In Vivo Respiratory-Gated Micro-CT Imaging in Small-Animal Oncology Models

Cavanaugh, Dawn; Johnson, Evan M.; Price, Roger E.; Kurie, Jonathan M.; Travis, Elizabeth L.; Cody, Dianna D.

doi:10.1162/15353500200403184

Cited by 43 publications

(38 citation statements)

References 21 publications

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“…Compensation for both cardiac and ventilatory motion is essential for successful pulmonary imaging. Cavanaugh et al have demonstrated ventilatory-gated micro-CT with exposure integration periods of 100 ms. 5 But as is demonstrated in Fig. 5, the cardiac motion can have a substantial impact on the surrounding lung tissue.…”

Section: Discussionmentioning

confidence: 94%

“…[1][2][3] However, cardiopulmonary studies have been limited. 4,5 Since the image noise is proportional to ͑⌬x͒ −2 , where ⌬x is the dimension of the isotropic voxel, the signal-to-noise ratio (SNR) will decrease significantly over that typical in clinical settings if the x-ray exposure to the animal is held constant relative to that in the clinical setting. 1,2,6 At the same time, the physiological motion in the mouse is at least 10ϫ faster than humans.…”

Section: Introductionmentioning

confidence: 99%

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Micro‐CT with respiratory and cardiac gating

2004

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Cardiopulmonary imaging in rodents using micro-computed tomography (CT) is a challenging task due to both cardiac and pulmonary motion and the limited fluence rate available from micro-focus x-ray tubes of most commercial systems. Successful imaging in the mouse requires recognition of both the spatial and temporal scales and their impact on the required fluence rate. Smaller voxels require an increase in the total number of photons (integrated fluence) used in the reconstructed image for constant signal-to-noise ratio. The faster heart rates require shorter exposures to minimize cardiac motion blur imposing even higher demands on the fluence rate. We describe a system with fixed tube/detector and with a rotating specimen. A large focal spot x-ray tube capable of producing high fluence rates with short exposure times was used. The geometry is optimized to match focal spot blur with detector pitch and the resolution limits imposed by the reproducibility of gating. Thus, it is possible to achieve isotropic spatial resolution of 100 μm with a fluence rate at the detector 250 times that of a conventional cone beam micro-CT system with rotating detector and microfocal x-ray tube. Motion is minimized for any single projection with 10 ms exposures that are synchronized to both cardiac and breathing motion. System performance was validated in vivo by studies of the cardiopulmonary structures in C57BL/6 mice, demonstrating the value of motion integration with a bright x-ray source.

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Section: Discussionmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 99%

Micro‐CT with respiratory and cardiac gating

2004

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“…Due to the non-invasive nature of our technique, imaging the same animal repeatedly over time is easily achieved. Other researchers have used ventilators to force the animals to breathe at a defined rate, 12,13 an invasive approach which requires the animals be intubated by experienced veterinary technicians. The use of an external pressure sensor avoids the need for an invasive measurement of airway pressure, which might alter the normal breathing pattern.…”

Section: A Advantages Of Respiratory-gated Micro-ct Of Freebreathingmentioning

confidence: 99%

“…Cavanaugh et al investigated lung tumors in intubated and respirated rats using an output signal from the respirator to initiate image acquisition just after peak inhalation. 12 Although lung tumors were detected, the respiration-induced motion was not eliminated in this study, as the images were acquired beginning just after peak inhalation and acquiring during exhalation over the full range of motion of the lungs ͑from peak capacity to fully deflated͒. During this portion of the respiratory cycle, the lungs, diaphragm, and ribs undergo sufficient positional changes to cause motion artifacts in the micro-CT image.…”

Section: Introductionmentioning

confidence: 99%

Prospective respiratory‐gated micro‐CT of free breathing rodents

et al. 2005

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Microcomputed tomography (Micro-CT) has the potential to noninvasively image the structure of organs in rodent models with high spatial resolution and relatively short image acquisition times. However, motion artifacts associated with the normal respiratory motion of the animal may arise when imaging the abdomen or thorax. To reduce these artifacts and the accompanying loss of spatial resolution, we propose a prospective respiratory gating technique for use with anaesthetized, free-breathing rodents. A custom-made bed with an embedded pressure chamber was connected to a pressure transducer. Anaesthetized animals were placed in the prone position on the bed with their abdomens located over the chamber. During inspiration, the motion of the diaphragm caused an increase in the chamber pressure, which was converted into a voltage signal by the transducer. An output voltage was used to trigger image acquisition at any desired time point in the respiratory cycle. Digital radiographic images were acquired of anaesthetized, free-breathing rats with a digital radiographic system to correlate the respiratory wave form with respiration-induced organ motion. The respiratory wave form was monitored and recorded simultaneously with the x-ray radiation pulses, and an imaging window was defined, beginning at end expiration. Phantom experiments were performed to verify that the respiratory gating apparatus was triggering the micro-CT system. Attached to the distensible phantom were 100 microm diameter copper wires and the measured full width at half maximum was used to assess differences in image quality between respiratory-gated and ungated imaging protocols. This experiment allowed us to quantify the improvement in the spatial resolution, and the reduction of motion artifacts caused by moving structures, in the images resulting from respiratory-gated image acquisitions. The measured wire diameters were 0.135 mm for the stationary phantom image, 0.137 mm for the image gated at end deflation, 0.213 mm for the image gated at peak inflation, and 0.406 mm for the ungated image. Micro-CT images of anaesthetized, free-breathing rats were acquired with a General Electric Healthcare eXplore RS in vivo micro-CT system. Images of the thorax were acquired using the respiratory cycle-based trigger for the respiratory-gated mode. Respiratory gated-images were acquired at inspiration and end expiration, during a period of minimal respiration-induced organ motion. Gated images were acquired with a nominal isotropic voxel spacing of 44 microm in 20-25 min (80 kVp, 113 mAs, 300 ms imaging window per projection). The equivalent ungated acquisitions were 11 min in length. We observed improved definition of the diaphragm boundary and increased conspicuity of small structures within the lungs in the gated images, when compared to the ungated acquisitions. In this work, we have characterized the externally monitored respiratory wave form of free-breathing, anaesthetized rats and correlated the respiration-induced organ motion to the respiratory cycle...

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“…Micro-CT may therefore be an important tool for research involving periapical bone lesions in small animals (von Stechow et al 2003). It provides highresolution images (Cavanaugh et al 2004) and permits the assessment of periapical lesions in a multi-planar fashion (von Stechow et al 2003). Micro-CT provides two-(2D) and three-dimensional (3D) images of the sample , and is noninvasive (Balto et al 2000).…”

Section: Introductionmentioning

confidence: 99%

Use of micro‐computed tomography for the assessment of periapical lesions in small rodents: a systematic review

et al. 2016

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This systematic review aimed to evaluate the literature on the acquisition-, reconstruction- and analysis parameters of micro-computed tomography (micro-CT) for the assessment of periapical lesions in rats and mice, and to illustrate the effect of variation in these parameters. The PubMed database was searched from 2000 to January 2015 (English-language publications) for reports on the use of micro-CT to evaluate periapical lesions in rats and mice. QUADAS criteria were used to rate the quality of the studies. To illustrate the effect of variations in acquisition-, reconstruction-, and analysis parameters on images of periapical lesions, micro-CT examination of two hemi-mandibles of mice, with periapical lesions around the first molar was undertaken. Twenty-one studies were identified, which analysed periapical lesions in rats or mice using micro-CT. According to the QUADAS, no study was classified as high-, seven were classified as moderate-, and 14 as low quality. The effect of variation in parameters was that voxel size may interfere with image sharpness, reconstruction may interfere with image sharpness and contrast, and inadequate plane orientation may alter the size of the periapical lesion. Nonpersonalized ROIs resulted in areas that were not part of the periapical lesion. Changing the limits of the threshold for bone-tissue visualization increased lesion size. There is no defined protocol for acquiring and analysing micro-CT images of periapical lesions in rats and mice. Furthermore, acquisition-, reconstruction- and analysis parameters are not adequately explained, which may compromise the scientific impact of the studies.

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In Vivo Respiratory-Gated Micro-CT Imaging in Small-Animal Oncology Models

Cited by 43 publications

References 21 publications

Micro‐CT with respiratory and cardiac gating

Micro‐CT with respiratory and cardiac gating

Prospective respiratory‐gated micro‐CT of free breathing rodents

Use of micro‐computed tomography for the assessment of periapical lesions in small rodents: a systematic review

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