Quantitative and qualitative evaluation of three MSCT for high resolution bone imaging.

INTRODUCTION: Strategies for achieving high resolution varies between manufacturers. In CT, the helical mode with narrow collimation has long been considered as the gold standard for high-resolution imaging. More recently, incremental modes with small dexels and focal spot, have been developed but have not been compared with helical acquisitions under optimal conditions. The aim of this work is to compare the high-resolution acquisition strategies currently proposed by recent MSCT. METHODS: Three CT systems were compared. A phantom was used to evaluate geometric accuracy, uniformity, scan slice geometry, and spatial resolution. Human dry bones were used to test different protocols on real bone architecture. A blind visual analysis was conducted by trained CT users for classifying the different acquisitions (p-values). RESULTS: All systems give satisfactory results in terms of geometric accuracy and uniformity. The in-plane MTF at 5% were respectively 13.4, 15.9 and 18.1 lp/cm. Dry-bones evaluation confirms that acquisition#3 is considered as the best. CONCLUSIONS: The incremental acquisition coupled with à small focal spot, and a high-sampling detector, overpasses the reference of low-pitch helical acquisitions for high-resolution imaging. Cortical bone, bony vessels, and tumoral matrix analysis are the very next challenges that will have to be managed to improve normal and pathologic bone imaging thanks to the availability UHR-CT systems.

Frequent, quantitative bone planar scintigraphy for determination of bone anabolism in growing mice.

BACKGROUND: To provide insight into bone turnover, quantitative measurements of bone remodeling are required. Radionuclide studies are widely used in clinical care, but have been rarely used in the exploration of the bone in preclinical studies. We describe a bone planar scintigraphy method for frequent assessment of bone activity in mice across the growing period. Since repeated venous radiotracer injections are hardly feasible in mice, we investigated the subcutaneous route. METHODS: Repeated 99mTc-hydroxymethylene diphosphonate (HMDP) tracer bone planar scintigraphy studies of the knee region and µCT to measure femur growth rate were performed in eight mice between week 6 and week 27 of life, i.e., during their growth period. Three independent investigators assessed the regions of interest (ROI). An index was calculated based on the counts in knees ROI (normalized by pixels and seconds), corrected for the activity administered, the decay between administration and imaging, and individual weights. RESULTS: A total of 93 scintigraphy studies and 85 µCT were performed. Repeated subcutaneous tracer injections were well tolerated and allowed for adequate radionuclide studies. Mean scintigraphic indexes in the knees ROI decreased from 87.4 ± 2.6 × 10-6 counts s-1 pixel-1 MBq-1 g-1 at week 6 to 15.0 ± 3.3 × 10-6 counts s-1 pixel-1 MBq-1 g-1 at week 27. The time constant of the fitted exponential decay was equal to 23.5 days. As control mean femur length assessed by µCT increased from 12.2 ± 0.8 mm at week 6 to 15.8 ± 0.2 mm at week 22. The time constant of the fitted Gompertz law was equal to 26.7 days. A correlation index of -0.97 was found between femur growth and decrease of bone tracer activity count between week 6 and 24. CONCLUSION: This methodological study demonstrates the potential of repeated bone planar scintigraphy in growing mice, with subcutaneous route for tracer administration, for quantitative assessment of bone remodeling.

Évaluation d'un dispositif de continuité pédagogique à distance mis en place auprès d'étudiants MERM pendant le confinement sanitaire lié au COVID-19.

INTRODUCTION: The specific context related to the COVID-19 pandemic necessitated the implementation of distance learning continuity for students. In France, teachers and radiography students in initial training, not specially prepared for this, had to adapt. An evaluation of the system was proposed to the students. MATERIALS AND METHODS: An anonymous online questionnaire with 4 main sections (pedagogy, communication, learning and concerns) was sent to 91 students at the end of the semester. RESULTS: 91 responses were received. The slideshows with sound or presented during a virtual class are appreciated by the students. Online quizzes are ideal for learning/reviewing. For assessments, individual assignments and online questionnaires are appreciated. Teacher/student interaction via e-mail or video conferencing was considered satisfactory by the large majority of students. Student-student interactions via social networks, for course explanations or document exchange, are very suitable. The majority of students felt they were working a lot and much more compared to face-to-face teaching. Less than half of the students worked more than 20 h per week. Their motivation varied widely. Organizational habits were disrupted, but the autonomy granted was appreciated. The students were mainly concerned about the health of their loved ones and not about their own health. DISCUSSION: The use of distance education tools requires teacher commitment and technical skills. The frequency of communication by e-mail and/or videoconference between members of the teaching team and students must be adapted to the situation. Exchanges by e-mail allow for traceability, while videoconferencing allows direct interaction and a way out of isolation. Autonomy, appreciated by the students, was nevertheless combined with a strong variation in motivation; the anxiety-provoking period in which pedagogical continuity was built up may explain this contradictory observation. CONCLUSION: The results obtained largely confirm the data in the literature. The experience gained through this survey should lead teachers to continue their reflection by test/integrating and evaluating distance education systems, while continuing face-to-face activities.

Development and Evaluation of a CT Pulmonary Angiography Protocol Dedicated to Pregnant and Postpartum Women.

INTRODUCTION: This study presents and evaluates a CT pulmonary angiography protocol dedicated to pregnant women. The specific feature of this protocol is to place the region of interest (ROI) (bolus detection) in the superior vena cava. The objective is to evaluate the performances of this method. MATERIALS AND METHODS: The protocol uses a iodine-based contrast agent at 300mgI/mL and an injection rate of 5 to 6 mL/sec for an injection volume of 50 mL of iodine contrast agent followed by 40 mL of NaCl. The ROI is positioned on the superior vena cava, with a 100 Hounsfield units (HU) threshold, and the acquisition is performed at 100 kVp. This protocol was evaluated retrospectively on a large population (n = 105: group 1) and compared with a control group that did not benefit from this protocol (n = 55: group 2). Both groups were studied on the same device in the same center. Each examination was evaluated and classified into 3 groups: optimal, suboptimal, and noncontributory. Dose length products (DLP) values were also recorded. Statistical tests were applied to the data collected. RESULTS: The rate of noncontributory examinations increased from 43.1% for the control group to 4.8% for the new protocol group. The reference enhancement level in the pulmonary trunk is 250 UH. The mean enhancement in the pulmonary trunk of the new protocol group (332 HU (±71 HU (±71 HU)) is significantly greater than the reference value of 250 HU (P < .0001), which is not the case for control group (P = .3485 > .05), which has a mean enhancement of 239 HU (±87 HU). The control group had a mean DLP of 225 mGy.cm (±81 mGy.cm), and the new-protocol group had a mean DLP of 189 mGy.cm (±75 mGy.cm). DISCUSSION: Our noncontributory examination rate is the lowest rate described in the literature. Our protocol contradicts standard practices of placing an ROI in the pulmonary trunk for bolus detection of iodinated contrast media. CONCLUSION: The results of this study showed that this protocol reduces the number of noncontributory examinations while reducing the dose delivered to patients. This robust protocol is applicable to other devices and meets perfectly radiation-safety requirements and injected contrast media volume limitation.

Building and Exploitation of Learning Curves to Train Radiographer Students in X-Ray CT Image Postprocessing.

INTRODUCTION: This study aims to construct learning curves related to the realization of standardized postprocessing by radiographer students and to discuss their exploitation and interest. MATERIALS AND METHODS: This study was carried out in 21 French students in their 3rd year of training. Two postprocessing protocols in CT (#1 traumatic shoulder; #2 petrous bone) were repeated 15 times by each student. Each achievement was timed to obtain overall learning curves. The realization accuracy was also assessed for each student at each repetition. RESULTS: The learning rates for the two protocols are 63% and 56%, respectively. The number of repetitions to reach the reference time for each protocol is 11 and 12, respectively. In both protocols, the standard deviations are significantly reduced and stabilized during repetitions. The mean accuracy progresses more quickly in protocol #1. DISCUSSION: The measured learning rates reflect a rapid learning process for each protocol. The analysis of the standard deviations shows that students have reached a homogeneous level. The average times and accuracies measured during the last repetitions show that the group has reached a high level of performance. Building learning curves helps students measure their progress and motivates them. CONCLUSION: Obtaining learning curves allows trainers/supervisors to qualify the learning difficulty of a task while motivating students/radiographers. The use of learning curves is inline with the competency-based training paradigm.

Estimation of subject coregistration errors during multimodal preclinical imaging using separate instruments: origins and avoidance of artifacts.

We use high-resolution [Formula: see text] data in multiple experiments to estimate the sources of error during coregistration of images acquired on separate preclinical instruments. In combination with experiments with phantoms, we completed in vivo imaging on mice, aimed at identifying the possible sources of registration errors, caused either by transport of the animal, movement of the animal itself, or methods of coregistration. The same imaging cell was used as a holder for phantoms and animals. For all procedures, rigid coregistration was carried out using a common landmark coregistration system, placed inside the imaging cell. We used the fiducial registration error and the target registration error to analyze the coregistration accuracy. We found that moving an imaging cell between two preclinical devices during a multimodal procedure gives an error of about [Formula: see text] at most. Therefore, it could not be considered a source of coregistration errors. Errors linked to spontaneous movements of the animal increased with time, to nearly 1 mm at most, excepted for body parts that were properly restrained. This work highlights the importance of animal intrinsic movements during a multiacquisition procedure and demonstrates a simple method to identify and quantify the sources of error during coregistration.

Comparison of bioimpedance spectroscopy and X-Ray micro-computed tomography for total fat volume measurement in mice.

Obesity and the metabolic syndrome are two pathologies whose prevalence are in a constant increase. Evaluation of the total fat mass but also of the distribution between visceral and subcutaneous adipose tissue are important factors while assessing the pathophysiology of these two pathologies. Computed tomography (CT) and bioimpedance (BIS) are the translational methods the most frequently used in human beings as well as in rodent models in longitudinal studies on adiposity and obesity. Surprisingly, no direct comparison of micro-CT and BIS was reported yet in mice. Therefore, the present study was carried out to evaluate and compare the accuracy and the uncertainty of measurement of micro-CT and BIS in this species. The proportion of fat mass was measured with BIS, micro-CT and direct post-mortem tissue weight, and correlations between the data were established to evaluate the accuracy of the methods but also the uncertainty of BIS and micro-CT. There were significant correlations between weights of fat tissues on scale and proportion of total fat mass determined by BIS or micro-CT (r = 0.81 and 0.86 respectively) but both methods overestimated the total fat mass, especially in the smallest animals; overestimation of fat mass was amplified with BIS compared to micro-CT. In addition BIS and micro-CT were highly correlated (r = 0.94). Test-test reliability showed a greater variability of the BIS with respect to the micro-CT (coefficient of variation = 17.2 vs 5.6% respectively). Hence, as far as subtle differences between groups or changes within one group are awaited, micro-CT may appear as the most reliable method for determination of fat mass in mice. Micro-CT, unlike BIS, will also allow to qualitatively and quantitatively differentiate between subcutaneous and visceral adipose tissues, which is of major importance in studies on adiposity and its complications.

Comparative study of fat-suppression techniques for hip arthroplasty MR imaging.

OBJECTIVES: The goal of this study was to evaluate different fat-suppressed fluid-sensitive sequences in association with different metal artifacts reduction techniques (MARS) to determine which combination allows better fat suppression around metallic hip implants. METHODS: An experimental study using an MRI fat-water phantom quantitatively evaluated contrast shift induced by metallic hip implant for different fat-suppression techniques and MARS. Then a clinical study with patients addressed to MRI unit for painful hip prosthesis compared these techniques in terms of fat suppression quality and diagnosis confidence. RESULTS: Among sequences without MARS, both T2 Dixon and short tau inversion recuperation (STIR) had significantly lower contrast shift (p < 0.05), Dixon offering the best fat suppression. Adding MARS (view-angle tilting or slice-encoding for metal artifact correction (SEMAC)) to STIR gave better results than Dixon alone, and also better than SPAIR and fat saturation with MARS (p < 0.05). There were no statistically significant differences between STIR with view-angle tilting and STIR with SEMAC in terms of fat suppression quality. CONCLUSIONS: STIR sequence is the preferred fluid-sensitive MR sequence in patients with metal implant. In combination with MARS (view-angle tilting or SEMAC), STIR appears to be the best option for high-quality fat suppression.

Image quality evaluation of small FOV and large FOV CBCT devices for oral and maxillofacial radiology.

OBJECTIVES: Quantitative and qualitative image quality evaluation of two different dental CBCT scanners. METHODS: Two CBCT systems were evaluated in this study: one small field-of-view (FOV) (50-mm diameter) system that also allows two-dimensional (2D) dental panoramic imaging and one large FOV CBCT system (60-180-mm diameter). These devices were all tested with installed acquisition default modes and proprietary reconstruction software, enabling high-resolution bone imaging. Quantitative analyses were carried out to measure spatial resolution, linearity and homogeneity. Small-size phantoms and a human dry skull were used to evaluate intrinsic performances. Visual qualitative analyses of specific anatomical parts were blindly performed by 10 operators. RESULTS: Concerning spatial resolution, small-voxel size protocols provide equivalent results on the two apparatus. In terms of linearity, all systems are highly linear (0.98 < r2 < 0.99) over the range of signal intensities encountered. Our results, coming from either phantoms or the dry skull, demonstrate that the small FOV CBCT suffers from a lack of homogeneity. CONCLUSIONS: For limited oral and maxillofacial volume imaging (diameter < 50 mm), the polyvalent small FOV CBCT (2D and three-dimensional imaging) system used in this study could reach performances similar to those of the large FOV CBCT.

Multimodal imaging of a humanized orthotopic model of hepatocellular carcinoma in immunodeficient mice.

The development of multimodal strategies for the treatment of hepatocellular carcinoma requires tractable animal models allowing for advanced in vivo imaging. Here, we characterize an orthotopic hepatocellular carcinoma model based on the injection of luciferase-expressing human hepatoma Huh-7 (Huh-7-Luc) cells in immunodeficient mice. Luciferase allows for an easy repeated monitoring of tumor growth by in vivo bioluminescence. The intrahepatic injection was more efficient than intrasplenic or intraportal injection in terms of survival, rate of orthotopic engraftment, and easiness. A positive correlation between luciferase activity and tumor size, evaluated by Magnetic Resonance Imaging, allowed to define the endpoint value for animal experimentation with this model. Response to standard of care, sorafenib or doxorubicin, were similar to those previously reported in the literature, with however a strong toxicity of doxorubicin. Tumor vascularization was visible by histology seven days after Huh-7-Luc transplantation and robustly developed at day 14 and day 21. The model was used to explore different imaging modalities, including microtomography, probe-based confocal laser endomicroscopy, full-field optical coherence tomography, and ultrasound imaging. Tumor engraftment was similar after echo-guided intrahepatic injection as after laparotomy. Collectively, this orthotopic hepatocellular carcinoma model enables the in vivo evaluation of chemotherapeutic and surgical approaches using multimodal imaging.

Reduced DICER1 Expression Bestows Rheumatoid Arthritis Synoviocytes Proinflammatory Properties and Resistance to Apoptotic Stimuli.

OBJECTIVE: While the regulatory role of individual microRNAs (miRNAs) in rheumatoid arthritis (RA) is well established, the role of DICER1 in the pathogenesis of the disease has not yet been investigated. The purpose of this study was to analyze the expression of factors involved in miRNA biogenesis in fibroblast-like synoviocytes (FLS) from RA patients and to monitor the arthritis triggered by K/BxN serum transfer in mice deficient in the Dicer gene (Dicer(d/d) ). METHODS: The expression of genes and precursor miRNAs was quantified by quantitative reverse transcription-polymerase chain reaction (qRT-PCR). MicroRNA macroarray profiling was monitored by qRT-PCR. Cytokines were quantified by enzyme-linked immunosorbent assay. Experimental arthritis in mice was achieved by the transfer of serum from K/BxN donors. Apoptosis was quantified using an enzyme-linked immunosorbent assay. RESULTS: We found decreased DICER1 and mature miRNA expression in synovial fibroblasts from RA patients. These cells were hyperresponsive to lipopolysaccharide, as evidenced by their increased interleukin-6 secretion upon stimulation. Experimental serum-transfer arthritis in Dicer(d/d) mice confirmed that an unbalanced biogenesis of miRNAs correlated with an enhanced inflammatory response. Synoviocytes from both RA patients and Dicer(d/d) mice exhibited increased resistance to apoptotic stimuli. CONCLUSION: The findings of this study further substantiate the important role of DICER1 in the maintenance of homeostasis and the regulation of inflammatory responses.

Radiological sinus lift: a new minimally invasive CT-guided procedure for maxillary sinus floor elevation in implant dentistry.

PURPOSE: Implant therapy has become an excellent treatment modality as its inception into the modern era of dentistry. However, when patients present with advanced atrophy of the maxillary alveolar ridge, the procedure of choice to restore the anatomic bone deficiency is surgical maxillary sinus floor elevation or sinus lift. The purpose of this study was to describe the CT guided sinus lift technique and to illustrate the minimally invasive aspect of this new radiological procedure called radiological sinus lift. MATERIAL AND METHODS: For this prospective study, 17 cadaver heads which met our inclusion criteria (edentulous posterior maxillary sector and bone height less than 5 mm) were analyzed using cone beam computed tomography (CBCT) and orthopantomography (OPT). CT and sinus endoscopy was used to guide each step in the procedure. The radiological sinus lift technique consists of the following four stages: Approach. A 14.5 G OstyCut needle was inserted mesial to the canine eminence, and manual drilling was performed parallel to the sinus floor. Osteotomy. An inner obturator with a blunt tip was introduced to compress bone, to push it in close proximity to the sinus membrane and finally to create an osseous window opening into the submucosal space. Lifting. The sinus lift was performed using hydrodissection with dilute iodinated contrast medium. Filling. The submucosal space was then filled with an injection of dilute collagen. Success of the radiological sinus lift procedure was defined by the presence of a dome shape visible within the maxillary alveolar recess. All cases were imaged postoperatively using OPT and maxillary CBCT. RESULTS: Twelve maxillary sinuses underwent the radiological sinus floor elevation procedure. A dome shape of the Schneiderian membrane was achieved in eight maxillary sinuses (66.7%). All failures (n = 4) were caused by mucosal perforation at the time of maxillary sinus osteotomy. Mean height of membrane elevation was 12.0 mm, with a mean intervention time of 45 min. CONCLUSION: This experimental study evaluates a new minimally radiological procedure for maxillary sinus floor elevation, which provides an interventional radiological alternative to the classical surgical lateral approach and achieves an equivalent success rate to that cited in the literature for the surgical approach, a low morbidity and a shorter operating time.

Virtual Endoscopy to Plan Transtympanic Approach to Labyrinthine Windows.

OBJECTIVE: The aim of this study was to evaluate the position and the accessibility of labyrinthine windows through the external auditory canal (EAC) by virtual endoscopy based on computed tomographic scan images. STUDY DESIGN: Prospective cross-sectional study. SETTING: Tertiary referral center. PATIENTS: Sixty-three high-resolution temporal bone computed tomographic scans were obtained from 34 adult patients undergoing various otologic procedures. INTERVENTION: Images were analyzed by the virtual endoscopy function included in Osirix (www.osirix-viewer.com). The endoscope was constrained in the EAC. The visible surfaces of target anatomic structures were assessed on multiplanar reconstruction views. RESULTS: The optimal angles of the virtual endoscope position showed a relatively high interindividual variability in the axial plane (64 ± 2.4 degrees for the oval window [OW] and 60 ± 2.5 degrees for the round window [RW]) position, but a low interindividual variation was noted in the coronal plane (107 ± 1.5 degrees for the OW and 112 ± 1.7 degrees for the RW). The RW was accessible in 87% of cases. The OW accessibility could be staged as follows: 1, invisible stapedial superstructure (10% of cases); 2, stapedial posterior crus partly visible (33%); 3, entire posterior crus and pyramid visible (44%); 4, posterior and anterior crus visible (13%). CONCLUSION: Virtual endoscopy through the EAC can evaluate the accessibility of the OW or RW via a transcanal route. This technique seems to be helpful in preplanning minimally invasive procedures by this approach such as cochlear implantation.

MSCT versus CBCT: evaluation of high-resolution acquisition modes for dento-maxillary and skull-base imaging.

OBJECTIVES: Our aim was to conduct a quantitative and qualitative evaluation of high-resolution skull-bone imaging for dentistry and otolaryngology using different architectures of recent X-ray computed tomography systems. MATERIAL AND METHODS: Three multi-slice computed tomography (MSCT) systems and one Cone-beam computed tomography (CBCT) system were used in this study. All apparatuses were tested with installed acquisition modes and proprietary reconstruction software enabling high-resolution bone imaging. Quantitative analyses were performed with small fields of view with the preclinical vmCT phantom, which permits to measure spatial resolution, geometrical accuracy, linearity and homogeneity. Ten operators performed visual qualitative analyses on the vmCT phantom images, and on dry human skull images. RESULTS: Quantitative analysis showed no significant differences between protocols in terms of linearity and geometric accuracy. All MSCT systems present a better homogeneity than the CBCT. Both quantitative and visual analyses demonstrate that CBCT acquisitions are not better than the collimated helical MSCT mode. CONCLUSION: Our results demonstrate that current high-resolution MSCT protocols could exceed the performance of a previous generation CBCT system for spatial resolution and image homogeneity. KEY POINTS: • Quantitative evaluation is a prerequisite for comparison of imaging equipment. • Bone imaging quality could be objectively assessed with a phantom and dry skull. • The current MSCT shows better image quality than a dental CBCT system. • CBCT remains a work-in-progress technology.