PubMed · 13846439
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C C YANG. 1959. [Analysis on damaged x-ray tubes].. https://pubmed.ncbi.nlm.nih.gov/13846439/
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PURPOSE: Fluoroscopy is widely used for evaluating tumor mobility in radiotherapy planning. Lung tumor mobility was scored using virtual fluoroscopy, and this was compared to mobility derived from contoured tumors in all phases of a respiration-correlated (or 4D) CT scan. METHODS AND MATERIALS: 4DCT datasets were reviewed and 29 patients were identified in whom tumors were visible on anterior-posterior fluoroscopy views. Mobility in all directions was estimated on fluoroscopy movie loops by four clinicians. These results were compared to mobility measured from contoured tumor volumes in all phases of the same 4DCT. Internal target volumes (ITV) were generated for both approaches. RESULTS: In eight patients, fluoroscopy did not allow for tumor mobility to be assessed in at least one direction. No significant inter-clinician variation was observed with respect to fluoroscopic assessment of mobility. Clinicians systematically overestimated mobility in all three directions (p<0.05). The mean ITVs derived using fluoroscopy were 52.2% larger than those derived using 4DCT contours, but the individual ITVs were smaller in three patients. CONCLUSION: Use of virtual fluoroscopy generally overestimates the mobility of visible lung tumors, and results in irradiation of unnecessarily large target volumes. In contrast, use of 4DCT minimizes the risk of normal tissue toxicity.
AIMS: Knowledge of the complex three-dimensional anatomy of the right atrium is mandatory for the electrophysiologist and interventional cardiologist, but its understanding remains difficult. We hypothesized that the left hand, loosely clenched, is a good three-dimensional model to understand the position of the different anatomical and electrical regions in the right atrium. For validation, we compared the hand with an endocast that had been prepared from an adult human right atrium and with a three-dimensional electro-anatomical CT image of the right atrium. METHODS AND RESULTS: Views of the left hand were photographed from various angles to replicate as closely as possible the standard fluoroscopic views. Using the nomenclature of the bones of the hand, we assigned the different regions of the hand to represent regions and structures of the right atrium. An endocast was prepared from an adult human right atrium. A three-dimensional electro-anatomical right atrial map with CT integration (CartoMerge) was used as the gold standard for the exact localization of electrical regions such as the sinus node (SN), bundle of His, and slow pathway region. Using the left hand, it is possible to mark the free wall, terminal crest, appendage, septal surface, oval fossa and orifices of the caval veins, tricuspid valve, and coronary sinus. We also marked the anticipated locations of the SN, His bundle, triangle of Koch, slow pathway region, inferior isthmus, and right atrial insertion of Bachmann's bundle. When compared with an endocast and a three-dimensional electro-anatomical CT image, the position and orientation of the marked regions were deemed to be anatomically correct. CONCLUSION: Compared with an endocast and a CT-guided electro-anatomical reconstruction of the right atrium, the left hand is a reliable model to understand the position and orientation of the different anatomical and electrical regions in the right atrium. Although an oversimplification of the complex right atrial anatomy, this model is 'handy' to understand, guide, and teach electrophysiological and interventional procedures.
The objectives of this work were first to develop a convenient method to quantify persistence in digital fluoroscopy systems, then to quantify the effect of variable temporal averaging on the detection of moving low-contrast test details within digital fluoroscopic and pulsed fluoroscopic images. The results were analysed to clarify the relationship between the optimum persistence required to see the lowest contrast for circular test details for a range of diameters and their speed of movement. The optimum persistence values obtained are compared with the limited data available on speeds of movement of patient organs during fluoroscopy. It is tentatively concluded that for imaging the abdomen, the optimum imaging system persistence time constant is approximately 0.15 s. For the much greater speeds associated with cardiac motion, no additional frame averaging is necessary, i.e. just the persistence provided by the observer's visual system appears to be optimal for small objects.