Prostate carcinoma: diffusion-weighted imaging as potential alternative to conventional MR and 11C-choline PET/CT for detection of bone metastases.

In a technical development study approved by the institutional ethics committee, the feasibility of fast diffusion-weighted imaging as a replacement for conventional magnetic resonance (MR) imaging sequences (short inversion time inversion recovery [STIR] and T1-weighted spin echo [SE]) and positron emission tomography (PET)/computed tomography (CT) in the detection of skeletal metastases from prostate cancer was evaluated. MR imaging and carbon 11 ((11)C) choline PET/CT data from 11 consecutive prostate cancer patients with bone metastases were analyzed. Diffusion-weighted imaging appears to be equal, if not superior, to STIR and T1-weighted SE sequences and equally as effective as (11)C-choline PET/CT in detection of bone metastases in these patients. Diffusion-weighted imaging should be considered for further evaluation and comparisons with PET/CT for comprehensive whole-body staging and restaging in prostate and other cancers.

Multimodal virtual bronchoscopy using PET/CT images.

OBJECTIVE: To demonstrate the possibilities, advantages and limitations of virtual bronchoscopy using data sets from positron emission tomography (PET) and computed tomography (CT). MATERIALS AND METHODS: Eight consecutive patients with non-small cell lung cancer (NSCLC) underwent PET/CT. PET was performed with a glucose analog, 2-[fluorine-18]-fluoro-2-deoxy-D-glucose (18F-FDG), using a state-of-the-art full-ring Pico-3D PET scanner. CT was performed with a venous-dominant contrast-enhanced phase using a 16-slice CT scanner. The tracheobronchial system was segmented using the CT data set with an interactive threshold interval volume-growing segmentation algorithm. The primary tumors and lymph node metastases were segmented for virtual CT-bronchoscopy using the CT data set and for virtual hybrid bronchoscopy using the PET/CT data set. The structures of interest were visualized with a color-coded shaded-surface rendering method. RESULTS: The use of CT and virtual CT-bronchoscopy primarily facilitates visualization of the anatomical details of the tracheobronchial system and detection of anatomical/morphologic structural changes caused by disease. PET/CT and virtual hybrid bronchoscopy, or virtual PET/CT-bronchoscopy, give superior results to virtual CT-bronchoscopy because the hybrid bronchoscopy uses both the CT information and the molecular/metabolic information about the disease obtained from PET. CONCLUSIONS: PET/CT imaging has proven to be a highly valuable oncological diagnostic modality. Virtual hybrid bronchoscopy can be performed using a low-dose CT scan or diagnostic CT. However, it is expected to improve diagnostic accuracy in identification and characterization of malignancies, verification of infections, and differentiation of viable tumor tissue from atelectases and scar tissue, as well as assessment of tumor staging and therapeutic response, and detection of early stage recurrences that are not detectable or are liable to be misjudged using virtual CT-bronchoscopy. It could also be useful as a screening examination method for patients with suspected endobronchial malignancy. Virtual hybrid bronchoscopy with a transparent color-coded shaded-surface rendering model offers a useful alternative to fiberoptic bronchoscopy, and is particularly promising for patients for whom fiberoptic bronchoscopy is not feasible, contraindicated or refused.

Detection of metastases from gastrointestinal neuroendocrine tumors: prospective comparison of 18F-TOCA PET, triple-phase CT, and PET/CT.

The purpose of the investigation was to assess positron emission tomography (PET), computed tomography (CT) and the image fusion of PET and CT (PET/CT) in the detection of metastases from gastrointestinal neuroendocrine tumors. In a prospective study, thirty-one patients were consecutively examined using a state-of-the-art PET/CT. PET was performed with a carbohydrated F-18-labeled somatostatin receptor ligand (Gluc-Lys([(18)F]FP-TOCA) from the base of the skull to the proximal thigh using a Pico-3D PET scanner. CT was performed with a noncontrast low-dose CT (LD-CT) and a venous-dominant contrast-enhanced CT (VD-CT) from the base of the skull to the proximal thigh and a hepatic arterial-dominant contrast-enhanced CT (AD-CT) from the epigastric region using a 16-slice CT. The data sets from PET and CT (LD-CT and VD-CT) were fused automatically. To assess a relative sensitivity of each imaging modality, the total number of metastases by summing the number of metastases depicted for each patient by the highest sensitive modality was used as reference standard. PET, LD-CT, AD-CT, VD-CT, PET/LD-CT and PET/VD-CT showed a lesion-by-lesion based overall detection rate for liver metastases (n=858) of 90.8% (P<0.001), 29.4% (P<0.001), 45.5% (P<0.001), 73.9% (P<0.001), 91.5% (P<0.001) and 100%. PET, LD-CT, VD-CT, PET/LD-CT and PET/VD-CT showed an overall detection rate for lymph node metastases (n=193) of 93.8% (P<0.001), 25.4% (P<0.001), 64.8% (P<0.001), 93.8% (P<0.001) and 100% and for osseous metastases (n=567) of 98.6% (P<0.005), 40.7% (P<0.001), 40.7% (P<0.001), 100% and 100%. Furthermore, PET revealed 2 (22.2%) of 9 intrapulmonal lesions seen on LD-CT, VD-CT, PET/LD-CT and PET/VD-CT. PET as single modality revealed most liver, lymph node and osseous metastases. The combination of molecular/metabolic with anatomical/morphological information improves the diagnostic accuracy for the detection of metastases in comparison to any single imaging modality. LD-CT cannot replace VD-CT in the detection of liver and lymph node metastases, but was equal in the detection of osseous metastases and identifying of pulmonary lesions.

Virtual positron emission tomography/computed tomography-bronchoscopy: possibilities, advantages and limitations of clinical application.

The aim of this study was to demonstrate the possibilities, advantages and limitations of virtual bronchoscopy using data sets from positron emission tomography (PET) and computed tomography (CT). Twelve consecutive patients with lung cancer underwent PET/CT. PET was performed with F-18-labelled 2-[fluorine-18]-fluoro-2-deoxy-D: -glucose ((18)F-FDG). The tracheobronchial system was segmented with a volume-growing algorithm, using the CT data sets, and visualized with a shaded-surface rendering method. The primary tumours and the lymph node metastases were segmented for virtual CT-bronchoscopy using the CT data set and for virtual PET/CT-bronchoscopy using the PET/CT data set. Virtual CT-bronchoscopy using the low-dose or diagnostic CT facilitates the detection of anatomical/morphological structure changes of the tracheobronchial system. Virtual PET/CT-bronchoscopy was superior to virtual CT-bronchoscopy in the detection of lymph node metastases (P=0.001), because it uses the CT information and the molecular/metabolic information from PET. Virtual PET/CT-bronchoscopy with a transparent colour-coded shaded-surface rendering model is expected to improve the diagnostic accuracy of identification and characterization of malignancies, assessment of tumour staging, differentiation of viable tumour tissue from atelectases and scars, verification of infections, evaluation of therapeutic response and detection of an early stage of recurrence that is not detectable or is misjudged in comparison with virtual CT-bronchoscopy.

In vivo tumor imaging in mice using a state-of-the-art clinical PET/CT in comparison with a small animal PET and a small animal CT.

The aim of this prospective study was to assess the feasibility of a state-of-the-art clinical PET/CT scanner for in vivo tumor imaging in mice in comparison to a small animal PET scanner and a small animal CT scanner. Seventeen female NMRI nude mice bearing a subcutaneous transplanted murine mammary carcinoma (EMT6) on the right hind limb were examined using a clinical PET/CT scanner (biograph Sensation 16), a dedicated small animal PET scanner (MOSAIC system), and a dedicated small animal CT scanner (MicroCAT II). 18F-fluoroazomycin arabinoside (18F-FAZA) was used as PET tracer for imaging of regional tumor hypoxia. The examination of tumor-bearing mice using a state-of-the-art clinical PET/CT scanner, a dedicated small animal PET scanner and a dedicated small animal CT scanner revealed good image quality and allowed the evaluation and correlation of molecular/metabolic alterations of cancers with anatomical/morphological findings. The tumor lesions showed a 1.89 +/- 0.6 higher mean tumor-to-background ratio +/- SD for the dedicated small animal PET scanner than the PET from the clinical PET/CT scanner (P<0.001). The mean tumor-to-background ratio of the PET of the clinical PET/CT scanner showed a high correlation with the mean tumor-to-background ratio of the dedicated small animal PET scanner (r2 = 0.92). The tissue hypoxia in the subcutaneous transplanted EMT6 tumors did not correlate with the tumor volume. Clinical PET/CT scanners are widely available and could contribute not only to human clinical routine examinations, but also to tumor research in animals. The molecular/metabolic information is reduced when imaging small tumors of mice with clinical PET/CT scanners due to the low spatial resolution and sensitivity of the PET scanners. The examination of small tumors in mice should be reserved to research centers with small animal PET/CT scanners because they provide promising hope to achieve accurate measurement of activity concentration. For tumor research in humans and animals using clinical PET/CT scanners, PET scanners with a higher spatial resolution and a higher sensitivity will be highly promising, but will be in competition to PET/MRI.

Assessment of the extent of metastases of gastrointestinal carcinoid tumors using whole-body PET, CT, MRI, PET/CT and PET/MRI.

OBJECTIVE: To assess the diagnostic value of whole-body positron emission tomography (PET), computed tomography (CT), magnetic resonance imaging (MRI), and the fusion of PET and CT (PET/CT) and PET and MRI (PET/MRI) in the detection of metastatic disease of gastrointestinal carcinoid tumors. MATERIALS AND METHODS: This prospective study included six patients with extensive nonresectable metastases of gastrointestinal carcinoid tumors which were consecutively examined from the base of the skull to the proximal thigh using a state-of-the-art PET/CT scanner and a 1.5 Tesla whole-body MRI scanner. PET was performed with a carbohydrated F-18-labeled somatostatin-receptor ligand ([ superset18 F]FP-Gluc-TOCA) using a Pico-3D PET scanner. CT was performed with a venous-dominant contrast-enhanced phase using a 16-slice CT scanner. MRI was performed with a coronal T2-weighted Half-Fourier Acquired Single-Shot Turbo Spin Echo (HASTE) sequence, a coronal T2-weighted Turbo-Short Tau Inversion-Recovery (STIR) sequence, a coronal T1-weighted Turbo Spin Echo (TSE) sequence and a high resolution axial T2-weighted TSE sequence. The data sets from PET and CT were fused automatically. The PET and MRI data sets were fused manually. Lesions were rated as metastases if they were not clearly identified as benign lesions according to standard radiological criteria. RESULTS: For PET, CT, MRI, PET/CT, and PET/MRI, the lesion-by-lesion based analysis showed an overall detection rate for liver metastases (n = 391) of 49.9% (P<.001), 37.1% (P<.001), 98.2%, 50.9% (P<.001) and 100%, for lymph node metastases (n = 37) of 91.9%, 83.8%, 64.9%, 100% and 97.3% and for osseous metastases (n = 12) of 100%, 8.3% (P<.005), 66.7%, 100% and 100%. CONCLUSIONS: PET as single modality revealed the most lymph node and osseous metastases. MRI as single modality revealed the most liver metastases. The combination of molecular/metabolic with anatomical/ morphological information improves the diagnostic accuracy for the detection of metastases in comparison to the single modalities. Whole-body PET/MRI is a very promising diagnostic modality for oncological imaging due to the missing radiation exposure and the high soft tissue resolution of MRI in contrast to CT.

Whole-body PET/MRI: the future in oncological imaging.

Positron emission tomography (PET) facilitates the evaluation of molecular aspects and metabolic alterations that are fundamental in detecting of malignancies, characterization of tumor stage and assessment of therapeutical response, and tumor recurrence. The main advantage of PET is its high sensitivity in identifying of areas of cancerous involvement at an early stage. In general, the accelerated radiotracer activity occurs before anatomical structure changes. The main difficulty with PET is the lack of an anatomical reference frame. Magnetic resonance imaging (MRI) is an excellent morphological imaging modality with a high anatomical resolution. Whole-body MRI produce large amounts of image data, resulting in the possibility of overlooking subtle pathological findings. The fusion of PET with MRI can compensate for their disadvantages and therefore offers several advantages in comparison to PET or MRI alone. The combination of these two excellent diagnostic imaging modalities into a single scanner improves the diagnostic accuracy by facilitating the accurate registration of molecular aspects and metabolic alterations of the diseases with exact correlation to anatomical findings and morphological information. Whole-body PET/MRI is a very promising diagnostic modality for oncological imaging and for use in cancer screening in the decades to come due to the considerably lower radiation exposure in contrast to PET/CT and the high soft tissue resolution of MRI.

ECG-gated 16-MDCT of the coronary arteries: assessment of image quality and accuracy in detecting stenoses.

OBJECTIVE: The aim of this study was to investigate image quality and diagnostic accuracy in detecting coronary artery lesions using a 16-MDCT scanner. MATERIALS AND METHODS: Thirty-seven patients (28 men, nine women) underwent unenhanced helical CT and MDCT angiography of the coronary arteries. After patients received oral beta-blocker medication, CT scans were obtained during a single breath-hold with a 16-MDCT scanner using ECG-gating (0.75-mm collimation, 2.8-mm table feed/rotation, 0.42-sec rotation time). The image quality was assessed in terms of artifacts and segment visibility by two reviewers. Stenosis severity was compared with the results of conventional invasive coronary angiography. RESULTS: The data evaluation of the image quality was based on a total of 488 segments, of which 380 segments were considered to have diagnostic image quality. One hundred eight segments (22.1%) could not be sufficiently evaluated because of severe calcifications (35 segments) and motion artifacts (73 segments). The mean calcium score (Agatston score equivalent [ASE]) was 524.3 +/- 807.6. Twenty-eight (75.7%) of the 37 patients had an ASE of less than 1,000 (mean ASE, 90.8 +/- 152.3 [SD]), and nine (24.3%) patients had an ASE of 1,000 or greater (mean ASE, 1,761.0 +/- 637.6). For detecting lesions 50% or greater (without any exclusion criteria), the overall sensitivity, specificity, positive predictive value, and negative predictive value were 59%, 87%, 61%, and 87%, respectively. When limiting the number of patients to those with a calcium score of less than 1,000 ASE, the threshold-corrected sensitivity for lesions 50% or greater was 93%; specificity, 94%; positive predictive value, 68%; and negative predictive value, 99%. CONCLUSION: In patients with no or moderate coronary calcification, MDCT of coronary arteries using 16-MDCT technology allows the reliable detection of coronary artery stenoses with high diagnostic accuracy. Obtaining an initial unenhanced scan was found to be mandatory to avoid performing useless examinations in patients with severe calcifications.

Human PET/CT scanners: feasibility for oncological in vivo imaging in mice.

PET/CT imaging is a highly valuable oncological imaging modality. The combination of positron emission tomography (PET) and computed tomography (CT) provides the ability to accurately register molecular and metabolic aspects of cancers with anatomical and morphological findings in human clinical routine examinations and for animals in vivo research. Small animal models of mice are widely used in biomedical research for mimicking and studying the human nature, because of their genetic resemblance and the feasibility of gene transfer and gene modification. The recent generation of high performance human PET/CT scanners combines a state of the art full-ring 3D PET scanner and a high-end 16-slice CT scanner (biograph Sensation 16, Siemens AG, Erlangen, Germany). Small animals can be examined with special scanning and reconstruction protocols. The examination of tumor-bearing small animals using a modern human PET/CT revealed excellent image quality. CT can be performed with a maximum spatial resolution of 0.6 x 0.6 x 0.6 mm and PET with a maximum spatial resolution of 6.3 x 6.3 x 6.0 mm. The examination of tumor-bearing small animals using human PET/CT allowed accurate correlation and evaluation of metabolic and anatomical information and is promising for in vivo research purposes. Although image quality is limited by spatial resolution, human PET/CT is widely available and expected to contribute significantly to research with small animal imaging. The investigation of cancer in small animals with PET/CT is probably one of the most challenging tasks in nuclear medicine for the evaluation of tumor growth and growth inhibition factors; development of new anti-tumor drugs and measuring of anti-tumor effects; and cancer treatment response of immunotherapy, chemotherapy and radiation therapy.

PET/CT: fundamental principles.

Positron emission tomography (PET) facilitates the evaluation of metabolic and molecular characteristics of a wide variety of cancers, but is limited in its ability to visualize anatomical structures. Computed tomography (CT) facilitates the evaluation of anatomical structures of cancers, but can not visualize their metabolic and molecular aspects. Therefore, the combination of PET and CT provides the ability to accurately register metabolic and molecular aspects of disease with anatomical findings, adding further information to the diagnosis and staging of tumors. The recent generation of high performance PET/CT scanners combines a state of the art full-ring 3D PET scanner and a high-end 16-slice CT scanner. In PET/CT scanners, a CT examination is used for attenuation correction of PET images rather than standard transmission scanning using superset 68 Ge sources. This reduces the examination time, but metallic objects and contrast agents that alter the CT image quality and quantitative measurements of standardized uptake values (SUV) may lead to artifacts in the PET images. Hybrid PET/CT imaging will be very important in oncological applications in the decades to come, and possibly for use in cancer screening and cardiac imaging.

Solitary pulmonary nodules: dynamic contrast-enhanced MR imaging--perfusion differences in malignant and benign lesions.

PURPOSE: To determine whether dynamic contrast material-enhanced magnetic resonance (MR) imaging with use of kinetic and morphologic parameters reveals statistically significant differences between malignant and benign solitary pulmonary nodules. MATERIALS AND METHODS: Fifty-eight patients met the inclusion criteria of a solitary 5-40-mm pulmonary nodule without calcification or fat at computed tomography. Fifty-one patients were examined successfully; 46 received a histologic diagnosis, and five received a diagnosis by means of observation over 2 years. Dynamic MR images were acquired every 10 seconds for a total of 4 minutes. Diagnostic characteristics for differentiation were examined by using threshold values for maximum peak enhancement, slope of enhancement, and washout. Receiver operating characteristic curves were calculated to test the usefulness of these parameters. The diagnostic performance of a combination of curve profiles and morphologic contrast material distribution were tested by using a decision tree. RESULTS: Frequency of malignancy was 53% (27 of 51 nodules). Malignant nodules showed stronger enhancement with a higher maximum peak and a faster slope (P <.001). Significant washout (>0.1% increase in signal intensity per second) was found only in malignant lesions (14 of 27 lesions). Sensitivity, specificity, and accuracy were 96%, 88%, and 92%, respectively, for maximum peak; 96%, 75%, and 86% for slope; and 52%, 100%, and 75% for washout. When curve profiles and morphologic enhancement patterns were combined, sensitivity increased to 100%. CONCLUSION: Dynamic MR imaging delineates significant kinetic and morphologic differences in vascularity and perfusion between malignant and benign solitary pulmonary nodules. Washout seems to be highly specific for malignancy.

Computed tomographic colonography (CTC): Possibilities and limitations of clinical application in colorectal polyps and cancer.

Colorectal cancer is the second leading cause of cancer-related deaths in Europe and the United States. Most colorectal cancers develop from adenomatous polyps over a number of years. Early detection of polyps eliminates the risk of subsequent carcinomas. Computed tomographic (CT) colonography is a diagnostic technique detecting colorectal neoplasms. With the introduction of multidetector-row computed tomography (MD-CT), CT colonography (CTC) has gained influence as a new diagnostic tool in early detection of colonic pathologies by acquiring volumetric CT data sets of the abdomen. This volumetric data is analyzed using CTC workstations, which provide an interactive display of 2D and 3D images of the colon. In several studies, CTC revealed a high accuracy (sensitivity/patient: 83-100% and specificity/patient: 93-100%) in detecting pathological colonic changes. Furthermore, CTC is an excellent diagnostic technique for the evaluation of patients with incomplete conventional colonoscopy and allows the assessment of extracolonic abdominal and pelvic organs. In this article, the status of CT colonography as a method of detecting colonic polyps and colorectal carcinomas using single- and multidetector-row CT will be reviewed.

Computed tomographic findings in bourneville-pringle disease.

Bourneville-Pringle disease (synonym: tuberous sclerosis, epiploia) is a neuroectodermal disorder. A characteristic clinical triad of adenoma sebaceum, mental retardartion, and seizures leads to early childhood diagnosis. Many patients show morphological changes of the visceral organs, vascular, and skeletal system. We review the computed tomographic findings of Bourneville-Pringle disease as relates to an oligosymptomatic 36-year-old woman with late onset of clinical symptoms.

Virtual bronchoscopy: comparison of different surface rendering models.

The aim of this study was to compare different representation models of surface-rendered virtual bronchoscopy. 10 consecutive patients with inoperable primary lung tumors underwent thin-section spiral computed tomography. The structures of interest, the tracheobronchial system and anatomical and pathological thoracic structures were segmented using an interactive threshold interval volume-growing segmentation algorithm and visualized with the aid of a color-coded surface rendering method. For virtual bronchoscopy, the tracheobronchial system was visualized using a triangle-surface rendering model, a shaded-surface rendering model and a transparent shaded-surface rendering model. The triangle-surface rendering model allowed optimum detailed spatial representation of the dimensions of extraluminal anatomical and pathological mediastinal structures. As the lumen of the tracheobronchial system was less well defined, the rendering model was of limited use for depiction of the airway surface. The shaded-surface rendering model facilitated an optimum assessment of the airway surface, but the mediastinal structures could not be depicted. The transparent shaded-surface rendering model provides simultaneous adequate to optimum visualization and assessment of the intraluminal airway surface and the extraluminal mediastinal structures as well as a quantitative assessment of the spatial relationship between these structures. Fast data acquisition with a multi-slice detector spiral computed tomography scanner and the use of virtual bronchoscopy with the transparent shaded-surface rendering model obviate the need for time consuming detailed analysis and presentation of axial source images by providing improved the diagnostic imaging of endotracheal and endobronchial diseases and offering a useful alternative to fiberoptic bronchoscopy.

Comparison of volume-rendered and surface-rendered MR colonography.

In the United States and Europe, colorectal cancer is the second leading cause of cancer-related deaths. It is well known that colorectal carcinomas may originate from preexisting adenomas. For the visualization of colorectal cancer and other pathologic changes such as polyps, two 3D methods (volume-rendering (VR) and surface-rendering (SR)) in MR colonography were compared in our study. MR colonography was carried out in 17 patients on a 1.5 T MR scanner using a 10 mmolar gadolinium water solution enema. Coronal as well as rotated VR and SR views were compared in order to examine the technical quality (TQ) of the visualization model and grade of confidence (GC) in the pathological findings. Colonoscopic findings revealed 8 colorectal carcinoma, 10 patients with polyps, 4 diverticular disease, and 2 with redundant bowel loops. Based on a total of 248 colonic segments for both visualization methods, volume rendering were significantly superior to surface rendering for both, TQ (p<0.0001) and GC (p<0.0001). Volume rendering and surface rendering were not dependent on individual colon segments (p=0.13 for TQ and p=0.18 for GC) or on image rotation (p=0.06 for TQ and p=0.062 for GC). It is also independent of the type of pathology (p=0.31 for TQ and p=0.42 for GC) and the reviewers (p=0.62 for TQ and p=0.88 for GC). This indicates, that for the purpose of interpreting the technical quality and pathological findings, volume rendering is superior to surface rendering in MR colonography. Volume rendering could be used as an 3D visualization tool, enabling MR colonography examinations to be completed sooner in cases where colon distension is sufficient, and it would also provide an overview of potential mass lesions.