Evaluation of Quantitative Imaging Biomarkers in the DSS Colitis Model

Purpose

In humans, colonoscopy is the gold standard for the diagnosis of inflammatory changes of the colon wall. Aim of this study was the identification of less invasive imaging biomarkers in the dextran sodium sulfate (DSS) colitis model to provide additional information on transmural changes of the colon wall.

Procedures

Colitis was induced in C57BL/6 mice by administration of 2, 3, and 4 % DSS over a period of 5 days. Colon wall thickness was measured using magnetic resonance imaging (MRI), ultrasound (US), and x-ray computed tomography (CT), gut inflammation by positron emission tomography/CT, and mucosal changes of the colon wall by colonoscopy. Colon samples were examined histologically.

Results

MRI, CT, US, and histological data revealed increased colon wall thickness in DSS-treated mice compared to healthy controls. Elevated 2-deoxy-2[¹⁸F]fluoro-d-glucose uptake and colonoscopy confirmed high inflammatory load in the guts of colitis mice.

Conclusions

The established quantitative imaging readouts offer promising perspectives to develop new compounds and to translate these methods into the clinical setting.

     

Repeatability of Radiomic Features in Non-Small-Cell Lung Cancer [<Superscript>18</Superscript>F]FDG-PET/CT Studies: Impact of Reconstruction and Delineation

Purpose

To assess (1) the repeatability and (2) the impact of reconstruction methods and delineation on the repeatability of 105 radiomic features in non-small-cell lung cancer (NSCLC) 2-deoxy-2-[¹⁸F]fluoro-D-glucose ([¹⁸F]FDG) positron emission tomorgraphy/computed tomography (PET/CT) studies.

Procedures

Eleven NSCLC patients received two baseline whole-body PET/CT scans. Each scan was reconstructed twice, once using the point spread function (PSF) and once complying with the European Association for Nuclear Medicine (EANM) guidelines for tumor PET imaging. Volumes of interest (n?=?19) were delineated twice, once on PET and once on CT images.

Results

Sixty-three features showed an intraclass correlation coefficient?≥?0.90 independent of delineation or reconstruction. More features were sensitive to a change in delineation than to a change in reconstruction (25 and 3 features, respectively).

Conclusions

The majority of features in NSCLC [¹⁸F]FDG-PET/CT studies show a high level of repeatability that is similar or better compared to simple standardized uptake value measures.

     

Radionuclide Imaging of Cardiac Device Infection

Purpose of Review

Accurate diagnosis of cardiac device infection is critical for clinical decision-making and represents a challenge for current diagnostic methods. A non-invasive test with sufficient sensitivity and specificity to confirm or exclude infection would be desirable. ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) has been emerging as a promising diagnostic tool for cardiac implantable electrophysiological devices (CIED) infection and its complications. The aim of this review is to describe the role of radionuclide imaging in cardiac device infection according to the different clinical presentations.

Recent Findings

¹⁸F-FDG PET/CT plays an important role in the diagnosis of CIED infection. It has been demonstrated that PET/CT imaging can accurately diagnose and distinguish deep pocket infection from superficial soft tissue infection. In lead infection, this technique has high specificity and is helpful when transthoracic echocardiography (TTE) does not detect vegetation. In addition, PET/CT may be useful in patients with suspected prosthesis valve endocarditis, in whom the initial TEE is negative or indeterminate.

Summary

The use of ¹⁸F-FDG PET/CT in the diagnosis of CIED infection has been implemented to respond to specific clinical needs. Different studies provided important data on the optimal conditions of PET/CT acquisition to better discriminate the infection. However, multicenter trials performed under standardized protocols for both acquisition and quantification of FDG uptake are needed. These efforts could help to achieve the level of evidence allowing FDG PET/CT to be included in clinical guidelines.

     

The Role of Nuclear Cardiac Imaging in Infective Endocarditis

Purpose of Review

Infective endocarditis (IE) remains a deadly disease despite improvements in its management. Echocardiography is crucial for the diagnosis of IE; however, its value is operator-dependent and its sensitivity can decrease in the presence of valvular prosthesis. This review aims to provide an overview on the role of nuclear cardiac imaging in the diagnosis of IE.

Recent Findings

Among all nuclear cardiac imaging modalities, both radiolabeled leukocyte scintigraphy and 2-deoxy-2-[fluorine-18]fluoro-D-glucose positron emission tomography/computed tomography ([¹⁸F]FDG-PET/CT) have been recently introduced in the guidelines of European Society of Cardiology (ESC) for the management of IE. The ESC guidelines included some minor criteria (mainly clinical), and two different sets of major criteria based on blood culture and imaging, respectively. The positivity of either radiolabeled leukocyte scintigraphy or [¹⁸F]FDG-PET/CT images is considered itself a major criterion to diagnose IE. However, nuclear cardiac imaging analysis may be tricky and methodological and technical aspects should be carefully considered.

Summary

Available evidence supports the role of nuclear cardiac imaging in the diagnosis and management of IE. However, all practitioners who act within the “Endocarditis Team” should present a very high level of expertise.

     

[<Superscript>89</Superscript>Zr]Trastuzumab: Evaluation of Radiation Dosimetry,Safety, and Optimal Imaging Parameters in Women with HER2-Positive Breast Cancer

Purpose

The purpose of the present study is to evaluate safety, human radiation dosimetry, and optimal imaging time of [⁸⁹Zr]trastuzumab in patients with HER2-positive breast cancer.

Procedures

Twelve women with HER2-positive breast cancer underwent [⁸⁹Zr]trastuzumab positron emission tomography (PET)/X-ray computed tomography (CT) twice within 7 days post-injection. Biodistribution data from whole-torso PET/CT images and organ time-activity curves were created using data from all patients. Human dosimetry was calculated using OLINDA with the adult female model.

Results

High-quality images and the greatest tumor-to-nontumor contrast were achieved with images performed 5?±?1 day post-injection. Increased [⁸⁹Zr]trastuzumab uptake was seen in at least one known lesion in ten patients. The liver was the dose-limiting organ (retention of ～12 % of the injected dose and average dose of 1.54 mSv/MBq). The effective dose was 0.47 mSv/MBq. No adverse effects of [⁸⁹Zr]trastuzumab were encountered.

Conclusion

[⁸⁹Zr]trastuzumab was safe and optimally imaged at least 4 days post-injection. The liver was the dose-limiting organ.

     

Investigation of Image Reconstruction Parameters of the Mediso nanoScan PC Small-Animal PET/CT Scanner for Two Different Positron Emitters Under NEMA NU 4-2008 Standards

Purpose

The Tera-Tomo 3D image reconstruction algorithm (a version of OSEM), provided with the Mediso nanoScan® PC (PET8/2) small-animal positron emission tomograph (PET)/x-ray computed tomography (CT) scanner, has various parameter options such as total level of regularization, subsets, and iterations. Also, the acquisition time in PET plays an important role. This study aims to assess the performance of this new small-animal PET/CT scanner for different acquisition times and reconstruction parameters, for 2-deoxy-2-[¹⁸F]fluoro-d-glucose ([¹⁸F]FDG) and Ga-68, under the NEMA NU 4-2008 standards.

Procedures

Various image quality metrics were calculated for different realizations of [¹⁸F]FDG and Ga-68 filled image quality (IQ) phantoms.

Results

[¹⁸F]FDG imaging produced improved images over Ga-68. The best compromise for the optimization of all image quality factors is achieved for at least 30 min acquisition and image reconstruction with 52 iteration updates combined with a high regularization level.

Conclusion

A high regularization level at 52 iteration updates and 30 min acquisition time were found to optimize most of the figures of merit investigated.

     

A Comparison of microCT and microPET for Evaluating Lymph Node Metastasis in a Rat Model

Purpose

The demand to optimize multidisciplinary treatment strategies in patients with benign and malignant diseases of the lung and other organs has led to the increased need of mechanistic proof-of-concept studies in preclinical small animal models using new non-invasive imaging methods. Therefore, we evaluated the role of microPET and microCT for mediastinal lymph node staging in an orthotopic lung cancer model in rats.

Procedures

Human lung cancer cells (NCI-H460) were injected transthoracically in nude rats (NIH-RNU). After 2 weeks of tumour growth, animals underwent multiphase contrast-enhanced microCT using ExiTron nano 12000 as a contrast agent and dynamic microPET using the tracer 2-deoxy-2-[¹⁸F]fluoro-d-glucose ([¹⁸F]FDG). Thereafter, animals were sacrificed for histological analysis.

Results

Late phase micro X-ray computed tomography (microCT) revealed the best delineation of lymph node metastases, as compared to earlier scans. In terms of an increased [¹⁸F]FDG uptake over time, dynamic micro positron emission tomography (microPET) delineated lymph node metastases and enabled metabolic examinations of the induced lung cancer metastases.

Conclusion

The combination of contrast-enhanced microCT and dynamic microPET is feasible in rats for the visualization of mediastinal lymph node metastases.

     

Role of CT Imaging for Coronary and Non-coronary Interventions

Purpose of Review

Pre-procedural imaging is essential for successful planning and performance of several cardiac interventions. Cardiac computed tomography (CT) is a non-invasive imaging modality capable of providing precise information required for different coronary and non-coronary interventions. The role of cardiac CT for the guidance of different cardiac interventions will be described in this review.

Recent Findings

Contrast-enhanced computed tomography imaging is increasingly being used for guiding transcatheter cardiac interventions. Anatomical and functional information provided by CT helps in successful planning and performance of several cardiac interventions.

Summary

Over the last decade, the continuous growth of interventional cardiology has been associated with widespread acknowledgment that CT is particularly useful for pre-interventional imaging with increasing implementation in clinical routine.

     

Incremental Value of Integrated FDG-PET/CT in Evaluating Indeterminate Solitary Pulmonary Nodule for Malignancy

Objectives

The objective of this study was to evaluate the increased diagnostic benefit of integrated positron emission tomography/computed tomography (PET/CT) interpretation in evaluating solitary pulmonary nodules for malignancy.

Methods

One hundred seventeen patients (67 men and 50 women; mean age ± SD, 61.7?±?13.6 years, range, 31–86 years) with indeterminate solitary pulmonary nodules and no previous history of malignancy were analyzed. PET/CT was performed with an integrated PET/CT scanner (Siemens Biograph BGO duo) 1 h after an intravenous injection of 370 MBq (10 mCi) ¹⁸F-fluorodeoxyglucose. Patients fasted for 6 h before imaging. PET was interpreted alone or combined with CT and was graded according to a five-point scale. A malignant diagnosis was based on histological findings or a clinical and radiological follow-up after at least 24 months. The diagnostic performances of PET alone and integrated PET/CT interpretation were evaluated using discriminant analysis.

Results

PET alone correctly classified 85% of nodules and integrated PET/CT interpretation increased the correct classification to 89%, with similar sensitivity and specificity of 88% and 89%, respectively. False-positive PET results mainly resulted from granulomatous disorders. Four (50%) of the eight cases deemed indeterminate on PET alone were resolved with combined PET/CT interpretation.

Conclusions

Although the benefit attributable to the CT component was limited when integrated PET/CT was used, PET and CT acted synergistically to significantly increase the diagnostic veracity for PET-indeterminate nodules.

     

Improvements in PET Image Quality in Time of Flight (TOF) Simultaneous PET/MRI

Purpose

An integrated positron emission tomography (PET)/magnetic resonance imaging (MRI) scanner with time of flight (TOF) technology is now available for clinical use. The aim of this study is to evaluate the potential of TOF PET in PET/MRI to reduce artifacts in PET images when compared to non-TOF PET/MRI, TOF PET/X-ray computed tomography (CT), and non-TOF PET/CT.

Procedures

All patients underwent a single 2-deoxy-2-[¹⁸F]fluoro-d-glucose ([¹⁸F]FDG) injection, followed first by PET/CT, and subsequently by PET/MRI. PET/CT exams were requested as standard-of-care for oncological indications. Using the PET acquisitions datasets, 4 series of images (TOF PET/CT, non-TOF PET/CT, TOF PET/MRI, and non-TOF PET/MRI) were reconstructed. These image series were visually evaluated for: (1) dental metal artifacts, (2) breathing artifacts, and (3) pelvic artifacts due to scatter correction errors from high bladder [¹⁸F]FDG concentration. PET image quality was assessed by a 3-point scale (1—clinically significant artifact, 2—non clinically significant artifact, and 3—no artifact).

Results

Twenty-five patients (mean?±?SD age: 56?±?13 years old; female: 10, male: 15) were enrolled. TOF PET/MRI, non-TOF PET/MRI, TOF PET/CT, and non-TOF PET/CT scores 2.8, 2.5, 2.4, and 2.3, respectively for the presence of dental artifacts, 2.8, 2.5, 2.2, and 1.9, respectively, for the presence of breathing artifacts, and 2.7, 1.7, 2.0, and 1.3, respectively, for the presence of pelvic artifacts TOF PET/MRI images showed the highest image quality scores among the 4 datasets of PET images.

Conclusion

The superior timing resolution and resulting TOF capability of the new PET/MRI scanner improved PET image quality in this cohort by reducing artifacts compared to non-TOF PET/MRI, TOF PET/CT, and non-TOF PET/CT.

     

CD80 Is Upregulated in a Mouse Model with Shear Stress-Induced Atherosclerosis and Allows for Evaluating CD80-Targeting PET Tracers

Purpose

A shear stress-induced atherosclerosis mouse model was characterized for its expression of inflammation markers with focus on CD80. With this model, we evaluated two positron emission tomography (PET) radiotracers targeting CD80 as well as 2-deoxy-2-[¹⁸F]fluoro-d-mannose ([¹⁸F]FDM) in comparison with 2-deoxy-2-[¹⁸F]fluoro-d-glucose ([¹⁸F]FDG).

Procedure

A flow constrictive cuff implanted around the common carotid artery in apolipoprotein E knockout mice resulted in plaque formation. CD80 expression levels and plaque histopathology were evaluated. Serial PET/X-ray computed tomography scans were performed to follow inflammation.

Results

Plaque formation with increased levels of CD80 was observed. Histologically, plaques presented macrophage-rich and large necrotic areas covered by a thin fibrous cap. Of the CD80-specific tracers, one displayed an increased uptake in plaques by PET. Both [¹⁸F]FDG and [¹⁸F]FDM accumulated in atherosclerotic plaques.

Conclusion

This mouse model presented, similar to humans, an increased expression of CD80 which renders it suitable for non-invasively targeting CD80-positive immune cells and evaluating CD80-specific radiotracers.

     

Tc-99m Radiolabeled Peptide p5 + 14 is an Effective Probe for SPECT Imaging of Systemic Amyloidosis

Purpose

Systemic peripheral amyloidosis is a rare disease in which misfolded proteins deposit in various organs. We have previously developed I-124 labeled peptide p5?+?14 as a tracer for positron emission tomography imaging of amyloid in patients. In this report, we now document the labeling efficiency, bioactivity, and stability of Tc-99m labeled p5?+?14 for single-photon emission computed tomography (SPECT) imaging of amyloidosis, validated in a mouse model of systemic amyloidosis.

Procedures

Radiochemical yield, purity, and biological activity of [^99mTc]p5?+?14 were documented by instant thin-layer chromatography (ITLC), SDS-PAGE and a quantitative amyloid fibril pulldown assay. The efficacy and stability were documented in serum amyloid protein A (AA) amyloid-bearing or wild-type (WT) control mice imaged with SPECT/X-ray computed tomography (CT) at two time points. The uptake and retention of [^99mTc]p5?+?14 in hepatosplenic amyloid was evaluated using region of interest (ROI) and tissue counting measurements.

Results

Tc-99m p5?+?14 was produced with a radiochemical yield of 75 % with greater than 90 % purity and biological activity comparable to that of radioiodinated peptide. AA amyloid was visualized by SPECT/CT imaging with specific uptake seen in amyloid-laden organs at levels ～5 folds higher than in healthy mice. ROI analyses of decay-corrected SPECT/CT images showed <20 % loss of radiolabel from the 1 to 4 h imaging time points. Biodistribution data confirmed the specificity of the probe accumulation by amyloid-laden organs as compared to non-diseased tissues.

Conclusion

[^99mTc]p5?+?14 is a specific and stable radiotracer for systemic amyloid in mice and may provide a convenient and inexpensive alternative to imaging of peripheral amyloidosis in patients.

     

Convenient Preparation of [<Superscript>68</Superscript>Ga]DKFZ-PSMA-11 Using a Robust Single-Vial Kit and Demonstration of Its Clinical Efficacy

Purpose

[⁶⁸Ga]DKFZ-PSMA-11 has proved to be an important diagnostic radiotracer for targeting prostate-specific membrane antigen (PSMA) overexpression in both recurrent prostate cancer (PC) and relevant metastatic sites. However, the widespread, routine clinical use of such a potential radiopharmaceutical demands availability of a ready-to-use kit formulation to enable convenient radiopharmaceutical preparation. Herein, we report the development of a freeze-dried kit vial for the formulation of [⁶⁸Ga]DKFZ-PSMA-11 and its clinical use in patients using a “shake-bake-inject” methodology.

Procedures

The freeze-dried kit vial was developed after optimization of ligand content (PSMA-11) and pH conditions. The kit was formulated using ⁶⁸Ga from two different commercially available generators. Positron emission tomography/X-ray computed tomography (PET/CT) images of PC patients were obtained using the kit-formulated radiotracer.

Results

[⁶⁸Ga]DKFZ-PSMA-11 was prepared in >98 % radiochemical yield and purity using the freeze-dried kit vials. Kits were optimized for the preparation of four patient doses. The clinical utility was evaluated in patients with histologically confirmed prostate cancer, and the images were of good quality as well as conforming to tumor marker and clinical expectations.

Conclusion

The development of a simple and ready-to-use freeze-dried DKFZ-PSMA-11 kit for the preparation of Ga-68-based radiotracers constitutes a major step towards the expedition of the widespread and economical screening of PC patients.

     

Single STE-MR Acquisition in MR-Based Attenuation Correction of Brain PET Imaging Employing a Fully Automated and Reproducible Level-Set Segmentation Approach

Purpose

The aim of this study is to introduce a fully automatic and reproducible short echo-time (STE) magnetic resonance imaging (MRI) segmentation approach for MR-based attenuation correction of positron emission tomography (PET) data in head region.

Procedures

Single STE-MR imaging was followed by generating attenuation correction maps (μ-maps) through exploiting an automated clustering-based level-set segmentation approach to classify head images into three regions of cortical bone, air, and soft tissue. Quantitative assessment was performed by comparing the STE-derived region classes with the corresponding regions extracted from X-ray computed tomography (CT) images.

Results

The proposed segmentation method returned accuracy and specificity values of over 90 % for cortical bone, air, and soft tissue regions. The MR- and CT-derived μ-maps were compared by quantitative histogram analysis.

Conclusions

The results suggest that the proposed automated segmentation approach can reliably discriminate bony structures from the proximal air and soft tissue in single STE-MR images, which is suitable for generating MR-based μ-maps for attenuation correction of PET data.

     

Role of CT Density in PET/CT-Based Assessment of Lymphoma

Purpose

In patients with Hodgkin (HL) and non-Hodgkin lymphoma (NHL), primary staging, as well as intermediate and late response assessment, is often performed by integrated 2-deoxy-2-[¹⁸F]fluoro-D-glucose ([¹⁸F]FDG) positron emission tomography/X-ray computed tomography (PET/CT). The purpose of this analysis was to evaluate if findings in patients with histopathologically proven HL or NHL might correlate with semi-automated density measurements of target lesions (TLs) in the CT component of the integrated PET/CT examination.

Procedures

After approval by the institutional review board, 176 lymph nodes (LN) in 90 PET/CT examinations of 90 patients were retrospectively analyzed (HL, 108 TLs out of 55 patients; NHL, 68 TLs out of 35 patients). PET/CT was performed for reasons of primary staging, response evaluation as interim PET, or as final examination after therapy, according to the clinical schedule. Analyses of TLs were performed on the basis of tracer uptake (SUV) 60 min after tracer injection and volumetric CT histogram analysis in non-contrast-enhanced CT.

Results

All patients were diagnosed with HL or NHL in a pretreatment biopsy. Prior to therapy induction, staging of all patients was performed using contrast-enhanced CT of the neck to the pelvis, or by [¹⁸F]FDG PET/CT. Of the 176 TLs, 119 were classified as malignant, and 57 were benign. Malignant TLs had significantly higher CT density values compared to benign (p?<?0.01).

Conclusion

Density measurements of TLs in patients with HL and NHL correlate with the dignity of TLs and might therefore serve as a complementary surrogate parameter for the differentiation between malignant and benign TLs. A possible density threshold in clinical routine might be a 20-Hounsfield units (HU) cutoff value to rule out benignancy in TLs that are above the 20-HU threshold.

     

Phase 1 Evaluation of [<Superscript>64</Superscript>Cu]DOTA-Patritumab to Assess Dosimetry,Apparent Receptor Occupancy,and Safety in Subjects with Advanced Solid Tumors

Purpose

The purpose of this study was to evaluate the safety, dosimetry, and apparent receptor occupancy (RO) of [⁶⁴Cu]DOTA-patritumab, a radiolabeled monoclonal antibody directed against HER3/ERBB3 in subjects with advanced solid tumors.

Procedures

Dosimetry subjects (n?=?5) received [⁶⁴Cu]DOTA-patritumab and underwent positron emission tomography (PET)/X-ray computed tomography (CT) at 3, 24, and 48 h. Evaluable RO subjects (n?=?3 out of 6) received [⁶⁴Cu]DOTA-patritumab at day 1 and day 8 (after 9.0 mg/kg patritumab) followed by PET/CT at 24 h post-injection. Endpoints included safety, tumor uptake, and efficacy.

Results

The tumor SUV_max (±?SD) was 5.6?±?4.5, 3.3?±?1.7, and 3.0?±?1.1 at 3, 24, and 48 h in dosimetry subjects. The effective dose and critical organ dose (liver) averaged 0.044?±?0.008 mSv/MBq and 0.46?±?0.086 mGy/MBq, respectively. In RO subjects, tumor-to-blood ratio decreased from 1.00?±?0.32 at baseline to 0.57?±?0.17 after stable patritumab, corresponding to a RO of 42.1?±?3.

Conclusions

[⁶⁴Cu]DOTA-patritumab was safe. These limited results suggest that this PET-based method can be used to determine tumor-apparent RO.

     

Radiomic Analysis using Density Threshold for FDG-PET/CT-Based N-Staging in Lung Cancer Patients

Purpose

Mediastinal nodal (N)-staging done by integrated 2-deoxy-2-[¹⁸F]fluoro-d-glucose ([¹⁸F]FDG) positron emission tomography/x-ray computed tomography (PET/CT) in lung cancer patients is not always accurate. In order to reduce the need for invasive staging procedures, additional surrogate parameters for the detection of malignant lymph node infiltration would be helpful. The purpose of this study was to evaluate if radiomic semi-automated density profiling in mediastinal lymph nodes can improve preclinical N-staging, irrespective of the specific lung cancer entity.

Procedures

This retrospective study was approved by the institutional review board. Two hundred forty-eight histologically proven lymph nodes in 122 lung cancer patients were investigated. In malignantly infiltrated lymph nodes, the specific lung cancer entity was histologically classified; benign lymph nodes were histologically classified as benign. Non-contrast enhanced [¹⁸F]FDG-PET/CT was performed before surgery/biopsy. Lymph node analyses were performed on the basis of FDG uptake and volumetric CT histogram analysis for metric lymph node sampling.

Results

Of the 248 lymph nodes, 118 were benign, 130 malignant. Malignant lymph nodes had a significantly higher median CT density (32.4 Hounsfield units (HU) (min 5.4/max 77.5 HU)) compared to benign lymph nodes (9.3 HU (min ?49.5/max 60.4 HU, p?<?0.05), irrespective of the histological subtype. The discrimination between different malignant tumour subtypes by means of volumetric density analysis failed. Irrespective of the malignant subtype, a possible cutoff value of 20 HU may help differentiate between benign and malignant lymph nodes.

Conclusion

Density measurements in unclear mediastinal and hilar lymph nodes with equivocal FDG uptake in PET might serve as a possible surrogate parameter for N-staging in lung cancer patients, irrespective of the specific lung cancer subtype. This could also help to find possible high yield targets in cases where invasive lymph node staging is necessary.

     

Comparison of FLT-PET/CT and CECT in gastric cancer diagnosis

Aim

To date, no data are available on the use of 18-fluorothymidine positron emission tomography/computed tomography (FLT-PET/CT) for preoperative gastric cancer staging. Herein, we attempt to assess the value of FLT-PET/CT for preoperative gastric cancer staging in comparison with contrast-enhanced computed tomography (CECT).

Materials and methods

In a group of 96 gastric cancer patients, 96 FLT-PET/CT, 56 abdominal cavity CECT, and 51 resective operations were done. All three (FLT-PET/CT, CECT, and resective operation) were done in 29 patients. The results of FLT-PET/CT, CECT, and histopathological examinations were used to assess the ability of FLT-PET/CT and CECT to identify primary tumors, regional nodal metastases, and distant abdominal metastases. Assessment of regional lymph nodes was based on SUVmax in FLT-PET/CT and SAD (short-axis diameter) in CECT.

Results

In the group of 56 patients examined with FLT-PET/CT and CECT, identification of the primary tumor was possible in 56 cases (100%) and in 53 cases (94.6%), respectively, (p = 0.013). Using ROC curve, the sensitivity and specificity of FLT-PET/CT in metastatic regional lymph node assessment were higher than those of CECT (p = 0.0033). FLT-PE/CT enabled identification of a greater number of extraregional abdominal metastases than CECT (n = 56; 19 vs. 15, respectively), but the difference was not statistically significant (p > 0.41).

Conclusions

The ability of FLT-PET/CT to identify primary tumors is greater than that of CECT, and thus FLT-PET/CT was better in evaluating regional nodal metastases. FLT-PET/CT enabled identification of a greater number of abdominal metastases than CECT, but the difference was not statistically significant.

     

Imaging in acute respiratory distress syndrome

Purpose

Imaging has become increasingly important across medical specialties for diagnostic, monitoring, and investigative purposes in acute respiratory distress syndrome (ARDS).

Methods

This review addresses the use of imaging techniques for the diagnosis and management of ARDS as well as gaining knowledge about its pathogenesis and pathophysiology. The techniques described in this article are computed tomography, positron emission tomography, and two easily accessible imaging techniques available at the bedside—ultrasound and electrical impedance tomography (EIT).

Results

The use of computed tomography has provided new insights into ARDS pathophysiology, demonstrating that ARDS does not homogeneously affect the lung parenchyma and that lung injury severity is widely distributed in the ARDS population. Positron emission tomography is a functional imaging technique whose value resides in adding incremental insights to morphological imaging. It can quantify regional perfusion, ventilation, aeration, lung vascular permeability, edema, and inflammation. Lung ultrasound and EIT are radiation-free, noninvasive tools available at the bedside. Lung ultrasound can provide useful information on ARDS diagnosis when x-rays or CT scan are not available. EIT is a useful tool to monitor lung ventilation and to assess the regional distribution of perfusion.

Conclusions

The future of imaging in critical care will probably develop in two main directions: easily accessible imaging techniques that can be used at the bedside and sophisticated imaging methods that will be used to aid in difficult diagnostic cases or to advance our understanding of the pathogenesis and pathophysiology of an array of critical illnesses.