Liver tumor F-18 FDG-PET before and immediately after microwave ablation enables imaging and quantification of tumor tissue contraction.

PURPOSE: Poor liver tumor visibility after microwave ablation (MWA) limits direct tumor ablation margin assessments using contrast-enhanced CT or ultrasound (US). Positron emission tomography (PET) or PET/CT may offer improved intraprocedural assessment of liver tumor ablation margins versus current imaging techniques, as 18F-fluorodeoxyglucose (18F-FDG)-avid tumors remain visible on PET immediately following ablation. The purpose of this study was to assess intraprocedural 18F-FDG PET scans before and immediately after PET/CT-guided MWA for visualization and quantification of metabolic liver tumor tissue contraction resulting from MWA. METHODS: This retrospective study, conducted at a large academic medical center after Institutional Review Board approval, included 36 patients (20 men; mean age 63 [range 37-85]) who underwent PET/CT-guided MWA of 42 18F-FDG-avid liver tumors from May 2013 to March 2018. Tumor metabolic diameters (short/long axes) were measured for each tumor on pre- and post-ablation PET images. Tumor metabolic volumes were calculated using tumor diameter measurements and compared with automated volumes using an SUV threshold algorithm. A two-tailed paired t test was used for the analyses. RESULTS: Comparing intraprocedural pre- and post-ablation PET images, mean metabolic tumor short- and long-axis diameters decreased from 21.4 to 14.9 mm [- 29%, p < 0.001, standard deviation (SD) 18%] and from 24.0 to 18.0 mm (- 24%, p < 0.001, SD 16%), respectively. The mean calculated tumor metabolic volume decreased from 10.5 to 4.6 mm3 (- 55%, p < 0.001, SD 26%). The mean automated tumor metabolic volume decreased from 10.6 to 5.8 mm3 (- 45%, p < 0.001, SD 30%). CONCLUSION: Intraprocedural PET images of 18F-FDG-avid liver tumors allow visualization and quantification of MWA-induced metabolic tumor tissue contraction during 18F-FDG PET/CT-guided procedures. The ability to visualize contracted tumor immediately post-MWA may facilitate emerging intraprocedural PET and PET/CT imaging techniques that address a clinical gap in directly assessing the ablation margin.

Assessing ablation margins of FDG-avid liver tumors during PET/CT-guided thermal ablation procedures: a retrospective study.

BACKGROUND: To retrospectively assess liver tumor ablation margins using intraprocedural PET/CT images from FDG PET/CT-guided microwave or cryoablation procedures and to correlate minimum margin measurements with local progression outcomes. METHODS: Fifty-six patients (ages 36 to 85, median 62; 32 females) with 77 FDG-avid liver tumors underwent 60 FDG PET/CT guided, percutaneous microwave, or cryoablation procedures. Single breath-hold PET/CT images were used for intraprocedural assessment of the tumor ablation margin: liver tumors remained visible on PET immediately following ablation; microwave ablation zones were visible using contrast-enhanced CT; cryoablation zones (ice balls) were visible using unenhanced CT. Two readers retrospectively determined ablation margin assessability and measured the minimum ablation margin on intraprocedural PET/CT (n = 77) and postprocedural MRI (n = 56). Local tumor progression was assessed on all available follow-up imaging (1-49 months, mean 15). Local tumor progression was correlated with PET/CT minimum margin measurements using clustered survival models for 61 tumors. RESULTS: Minimum ablation margins were more often assessable using intraprocedural PET/CT (≥ 73/77 tumors, 95%) than postprocedural MRI (≤ 35/56 tumors, 63%). In 61 tumors with PET/CT-assessable margins (excluding tumors with overlapping ablations after PET/CT), there was a 6-fold increased risk of local tumor progression [hazard ratio (HR) 6.05; P = 0.004] for minimum ablation margins < 5 mm. CONCLUSION: Breath-hold PET/CT scans, during PET/CT-guided microwave or cryoablation procedures for FDG-avid liver tumors, enable reliable intraprocedural assessment of the entire tumor ablation margin; a minimum PET/CT ablation margin threshold of 5 mm correlates well with local tumor progression outcomes.

Intraprocedural Ablation Margin Assessment by Using Ammonia Perfusion PET during FDG PET/CT-guided Liver Tumor Ablation: A Pilot Study.

Purpose To prospectively determine whether nitrogen 13 (13N) ammonia perfusion positron emission tomography (PET) during fluorine 18 fluorodeoxyglucose (FDG) PET/computed tomography (CT)-guided liver tumor ablation can be used to intraprocedurally assess ablation margins. Materials and Methods Eight patients (five women and three men; age range, 36-74 years; mean age, 57 years) were enrolled in this pilot study and underwent FDG PET/CT-guided microwave ablation of 11 FDG-avid liver metastases (mean diameter, 22 mm; range, 11-34 mm). All procedures were performed between March 2014 and December 2016. Complete ablation margin visibility and minimum ablation margin thickness were assessed by using intraprocedural 13N-ammonia perfusion PET compared with 24-hour postprocedural MR imaging by two independent blinded radiologists. Local tumor progression for each ablated tumor was assessed at follow-up imaging for 3-38 months (median, 17.6 months). Descriptive analysis was performed. Results Eleven of 11 (100%) ablation margins were fully assessable by using intraprocedural perfusion PET by both readers; six of eleven (55%) margins were fully assessable by both readers at postprocedural 24-hour MR imaging. By using perfusion PET, one tumor that had been judged by both readers to have a minimum margin of 0 mm progressed locally. No tumors judged to have a minimum margin greater than 0 mm at perfusion PET progressed locally. Conclusion 13N-ammonia perfusion PET during FDG PET/CT-guided liver tumor ablations can potentially be used to intraprocedurally assess the entire ablation margin, including the minimum margin. © RSNA, 2018.

Imaging characteristics of pathologically proven thymic hyperplasia: identifying features that can differentiate true from lymphoid hyperplasia.

OBJECTIVE: The purpose of this article is to investigate the imaging characteristics of pathologically proven thymic hyperplasia and to identify features that can differentiate true hyperplasia from lymphoid hyperplasia. MATERIALS AND METHODS: Thirty-one patients (nine men and 22 women; age range, 20-68 years) with pathologically confirmed thymic hyperplasia (18 true and 13 lymphoid) who underwent preoperative CT (n=27), PET/CT (n=5), or MRI (n=6) were studied. The length and thickness of each thymic lobe and the transverse and anterior-posterior diameters and attenuation of the thymus were measured on CT. Thymic morphologic features and heterogeneity on CT and chemical shift on MRI were evaluated. Maximum standardized uptake values were measured on PET. Imaging features between true and lymphoid hyperplasia were compared. RESULTS: No significant differences were observed between true and lymphoid hyperplasia in terms of thymic length, thickness, diameters, morphologic features, and other qualitative features (p>0.16). The length, thickness, and diameters of thymic hyperplasia were significantly larger than the mean values of normal glands in the corresponding age group (p<0.001). CT attenuation of lymphoid hyperplasia was significantly higher than that of true hyperplasia among 15 patients with contrast-enhanced CT (median, 47.9 vs 31.4 HU; Wilcoxon p=0.03). The receiver operating characteristic analysis yielded greater than 41.2 HU as the optimal threshold for differentiating lymphoid hyperplasia from true hyperplasia, with 83% sensitivity and 89% specificity. A decrease of signal intensity on opposed-phase images was present in all four cases with in- and opposed-phase imaging. The mean maximum standardized uptake value was 2.66. CONCLUSION: CT attenuation of the thymus was significantly higher in lymphoid hyperplasia than in true hyperplasia, with an optimal threshold of greater than 41.2 HU in this cohort of patients with pathologically confirmed thymic hyperplasia.

Considerations for Imaging of Malignant Pleural Mesothelioma: A Consensus Statement from the International Mesothelioma Interest Group.

Malignant pleural mesothelioma (MPM) is an aggressive primary malignancy of the pleura that presents unique radiologic challenges with regard to accurate and reproducible assessment of disease extent at staging and follow-up imaging. By optimizing and harmonizing technical approaches to imaging MPM, the best quality imaging can be achieved for individual patient care, clinical trials, and imaging research. This consensus statement represents agreement on harmonized, standard practices for routine multimodality imaging of MPM, including radiography, computed tomography, 18F-2-deoxy-D-glucose positron emission tomography, and magnetic resonance imaging, by an international panel of experts in the field of pleural imaging assembled by the International Mesothelioma Interest Group. In addition, modality-specific technical considerations and future directions are discussed. A bulleted summary of all technical recommendations is provided.

Exposing exposure: enhancing patient safety through automated data mining of nuclear medicine reports for quality assurance and organ dose monitoring.

PURPOSE: To develop and validate an open-source informatics toolkit capable of creating a radiation exposure data repository from existing nuclear medicine report archives and to demonstrate potential applications of such data for quality assurance and longitudinal patient-specific radiation dose monitoring. MATERIALS AND METHODS: This study was institutional review board approved and HIPAA compliant. Informed consent was waived. An open-source toolkit designed to automate the extraction of data on radiopharmaceuticals and administered activities from nuclear medicine reports was developed. After iterative code training, manual validation was performed on 2359 nuclear medicine reports randomly selected from September 17, 1985, to February 28, 2011. Recall (sensitivity) and precision (positive predictive value) were calculated with 95% binomial confidence intervals. From the resultant institutional data repository, examples of usage in quality assurance efforts and patient-specific longitudinal radiation dose monitoring obtained by calculating organ doses from the administered activity and radiopharmaceutical of each examination were provided. RESULTS: Validation statistics yielded a combined recall of 97.6% ± 0.7 (95% confidence interval) and precision of 98.7% ± 0.5. Histograms of administered activity for fluorine 18 fluorodeoxyglucose and iodine 131 sodium iodide were generated. An organ dose heatmap which displays a sample patient's dose accumulation from multiple nuclear medicine examinations was created. CONCLUSION: Large-scale repositories of radiation exposure data can be extracted from institutional nuclear medicine report archives with high recall and precision. Such repositories enable new approaches in radiation exposure patient safety initiatives and patient-specific radiation dose monitoring.

Epithelial malignant pleural mesothelioma after extrapleural pneumonectomy: stratification of survival with CT-derived tumor volume.

OBJECTIVE: The purpose of this study was to assess the usefulness of CT-derived tumor volume, with control for other prognostic factors, for stratifying survival after surgery-based multimodality treatment of a large cohort of patients with epithelial malignant pleural mesothelioma. MATERIALS AND METHODS: We retrospectively reviewed 338 patients with mesothelioma who underwent extrapleural pneumonectomy between 2001 and 2007. The study cohort comprised 88 patients with epithelial subtype tumors, DICOM-format CT scans, and data regarding neoadjuvant and adjuvant therapy. Tumor volume was calculated, and Kaplan-Meier survival and Cox regression analyses were performed to compare the estimated survival functions of patient subgroups based on volume and other covariates related to outcome (sex, age, preoperative platelet count, hemoglobin concentration, WBC count, clinical and pathologic TNM category, and administration of neoadjuvant and adjuvant therapy). A multivariate regression model was derived on the basis of the most significant univariate predictors. RESULTS: The median estimated tumor volume was 319 cm(3) (range, 4-3256 cm(3)). In univariate analysis, tumor volume, hemoglobin concentration, platelet count, pathologic TNM category, and administration of adjuvant chemotherapy or radiation therapy met the criteria for inclusion in the reverse stepwise regression analysis. In the final model, tumor volume, hemoglobin concentration, and administration of adjuvant chemotherapy or radiotherapy were identified as independently associated with overall survival. CONCLUSION: With control of prognostic covariates, CT-derived tumor volume can be used to stratify survival of patients with epithelial mesothelioma after extrapleural pneumonectomy and should be included in prognostic evaluation of patients for whom resection is being considered.

Clinical Applications of Artificial Intelligence in Positron Emission Tomography of Lung Cancer.

The ability of a computer to perform tasks normally requiring human intelligence or artificial intelligence (AI) is not new. However, until recently, practical applications in medical imaging were limited, especially in the clinic. With advances in theory, microelectronic circuits, and computer architecture as well as our ability to acquire and access large amounts of data, AI is becoming increasingly ubiquitous in medical imaging. Of particular interest to our community, radiomics tries to identify imaging features of specific pathology that can represent, for example, the texture or shape of a region in the image. This is conducted based on a review of mathematical patterns and pattern combinations. The difficulty is often finding sufficient data to span the spectrum of disease heterogeneity because many features change with pathology as well as over time and, among other issues, data acquisition is expensive. Although we are currently in the early days of the practical application of AI to medical imaging, research is ongoing to integrate imaging, molecular pathobiology, genetic make-up, and clinical manifestations to classify patients into subgroups for the purpose of precision medicine, or in other words, predicting a priori treatment response and outcome. Lung cancer is a functionally and morphologically heterogeneous disease. Positron emission tomography (PET) is an imaging technique with an important role in the precision medicine of patients with lung cancer that helps predict early response to therapy and guides the selection of appropriate treatment. Although still in its infancy, early results suggest that the use of AI in PET of lung cancer has promise for the detection, segmentation, and characterization of disease as well as for outcome prediction.

FDG PET/CT patterns of treatment failure of malignant pleural mesothelioma: relationship to histologic type, treatment algorithm, and survival.

PURPOSE: This study investigated the diagnostic performance and prognostic value of fluorodeoxyglucose (FDG) positron emission tomography (PET)/CT in suspected malignant pleural mesothelioma (MPM) recurrence, in the context of patterns and intensity of FDG uptake, histologic type, and treatment algorithm. METHODS: Fifty patients with MPM underwent FDG PET/CT for restaging 11 ± 6 months after therapy. Tumor relapse was confirmed by histopathology, and by clinical evolution and subsequent imaging. Progression-free survival was defined as the time between treatment and the earliest clinical evidence of recurrence. Survival after FDG PET/CT was defined as the time between the scan and death or last follow-up. Overall survival was defined as the time between initial treatment and death or last follow-up date. RESULTS: Treatment failure was confirmed in 42 patients (30 epithelial and 12 non-epithelial MPM). Sensitivity, specificity, accuracy, negative predictive value, and positive predictive value for FDG PET/CT were 97.6, 75, 94, 86, and 95.3%, respectively. FDG PET/CT evidence of single site of recurrence was observed in the ipsilateral hemithorax in 18 patients (44%), contralaterally in 2 (5%), and in the abdomen in 1 patient (2%). Bilateral thoracic relapse was detected in three patients (7%). Simultaneous recurrence in the ipsilateral hemithorax and abdomen was observed in ten (24%) patients and in seven (17%) in all three cavities. Unsuspected distant metastases were detected in 11 patients (26%). Four patterns of uptake were observed in recurrent disease: focal, linear, mixed (focal/linear), and encasing, with a significant difference between the intensity of uptake in malignant lesions compared to benign post-therapeutic changes. Lesion uptake was lower in patients previously treated with more aggressive therapy and higher in intrathoracic lesions of patients with distant metastases. FDG PET/CT helped in the selection of 12 patients (29%) who benefited from additional previously unplanned treatment at the time of failure. Multivariate analysis showed that histologic type remained the only independent predictor of progression-free survival. Survival after relapse was independently predicted by the pattern of FDG uptake and PET nodal status, and overall survival by the maximum standard uptake value. CONCLUSION: FDG PET/CT is an accurate modality to diagnose and to estimate the extent of locoregional and distant MPM recurrence, and it carries independent prognostic value. Once the disease recurs, survival outcomes seem to be independent of histologic type and highly dependent on the intensity of lesion uptake and on the pattern of metabolically active disease in FDG PET/CT. Our observations should be considered limited to patients treated surgically with or without perioperative therapies and should not be extrapolated to those unresectable cases treated with chemotherapy alone.

Dual phase FDG-PET imaging of brain metastases provides superior assessment of recurrence versus post-treatment necrosis.

To study the ability of dual phase FDG-PET/CT imaging to accurately distinguish tumor versus necrosis in patients treated for brain metastases. 32 (22 female, 10 male) consecutive patients with treated brain metastases, lesion size greater than 0.5 cm(3) and suspected recurrence on MRI underwent dual-phase FDG-PET/CT. Clinical outcome was assessed by biopsy or by MRI. SUVmax and SUVmean values of the lesion (L) and gray matter (GM) at the level of the thalamus were measured on early (1) and delayed (2) imaging. L1/GM1 and L2/GM2 and the change of L/GM ratios as a function of time were calculated [(L2/GM2 - L1/GM1)/(L1/GM1)]. Cut-off values were obtained by ROC analysis. P < 0.05 defined statistical significance. Seven patients were excluded due to indeterminate outcomes. 25 patients (16 female, 9 male; 27 lesions; 28 scan sessions) had clear outcomes, proven by either biopsy (n = 16 patients) or serial follow-up MRI (n = 9 patients). Primary subtypes included breast (n = 9), lung (n = 7), melanoma (n = 3), squamous cell cancer of the head and neck (n = 2) and other (n = 4). Twenty-two patients underwent prior radiation (2-113 months) and three received only prior chemotherapy (5 months to 3 years). A change >0.19 of L/GM ratios as a function of time was 95% sensitive, 100% specific, and 96.4% accurate (P = 0.0001; AUC = 0.97) for distinguishing tumor versus radiation necrosis. The ratio of the change of the lesion to WM ratios over time was the second best indicator of outcome when compared to all indices used (ROC cut-off = 0.25, sensitivity 89.5% and specificity 90.9%, and accuracy 89.2%; P = 0.0001; AUC = 0.95), Early or late SUVs of the lesion alone did not differentiate between tumor and necrosis. Regardless of histological type, differentiation of necrosis from metastatic brain lesions was improved by using the change of lesion to gray matter SUVmax ratios as a function of time.

PET/CT-guided percutaneous biopsy of abdominal masses: initial experience.

PURPOSE: To develop a technique for guiding percutaneous biopsies of abdominal masses in a positron emission tomography (PET)/computed tomography (CT) scanner, and test its feasibility and safety in patients. MATERIALS AND METHODS: The authors conducted a prospective study in 12 patients who were in need of both a diagnostic (18)F-fluoro-deoxy-D-glucose (FDG) PET/CT scan and a percutaneous biopsy of an abdominal mass, located in the liver (n = 7), presacral soft tissue (n = 2), lymph node (n = 2), and kidney (n = 1). After completion of the PET/CT scan, with the patient remaining on the table, a one-table-position PET/CT scan was obtained with a radiopaque grid in place, and the biopsy procedure was planned. Then, a biopsy needle was placed into the mass using one-table-position CT scan registered to the planning PET scan. Masses were sampled after confirming accurate positioning of the needle tips with a final one-table-position PET/CT scan. Negative results were confirmed independently with follow-up imaging. RESULTS: All biopsy procedures yielded diagnostic results; nine were positive for malignancy, and three were negative (fibrosis, steatosis, and Escherichia coli infection). One non-FDG-avid mass biopsy yielded a malignant result. Seven masses were either invisible or poorly depicted with unenhanced CT scan, and two masses contained FDG avidity in only a portion of the mass. There were no complications. CONCLUSIONS: Although our data are preliminary, this initial experience suggests that abdominal masses can undergo successful biopsy in a PET/CT scanner. PET/CT guidance may be helpful when performing biopsy on FDG-avid masses that are either not visible with unenhanced CT or are FDG avid in only a portion.

Motion artifacts occurring at the lung/diaphragm interface using 4D CT attenuation correction of 4D PET scans.

For PET/CT, fast CT acquisition time can lead to errors in attenuation correction, particularly at the lung/diaphragm interface. Gated 4D PET can reduce motion artifacts, though residual artifacts may persist depending on the CT dataset used for attenuation correction. We performed phantom studies to evaluate 4D PET images of targets near a density interface using three different methods for attenuation correction: a single 3D CT (3D CTAC), an averaged 4D CT (CINE CTAC), and a fully phase matched 4D CT (4D CTAC). A phantom was designed with two density regions corresponding to diaphragm and lung. An 8 mL sphere phantom loaded with 18F-FDG was used to represent a lung tumor and background FDG included at an 8:1 ratio. Motion patterns of sin(x) and sin4(x) were used for dynamic studies. Image data was acquired using a GE Discovery DVCT-PET/CT scanner. Attenuation correction methods were compared based on normalized recovery coefficient (NRC), as well as a novel quantity "fixed activity volume" (FAV) introduced in our report. Image metrics were compared to those determined from a 3D PET scan with no motion present (3D STATIC). Values of FAV and NRC showed significant variation over the motion cycle when corrected by 3D CTAC images. 4D CTAC- and CINE CTAC-corrected PET images reduced these motion artifacts. The amount of artifact reduction is greater when the target is surrounded by lower density material and when motion was based on sin4(x). 4D CTAC reduced artifacts more than CINE CTAC for most scenarios. For a target surrounded by water equivalent material, there was no advantage to 4D CTAC over CINE CTAC when using the sin(x) motion pattern. Attenuation correction using both 4D CTAC or CINE CTAC can reduce motion artifacts in regions that include a tissue interface such as the lung/diaphragm border. 4D CTAC is more effective than CINE CTAC at reducing artifacts in some, but not all, scenarios.

Update on Molecular Imaging and Precision Medicine in Lung Cancer.

Precision medicine integrates molecular pathobiology, genetic make-up, and clinical manifestations of disease in order to classify patients into subgroups for the purposes of predicting treatment response and suggesting outcome. By identifying those patients who are most likely to benefit from a given therapy, interventions can be tailored to avoid the expense and toxicity of futile treatment. Ultimately, the goal is to offer the right treatment, to the right patient, at the right time. Lung cancer is a heterogeneous disease both functionally and morphologically. Further, over time, clonal proliferations of cells may evolve, becoming resistant to specific therapies. PET is a sensitive imaging technique with an important role in the precision medicine algorithm of lung cancer patients. It provides anatomo-functional insight during diagnosis, staging, and restaging of the disease. It is a prognostic biomarker in lung cancer patients that characterizes tumoral heterogeneity, helps predict early response to therapy, and may direct the selection of appropriate treatment.

F-18 FDG perfusion PET: intraprocedural assessment of the liver tumor ablation margin.

PURPOSE: To evaluate 18F-fluorodeoxyglucose (FDG) perfusion PET during FDG PET/CT-guided liver tumor microwave ablation procedures for assessing the ablation margin and correlating minimum margin measurements with local progression. METHODS: This IRB-approved, HIPAA-compliant study included 20 adult patients (11 M, 9 F; mean age 65) undergoing FDG PET/CT-guided liver microwave ablation to treat 31 FDG-avid tumors. Intraprocedural FDG perfusion PET was performed to assess the ablation margin. Intraprocedural decisions regarding overlapping ablations were recorded. Two readers retrospectively interpreted intraprocedural perfusion PET and postprocedural contrast-enhanced MRI. Assessability of the ablation margin and minimum margin measurements were recorded. Imaging follow-up for local progression ranged from 30 to 574 days (mean 310). Regression modeling of minimum margin measurements was performed. Hazard ratios were calculated to correlate an ablation margin threshold of 5 mm with outcomes. RESULTS: Intraprocedural perfusion PET prompted additional overlapping ablations of two tumors, neither of which progressed. Incomplete ablation or local progression occurred in 8/31 (26%) tumors. With repeat ablation, secondary efficacy was 26 (84%) of 31. Both study readers deemed ablation margins fully assessable more often using perfusion PET than MRI (OR 69.7; CI 6.0, 806.6; p = 0.001). Minimum ablation margins ≥ 5 mm on perfusion PET correlated with a low risk of incomplete ablation/local progression by both study readers (HR 0.08 and 0.02, p < 0.001). CONCLUSION: Intraprocedural FDG perfusion PET consistently enabled complete liver tumor microwave ablation margin assessments, and the perfusion PET minimum ablation margin measurements correlated well with local outcomes. Clinical trial registration clinicaltrials.gov (NCT02018107).

Abdominal masses sampled at PET/CT-guided percutaneous biopsy: initial experience with registration of prior PET/CT images.

PURPOSE: To establish the feasibility of performing combined positron emission tomography (PET)/computed tomography (CT)-guided biopsy of abdominal masses by using previously acquired PET/CT images registered with intraprocedural CT images. MATERIALS AND METHODS: In this HIPAA-compliant institutional review board-approved study, 14 patients underwent clinically indicated percutaneous biopsy of abdominal masses (mean size, 3.3 cm; range, 1.2-5.0 cm) in the liver (n = 6), presacral soft tissue (n = 3), retroperitoneal lymph nodes (n = 2), spleen (n = 2), and pancreas (n = 1). PET/CT images obtained no more than 62 days (mean, 18.3 days) before the biopsy procedure were registered with intraprocedural CT images by using image registration software. The registered images were used to plan the procedure and help target the masses. RESULTS: The image registrations were technically successful in all but one patient, who had severe scoliosis. The remaining 13 biopsy procedures yielded diagnostic results, which were positive for malignancy in 10 cases and negative in three cases. CONCLUSION: PET/CT-guided abdominal biopsy with use of prior PET/CT images registered with intraprocedural CT scans is feasible and may be helpful when fluorine 18 fluorodeoxyglucose-avid masses that are not seen sufficiently with nonenhanced CT are sampled at biopsy.

Contribution of FDG-PET/CT to the management of esophageal cancer patients at multidisciplinary tumor board conferences.

BACKGROUND: A multidisciplinary team approach to the management of esophageal cancer patients leads to better clinical decisions. PURPOSE: The contribution of CT, endoscopic and laparoscopic ultrasound to clinical staging and treatment selection by multidisciplinary tumor boards (MTB) in patients with esophageal cancer is well documented. However, there is a paucity of data addressing the role that FDG-PET/CT (PET/CT) plays to inform the clinical decision-making process at MTB conferences. The aim of this study was to assess the impact and contribution of PET/CT to clinical management decisions and to the plan of care for esophageal cancer patients at the MTB conferences held at our institution. MATERIALS AND METHODS: This IRB approved study included all the cases discussed in the esophageal MTB meetings over a year period. The information contributed by PET/CT to MTB decision making was grouped into four categories. Category I, no additional information provided for clinical management; category II, equivocal and misguiding information; category III, complementary information to other imaging modalities, and category IV, information that directly changed clinical management. The overall impact on management was assessed retrospectively from prospectively discussed clinical histories, imaging, histopathology, and the official minutes of the MTB conferences. RESULTS: 79 patients (61 males and 18 females; median age, 61 years, range, 33-86) with esophageal cancer (53 adenocarcinomas and 26 squamous cell carcinomas) were included. The contribution of PET/CT-derived information was as follows: category I in 50 patients (63%); category II in 3 patients (4%); category III in 8 patients (10%), and category IV information in 18 patients (23%). Forty-five patients (57%) had systemic disease, and in 5 (11%) of these, metastatic disease was only detected by PET/CT. In addition, PET/CT detected previously unknown recurrence in 4 (9%) of 43 patients. In summary, PET/CT provided clinically useful information to guide management in 26 of 79 esophageal cancer patients (33%) discussed at the MTB. CONCLUSION: The study showed that PET/CT provided additional information and changed clinical management in 1 out of 3 (33%) esophageal cancer cases discussed at MTB conferences. These results support the inclusion whenever available, of FDG-PET/CT imaging information to augment and improve the patient management decision process in MTB conferences.

Current trends in radiologic management of malignant pleural mesothelioma.

Malignant pleural mesothelioma (MPM) is an aggressive pleural tumor with a complex growth pattern. Imaging plays a crucial role in diagnosis and management. Computed tomography (CT) has been the mainstay in the clinical evaluation of MPM; however it underestimates early chest wall invasion, peritoneal involvement, and has well-known limitations in nodal metastatic evaluation. Perfusion CT can evaluate the microvasculature of tumors; however its disadvantages, such as high radiation exposure and side effects from iodinated contrast, have limited its use to research settings. Magnetic resonance imaging (MRI) is superior to CT, both in the differentiation of malignant from benign pleural disease and in the assessment of chest wall and diaphragmatic involvement. Perfusion and diffusion MRI are promising new techniques for the assessment of tumor cellularity and microvasculature and can be used for quantitative and qualitative assessment of treatment response. Fluorodeoxyglucose positron emission tomography (FDG-PET) is useful for the differentiation of benign from malignant lesions, for staging, and for monitoring response to therapy. PET-CT is superior to other imaging modalities in detecting more extensive disease involvement and identifying unsuspected occult distant metastases. This review focuses on the practical aspects of the radiological assessment of MPM, highlighting the role of the radiologist in preoperative and postoperative evaluation with a multimodality approach.

99mTc-Methyl-Diphosphonate Binding to Mineral Deposits in Cultures of Marrow-Derived Mesenchymal Stem Cells in Osteogenic Medium.

IMPACT STATEMENT: The work is notable for describing a highly sensitive, quantitative, and nondestructive method for evaluating the in vitro amount of mineral accompanying different types of osteogenic differentiation of mesenchymal stem cells in a monolayer cell culture. What is so unique and useful about the method is that it has the potential to be used to define the kinetics of the differentiation process, reflected in the mineralization, without destroying the monolayer. Therefore, it remains intact for further experiments.

Evaluation of the combined effects of target size, respiratory motion and background activity on 3D and 4D PET/CT images.

Gated (4D) PET/CT has the potential to greatly improve the accuracy of radiotherapy at treatment sites where internal organ motion is significant. However, the best methodology for applying 4D-PET/CT to target definition is not currently well established. With the goal of better understanding how to best apply 4D information to radiotherapy, initial studies were performed to investigate the effect of target size, respiratory motion and target-to-background activity concentration ratio (TBR) on 3D (ungated) and 4D PET images. Using a PET/CT scanner with 4D or gating capability, a full 3D-PET scan corrected with a 3D attenuation map from 3D-CT scan and a respiratory gated (4D) PET scan corrected with corresponding attenuation maps from 4D-CT were performed by imaging spherical targets (0.5-26.5 mL) filled with (18)F-FDG in a dynamic thorax phantom and NEMA IEC body phantom at different TBRs (infinite, 8 and 4). To simulate respiratory motion, the phantoms were driven sinusoidally in the superior-inferior direction with amplitudes of 0, 1 and 2 cm and a period of 4.5 s. Recovery coefficients were determined on PET images. In addition, gating methods using different numbers of gating bins (1-20 bins) were evaluated with image noise and temporal resolution. For evaluation, volume recovery coefficient, signal-to-noise ratio and contrast-to-noise ratio were calculated as a function of the number of gating bins. Moreover, the optimum thresholds which give accurate moving target volumes were obtained for 3D and 4D images. The partial volume effect and signal loss in the 3D-PET images due to the limited PET resolution and the respiratory motion, respectively were measured. The results show that signal loss depends on both the amplitude and pattern of respiratory motion. However, the 4D-PET successfully recovers most of the loss induced by the respiratory motion. The 5-bin gating method gives the best temporal resolution with acceptable image noise. The results based on the 4D scan protocols can be used to improve the accuracy of determining the gross tumor volume for tumors in the lung and abdomen.