

Combined PET/CT Imaging in Oncology. Impact on Patient Management

Purpose: In this work, we describe five oncology patients whose clinical management were uniquely benefited by a novel scanner that acquires positron emission tomography (PET) and x-ray computed tomography (CT) in the same imaging session.Procedures: Co-registered 2-[F(18)]-fluoro-2-deoxy-D-glucose (FDG)-PET and CT images were acquired using a combined PET/CT scanner. Pathology and clinical follow-up data were used to confirm PET/CT scan results.Results: The combined PET/CT scanner demonstrated the ability to distinguish malignant lesions from normal physiologic FDG uptake in the striated muscles of the head and neck as well as excretory and bowel activity in the abdomen and pelvis. Additionally, the technology positively affected patient management through localization for surgical and radiation therapy planning as well as assessment of tumor response.Conclusion: Our experience indicates that simultaneous acquisition of co-registered PET and CT images enabled physicians to more precisely discriminate between physiologic and malignant FDG uptake and more accurately localize lesions, improving the value of diagnostic PET in oncologic applications.     

Evaluating and comparing the image quality and quantification accuracy of SiPM-PET/CT and PMT-PET/CT

Annals of Nuclear Medicine - The aim of this study was to evaluate the image quality and the quantification accuracy of Biograph Vision PET/CT scanner as a SiPM-PET in comparison to the...     

Detection of sub-centimeter lesions using digital TOF-PET/CT system combined with Bayesian penalized likelihood reconstruction algorithm

Annals of Nuclear Medicine - Many advances in PET/CT technology can potentially improve image quality and the ability to detect small lesions. A new digital TOF-PET/CT scanner based on silicon...     

Comparison of diagnostic ability between 99mTc-MDP bone scan and 18F-FDG PET/CT for bone metastasis in patients with small cell lung cancer

Objective

The aim of this study was to compare the diagnostic ability of ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography/computed tomography (PET/CT) with that of ^99mTc-methylene diphosphonate (^99mTc-MDP) bone scan for bone metastasis in staging patients with small cell lung cancer (SCLC).

Methods

Ninety-five patients with SCLC who underwent both ¹⁸F-FDG PET/CT and ^99mTc-MDP bone scan for initial staging work-up were retrospectively enrolled. All ¹⁸F-FDG PET/CT and bone scan images were visually assessed. Bone metastasis was confirmed by histopathological results and all available clinical information.

Results

Of 95 patients with SCLC, metastatic bone lesions were found in 30 patients, and 84 metastatic lesions were evaluated on a lesion-basis analysis. The sensitivity of ¹⁸F-FDG PET/CT was 100?% on a per-patient basis and 87?% on a per-lesion basis, and there was no false-positive lesion on PET/CT images. In contrast, the sensitivity of the bone scan was 37?% on a per-patient basis and 29?% on a per-lesion basis. The bone scan showed 11 false-positive lesions. The bone scan detected two metastatic lesions that were not detected by PET/CT, which were outside the region scanned by PET/CT. On follow-up bone scan, 21 lesions that were not detected by the initial bone scan but were detected by PET/CT were newly detected.

Conclusions

In patients with SCLC, ¹⁸F-FDG PET/CT showed higher detection rate of bone metastasis than ^99mTc-MDP bone scan. Thus, ¹⁸F-FDG PET/CT can replace bone scan in staging patients with SCLC.     

Radiotherapy planning: PET/CT scanner performances in the definition of gross tumour volume and clinical target volume

Purpose Positron emission tomography is the most advanced scintigraphic imaging technology and can be employed in the planning of radiation therapy (RT). The aim of this study was to evaluate the possible role of fused images (anatomical CT and functional FDG-PET), acquired with a dedicated PET/CT scanner, in delineating gross tumour volume (GTV) and clinical target volume (CTV) in selected patients and thus in facilitating RT planning.Methods Twenty-eight patients were examined, 24 with lung cancer (17 non-small cell and seven small cell) and four with non-Hodgkins lymphoma in the head and neck region. All patients underwent a whole-body PET scan after a CT scan. The CT images provided morphological volumetric information, and in a second step, the corresponding PET images were overlaid to define the effective target volume. The images were exported off-line via an internal network to an RT simulator.Results Three patient were excluded from the study owing to change in the disease stage subsequent to the PET/CT study. Among the remaining 25 patients, PET significantly altered the GTV or CTV in 11 (44%) . In five of these 11 cases there was a reduction in GTV or CTV, while in six there was an increase in GTV or CTV.Conclusion FDG-PET is a highly sensitive imaging modality that offers better visualisation of local and locoregional tumour extension. This study confirmed that co-registration of CT data and FDG-PET images may lead to significant modifications of RT planning and patient management.An erratum to this article can be found at     

A method for reducing radiation dose in cerebral CT perfusion study with variable scan schedule

PURPOSE: To propose a method for reducing the radiation dose in cerebral CT perfusion studies by using a variable scan schedule. MATERIALS AND METHODS: Original images were obtained with a multi detector-row CT (MDCT) scanner using the following CT perfusion protocol: continuous scans of 1 sec/rotation x 60 sec, four 5-mm-thick contiguous slices. The original images were thinned-out using combinations of various numbers of former continuous images (10, 15, 20, 25, and 30), and the later skipped images with various scan intervals (2, 5, 10, 15 and 20 sec). The thinned-out images were interpolated by linear interpolation. In five patients with cerebrovascular disease, we generated functional images of cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT) from both original and interpolated data. The correlation coefficients (CC) for these parameters between the original and interpolated images were evaluated. RESULTS: The CC decreased with dose reduction. To keep the correlation coefficients greater than 0.9, the estimated dose was reduced to 33.3% on CBF with a set of 10 continuous images and scan interval of 5 sec, to 20.0% on CBV with a set of 10 continuous images and scan interval of 20 sec, and to 58.3% on MTT with a set of 10 continuous images and scan interval of 2 sec. CONCLUSION: The variable scan schedule method would be useful to reduce radiation dose while maintaining the accuracy of CT perfusion (CTP) parameters.     

Japanese guideline for the oncology FDG-PET/CT data acquisition protocol: synopsis of Version 2.0

This synopsis outlines the Japanese guideline Version 2.0 for the data acquisition protocol of oncology FDG-PET/CT scans that was created by a joint task force of the Japanese Society of Nuclear Medicine Technology, the Japanese Society of Nuclear Medicine and the Japanese Council of PET Imaging, and was published in Kakuigaku-Gijutsu 2013; 33:377–420 in Japanese. The guideline aims at standardizing the PET image quality among PET centers and different PET camera models by providing criteria for the IEC body phantom image quality as well as for the patient PET image quality based on the noise equivalent count (NEC), NEC density and liver signal-to-noise ratio, so that the appropriate scanning parameters can be determined for each PET camera. This Version 2.0 covers issues that were not focused on in Version 1.0, including the accuracy of the standardized uptake value (SUV), effect of body size together with adjustment of scanning duration, and time-of-flight (TOF) reconstruction technique. Version 2.0 also presents data acquired with new PET camera models that were not tested in Version 1.0. Reference values for physical indicators of phantom image quality have been updated as well.     

Nuclear medicine equipment and PET cameras in Greece and abroad

TO THE EDITOR: Referring to recent discussions among many of our colleagues in Greece and to what Greek newspapers write about programming to buy more SPET and PET cameras in Greece and also relating to the usefulness of the PET camera, I would like to mention the number of PET cameras now functioning in many European countries and the important contribution of this new camera in diagnostic nuclear medicine. About 40% of the papers presented at the European Association of Nuclear Medicine Scientific Meeting last year, referred to studies performed by PET camera. In oncology, the PET camera may increase the diagnostic efficacy of SPET camera studies by about 30%. Unfortunately the PET camera is not used for all nuclear medicine applications and not all insurance companies agree to pay in full the cost of diagnostic procedures performed by the PET camera. Nuclear Medicine Societies of Greece should strongly suggest to the Ministries of Health and Education to provide public and especially university hospitals with a reasonable number of PET cameras. Also more SPET cameras should be bought to reach a ratio of at least one SPET camera per 100,000 inhabitants.     

7. Survey of Results of Whole Body Imaging Using the PET/CT at the University of Pittsburgh Medical Center PET Facility

Purpose: At the University Of Pittsburgh Medical Center, over 100 oncology studies have been performed using a combined PET/CT scanner. The scanner is a prototype, which combines clinical PET and clinical CT imaging in a single unit. The sensitivity achieved using three-dimensional PET imaging as well as the use of the CT for attenuation correction and image fusion make the device ideal for clinical oncology. Clinical indications imaged on the PET/CT scanner include, but are not limited to, tumor staging, solitary pulmonary nodule evaluation, and evaluation of tumor reoccurrence in melanoma, lymphoma, colorectal cancer, lung cancer, pancreatic cancer, head and neck cancer, and renal cancer.Methods: For all studies, seven millicuries of F(18)-fluorodeoxyglucose is injected and a forty-five minute uptake period is allowed prior to positioning the patient in the scanner. A helical CT scan is acquired over the region, or regions of interest followed by a multi-bed whole body PET scan for the same axial extent. The CT scan is used to correct the PET data for attenuation. The entire imaging session lasts 1-1.5 hours depending on the number of beds acquired, and is generally well tolerated by the patient.Results and Conclusion: Based on our experience in over 100 studies, combined PET/CT imaging offers significant advantages, including more accurate localization of focal uptake, distinction of pathology from normal physiological uptake, and improvements in evaluating therapy. These benefits will be illustrated with a number of representative, fully documented studies.     

Positron emission tomography: a technology assessment of PET imaging--past, present, and future

Emerging from its origins in the basements of research laboratories, positron emission tomography (PET), has established itself as a premier clinical imaging modality. It just took 50 years to get there. PET and the ever-popular, dual imaging modality combination of positron emission tomography/computed tomography (PET/CT) have taken hold of the spotlight at the national meetings of the Radiological Society of North America (RSNA) and the Society of Nuclear Medicine (SNM)--and they are not about to give it up. Many major imaging manufacturers--those companies that make up the majority of imaging sales in the US--now offer some type of PET and or PET/CT scanner. The technology of PET imaging continues to improve in image resolution, speed, and acceptance by its skeptical, but continually growing, referral base. With the increasing number of regional cyclotron facilities throughout the US each year, the abundance of mobile PET companies competing for business, and, most important, the number of clinical procedures that now qualify for reimbursement, more facilities now have the ability to implement PETimaging. This article discusses the progress of PET, from its beginnings 50 years ago, to where it is today--and the direction it is headed in the future.     

Hybrid cardiac imaging: SPECT/CT and PET/CT. A joint position statement by the European Association of Nuclear Medicine (EANM), the European Society of Cardiac Radiology (ESCR) and the European Council of Nuclear Cardiology (ECNC)

Improvements in software and hardware have enabled the integration of dual imaging modalities into hybrid systems, which allow combined acquisition of the different data sets. Integration of positron emission tomography (PET) and computed tomography (CT) scanners into PET/CT systems has shown improvement in the management of patients with cancer over stand-alone acquired CT and PET images. Hybrid cardiac imaging either with single photon emission computed tomography (SPECT) or PET combined with CT depicts cardiac and vascular anatomical abnormalities and their physiologic consequences in a single setting and appears to offer superior information compared with either stand-alone or side-by-side interpretation of the data sets in patients with known or suspected coronary artery disease (CAD). Hybrid systems are also advantageous for the patient because of the single short dual data acquisition. However, hybrid cardiac imaging has also generated controversy with regard to which patients should undergo such integrated examination for clinical effectiveness and minimization of costs and radiation dose, and if software-based fusion of images obtained separately would be a useful alternative. The European Association of Nuclear Medicine (EANM), the European Society of Cardiac Radiology (ESCR) and the European Council of Nuclear Cardiology (ECNC) in this paper want to present a position statement of the institutions on the current roles of SPECT/CT and PET/CT hybrid cardiac imaging in patients with known or suspected CAD.     

Evaluation of physiological Waldeyer’s ring,mediastinal blood pool,thymic, bone marrow,splenic and hepatic activity with 18F-FDG PET/CT: exploration of normal range among pediatric patients

Annals of Nuclear Medicine - While 18F-FDG PET/CT pediatrics applications have increased in number and indications, few studies have addressed normal maximum standardized uptake values (SUVmax) of...     

Intermittent cystocele diagnosed on 18F-FDG PET/CT scan

A 78-year-old woman was diagnosed with stage III diffuse large B-cell lymphoma, and treated with chemotherapy in 2004. Imaging follow-up was performed by serial 6-month diagnostic PET/CT scans. A PET/CT scan performed in June 2011 showed an unusual hourglass appearance of activity in the pelvis that prompted further investigation. Retrospective review of the prior diagnostic PET/CT scans revealed that the patient had a sliding bladder, located either above or below the pubococcygeal line at different imaging times, but during this scan, the bladder was "caught" moving up to its normal position.     

How often do patients undergo repeat PET or PET/CT examinations? Experience from a UK institution

BACKGROUND AND AIM: According to the report of the Intercollegiate Standing Committee on Nuclear Medicine, the UK requires 40-60 positron emission tomography (PET) machines in the next decade (Intercollegiate Standing Committee on Nuclear Medicine). Positron Emission Tomography: a Strategy for Provision in the UK. London: Royal College of Physicians of London; 2003, pp. 1-9). This figure is based mainly on patients receiving only one examination and restricting the clinical indication to three primary diagnoses. The aim of this study was to assess the appropriateness of this figure and the assumptions made in the Intercollegiate report on UK PET provision. METHODS: We examined retrospectively our institution's entire PET and PET/computed tomography (CT) database, which spans 4 years and 9 months. We recorded the number of patients who received repeat examinations. RESULTS: Reports were available for 3354 PET/CT or PET-only studies; 418 of 2268 patients (18.4%) received at least one repeat PET/CT examination. The three main indications for PET examination in the Intercollegiate report only accounted for approximately 60% of the examinations undertaken. CONCLUSION: Our records suggest that basing the UK's future PET provision on a single examination and on three clinical indications only is no longer realistic.     

MRI-based attenuation correction for PET/MRI: a novel approach combining pattern recognition and atlas registration

For quantitative PET information, correction of tissue photon attenuation is mandatory. Generally in conventional PET, the attenuation map is obtained from a transmission scan, which uses a rotating radionuclide source, or from the CT scan in a combined PET/CT scanner. In the case of PET/MRI scanners currently under development, insufficient space for the rotating source exists; the attenuation map can be calculated from the MR image instead. This task is challenging because MR intensities correlate with proton densities and tissue-relaxation properties, rather than with attenuation-related mass density. METHODS: We used a combination of local pattern recognition and atlas registration, which captures global variation of anatomy, to predict pseudo-CT images from a given MR image. These pseudo-CT images were then used for attenuation correction, as the process would be performed in a PET/CT scanner. RESULTS: For human brain scans, we show on a database of 17 MR/CT image pairs that our method reliably enables estimation of a pseudo-CT image from the MR image alone. On additional datasets of MRI/PET/CT triplets of human brain scans, we compare MRI-based attenuation correction with CT-based correction. Our approach enables PET quantification with a mean error of 3.2% for predefined regions of interest, which we found to be clinically not significant. However, our method is not specific to brain imaging, and we show promising initial results on 1 whole-body animal dataset. CONCLUSION: This method allows reliable MRI-based attenuation correction for human brain scans. Further work is necessary to validate the method for whole-body imaging.