Low-dose Technique Research Articles

203. Cobb angle measurement reliability using low-dose radiographs in early-onset idiopathic scoliosis

BACKGROUND CONTEXT Early-onset idiopathic scoliosis (EOIS) management needs a long follow-up during the entire patient growth. The very young patient's age at the diagnosis can expose them to high cumulated radiation doses. Low-dose radiographs allow high-quality view of the spine in standing position. Accuracy and reproducibility of digital measurements of Cobb angle have already been assessed in adults and adolescents. Nevertheless, reliability of Cobb angle measurement has not been evaluated in EOIS follow-up PURPOSE Low dose stereoradiography could be a minimally invasive way to evaluate early-onset scoliosis before six years of age. STUDY DESIGN/SETTING Prospective data collection. PATIENT SAMPLE Forty-one patients younger than 6 years with thoracic or thoracolumbar scoliosis were evaluated. Patients with spine congenital abnormalities were excluded. OUTCOME MEASURES Intra- and interoperator reliability of 2D Cobb angle measurement in EOIS low-dose radiographs. METHODS Patients underwent low-dose standing radiographs. Three operators independently measured Cobb angles on two separate occasions. A fourth trained operator had previously labeled the superior and inferior limits vertebrae to avoid a potential source of uncertainty unrelated to low-dose radiography. Interoperator reproducibility, intraoperator repeatability and intraclass correlation coefficients (ICC) were calculated. Bland-Altmann plot was used to present the limits of agreement. RESULTS The mean age was 4.4 years (SD 0.8 years, range 2.2-5.8). Average Cobb angle was 22° (SD 9°, range 11-80°). ICCs were higher than 0.98 for all three operators, showing an excellent agreement. Reproducibility and repeatability were respectively of 1.2° (coefficient of variation: 4.5 %) and 0.8° (coefficient of variation 3.2%). Measurements were easily feasible in all cases. There was no effect of age or curve severity on uncertainty. CONCLUSIONS EOIS management includes bracing or surgical growth-friendly techniques. These require multiple radiological assessments responsible for a significant cumulative radiation exposure. Cobb angle measurements on low-dose radiographs showed an excellent reproducibility despite bone immaturity. Clinical follow-up could be done with this low-dose technique. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

Early Changes in CT Perfusion Parameters: Primary Renal Carcinoma Versus Metastases After Treatment with Targeted Therapy.

Computed tomography (CT) perfusion is a novel imaging method to determine tumor perfusion using a low-dose CT technique to measure iodine concentration at multiple time points. We determined if early changes in perfusion differ between primary renal tumors and metastatic tumor sites in patients with renal cell carcinoma (RCC) receiving targeted anti-angiogenic therapy. A total of 10 patients with advanced RCC underwent a CT perfusion scan at treatment baseline and at one week after initiating treatment. Perfusion measurements included blood volume (BV), blood flow (BF), and flow extraction product (FEP) in a total of 13 lesions (six primary RCC tumors, seven RCC metastases). Changes between baseline and week 1 were compared between tumor locations: primary kidney tumors vs metastases. Metastatic lesions had a greater decrease in BF (average BF difference ± standard deviation (SD): −75.0 mL/100 mL/min ± 81) compared to primary kidney masses (−25.5 mL/100 mL/min ± 35). Metastatic tumors had a wider variation of change in BF, BV and FEP measures compared to primary renal tumors. Tumor diameters showed little change after one week, but early perfusion changes are evident, especially in metastatic lesions compared to primary lesions. Future studies are needed to determine if these changes can predict which patients are benefiting from targeted therapy.

Mini-Review: A Brief History of Nitrous Oxide (N2O) Use in Neuropsychiatry.

Background:Joseph Priestley’s discovery of nitrous oxide (N2O) was recorded in 1772. In the late 1790’s, Humphry Davy experimented with the psychotropic properties of N2O, describing his observations in a book, published in 1800. A dentist, Horace Wells discovered anaesthesia with N2O in 1844. Over a century after Davy, its potential usefulness in psychiatry was first recognised. The seminal researches in neuropsychiatry, between 1920 and 1950, mainly used anaesthetic concen-trations of the gas. The psychotropic actions of N2O, at non-anaesthetic doses, were first used by den-tists, mainly for its anxiolytic action. In modern dentistry, N2O is always mixed with at least 30% ox-ygen and titrated to doses rarely exceeding 40% of N2O. At these lower concentrations, untoward ef-fects are almost always avoided, including over-sedation and/or anaesthesia. In the early 1980’s, the low-dose dental titration technique was first used to investigate and treat psychiatric conditions, includ-ing substance abuse. Until then, most physicians regarded the gas only as an anaesthetic agent. An ex-ception was obstetricians who used a fixed 50% concentration of N2O diluted with oxygen for analge-sia during parturition. In 1994, to clearly distinguish between anaesthetic and non-anaesthetic concen-trations (as used in dentistry), the term Psychotropic Analgesic Nitrous oxide (PAN) was introduced.Objective:This paper will give a brief history of the use of the N2O in psychiatry since the psycho-tropic actions were first recognised in the 18th century until the present.Conclusion:The role of other non- opioid systems, and the extent to which they contribute to the psy-chotropic properties of N2O, still remains to be established.

Evaluation of diagnostic accuracy: multidetector CT image noise correction improves specificity of a Gaussian model-based algorithm used for characterization of incidental adrenal nodules.

To investigate whether the histogram analysis method of characterizing adrenal nodules as adenomas is affected by increased noise with modern CT technique, and if an extension that allows for noise correction will improve diagnostic performance. This is a HIPAA-compliant, IRB-approved retrospective study performed on 58 total patients. The first group of 29 patients had 33 adrenal lesions that were pathology-proven non-adenomas. The second group had 29 patients with 33 pathology-proven or presumed adenomas based on established imaging criteria. The nodules were evaluated using the histogram method, mean attenuation method, and a Gaussian model-based algorithm without (uncorrected Gaussian algorithm) and with correction (corrected Gaussian algorithm) for image noise. Sensitivity, specificity, and accuracy for identifying adenoma were derived. There were no significant differences in identifying adenoma from non-adenoma when using the histogram analysis method and the uncorrected Gaussian algorithm, both of which had low specificities of 42.4% and 47.0%, respectively (p = 0.30). Adding noise correction to the Gaussian algorithm resulted in a statistically significant increase in specificity relative to the histogram method (86.4% vs. 42.4%, p < 0.001). The corrected Gaussian algorithm improved sensitivity compared to the mean attenuation method (71.2% vs. 54.5%, p < 0.001), but had lower specificity (86.4% vs. 100%, p < 0.001), and similar overall accuracy (78.8% vs. 77.3%, p = 0.74). With modern low-dose CT technique, the specificity scores of the histogram method for discrimination of adrenal adenomas and non-adenomas are lower than with previous higher dose scans. The specificity and accuracy of a histogram-equivalent method can be increased mathematically through image noise correction, and the corrected Gaussian algorithm has improved sensitivity to the mean attenuation with similar accuracy albeit with lower specificity. Although this suggests limited utility for histogram analysis in adrenal nodule characterization, our study demonstrates the potential mathematical application for other noise-dependent CT characterization methods.

An efficient low-dose CT reconstruction technique using partial derivatives based guided image filter

Low-dose Computed Tomography (CT) reconstruction techniques have been implemented to minimize the X-ray radiation in a human body. Many researchers have designed different low-dose CT reconstruction techniques to reduce the effect of radiation in a human body. However, the majority of these techniques suffer from over-smoothing, edge distortion, halo artifacts, gradient reversal artifacts etc. problems. Therefore, in this paper, novel partial differential equations and dictionary learning based reconstruction technique have been designed to reconstruct the low-dose CT images. Extensive experiments have been carried out to evaluate the effectiveness of the proposed technique that existing image reconstruction techniques. It has been observed that the proposed technique significantly preserves the radiometric information of low-dose CT images with a lesser number of edge distortion, halo and gradient reversal artifacts. Also, the proposed technique is computationally faster than existing techniques, therefore most suitable for real-time low-dose CT reconstruction systems.

Denoising Low-Dose CT Images Using Multiframe Blind Source Separation and Block Matching Filter

In order to reduce radiation effect during CT scans, low-dose techniques are employed in different medical imaging applications. But images in the low-dose CT tend to be rather noisy to be diagnostically useful. One way to improve the quality of low-dose CT images is to use a multiframe imaging technique. Here, we proposed a blind source separation (BSS) based CT image method using a multiframe low-dose image sequence. Because we found that BSS alone cannot denoise the image completely, we incorporated a nonlocal GroupWise block matching 3-D filter with BSS using the noise statistics, extracted from the noise components. With this technique, we produced a better quality image than that produced with a single frame half dose CT image and other multiframe imaging techniques, such as, frame averaging and applying the Wiener filter after BSS. Denoising performance, spatial resolution, and noise characteristics were measured by evaluating the peak signal to noise ratio, structural similarity index, modulation transfer function, and Bland–Altman analysis. This hybrid model shows a better denoising performance with less compromise in image details as more frames are included in an image sequence.

Radiation dose in non-dental cone beam CT applications: a systematic review.

Radiation-induced health risks are broadly questioned in the literature. As cone beam computed tomography (CBCT) is increasingly used in non-dental examinations, its effective dose needs to be known. This study aimed to review the published evidence on effective dose of non-dental CBCT for diagnostic use by focusing on dosimetry system used to estimate dose. A systematic review of the literature was performed on 12 November 2017. All the literature up to this date was included. The PubMed and web of science databases were searched. Studies were screened for inclusion based on defined inclusion and exclusion criteria according to the preferred reporting items for systematic reviews. Fifteen studies met the inclusion criteria and were included in our review. Thirteen and two of them examined one and two anatomical areas, respectively. The anatomical areas were: ear (6), paranasal sinuses (4), ankle (3), wrist (2), knee (1), and cervical spine (1). Effective dose was estimated by different methods: (i) RANDO phantom associated with thermoluminescent dosimeters (6), metal oxide semiconductor field-effect transistor dosimeters (3), and optically stimulated luminescent dosimeters (1). (ii) Scanner outputs, namely computed tomography dose index (1) and dose area product (2). (iii) Monte Carlo simulations (2). CBCT of extremities, cervical spine, ears and paranasal sinuses was found to be a low-dose volumetric imaging technique. Effective doses varied significantly because of different exposure settings of CBCT-units and different dosimetry systems used to estimate dose.

Low-dose CT image reconstruction using gain intervention-based dictionary learning

Computed tomography (CT) approach is extensively utilized in clinical diagnoses. However, X-ray residue in human body may introduce somatic damage such as cancer. Owing to radiation risk, research has focused on the radiation exposure distributed to patients through CT investigations. Therefore, low-dose CT has become a significant research area. Many researchers have proposed different low-dose CT reconstruction techniques. But, these techniques suffer from various issues such as over smoothing, artifacts, noise, etc. Therefore, in this paper, we have proposed a novel integrated low-dose CT reconstruction technique. The proposed technique utilizes global dictionary-based statistical iterative reconstruction (GDSIR) and adaptive dictionary-based statistical iterative reconstruction (ADSIR)-based reconstruction techniques. In case the dictionary (D) is predetermined, then GDSIR can be used and if D is adaptively defined then ADSIR is appropriate choice. The gain intervention-based filter is also used as a post-processing technique for removing the artifacts from low-dose CT reconstructed images. Experiments have been done by considering the proposed and other low-dose CT reconstruction techniques on well-known benchmark CT images. Extensive experiments have shown that the proposed technique outperforms the available approaches.

A novel fluoroscopic method for multidimensional evaluation of swallowing function

ObjectiveDynamic videofluoroscopic swallow study (VFSS) is used to investigate swallowing movements. However, it requires prolonged radiation exposure and mainly provides qualitative information. Herein, we present a multi-dimensional method for analyzing swallowing based on a pulsed, low-dose fluoroscopy technique that uses serial-shot images and evaluates the size, position, and temporal profile of the bolus to obtain a more comprehensive and realistic analysis of swallowing movements. MethodsFifteen healthy adults drank two liquids: 20mL of pure water followed by 20mL of contrast medium mixture in a fluoroscopic study. Data were recorded in serial-shot images (7.5 frames/second, 1024×1024-pixel resolution, DICOM format). The images from the water and contrast swallows were inverted, synchronized, and subtracted to visualize the bolus in each frame. The pathway of the bolus was divided into 15 parts traversing the oropharynx, hypopharynx, and upper esophagus, and the total gray value was measured in each section. The results were presented as contour graphs. ResultsThe contour graphs allowed for information on the size, anatomical location, and temporal location of the bolus during swallowing to be displayed simultaneously. Two distinct swallowing patterns were observed in the subjects. The bolus showed two peaks—one in the hypopharynx and one in the upper esophagus—in all subjects. However, in nine of the 15 subjects, the two peaks were in different frames, whereas in six of the subjects, the two peaks were in the same frame. ConclusionWe developed a new method for quantitatively evaluating swallowing. The technique allows for multidimensional assessment of the size, position, and temporal profile of the movement of the bolus across the pharynx. This method evaluates the swallowing movements using sharp, high-resolution images obtained by serial-shot, pulsed fluoroscopy with low radiation exposure. Additional studies are required to further clarify the variability of swallowing patterns and their clinical relevance in the evaluation of swallowing movements in healthy subjects and in patients with swallowing disorders.

Cone-beam computed tomography, a new low-dose three-dimensional imaging technique for assessment of bone erosions in rheumatoid arthritis: reliability assessment and comparison with conventional radiography – a BARFOT study

Objectives: To determine the intra- and inter-observer agreement of erosions detected and scored with cone-beam computed tomography (CBCT) of bones in the hands and feet, and to compare CBCT with conventional radiography (CR) for assessment of bone erosions in patients with long-standing rheumatoid arthritis (RA).Method: Thirty patients with long-standing RA from the Better Anti-Rheumatic PharmacOTherapy (BARFOT) cohort were examined with CBCT and CR of hands and feet at their 15 year follow-up. Intra- and inter-class correlation coefficients (ICCs) were calculated. Erosions were analysed with the total rheumatoid arthritis magnetic resonance imaging erosion score (RAMRIS erosion score) for ICCs with CBCT, and with the modified RAMRIS erosion score (RAMRIS-mod.) for the same locations as used in the Sharp van der Heijde score and Sharp van der Heijde erosion score for CR.Results: All 30 patients showed erosions on CBCT and 26 on CR. The ICCs for both intra- and inter-observer reliability were 0.92–0.99. CBCT showed numerically more erosions than CR for all regions compared, although a statistically significant difference was found only for the metacarpophalangeal joints [median number of eroded joints 1.0 (range 0–14) with CBCT and 0.5 (0–13) with CR, p = 0.044].Conclusion: CBCT has high reproducibility and is more sensitive than CR in detecting erosions in this cohort of patients with long-standing RA. CBCT has the potential to become an important tool in the detection and follow-up of erosions in patients with RA.

Cone Beam Computed Tomography in Orthodontics

Abstract: Cone Beam Computed Tomography (CBCT) is becoming increasingly used in dentistry. It is a high resolution low dose technique that can provide invaluable 3D information about the teeth and jaws. This article aims to outline the current selection criteria relating to orthodontics and dose optimization. The article will also briefly outline the training requirement related to evaluation of CBCT images. CPD/Clinical Relevance: Cone beam computed tomography is increasingly being used in orthodontics. Clinicians must know the clinical indications for cone beam CT imaging as well as the practical methods of dose reduction.

Low-dose CT perfusion with projection view sharing.

CT Perfusion (CTP) is a widely used clinical imaging modality. However, CTP typically involves the use of substantial radiation dose (CTDIvol ≥~200mGy). The purpose of this study is to present a low-dose CTP technique using a projection view-sharing reconstruction algorithm originally developed for dynamic MRI - "K-space Weighted Image Contrast" (KWIC). The KWIC reconstruction is based on an angle-bisection scheme. In KWIC, a Fourier transform was performed along each projection to form a "k-space"-like CT data space, based on the central-slice theorem. As a projection view-sharing technique, KWIC preserves the spatiotemporal resolution of undersampled CTP data by progressively increasing the number of projection views shared for more distant regions of "k-space". KWIC reconstruction was evaluated on a digital FORBILD head phantom with numerically simulated time-varying objects. The numerically simulated scans were undersampled using the angle-bisection scheme to achieve 50%, 25%, and 12.5% of the original dose (288, 144, and 72 projections, respectively). The area-under-the-curve (AUC), time-to-peak (TTP), and full width half maximum (FWHM) were measured in KWIC recons and compared to fully sampled filtered back projection (FBP) reconstructions. KWIC reconstruction and dose reduction was also implemented for three clinical CTP cases (45s, 1156 projections per turn, 1s/turn, CTDIvol 217mGy). Quantitative perfusion metrics were computed and compared between KWIC reconstructed CTP data and those of standard FBP reconstruction. The AUC, TTP, and FWHM in the numerical simzulations were unaffected by the undersampling/dose reduction (down to 12.5% dose) with KWIC reconstruction compared to the fully sampled FBP reconstruction. The normalized root-mean-square-error (NRMSE) of the AUC in the FORBILD head phantom is 0.04, 0.05, and 0.07 for 50%, 25%, and 12.5% KWIC, respectively, as compared to FBP reconstruction. The cerebral blood flow (CBF) and cerebral blood volume had no significant difference between FBP and 50%, 25%, and 12.5% KWIC reconstructions (P>0.05). This study demonstrates that KWIC preserves perfusion metrics for CTP with substantially reduced dose. Clinical implementation will require further investigation into methods of rapid switching of a CT x-ray source.

Effect of Intrathecal Bupivacaine Dose on the Success of External Cephalic Version for Breech Presentation: A Prospective, Randomized, Blinded Clinical Trial.

Breech presentation is a leading cause of cesarean delivery. The use of neuraxial anesthesia increases the success rate of external cephalic version procedures for breech presentation and reduces cesarean delivery rates for fetal malpresentation. Meta-analysis suggests that higher-dose neuraxial techniques increase external cephalic version success to a greater extent than lower-dose techniques, but no randomized study has evaluated the dose-response effect. We hypothesized that increasing the intrathecal bupivacaine dose would be associated with increased external cephalic version success. We conducted a randomized, double-blind trial to assess the effect of four intrathecal bupivacaine doses (2.5, 5.0, 7.5, 10.0 mg) combined with fentanyl 15 μg on the success rate of external cephalic version for breech presentation. Secondary outcomes included mode of delivery, indication for cesarean delivery, and length of stay. A total of 240 subjects were enrolled, and 239 received the intervention. External cephalic version was successful in 123 (51.5%) of 239 patients. Compared with bupivacaine 2.5 mg, the odds (99% CI) for a successful version were 1.0 (0.4 to 2.6), 1.0 (0.4 to 2.7), and 0.9 (0.4 to 2.4) for bupivacaine 5.0, 7.5, and 10.0 mg, respectively (P = 0.99). There were no differences in the cesarean delivery rate (P = 0.76) or indication for cesarean delivery (P = 0.82). Time to discharge was increased 60 min (16 to 116 min) with bupivacaine 7.5 mg or higher as compared with 2.5 mg (P = 0.004). A dose of intrathecal bupivacaine greater than 2.5 mg does not lead to an additional increase in external cephalic procedural success or a reduction in cesarean delivery.

Novel low-dose imaging technique for characterizing atomic structures through scanning transmission electron microscope

To investigate dislocations or heterostructures across interfaces is now of great interest to condensed matter and materials scientists. With the advances in aberration-corrected electron optics, the scanning transmission electron microscope has demonstrated its excellent capability of characterizing atomic structures within nanomaterials, and well-resolved atomic-resolution images can be obtained through long-exposure data acquisition. However, the sample drifting, carbon contamination, and radiation damage hinder further analysis, such as deriving three-dimensional (3D) structures from a series of images. In this study, a method for obtaining atomic-resolution images with significantly reduced exposure time was developed, using which an original high-resolution image with approximately one tenth the electron dose can be obtained by combining a fast-scan high-magnification image and a slow-scan low-magnification image. The feasibility of obtaining 3D atomic structures using the proposed approach was demonstrated through multislice simulation. Finally, the feasibility and accuracy of image restoration were experimentally verified. This general method cannot only apply to electron microscopy but also benefit to image radiation-sensitive materials using various light sources.

Operational and Dosimetric Aspects of Pediatric PET/CT.

No consistent guidelines exist for the acquisition of a CT scan as part of pediatric PET/CT. Given that children may be more vulnerable to the effects of ionizing radiation, it is necessary to develop methods that provide diagnostic-quality imaging when needed, in the shortest time and with the lowest patient radiation exposure. This article describes the basics of CT dosimetry and PET/CT acquisition in children. We describe the variability in pediatric PET/CT techniques, based on a survey of 19 PET/CT pediatric institutions in North America. The results of the survey demonstrated that, although most institutions used automatic tube current modulation, there remained a large variation of practice, on the order of a factor of 2-3, across sites, pointing to the need for guidelines. We introduce the approach developed at our institution for using a multiseries PET/CT acquisition technique that combines diagnostic-quality CT in the essential portion of the field of view and a low-dose technique to image the remainder of the body. This approach leads to a reduction in radiation dose to the patient while combining the PET and the diagnostic CT into a single acquisition. The standardization of pediatric PET/CT provides an opportunity for a reduction in the radiation dose to these patients while maintaining an appropriate level of diagnostic image quality.

Diagnostic Imaging in pediatric thoracic trauma.

Thoracic trauma accounts for approximately 14% of blunt force traumatic deaths, second only to head injuries. Chest trauma can be blunt (90% of cases) or penetrating. In young patients, between 60 and 80% of chest injuries result from blunt trauma, with over half as a consequence of impact with motor vehicles, whereas in adolescents and adults, penetrating trauma has a statistically more prominent role. Pulmonary contusions and rib fractures are the most frequent injuries occurring. Chest X-ray is the first imaging modality of choice to identify patients presenting with life-threatening conditions (i.e., tension pneumothorax, huge hemothorax, and mediastinal hematoma) and those who require a CT examination. Multi-Slice Computed Tomography is the gold standard to evaluate chest injuries. In fact, the high spatial resolution, along with multiplanar reformation and three-dimensional (3D) reconstructions, makes MDCT the ideal imaging method to recognize several chest injuries such as rib fractures, pneumothorax, hemothorax, lung contusions and lacerations, diaphragmatic rupture, and aortic injuries. Nevertheless, when imaging a young patient, one should always keep into account the ALARA concept, to balance an appropriate and low-dose technique with imaging quality and to reduce the amount of ionizing radiation exposure. According to this concept, in the recent years, the current trends in pediatric imaging support the rising use of alternative imaging modalities, such as US and MRI, to decrease radiation exposure and to answer specific clinical questions and during the observation period also. As an example, ultrasound is the first technique of choice for the diagnosis and treatment of pleural and pericardial effusion; its emerging indications include the evaluation of pneumothoraces, costocondral and rib fractures, and even pulmonary contusions.

Computed Tomography in Cystic Fibrosis: Combining Low-Dose Techniques and Iterative Reconstruction.

The aim of the study was to evaluate the impact of iterative reconstruction (IR) and low-kilovolt technique on dose reduction and image quality of chest computed tomography scans obtained in patients with cystic fibrosis (CF). A total of 124 CF patients were examined; group A (n = 63) was examined with a dose reduction protocol using IR and group B (n = 61) with a standard protocol using filtered back projection. Further subgroups with tube voltage modulations were established. Quantitative and qualitative image quality was assessed. The radiation dose in groups with comparable image quality was approximately 40% lower using IR compared with filtered back projection. The IR protocol combined with 80-kV tube voltage showed adequate image quality with a mean effective dose of only 0.47 mSv. Iterative reconstruction helps extensively reduce radiation dose by improving image quality. It permits the use of low-kilovolt protocols without significantly degrading image reading ability in the monitoring of the predominantly young patients with CF.

Ultrathin Two-Dimensional Covalent Organic Framework Nanosheets: Preparation and Application in Highly Sensitive and Selective DNA Detection.

The ability to prepare ultrathin two-dimensional (2D) covalent organic framework (COF) nanosheets (NSs) in high yield is of great importance for the further exploration of their unique properties and potential applications. Herein, by elaborately designing and choosing two flexible molecules with C3v molecular symmetry as building units, a novel imine-linked COF, namely, TPA-COF, with a hexagonal layered structure and sheet-like morphology, is synthesized. Since the flexible building units are integrated into the COF skeletons, the interlayer stacking becomes weak, resulting in the easy exfoliation of TPA-COF into ultrathin 2D NSs. Impressively, for the first time, the detailed structural information, i.e., the pore channels and individual building units in the NSs, is clearly visualized by using the recently developed low-dose imaging technique of transmission electron microscopy (TEM). As a proof-of-concept application, the obtained ultrathin COF NSs are used as a novel fluorescence sensing platform for the highly sensitive and selective detection of DNA.

Influence of Ultra-Low-Dose and Iterative Reconstructions on the Visualization of Orbital Soft Tissues on Maxillofacial CT.

Dose reduction on CT scans for surgical planning and postoperative evaluation of midface and orbital fractures is an important concern. The purpose of this study was to evaluate the variability of various low-dose and iterative reconstruction techniques on the visualization of orbital soft tissues. Contrast-to-noise ratios of the optic nerve and inferior rectus muscle and subjective scores of a human cadaver were calculated from CT with a reference dose protocol (CT dose index volume = 36.69 mGy) and a subsequent series of low-dose protocols (LDPs I-4: CT dose index volume = 4.18, 2.64, 0.99, and 0.53 mGy) with filtered back-projection (FBP) and adaptive statistical iterative reconstruction (ASIR)-50, ASIR-100, and model-based iterative reconstruction. The Dunn Multiple Comparison Test was used to compare each combination of protocols (α = .05). Compared with the reference dose protocol with FBP, the following statistically significant differences in contrast-to-noise ratios were shown (all, P ≤ .012) for the following: 1) optic nerve: LDP-I with FBP; LDP-II with FBP and ASIR-50; LDP-III with FBP, ASIR-50, and ASIR-100; and LDP-IV with FBP, ASIR-50, and ASIR-100; and 2) inferior rectus muscle: LDP-II with FBP, LDP-III with FBP and ASIR-50, and LDP-IV with FBP, ASIR-50, and ASIR-100. Model-based iterative reconstruction showed the best contrast-to-noise ratio in all images and provided similar subjective scores for LDP-II. ASIR-50 had no remarkable effect, and ASIR-100, a small effect on subjective scores. Compared with a reference dose protocol with FBP, model-based iterative reconstruction may show similar diagnostic visibility of orbital soft tissues at a CT dose index volume of 2.64 mGy. Low-dose technology and iterative reconstruction technology may redefine current reference dose levels in maxillofacial CT.

A new low-dose multi-phase trauma CT protocol and its impact on diagnostic assessment and radiation dose in multi-trauma patients

PurposeComputed tomography (CT) examinations, often using high-radiation dosages, are increasingly used in the acute management of polytrauma patients. This study compares a low-dose polytrauma multi-phase whole-body CT (WBCT) protocol on a latest generation of 16-cm detector 258-slice multi-detector CT (MDCT) scanner with advanced dose reduction techniques to a single-phase polytrauma WBCT protocol on a 64-slice MDCT scanner.MethodsBetween March and September 2015, 109 polytrauma patients (group A) underwent acute WBCT with a low-dose multi-phase WBCT protocol on a 258-slice MDCT whereas 110 polytrauma patients (group B) underwent single-phase trauma CT on a 64-slice MDCT. The diagnostic accuracy to trauma-related injuries, radiation dose, quantitative and semiquantitative image quality parameters, subjective image quality scorings, and workflow time parameters were compared.ResultsIn group A, statistically significantly more arterial injuries (p = 0.04) and arterial dissections (p = 0.002) were detected. In group A, the mean (±SD) dose length product value was 1681 ± 183 mGy*cm and markedly lower when compared to group B (p < 0.001). The SDs of the mean Houndsfield unit values of the brain, liver, and abdominal aorta were lower in group A (p < 0.001). Mean signal-to-noise ratios (SNRs) for the brain, liver, and abdominal aorta were significantly higher in group A (p < 0.001). Group A had significantly higher image quality scores for all analyzed anatomical locations (p < 0.02). However, the mean time from patient registration until completion of examination was significantly longer for group A (p < 0.001).ConclusionsThe low-dose multi-phase CT protocol improves diagnostic accuracy and image quality at markedly reduced radiation. However, due to technical complexities and surplus electronic data provided by the newer low-dose technique, examination time increases, which reduces workflow in acute emergency situations.