Multimodal target correction by local bone registration: a PET/CT evaluation

PET/CT guidance for percutaneous interventions allows biopsy of suspicious metabolically active bone lesions even when no morphological correlation is delineable in the CT images. Clinical use of PET/CT guidance with conventional step-by-step technique is time consuming and complicated especially in cases in which the target lesion is not shown in the CT image. Our recently developed multimodal instrument guidance system (IGS) for PET/CT improved this situation. Nevertheless, bone biopsies even with IGS have a trade-off between precision and intervention duration which is proportional to patient and personnel exposure to radiation. As image acquisition and reconstruction of PET may take up to 10 minutes, preferably only one time consuming combined PET/CT acquisition should be needed during an intervention. In case of required additional control images in order to check for possible patient movements/deformations, or to verify the final needle position in the target, only fast CT acquisitions should be performed. However, for precise instrument guidance accounting for patient movement and/or deformation without having a control PET image, it is essential to be able to transfer the position of the target as identified in the original PET/CT to a changed situation as shown in the control CT.

Low-Dose Temporal Bone CT in Infants and Young Children: Effective Dose and Image Quality

The temporal bone is ideal for low-dose CT because of its intrinsic high contrast. The aim of this study was to retrospectively evaluate image quality and radiation doses of a new low-dose versus a standard high-dose pediatric temporal bone CT protocol and to review dosimetric data from the literature.

Applicability of Tableside Flat Panel Detector CT Parenchymal Cerebral Blood Volume Measurement in Neurovascular Interventions: Preliminary Clinical Experience

CBV is a vital perfusion parameter in estimating the viability of brain parenchyma (eg, in cases of ischemic stroke or after interventional vessel occlusion). Recent technologic advances allow parenchymal CBV imaging tableside in the angiography suite just before, during, or after an interventional procedure. The aim of this work was to analyze our preliminary clinical experience with this new imaging tool in different neurovascular interventions.

68Ga-DOTATOC versus 68Ga-DOTATATE PET/CT in functional imaging of neuroendocrine tumors

Radiolabeled somatostatin analogs represent valuable tools for both in vivo diagnosis and therapy of neuroendocrine tumors (NETs) because of the frequent tumoral overexpression of somatostatin receptors (sst). The 2 compounds most often used in functional imaging with PET are (68)Ga-DOTATATE and (68)Ga-DOTATOC. Both ligands share a quite similar sst binding profile. However, the in vitro affinity of (68)Ga-DOTATATE in binding the sst subtype 2 (sst2) is approximately 10-fold higher than that of (68)Ga-DOTATOC. This difference may affect their efficiency in the detection of NET lesions because it is the sst2 that is predominantly overexpressed in NET. We thus compared the diagnostic value of PET/CT with both radiolabeled somatostatin analogs ((68)Ga-DOTATATE and (68)Ga-DOTATOC) in the same NET patients.

Comparison of FDG-PET/CT and bone scintigraphy for detection of bone metastases in breast cancer

Bone scintigraphy is the standard procedure for the detection of bone metastases in breast cancer patients. FDG-PET/CT has been reported to be a sensitive tool for tumor staging in different malignant diseases. However, its accuracy for the detection of bone metastases has not been compared to bone scintigraphy.

68Ga-DOTATOC PET/CT and somatostatin receptor (sst1-sst5) expression in normal human tissue: correlation of sst2 mRNA and SUVmax

By targeting somatostatin receptors (sst) radiopeptides have been established for both diagnosis and therapy. For physiologically normal human tissues the study provides a normative database of maximum standardized uptake value (SUV(max)) and sst mRNA.

A virtual source model for kilo-voltage cone beam CT: source characteristics and model validation

The purpose of this investigation was to study the source characteristics of a clinical kilo-voltage cone beam CT unit and to develop and validate a virtual source model that could be used for treatment planning purposes.

A navigation system for percutaneous needle interventions based on PET/CT images: design, workflow and error analysis of soft tissue and bone punctures

Percutaneous needle intervention based on PET/CT images is effective, but exposes the patient to unnecessary radiation due to the increased number of CT scans required. Computer assisted intervention can reduce the number of scans, but requires handling, matching and visualization of two different datasets. While one dataset is used for target definition according to metabolism, the other is used for instrument guidance according to anatomical structures. No navigation systems capable of handling such data and performing PET/CT image-based procedures while following clinically approved protocols for oncologic percutaneous interventions are available. The need for such systems is emphasized in scenarios where the target can be located in different types of tissue such as bone and soft tissue. These two tissues require different clinical protocols for puncturing and may therefore give rise to different problems during the navigated intervention. Studies comparing the performance of navigated needle interventions targeting lesions located in these two types of tissue are not often found in the literature. Hence, this paper presents an optical navigation system for percutaneous needle interventions based on PET/CT images. The system provides viewers for guiding the physician to the target with real-time visualization of PET/CT datasets, and is able to handle targets located in both bone and soft tissue. The navigation system and the required clinical workflow were designed taking into consideration clinical protocols and requirements, and the system is thus operable by a single person, even during transition to the sterile phase. Both the system and the workflow were evaluated in an initial set of experiments simulating 41 lesions (23 located in bone tissue and 18 in soft tissue) in swine cadavers. We also measured and decomposed the overall system error into distinct error sources, which allowed for the identification of particularities involved in the process as well as highlighting the differences between bone and soft tissue punctures. An overall average error of 4.23 mm and 3.07 mm for bone and soft tissue punctures, respectively, demonstrated the feasibility of using this system for such interventions. The proposed system workflow was shown to be effective in separating the preparation from the sterile phase, as well as in keeping the system manageable by a single operator. Among the distinct sources of error, the user error based on the system accuracy (defined as the distance from the planned target to the actual needle tip) appeared to be the most significant. Bone punctures showed higher user error, whereas soft tissue punctures showed higher tissue deformation error.

Dose modulated retrospective ECG-gated versus non-gated 64-row CT angiography of the aorta at the same radiation dose: Comparison of motion artifacts, diagnostic confidence and signal-to-noise-ratios

To compare ECG-gated and non-gated CT angiography of the aorta at the same radiation dose, with regard to motion artifacts (MA), diagnostic confidence (DC) and signal-to-noise-ratios (SNRs).

Death by biscuit--exhumation, post-mortem CT, and revision of the cause of death one year after interment

We describe a case of exhumation, performed to investigate the circumstances and cause of death, one year after burial. Post mortem computed tomography (PMCT) revealed a mass in the pharynx. Imaging directed the subsequent forensic autopsy to careful retrieval of a foreign body. Histological analysis revealed a non-cellular composition. The detection of foreign material in the pharynx and its composition indicated accidental, rather than natural death, secondary to choking on food. This unusual case illustrates how post mortem imaging can significantly contribute to forensic investigation and stresses the importance of interdisciplinary collaboration between forensic pathologists and radiologists.

Sex determination from os sacrum by postmortem CT

Sex determination in forensic practice is performed mostly on sexually dimorphic bones, including pelvic bones such as the os sacrum. Postmortem CT scan provides an easy and fast method for depicting and measuring bone structures prior to elaborate autopsy preparations. To develop a simple and objective method for sex determination in postmortem CT, metric data were evaluated from CT images of the pelvic-associated os sacrum of 95 corpses (49 men and 46 women) from the Canton of Bern, Switzerland. Discriminant function analysis of the data showed that the best accuracy in determining sex was 76.8% and 78.9% with two different observers. It is concluded that measuring the os sacrumin postmortem CT for sex determination has moderate accuracy and should only be applied in combination with other methods.

Sudden Death after Chest Pain: Feasibility of Virtual Autopsy with Postmortem CT Angiography and Biopsy

Purpose:To determine the potential of minimally invasive postmortem computed tomographic (CT) angiography combined with image-guided tissue biopsy of the myocardium and lungs in decedents who were thought to have died of acute chest disease and to compare this method with conventional autopsy as the reference standard.Materials and Methods:The responsible justice department and ethics committee approved this study. Twenty corpses (four female corpses and 16 male corpses; age range, 15-80 years), all of whom were reported to have had antemortem acute chest pain, were imaged with postmortem whole-body CT angiography and underwent standardized image-guided biopsy. The standard included three biopsies of the myocardium and a single biopsy of bilateral central lung tissue. Additional biopsies of pulmonary clots for differentiation of pulmonary embolism and postmortem organized thrombus were performed after initial analysis of the cross-sectional images. Subsequent traditional autopsy with sampling of histologic specimens was performed in all cases. Thereafter, conventional histologic and autopsy reports were compared with postmortem CT angiography and CT-guided biopsy findings. A Cohen k coefficient analysis was performed to explore the effect of the clustered nature of the data.Results:In 19 of the 20 cadavers, findings at postmortem CT angiography in combination with CT-guided biopsy validated the cause of death found at traditional autopsy. In one cadaver, early myocardial infarction of the papillary muscles had been missed. The Cohen κ coefficient was 0.94. There were four instances of pulmonary embolism, three aortic dissections (Stanford type A), three myocardial infarctions, three instances of fresh coronary thrombosis, three cases of obstructive coronary artery disease, one ruptured ulcer of the ascending aorta, one ruptured aneurysm of the right subclavian artery, one case of myocarditis, and one pulmonary malignancy with pulmonary artery erosion. In seven of 20 cadavers, CT-guided biopsy provided additional histopathologic information that substantiated the final diagnosis of the cause of death.Conclusion:Postmortem CT angiography combined with image-guided biopsy, because of their minimally invasive nature, have a potential role in the detection of the cause of death after acute chest pain.© RSNA, 2012.

Importance of 3D-CT imaging in single-bullet cranioencephalic gunshot wounds

PURPOSE: The aim of this paper is to demonstrate that computed tomography (CT) and three-dimensional (3D) CT imaging techniques can be useful tools for evaluating gunshot wounds of the skull in forensic medicine. Three purposes can be achieved: (1) identifying and recognising the bullet entrance wound - and exit wound, if present; (2) recognising the bullet's intracranial course by studying damage to bone and brain tissue; (3) suggesting hypotheses as to the dynamics of the event. MATERIALS AND METHODS: Ten cadavers of people who died of a fatal head injury caused by a single gunshot were imaged with total-body CT prior to conventional autoptic examination. Three-dimensional-CT reconstructions were obtained with the volume-rendering technique, and data were analysed by two independent observers and compared with autopsy results. RESULTS: In our experience, CT analysis and volumetric reconstruction techniques allowed the identification of the bullet entrance and exit wounds and intracranial trajectory, as well as helping to formulate a hypothesis on the extracranial trajectory to corroborate circumstantial evidence. CONCLUSIONS: CT imaging techniques are excellent tools for addressing the most important questions of forensic medicine in the case of gunshot wounds of the skull, with results as good as (or sometimes better than) traditional autoptic methods.

CT based volume measurement and estimation in cases of pericardial effusion

The measurement of fluid volumes in cases of pericardial effusion is a necessary procedure during autopsy. With the increased use of virtual autopsy methods in forensics, the need for a quick volume measurement method on computed tomography (CT) data arises, especially since methods such as CT angiography can potentially alter the fluid content in the pericardium. We retrospectively selected 15 cases with hemopericardium, which underwent post-mortem imaging and autopsy. Based on CT data, the pericardial blood volume was estimated using segmentation techniques and downsampling of CT datasets. Additionally, a variety of measures (distances, areas and 3D approximations of the effusion) were examined to find a quick and easy way of estimating the effusion volume. Segmentation of CT images as shown in the present study is a feasible method to measure the pericardial fluid amount accurately. Downsampling of a dataset significantly increases the speed of segmentation without losing too much accuracy. Some of the other methods examined might be used to quickly estimate the severity of the effusion volumes.

Radiologic identification of disaster victims: a simple and reliable method using CT of the paranasal sinuses

To assess the reliability of radiologic identification using visual comparison of ante and post mortem paranasal sinus computed tomography (CT).