Cardiac PET-CT: advanced hybrid imaging for the detection of coronary artery disease

Hybrid imaging of positron emission tomography (PET) together with computed tomography (CT) is rapidly emerging. In cardiology, this new advanced hybrid imaging modality allows quantification of cardiac perfusion in combination with assessment of coronary anatomy within a single scanning session of less than 45 minutes. The near-simultaneous anatomical evaluation of coronary arteries using CT and corresponding functional status using PET provides a wealth of complementary information in patients who are being evaluated for (suspected) coronary artery disease, and could help guide clinical patient management in a novel manner. Clinical experience gained with this recently introduced advanced hybrid imaging tool, however, is still limited and its implementation into daily clinical practice remains largely unchartered territory. This review discusses principles of perfusion PET, its diagnostic accuracy, and potential clinical applications of cardiac PET-CT in patients with ischaemic heart disease. (Neth Heart J 2010;18:90–8.)     

Cancer de la prostate : utilité de la TEP-TDM à la F-fluorocholine

In oncology, positron emission computed tomography (PET/CT) has become an essential tool for initial staging, response evaluation and follow-up of cancer patients. Most of the frequent tumors (lung, breast, esophagus, and lymphomas) are highly avid for ¹⁸F-fluorodeoxyglucose (¹⁸FDG), but prostate cancer has not demonstrated significant uptake of FDG. The development of new tracers labeled with ¹⁸F such as choline analogs allowed already to obtain interesting results particularly in patients with biological relapse and inconclusive conventional imaging work-up. The impact of ¹⁸F-flurocholine PET/CT on patient management needs to be validated in large studies, but many centers use already this examination in order to guide further management, including radiotherapy planning.     

Human Brown Adipose Tissue Depots Automatically Segmented by Positron Emission Tomography/Computed Tomography and Registered Magnetic Resonance Images

Reliably differentiating brown adipose tissue (BAT) from other tissues using a non-invasive imaging method is an important step toward studying BAT in humans. Detecting BAT is typically confirmed by the uptake of the injected radioactive tracer ¹⁸F-Fluorodeoxyglucose (¹⁸F-FDG) into adipose tissue depots, as measured by positron emission tomography/computed tomography (PET-CT) scans after exposing the subject to cold stimulus. Fat-water separated magnetic resonance imaging (MRI) has the ability to distinguish BAT without the use of a radioactive tracer. To date, MRI of BAT in adult humans has not been co-registered with cold-activated PET-CT. Therefore, this protocol uses ¹⁸F-FDG PET-CT scans to automatically generate a BAT mask, which is then applied to co-registered MRI scans of the same subject. This approach enables measurement of quantitative MRI properties of BAT without manual segmentation. BAT masks are created from two PET-CT scans: after exposure for 2 hr to either thermoneutral (TN) (24 °C) or cold-activated (CA) (17 °C) conditions. The TN and CA PET-CT scans are registered, and the PET standardized uptake and CT Hounsfield values are used to create a mask containing only BAT. CA and TN MRI scans are also acquired on the same subject and registered to the PET-CT scans in order to establish quantitative MRI properties within the automatically defined BAT mask. An advantage of this approach is that the segmentation is completely automated and is based on widely accepted methods for identification of activated BAT (PET-CT). The quantitative MRI properties of BAT established using this protocol can serve as the basis for an MRI-only BAT examination that avoids the radiation associated with PET-CT.     

功能与分子影像在头颈部肿瘤放射治疗计划和疗效评价中的应用

目前临床普遍采用功能与分子影像检测手段能来评价头颈部肿瘤的放射治疗计划和疗效,可指导个体化治疗从而提高疗效。文章概述了功能与分子影像技术CT,MRI,PET-CT,超声检测技术在头颈部肿瘤放射治疗计划制定和疗效评价中的应用进展。结果显示,不同分子影像检测方法如在检查时机的选择、诊断和鉴别诊断的价值、观察放射治疗后肿瘤的残存和复发、预测放射治疗效果、指导后续治疗等方面均可起到重要作用。采用图像融合技术进行联合应用,如PET-CT和MRI-CT等,可提高检测的准确率。临床医生需在常规影像学手段的基础上,根据头颈部肿瘤患者病情和治疗方法的不同选用正确的功能和分子影像检测手段,更好地指导制定放射治疗计划及综合评价放射治疗后的疗效。     

Impact of 68Ga-PSMA PET/CT in the treatment of prostate cancer: Initial experience in Spain

AimTo evaluate whether positron-emission tomography/computed tomography with ⁶⁸Ga-PSMA (⁶⁸Ga-PSMA PET/CT) influences the therapeutic management of patients with primary or recurrent prostate cancer (PCa).BackgroundAlthough ⁶⁸Ga-PSMA PET/CT is one of the best options for staging or restaging patients with PCa, its availability is still very limited in Spain. The present study reports the results of the first group of patients in Spain who underwent ⁶⁸Ga-PSMA PET/CT imaging.Materials and methodsAll patients (n = 27) with a histological diagnosis of PCa who underwent ⁶⁸Ga-PSMA PET/CT prior to the definitive treatment decision at the only centre with this technology in Spain during 2017–2018 were included. Two nuclear medicine physicians and a radiologist reviewed the imaging studies. The clinical impact was assessed from a theoretical perspective, based on the treatment that would have been applied if no data from the ⁶⁸Ga-PSMA PET/CT were available.ResultsMost patients (n = 26; 96%) had persistent disease or biochemical recurrence after radical prostatectomy, radiotherapy, or combined treatment. One patient underwent ⁶⁸Ga-PSMA PET/CT imaging to stage high-risk PCa. Overall, ⁶⁸Ga-PSMA PET/CT was positive in 19 patients (70.4%). In 68.75% of these patients, none of the other imaging tests—MRI, CT, or bone scans—performed prior to the ⁶⁸Ga-PSMA PET/CT were able to detect the presence of cancerous lesions. Overall, the findings of the ⁶⁸Ga-PSMA PET/CT led to a modification of the therapeutic approach in 62.96% of the patients in the study.Conclusions⁶⁸Ga-PSMA PET/CT alters the therapeutic approach in a substantial proportion of patients with PCa.     

Early positron emission tomography/computed tomography as a predictor of response after CTL019 chimeric antigen receptor –T-cell therapy in B-cell non-Hodgkin lymphomas

Molecular imaging with ¹⁸F-Fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) is an established modality for response assessment in patients with lymphoma undergoing treatment. However, patients treated with novel immunotherapies may have false-positive PET/CT findings due to tumor site and systemic inflammation. In particular, treatment with autologous chimeric antigen receptor modified T-cells redirected at CD19 (CTL019 CAR-T cells) is often complicated by “cytokine release syndrome” (CRS) due to a severe systemic inflammatory reaction. Infiltration of tumors by activated CTL019 cells may impact radiographic and functional imaging findings. The role of PET/CT in patients treated with CTL019 has not previously been described. We performed a pilot, single-arm, prospective study to explore the utility of early PET/CT in patients with diffuse large B-cell lymphoma (DLBCL) and follicular lymphoma (FL) undergoing treatment with CTL019 CAR-T cells. Patients had PET/CT prior to CTL019 infusion and then early PET/CT at 1 month after treatment. The primary outcome was the amount/change in metabolically active tumor volume (MTV) and FDG uptake. We enrolled seven patients (DLBCL, three; FL, four). Six of 7 had baseline PET/CT with active disease. On post-treatment PET/CT, three patients had no residual MTV, two patients had a decrease in MTV and two patients had an increase in MTV. The three patients with no residual MTV all remain in remission >2 years post-treatment. The patients with less than complete response all subsequently relapsed. Development of CRS did not confound PET/CT findings. In patients with DLBCL and FL receiving CTL019 CAR-T cells, early PET/CT may predict response to this novel immunotherapy.     

A case of heterotopic pancreas mimicking an intestinal neuroendocrine tumor in 18F-DOPA PET-CT and a review of the literature

18-Fluoro-L-dihydroxyphenylalanine positron emission tomography/computed tomography (18F-DOPA PET-CT) is a nuclear medicine imaging modality indicated for the diagnosis and staging of neuroendocrine tumors (NETs), particularly for the midgut tumors, due to its excellent sensitivity and specificity. Its performance for the detection of foregut-derived NETs (duodenopancreas and proximal jejunum) and for the detection of hindgut-derived NETs is poor and inferior to PET somatostatin receptor imaging such as DOTATOC PET-CT and even inferior to somatostatin analog scintigraphy (octreoscan). There are few studies in the literature on heterotopic pancreas (HP) which is a rare entity, and which can be in some cases a false positive in 18F-DOPA PET-CT. We report a case of HP showing focal uptake on 18F-DOPA PET-CT mimicking an intestinal NET. This case suggests that HP should be included as a possible false positive on 18F-DOPA PET-CT.     

A realistic utilization of nanotechnology in molecular imaging and targeted radiotherapy of solid tumors

Precise dose delivery to malignant tissue in radiotherapy is of paramount importance for treatment efficacy while minimizing morbidity of surrounding normal tissues. Current conventional imaging techniques, such as magnetic resonance imaging (MRI) and computerized tomography (CT), are used to define the three-dimensional shape and volume of the tumor for radiation therapy. In many cases, these radiographic imaging (RI) techniques are ambiguous or provide limited information with regard to tumor margins and histopathology. Molecular imaging (MI) modalities, such as positron emission tomography (PET) and single photon-emission computed-tomography (SPECT) that can characterize tumor tissue, are rapidly becoming routine in radiation therapy. However, their inherent low spatial resolution impedes tumor delineation for the purposes of radiation treatment planning. This review will focus on applications of nanotechnology to synergize imaging modalities in order to accurately highlight, as well as subsequently target, tumor cells. Furthermore, using such nano-agents for imaging, simultaneous coupling of novel therapeutics including radiosensitizers can be delivered specifically to the tumor to maximize tumor cell killing while sparing normal tissue.     

68Ga-labelled peptides for diagnosis of neuroendocrine tumours

On the basis of available literature, the aim of this paper is to describe the advantages and limitations of ⁶⁸Ga-DOTA peptide PET/CT imaging for the assessment of neuroendocrine tumours (NET) and to examine potential future perspectives. The introduction of new PET tracers labelled with ⁶⁸Ga has changed the diagnostic approach to NET. While in the past decades the gold standard imaging modality for NET detection was the somatostatin analogue tracers labelled with ¹¹¹In, several advantages now emerge by using both labelled somatostatin analogues with ⁶⁸Ga and PET/CT tomography for image acquisition, leading to a larger use of these tracers in clinical practice. There is an increasing number of reports showing the higher accuracy of ⁶⁸Ga-DOTA peptide PET/CT for the detection of NET lesions as compared to morphological imaging procedures and somatostatin receptor scintigraphy. The use of ⁶⁸Ga-DOTA peptides offers the possibility to non-invasively evaluate NET cells for the presence of somatostatin receptor expression, with direct therapeutic implications. Last but not least, the use of ⁶⁸Ga-DOTA peptides also leads to several practical advantages including the relatively easy and economic synthesis process and the fact that ⁶⁸Ga labelling can be performed in centres without an on-site cyclotron.     

Comparaison de la dose efficace en TEP/TDM et en TDM

Hybrid imaging, particularly positron emission tomography (PET) combined with CT has emerged in the field of oncology as a modality of choice. The concomitant realization of a standard CT examination, however, raises the question of the additional dose delivered to the patient. This radiation burden could be avoided by performing a single PET/CT examination with injection of contrast media. To verify the potential dosimetric gain of this strategy, we compared the effective dose associated with each modality in a retrospective cohort of 151 patients, homogeneous in weight and size. The average effective dose for a PET/CT (injection of 5-6 MBq/kg of ¹⁸FDG) was 13.5 mSv, the CT dose representing approximately 80% of the PET dose. In our study, the average effective dose in CT thorax/abdomen/pelvis was 21.4 mSv, 60% higher than the PET/CT effective dose.     

Clinicopathologic features and outcomes following surgery for pancreatic adenosquamous carcinoma

Background

The use of diagnostic ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography/computed tomography (PET/CT) imaging for the staging, restaging, and treatment monitoring of melanoma patients has become a well-recognized standard of care. It plays a key role in detecting sites of occult disease and is widely utilized in the medical and surgical planning of such patients. In the current report, we describe an innovative multimodality approach of perioperative ¹⁸F-FDG PET/CT imaging, intraoperative ¹⁸F-FDG handheld gamma probe detection, and intraoperative ultrasound for tumor localization and verification of resection of all sites of hypermetabolic tumor foci in a case of occult recurrent metastatic melanoma.

Case presentation

This report discusses a case of occult recurrent metastatic melanoma, isolated to three separate sites within the subcutaneous tissues of the left thigh region, which was not clinically apparent but was found on diagnostic restaging whole body ¹⁸F-FDG PET/CT scan utilizing an intravenous injection of 14.8 mCi ¹⁸F-FDG. Then, on the day of surgery, the patient received an intravenous injection of 12.8 mCi ¹⁸F-FDG. A multimodality approach of intraoperative handheld gamma probe detection, intraoperative ultrasound tumor localization, specimen PET/CT imaging, and postoperative PET/CT imaging was utilized for accomplishing and verifying the excision of all three sites of occult recurrent metastatic melanoma within the left thigh region.

Conclusion

This innovative multimodality approach of perioperative ¹⁸F-FDG PET/CT imaging, intraoperative ¹⁸F-FDG handheld gamma probe detection, and intraoperative ultrasound is promising combined technology for aiding in tumor localization and verification of excision and may ultimately impact positively upon long-term outcome of selected patients.     

18F-Fluorothymidine PET-CT for Resected Malignant Gliomas before Radiotherapy: Tumor Extent according to Proliferative Activity Compared with MRI

Objective

To compare the presence of post-operative residual disease by magnetic resonance imaging (MRI) and [18F]fluorothymidine (FLT)-positron emission tomography (PET)-computer tomography (CT) in patients with malignant glioma and to estimate the impact of ¹⁸F-FLT PET on the delineation of post-operative target volumes for radiotherapy (RT) planning.

Methods

Nineteen patients with post-operative residual malignant gliomas were enrolled in this study. For each patient, ¹⁸F- FLT PET-CT and MRI were acquired in the same week, within 4 weeks after surgery but before the initiation of RT. The PET-CT and MRI data were co-registered based on mutual information. The residual tumor volume defined on the ¹⁸F-FLT PET (Vol-PET) was compared with that of gadolinium [Gd] enhancement on T1-weighted MRI (Vol-T1) and areas of hyperintensity on T2-weighted MRI (Vol-T2).

Results

The mean Vol-PET (14.61 cm³) and Vol-T1 (13.60 cm³) were comparable and smaller than the mean Vol-T2 (32.93 cm³). The regions of ¹⁸F-FLT uptake exceeded the contrast enhancement and the hyperintense area on the MRI in 14 (73.68%) and 8 patients (42.11%), respectively. In 5 (26.32%) of the 19 patients, Vol-PET extended beyond 25 mm from the margin of Vol-T1; in 2 (10.53%) patients, Vol-PET extended 20 mm from the margin of Vol-T2. Vol-PET was detected up to 35 mm away from the edge of Vol-T1 and 24 mm away from the edge of Vol-T2. In 16 (84.21%) of the 19 patients, the Vol-T1 extended beyond the Vol-PET. In all of the patients, at least some of the Vol-T2 was located outside of the Vol-PET.

Conclusions

The volumes of post-operative residual tumor in patients with malignant glioma defined by ¹⁸F-FLT uptake on PET are not always consistent with the abnormalities shown on post-operative MRI. Incorporation of ¹⁸F-FLT-PET in tumor delineation may have the potential to improve the definition of target volume in post-operative radiotherapy.     

New perspectives of PET/CT in oncology

The fusion of PET and computed tomography, which provide metabolic and structural images, respectively, has improved the diagnostic precision of PET in oncology. Some current procedures in the PET/CT acquisition as contrast enhanced CT/PET, the use of PET/CT in radiotherapy planning and the PET-MRI can drastically change the approach of oncologic patients. Finally, inclusions of PET/CT in oncologic diagnostic algorithm and prognostic nomograms are pending issues.     

Metformin May Be Associated with False-Negative Cancer Detection in the Gastrointestinal Tract on Pet/Ct

ObjectiveConcurrent therapy with the antihyperglycemic drug metformin can hinder the detection of malignancy in the abdominal and pelvic portions of ¹⁸F-fluordeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) imaging performed for the diagnosis or staging of malignancy, as well as for treatment response and radiation therapy planning. This is due to the metformin-induced increase in intestinal FDG radiotracer uptake. We aim to bring this potentially important interaction to the attention of clinicians who care for cancer patients with diabetes.MethodsWe searched MEDLINE (from 1970 to January 2014)and Google Scholar for relevant English-language articles using the following search terms: “metformin and FDG/PET, metformin and bowel uptake, metformin, and cancer, metformin and the intestine, metformin pharmacokinetics, hyperglycemia and FDG/PET.” We reviewed the reference lists of pertinent articles with respect to metformin gut physiology, impact on FDG uptake and the effect on diagnostic accuracy of abdominal-pelvic PET/CT scans with concurrent metformin therapy.ResultsWe reviewed the action of metformin in the intestine, with particular emphasis on the role of metformin in PET/CT imaging and include a discussion of clinical studies on the topic to help refine knowledge and inform practice. Finally, we discuss aspects pertinent to the management of type 2 diabetes (T2D) patients on metformin undergoing PET/CT.ConclusionsMetformin leads to intense, diffusely increased FDG uptake in the colon, and to a lesser degree, the small intestine, which limits the diagnostic capabilities of FDG PET/CT scanning and may mask gastrointestinal malignancies. We suggest that metformin be discontinued 48 hours before FDG PET/CT scanning is performed in oncology patients. More rigorous data are needed to support the widespread generalizability of this recommendation. (Endocr Pract. 2014;20:1079-1083)     

Application of metabolic PET imaging in radiation oncology

Positron emission tomography (PET) is a noninvasive imaging technique that provides functional or metabolic assessment of normal tissue or disease conditions and is playing an increasing role in cancer radiotherapy planning. (18)F-Fluorodeoxyglucose PET imaging (FDG-PET) is widely used in the clinic for tumor imaging due to increased glucose metabolism in most types of tumors; its role in radiotherapy management of various cancers is reviewed. In addition, other metabolic PET imaging agents at various stages of preclinical and clinical development are reviewed. These agents include radiolabeled amino acids such as methionine for detecting increased protein synthesis, radiolabeled choline for detecting increased membrane lipid synthesis, and radiolabeled acetate for detecting increased cytoplasmic lipid synthesis. The amino acid analogs choline and acetate are often more specific to tumor cells than FDG, so they may play an important role in differentiating cancers from benign conditions and in the diagnosis of cancers with either low FDG uptake or high background FDG uptake. PET imaging with FDG and other metabolic PET imaging agents is playing an increasing role in complementary radiotherapy planning.     

Combined PET/CT for IMRT treatment planning of NSCLC: Contrast-enhanced CT images for Monte Carlo dose calculation

PurposeCombined PET/CT imaging has been proposed as an integral part of radiotherapy treatment planning (TP). Contrast-enhanced CT (ceCT) images are frequently acquired as part of the PET/CT examination to support target delineation. The aim of this dosimetric planning study was to investigate the error introduced by using a ceCT for intensity modulated radiotherapy (IMRT) TP with Monte Carlo dose calculation for non-small cell lung cancer (NSCLC).Material and methodsNine patients with NSCLC prior to chemo-RT were included in this retrospective study. For each patient non-enhanced, low-dose CT (neCT), ceCT and [¹⁸F]-FDG-PET emission data were acquired within a single examination. Manual contouring and TP were performed on the ceCT. An additional set of independent target volumes was auto-segmented in PET images. Dose distributions were recalculated on the neCT. Differences in dosimetric parameters were evaluated.ResultsDose differences in PTV and lungs were small for all patients. The maximum difference in all PTVs when using ceCT images for dose calculation was ?2.1%, whereas the mean difference was less than ?1.7%. Maximum differences in the lungs ranged from ?1.8% to 2.1% (mean: ?0.1%). In four patients an underestimation of the maximum spinal cord dose between 2% and 3.2% was observed, but treatment plans remained clinically acceptable.ConclusionsMonte Carlo based IMRT planning for NSCLC patients using ceCT allows for correct dose calculation. A direct comparison to neCT-based treatment plans revealed only small dose differences. Therefore, ceCT-based TP is clinically safe as long as the maximum acceptable dose to organs at risk is not approached.     

Effectiveness of PET/CT with 18F-fluorothymidine in the staging of patients with squamous cell head and neck carcinomas before radiotherapy

Aim

The aim of our study was to compare the staging of the disease declared before anticancer treatment was begun with the staging that was found after the planning PET/CT scanning with ¹⁸F-FLT was performed.

Background

PET/CT in radiotherapy planning of head and neck cancers can facilitate the contouring of the primary tumour and the definition of metastatic lymph nodes.

Materials and methods

Between November 2010 and November 2013, 26 patients suffering from head and neck carcinomas underwent planning PET/CT examination with ¹⁸F-FLT. We compared the staging of the disease and the treatment strategy declared before and after ¹⁸F-FLT-PET/CT was performed.

Results

The findings from ¹⁸FLT-PET/CT led in 22 patients to a change of staging: in 19 patients it led to upstaging of the disease and in 3 patients it led to downstaging of the disease. In one patient, a secondary malignancy was found.

Conclusions

We have confirmed in this study that the use of ¹⁸F-FLT-PET/CT scanning in radiotherapy planning of squamous cell head and neck carcinomas has a great potential in the precise evaluation of disease staging and consequently in the precise determination of target volumes.     

TEP/IRM hybride en neuro-imagerie

The hybrid Positron Emission Tomography/Magnetic Resonance Imaging (PET/MRI) is a newly available imaging modality combining the molecular and metabolic PET information with the morphological and functional data provided by MRI. Integrated PET/MRI tomographs were conceived in analogy to the current PET/Computed Tomography (PET/CT) technology, with specific properties linked to the intrinsic differences of MRI and CT imaging. In the field of neuro-imaging, in particular, MRI provides a larger panel of information, as compared with CT, and is already systematically fused and used as a support for PET images for diagnostic and research purposes. We summarize here our current experience with the first integrated PET/MRI tomograph installed in Switzerland, concerning specifically three clinical applications: brain tumors characterization, the diagnosis of neurodegenerative dementias and the presurgical evaluation of pharmaco-resistant epilepsy. With this sequential tomograph, we could combine the full range of diagnostic MR sequences (including diffusion tensor imaging, tractography, spectroscopy, functional MR) with PET imaging of brain glucose metabolism (by ¹⁸F-Fluorodeoxyglucose–FDG) and of amino acid transport (by ¹⁸F-Fluoroethyltyrosine–FET). We also summarize the main results obtained in neuro-imaging by the different groups working with these new hybrid tomographs. These data show that PET/MRI, acquired in a single imaging session, may represent the modality of choice for neuro-imaging.     

Coronary computed tomography angiography and [15O]H2O positron emission tomography perfusion imaging for the assessment of coronary artery disease

Determining the anatomic severity and extent of coronary artery disease (CAD) by means of coronary computed tomography angiography (CCTA) and its effect on perfusion using myocardial perfusion imaging (MPI) form the pillars of the non-invasive imaging assessment of CAD. This review will 1) focus on CCTA and [¹⁵O]H₂O positron emission tomography MPI as stand-alone imaging modalities and their combined use for detecting CAD, 2) highlight some of the lessons learned from the PACIFIC trial (Comparison of Coronary CT Angiography, SPECT, PET, and Hybrid Imaging for Diagnosis of Ischemic Heart Disease Determined by Fractional Flow Reserve (FFR) (NCT01521468)), and 3) discuss the use of [¹⁵O]H₂O PET MPI in the clinical work-up of patients with a chronic coronary total occlusion (CTO).