Analysis of dual-energy mammography subtraction technique for the dose and image quality evaluation using 3D-printed breast phantom.

This study aimed to quantitatively assess the radiation dose using XR-QA2 and the image quality of the dual-energy subtraction mammography technique on an in-house phantom. The analysis was carried out to investigate the effect of targets/filters on dose value and image quality using an in-house phantom made of PLA + as an object representing compressed breasts. All irradiation parameters were performed in the craniocaudal position with manual mode. Mean glandular dose (MGD) was recorded, followed by the calculation of the signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and modulation transfer function (MTF) for image quality assessment parameters. The results showed that the image quality was accepted at dose levels within the IAEA and BAPETEN tolerance limit for 60 mm equivalent compressed breast using dual-energy mammography. Furthermore, the target/filter (W/Rh) reduced the dose by 1.03 mGy compared to the Mo/Mo and Mo/Rh with an enhancement in image quality. This indicated that the target/filter (W/Rh) combination was optimal due to the image quality improvement obtained with lower MGD.

Design and development of a novel flexible ultra-short echo time (FUSE) sequence.

PURPOSE: To present the validation of a new Flexible Ultra-Short Echo time (FUSE) pulse sequence using a short-T2 phantom. METHODS: FUSE was developed to include a range of RF excitation pulses, trajectories, dimensionalities, and long-T2 suppression techniques, enabling real-time interchangeability of acquisition parameters. Additionally, we developed an improved 3D deblurring algorithm to correct for off-resonance artifacts. Several experiments were conducted to validate the efficacy of FUSE, by comparing different approaches for off-resonance artifact correction, variations in RF pulse and trajectory combinations, and long-T2 suppression techniques. All scans were performed on a 3 T system using an in-house short-T2 phantom. The evaluation of results included qualitative comparisons and quantitative assessments of the SNR and contrast-to-noise ratio. RESULTS: Using the capabilities of FUSE, we demonstrated that we could combine a shorter readout duration with our improved deblurring algorithm to effectively reduce off-resonance artifacts. Among the different RF and trajectory combinations, the spiral trajectory with the regular half-inc pulse achieves the highest SNRs. The dual-echo subtraction technique delivers better short-T2 contrast and superior suppression of water and agar signals, whereas the off-resonance saturation method successfully suppresses water and lipid signals simultaneously. CONCLUSION: In this work, we have validated the use of our new FUSE sequence using a short T2 phantom, demonstrating that multiple UTE acquisitions can be achieved within a single sequence. This new sequence may be useful for acquiring improved UTE images and the development of UTE imaging protocols.

[Comparison of Lower Extremity Computed Tomography Angiography by Using Different Subtraction Techniques].

PURPOSE: To compare the diagnostic capabilities of orbital synchronized helical scanning at lower extremity computed tomography angiography between the Add/Sub software and the deformable image registration. METHODS: From March 2015 to December 2016, 100 dialysis patients underwent orbital synchronized lower limb CT subtraction angiography and lower limb endovascular treatment within 4 months. For the visual evaluation of blood vessels in the lower extremities, a stenosis rate of 50% or more was considered to be stenosis. It was classified into two areas: above-knee (AK) region (superficial femoral artery and popliteal artery) and below-knee (BK) region (anterior tibial artery, posterior tibial artery, and fibula artery). Considering angiography for the lower limb endovascular treatment as the golden standard, we calculated the sensitivity, specificity, positive-predictive value, negative-predictive value, and diagnostic capabilities. Receiver operating characteristic curve (ROC) analysis was performed to calculate the area under curve (AUC). RESULTS: Calcification subtraction failure was observed to be 11% in the AK region and 2% in the BK region using the Add/Sub software. The specificity, positive-predictive value, diagnostic capabilities, and AUC of the deformable image registration were lower than those of the Add/Sub software. CONCLUSIONS: Add/Sub software and deformable image registration have high diagnostic capability to remove calcification. On the other hand, the specificity and AUC of the deformable image registration were lower than those of the Add/Sub software. Also, even if the same deformable image registration is used, caution is required because the diagnostic performance varies depending on the site.

Evaluation of calculation processes of apparent diffusion coefficient subtraction method (ASM) imaging.

A number of restricted diffusion (RD) imaging techniques, such as diffusion kurtosis (DK) imaging and Q space imaging, have been developed and proven to be useful for the diagnosis of diseases, including cerebral gliomas and cerebrovascular infarction. In particular, apparent diffusion coefficient (ADC) subtraction method (ASM) imaging has become available recently as a novel RD imaging technique. ASM is based on the difference between the ADC values in an image pair of two ADC maps, ADC basic (ADCb) and ADC modify (ADCm), which are created from diffusion-weighted images taken using short and long effective diffusion times, respectively. The present study aimed to assess the potential of different types of ASM imaging by comparing them with DK imaging which is the gold-standard RD imaging technique. In the present basic study using both polyethylene glycol phantom and cell-containing bio-phantom, three different types of ASM images were created using different calculation processes. ASM/A is an image calculated by dividing the absolute difference between ADCb and ADCm by ADCb several times. By contrast, ASM/S is an image created by dividing the absolute difference between ADCb and ADCm by the standard deviation of ADCb several times. As for positive ASM/A image (PASM/A), the positive image, which was resultant after subtracting ADCb from ADCm, was divided by ADCb several times. A comparison was made between the types of ASM and DK images. The results showed the same tendency between ASM/A in addition to both ASM/S and PASM/A. By increasing the number of divisions by ADCb from three to five times, ASM/A images transformed from DK-mimicking to more RD-sensitive images compared with DK images. These observations suggest that ASM/A images may prove useful for future clinical applications in RD imaging protocols for the diagnosis of diseases.

Coronary Artery Stent Evaluation by CTA: Impact of Deep Learning Reconstruction and Subtraction Technique.

BACKGROUND. Coronary CTA with hybrid iterative reconstruction (HIR) is prone to false-positive results for in-stent restenosis due to stent-related blooming artifact. OBJECTIVE. The purpose of this study is to assess the impact of deep learning reconstruction (DLR), subtraction images, and the combination of DLR and subtraction images on the diagnostic performance of coronary CTA for the detection of in-stent restenosis. METHODS. This prospective study included patients with coronary stents who underwent coronary CTA between March 2020 and August 2021. CTA used a technique with two breath-holds (noncontrast and contrast-enhanced acquisitions). Conventional and subtraction images were reconstructed for HIR and DLR. The maximum visible instent lumen diameter was measured. Two readers independently evaluated images for in-stent restenosis (≥ 50% stenosis). A simulated assessment of combined conventional and subtraction images was generated, reflecting assessment of conventional and subtraction images in the presence or absence of severe misregistration artifact, respectively. Invasive angiography served as reference standard. RESULTS. The study enrolled 30 patients (22 men and eight women; mean age, 63.6 ± 7.4 [SD] years) with a total of 59 stents; severe misregistration artifact was present for 32 stents. Maximum visible in-stent lumen diameter was higher for DLR than for HIR (2.3 ± 0.5 vs 2.1 ± 0.5 mm, p < .001), and among stents without severe misregistration artifact, it was higher for subtraction than conventional DLR (3.0 ± 0.5 vs 2.4 ± 0.5, p < .001). Among conventional CTA with HIR, conventional CTA with DLR, combination (conventional and subtraction) approach with HIR, and combination (conventional and subtraction) approach with DLR, the highest patient-level diagnostic performance measures were as follows: for reader 1, sensitivity was identical (62.5%), specificity was highest for combination with DLR (90.1%), PPV was highest for combination with DLR (71.4%), NPV was highest for combination with DLR (87.0%), and accuracy was highest for combination with DLR (83.3%); for reader 2, sensitivity was identical (50.0%), specificity was highest for combination with HIR or DLR (both 95.5%), PPV was highest for combination with HIR or DLR (both 80.0%), NPV was highest for combination with HIR or DLR (84.0%), and accuracy was highest for combination with HIR or DLR (both 83.3%). CONCLUSION. The combined DLR and subtraction technique yielded optimal diagnostic performance for detecting in-stent restenosis by coronary CTA. CLINICAL IMPACT. The described technique could guide patient selection for invasive coronary stent evaluation.

Effectiveness of temporal subtraction computed tomography images using deep learning in detecting vertebral bone metastases.

PURPOSE: To assess the clinical effectiveness of temporal subtraction computed tomography (TS CT) using deep learning to improve vertebral bone metastasis detection. METHOD: This retrospective study used TS CT comprising bony landmark detection, bone segmentation with a multi-atlas-based method, and spatial registration of two images by a log-domain diffeomorphic Demons algorithm. Paired current and past CT images of 50 patients without vertebral metastasis, recorded during June 2011-September 2016, were included as training data. A deep learning-based method estimated registration errors and suppressed false positives. Thereafter, paired CT images of 40 cancer patients with newly developed vertebral metastases and 40 control patients without vertebral metastases were evaluated. Six board-certified radiologists and five radiology residents independently interpreted 80 paired CT images with and without TS CT. RESULTS: Records of 40 patients in the metastasis group (median age: 64.5 years; 20 males) and 40 patients in the control group (median age: 64.0 years; 20 males) were evaluated. With TS CT, the overall figure of merit (FOM) of the board-certified radiologist and resident groups improved from 0.848 to 0.876 (p = 0.01) and from 0.752 to 0.799 (p = 0.02), respectively. The sub-analysis focusing on attenuation changes in lesions revealed that the FOM of osteoblastic lesions significantly improved in both the board-certified radiologist and resident groups using TS CT. The sub-analysis focusing on lesion location showed that the FOM of the resident group significantly improved in the vertebral arch (p = 0.04). CONCLUSIONS: TS CT was effective in detecting bone metastasis by both board-certified radiologists and radiology residents.

Recording brain responses to TMS of primary motor cortex by EEG - utility of an optimized sham procedure.

INTRODUCTION: Electroencephalography (EEG) is increasingly used to investigate brain responses to transcranial magnetic stimulation (TMS). A relevant issue is that TMS is associated with considerable auditory and somatosensory stimulation, causing peripherally evoked potentials (PEPs) in the EEG, which contaminate the direct cortical responses to TMS (TEPs). All previous attempts to control for PEPs suffer from significant limitations. OBJECTIVE/HYPOTHESIS: To design an optimized sham procedure to control all sensory input generated by subthreshold real TMS targeting the hand area of the primary motor cortex (M1), enabling reliable separation of TEPs from PEPs. METHODS: In 23 healthy (16 female) subjects, we recorded EEG activity evoked by an optimized sham TMS condition which masks and matches auditory and somatosensory co-stimulation during the real TMS condition: auditory control was achieved by noise masking and by using a second TMS coil that was placed on top of the real TMS coil and produced a calibrated sound pressure level. Somatosensory control was obtained by electric stimulation (ES) of the scalp with intensities sufficient to saturate somatosensory input. ES was applied in both the sham and real TMS conditions. Perception of auditory and somatosensory inputs in the sham and real TMS conditions were compared by psychophysical testing. Transcranially evoked EEG signal changes were identified by subtraction of EEG activity in the sham condition from EEG activity in the real TMS condition. RESULTS: Perception of auditory and somatosensory inputs in the sham vs. real TMS conditions was comparable. Both sham and real TMS evoked a series of similar EEG signal deflections and induced broadband power increase in oscillatory activity. Notably, the present procedure revealed EEG potentials and a transient increase in beta band power at the site of stimulation that were only present in the real TMS condition. DISCUSSION: The results validate the effectiveness of our optimized sham approach. Despite the presence of typical responses attributable to sensory input, the procedure provided evidence for direct cortical activation by subthreshold TMS of M1. The findings are relevant for future TMS-EEG experiments that aim at measuring regional brain target engagement controlled by an optimized sham procedure.

Brain Tumour Temporal Monitoring of Interval Change Using Digital Image Subtraction Technique.

A process that involves the registration of two brain Magnetic Resonance Imaging (MRI) acquisitions is proposed for the subtraction between previous and current images at two different follow-up (FU) time points. Brain tumours can be non-cancerous (benign) or cancerous (malignant). Treatment choices for these conditions rely on the type of brain tumour as well as its size and location. Brain cancer is a fast-spreading tumour that must be treated in time. MRI is commonly used in the detection of early signs of abnormality in the brain area because it provides clear details. Abnormalities include the presence of cysts, haematomas or tumour cells. A sequence of images can be used to detect the progression of such abnormalities. A previous study on conventional (CONV) visual reading reported low accuracy and speed in the early detection of abnormalities, specifically in brain images. It can affect the proper diagnosis and treatment of the patient. A digital subtraction technique that involves two images acquired at two interval time points and their subtraction for the detection of the progression of abnormalities in the brain image was proposed in this study. MRI datasets of five patients, including a series of brain images, were retrieved retrospectively in this study. All methods were carried out using the MATLAB programming platform. ROI volume and diameter for both regions were recorded to analyse progression details, location, shape variations and size alteration of tumours. This study promotes the use of digital subtraction techniques on brain MRIs to track any abnormality and achieve early diagnosis and accuracy whilst reducing reading time. Thus, improving the diagnostic information for physicians can enhance the treatment plan for patients.

Development of a novel detection method for changes in lung conditions during radiotherapy using a temporal subtraction technique.

We aimed to develop a novel method of detecting changes in lung conditions during radiotherapy using temporal subtraction technique. Twenty patients who underwent radiotherapy were retrospectively assessed by calculating optimal direct similarity error (ODSE) between initial and mid-treatment registered images. Patients were grouped according to region in tumor size and atelectasis for lung of < 20 or ≥ 20 cm3, which analyzed two field regions (1024 × 768 pixels, 512 × 512 pixels). Correlations between ODSE and changes in lung conditions were analyzed based on effect of radiation dose; receiver operating characteristic (ROC) analysis was performed to evaluate whether changes can be detected during treatment period. The ODSE of 1024 × 768 pixels was changed to 1.00 (0.28-3.48) for lung lesion size of < 20 cm3 and 1.86 (0.55-6.58) for the ≥ 20 cm3 lung lesion size. ODSE of 512 × 512 pixels was 1.03 (0.40-2.12) for the region in tumor size and atelectasis of < 20 cm3 and 1.90 (0.39-27.8) for the ≥ 20 cm3 lung lesion size. The region under the curve values from ROC analysis were 0.796 (1024 × 768 pixels) and 0.983 (512 × 512 pixels). A novel method can visually and numerically help to detect changes in lung condition at early treatment stages. Using this method, difference between plan and actual positional relationship for target and risk organs that cannot be predicted at the time of planning can be avoided, ensuring high safety and accuracy in lung radiotherapy.

Lung cancer screening by single-shot dual-energy subtraction using flat-panel detector.

PURPOSE: The purpose of this study was to evaluate the usefulness of single-shot dual-energy subtraction (DES) method using a flat-panel detector for lung cancer screening MATERIALS AND METHODS: The subjects were 13,315 residents (5801 males and 7514 females) aged 50 years or older (50-97 years, with an intermediate value of 68 years) who underwent lung cancer screening for a period of 1 year and 6 months from January 2019 to June 2020. We investigated whether the number of lung cancers detected, the detection rate, and the rate of required scrutiny changed, when DES images were added to the judgment based on conventional chest radiography. RESULTS: When DES images were added, the number and percentage of cancer detection increased from 16 (0.12%) to 23 (0.17%) (P < 0.05). Five of the newly detected 7 lung cancers were in the early stages of resectable cancer. The rate of participants requiring scrutiny increased slightly from 1.1 to 1.3%. CONCLUSION: DES method improved the detection of lung cancer in screening. The increase in the percentage of participants requiring scrutiny was negligible.

Reduced motion artifacts and speed improvements in enhanced line-scanning fiber bundle endomicroscopy.

SIGNIFICANCE: Confocal laser scanning enables optical sectioning in fiber bundle endomicroscopy but limits the frame rate. To be able to better explore tissue morphology, it is useful to stitch sequentially acquired frames into a mosaic. However, low frame rates limit the maximum probe translation speed. Line-scanning (LS) confocal endomicroscopy provides higher frame rates, but residual out-of-focus light degrades images. Subtraction-based approaches can suppress this residue at the expense of introducing motion artifacts. AIM: To generate high-frame-rate endomicroscopy images with improved optical sectioning, we develop a high-speed subtraction method that only requires the acquisition of a single camera frame. APPROACH: The rolling shutter of a CMOS camera acts as both the aligned and offset detector slits required for subtraction-based sectioning enhancement. Two images of the bundle are formed on different regions of the camera, allowing both images to be acquired simultaneously. RESULTS: We confirm improved optical sectioning compared to conventional LS, particularly far from focus, and show that motion artifacts are not introduced. We demonstrate high-speed mosaicing at frame rates of up to 240 Hz. CONCLUSION: High-speed acquisition of optically sectioned images using the new subtraction based-approach leads to improved mosaicing at high frame rates.

Development of a Fission Neutron Spectrum from a D-T Neutron Generator by Spectrum Subtraction Technique.

ABSTRACT: Californium-252 (252Cf) is considered essential by the National Institute of Standards and Technology for the calibration of neutron instrumentation and dosimetry. Californium-252 has a relatively short half-life of 2.645 y; consequently, it must be replaced frequently to produce an adequate neutron flux for calibration. The user community is currently looking for a replacement for 252Cf. The patented technology described herein has a high probability of being that replacement. A preferred method to replace 252Cf would use an affordable and easily maintained neutron source that generates neutrons in an energy spectrum as close to that of 252Cf as possible. Deuterium-tritium (D-T) neutron generators are both affordable and easily maintained, which makes them highly attractive for replacing 252Cf. The patented technology discussed in this paper simulates the 252Cf fission spectrum through a D-T neutron generator by using spectral subtraction. The primary spectrum is built using principally (n,xn) and (n,n') reactions in a variety of materials. In conjunction with the primary spectrum, an engineered background spectrum is generated using a second set of materials. This engineered background spectrum corrects for differences between the primary and desired spectra. This subtraction technique generates a spectrum very similar to 252Cf while maintaining a reasonable flux. Further, by choosing different scattering materials, any fission spectrum can be matched, including the thermal and epithermal components. This flexibility expands the potential use of this technology beyond simulating 252Cf to any desired neutron spectrum below 14 MeV.

The potential application of dual-energy subtraction radiography for COVID-19 pneumonia imaging.

X-ray imaging plays a crucial role in the confirmation of COVID-19 pneumonia. Chest X-ray radiography and CT are two major imaging techniques that are currently adopted in the diagnosis of COVID-19 pneumonia. However, dual-energy subtraction radiography is hardly discussed as potential COVID-19 imaging application. More advanced X-ray radiography equipment often supports dual-energy subtraction X-ray radiography. Dual-energy subtraction radiography enables the calculation of pseudo-radiographs, in which bones are removed and only soft-tissues are highlighted. In this commentary, the author would like to draw the attention to the potential use of dual-energy subtraction X-ray radiography (i.e. soft-tissue pseudo-radiography) for the assessment and the longitudinal follow-up of COVID-19 pneumonia.

Highly accelerated subtractive femoral non-contrast-enhanced MRA using compressed sensing with k-space subtraction, phase and intensity correction.

PURPOSE: To develop an improved reconstruction method, k-space subtraction with phase and intensity correction (KSPIC), for highly accelerated, subtractive, non-contrast-enhanced MRA. METHODS: The KSPIC method is based on k-space subtraction of complex raw data. It applies a phase-correction procedure to restore the polarity of negative signals caused by subtraction and an intensity-correction procedure to improve background suppression and thereby sparsity. Ten retrospectively undersampled data sets and 10 groups of prospectively undersampled data sets were acquired in 12 healthy volunteers. The performance of KSPIC was compared with another improved reconstruction based on combined magnitude subtraction, as well as with conventional k-space subtraction reconstruction and magnitude subtraction reconstruction, both using quantitative metrics and using subjective quality scoring. RESULTS: In the quantitative evaluation, KSPIC had the best performance in terms of peak SNR, structural similarity index measure, contrast-to-noise ratio of artery-to-background and sharpness, especially at high acceleration factors. The KSPIC method also had the highest subjective scores for all acceleration factors in terms of vessel delineation, image noise and artifact, and background contamination. The acquisition can be accelerated by a factor of 20 without significant decreases of subjective scores. The optimal size of the phase-correction region was found to be 12-20 pixels in this study. CONCLUSION: Compared with combined magnitude subtraction and conventional reconstructions, KSPIC has the best performance in all of the quantitative and qualitative measurements, permitting good image quality to be maintained up to higher accelerations. The KSPIC method has the potential to further reduce the acquisition time of subtractive MRA for clinical examinations.

MNI SISCOM: an Open-Source Tool for Computing Subtraction Ictal Single-Photon Emission CT Coregistered to MRI.

Subtraction ictal single-photon emission computed tomography (SPECT) coregistered to MRI (SISCOM) is a well-established technique for quantitative analysis of ictal vs interictal SPECT images that can contribute to the identification of the seizure onset zone in patients with drug-resistant epilepsy. However, there is presently a lack of user-friendly free and open-source software to compute SISCOM results from raw SPECT and MRI images. We aimed to develop a simple graphical desktop application for computing SISCOM. MNI SISCOM is a new free and open-source software application for computing SISCOM and producing practical MRI/SPECT/SISCOM image panels for review and reporting. The graphical interface allows any user to quickly and easily obtain SISCOM images with minimal user interaction. Additionally, MNI SISCOM provides command line and Python interfaces for users who would like to integrate these features into their own scripts and pipelines. MNI SISCOM is freely available for download from: https://github.com/jeremymoreau/mnisiscom .

Value of bone suppression software in chest radiographs for improving image quality and reducing radiation dose.

OBJECTIVES: To compare image quality and radiation dose between dual-energy subtraction (DES)-based bone suppression images (D-BSIs) and software-based bone suppression images (S-BSIs). METHODS: Chest radiographs (CXRs) of forty adult patients were obtained with the two X-ray devices, one with DES and one with bone suppression software. Three image quality metrics (relative mean absolute error (RMAE), peak signal-to-noise ratio (PSNR), and structural similarity index (SSIM)) between original CXR and BSI for each of D-BSI and S-SBI groups were calculated for each bone and soft tissue areas. Two readers rated the visual image quality for original CXR and BSI for each of D-BSI and S-SBI groups. The dose area product (DAP) values were recorded. Paired t test was used to compare the image quality and DAP values between D-BSI and S-BSI groups. RESULTS: In bone areas, S-BSIs had better SSIM values than D-BSI (94.57 vs. 87.77) but worse RMAE and PSNR values (0.50 vs. 0.20; 20.93 vs. 34.37) (all p < 0.001). In soft tissue areas, S-BSIs had better SSIM values than D-BSI (97.56 vs. 91.42) but similar RMAE and PSNR values (0.29 vs. 0.27; 31.35 vs. 29.87) (all p < 0.001). Both readers gave S-BSIs significantly higher image quality scores than D-BSI (p < 0.001). The mean DAP in software-related images (0.98 dGy·cm2) was significantly lower than that in the DES-related images (1.48 dGy·cm2) (p < 0.001). CONCLUSION: Bone suppression software significantly improved the image quality of bone suppression images with a relatively lower radiation dose, compared with dual-energy subtraction technique. KEY POINTS: • Bone suppression software preserves structure similarity of soft tissues better than dual-energy subtraction technique in bone suppression images. • Bone suppression software achieves superior image quality for lung lesions than dual-energy subtraction technique in bone suppression images. • Bone suppression software can decrease the radiation dose over the hardware-based image processing technique.

A vascular subtraction method for improving the variability of evoked tympanic membrane displacement measurements.

OBJECTIVE: Evoked tympanic membrane displacement (TMD) measurements show a correlation with intracranial pressure (ICP). Attempts to use these measurements for non-invasive monitoring of ICP in patients have been limited by high measurement variability. Pulsing of the tympanic membrane at the cardiac frequency has been shown to be a significant source of the variability. In this study we describe a post processing method to remove the cardiac pulse waveform and assess the impact of this on the measurement and its repeatability. APPROACH: Three-hundred and sixteen healthy volunteers were recruited for evoked TMD measurements. The measurements were quantified by V m, defined as the mean displacement between the point of maximum inward displacement and the end of the stimulus. A sample of spontaneously pulsing TMDs was measured immediately before the evoked measurements. Simultaneous recording of the ECG allowed a heartbeat template to be extracted from the spontaneous data and subtracted from the evoked data. Intra-subject repeatability of V m was assessed from 20 repeats of the evoked measurement. Results with and without subtraction of the heartbeat template were compared. The difference was tested for significance using the Wilcoxon sign rank test. MAIN RESULTS: In left and right ears, both sitting and supine, application of the pulse correction significantly reduced the intra-subject variability of V m (p value range 4.0 × 10-27 to 2.0 × 10-31). The average improvement was from 98 ± 6 nl to 56 ± 4 nl. SIGNIFICANCE: The pulse subtraction technique substantially improves the repeatability of evoked TMD measurements. This justifies further investigations to assess the use of TMD measurements in clinical applications where non-invasive tracking of changes in ICP would be useful.

Brain ultrashort T2 component imaging using a short TR adiabatic inversion recovery prepared dual-echo ultrashort TE sequence with complex echo subtraction (STAIR-dUTE-ES).

Long T2 water contamination is a major challenge with direct in vivo UTE imaging of ultrashort T2 components in the brain since water contributes most of the signal detected from white and gray matter. The Short TR Adiabatic Inversion Recovery prepared Ultrashort TE (STAIR-UTE) sequence can significantly suppress water signals and simultaneously image ultrashort T2 components. However, the TR used may not be sufficiently short to allow the STAIR preparation to completely suppress all the water signals in the brain due to specific absorption rate (SAR) limitations on clinical MR scanners. In this study, we describe a STAIR prepared dual-echo UTE sequence with complex Echo Subtraction (STAIR-dUTE-ES) which improves water suppression for selective ultrashort T2 imaging compared with that achieved with the STAIR-UTE sequence. Numerical simulations showed that the STAIR-dUTE-ES technique can effectively suppress water signals and allow accurate quantification of ultrashort T2 protons. Volunteer and Multiple Sclerosis (MS) patient studies demonstrated the feasibility of the STAIR-dUTE-ES technique for selective imaging and quantification of ultrashort T2 components in vivo. A significantly lower mean UltraShort T2 Proton Fraction (USPF) was found in lesions in MS patients (5.7 ± 0.7%) compared with that in normal white matter of healthy volunteers (8.9 ± 0.6%). The STAIR-dUTE-ES sequence provides robust water suppression for volumetric imaging and quantitation of ultrashort T2 component. The reduced USPF in MS lesions shows the clinical potential of the sequence for diagnosis and monitoring treatment in MS.

The Utility of the Energy Subtraction Method for Thoracic Spine Radiography in Clinical Practice: An Analysis of 25 Patients With Multiple Myeloma.

Interpretation of thoracic spine radiographs is difficult because they cannot clearly depict the vertebrae due to overlap with soft tissues. This study aimed to evaluate whether thoracic spine radiographs obtained using the energy subtraction method could improve the accuracy of a diagnosis of thoracic osteolytic lesions. The authors analyzed 300 thoracic vertebrae from 25 patients with multiple myeloma who underwent thoracic spine radiography. All patients underwent thoracic spine radiography with 2 views. Two sets of images were prepared: computed radiography images (CR images) acquired using conventional processing parameters; and processed images for specifically visualizing bone, using the energy subtraction method (ES images). The CR images (CR group) and paired CR and ES images (CR+ES group) were interpreted in parallel by 5 orthopedic surgeons. The presence of osteolytic lesions was evaluated for each of the 12 thoracic vertebrae, and the sensitivity and specificity of the method were compared with computed tomography (CT), which is considered the gold standard. Subgroup analysis was also performed based on location. Osteolytic lesions were found on CT in 28 (9.3%) vertebrae of 12 patients. The overall sensitivities and specificities of the CR and CR+ES groups were 17.2% and 54.3%, respectively, and 95.6% and 98.0%, respectively, with statistically significant differences. Subgroup analysis showed particular improvement in the sensitivity for the CR+ES group in the middle thoracic spine compared with that at other locations. Thoracic spine radiographs generated using this method may improve the accuracy of diagnosis of thoracic osteolytic lesions. [Orthopedics. 2021;44(1):e31-e35.].

Liver perfusion MRI in a rodent model of cirrhosis: Agreement with bulk-flow phase-contrast MRI and noninvasive evaluation of inflammation in chronic liver disease using flow-sensitive alternating inversion recovery arterial spin labelling and tissue T1.

Noninvasive measurements of liver perfusion and fibrosis in cirrhotic small animals can help develop treatments for haemodynamic complications of liver disease. Here, we measure liver perfusion in cirrhotic rodents using flow-sensitive alternating inversion recovery arterial spin labelling (FAIR ASL), evaluating agreement with previously validated caval subtraction phase-contrast magnetic resonance imaging (PCMRI) total liver blood flow (TLBF). Baseline differences in cirrhotic rodents and the haemodynamic effects of acute inflammation were investigated using FAIR ASL and tissue T1. Sprague-Dawley rats (nine bile duct ligated [BDL] and ten sham surgery controls) underwent baseline hepatic FAIR ASL with T1 measurement and caval subtraction PCMRI (with two-dimensional infra-/supra-hepatic inferior vena caval studies), induction of inflammation with intravenous lipopolysaccharide (LPS) and repeat liver FAIR ASL with T1 measurement after ~90 minutes. The mean difference between FAIR ASL hepatic perfusion and caval subtraction PCMRI TLBF was -51 ± 30 ml/min/100 g (Bland-Altman 95% limits-of-agreement ±258 ml/min/100 g). The FAIR ASL coefficient of variation was smaller than for caval subtraction PCMRI (29.3% vs 50.1%; P = .03). At baseline, FAIR ASL liver perfusion was lower in BDL rats (199 ± 32 ml/min/100 g vs sham 316 ± 24 ml/min/100 g; P = .01) but liver T1 was higher (BDL 1533 ± 50 vs sham 1256 ± 18 ms; P = .0004). Post-LPS FAIR ASL liver perfusion response differences were observed between sham/BDL rats (P = .02), approaching significance in sham (+78 ± 33 ml/min/100 g; P = .06) but not BDL rats (-49 ± 40 ml/min/100 g; P = .47). Post-LPS differences in liver tissue T1 were nonsignificant (P = .35). FAIR ASL hepatic perfusion and caval subtraction PCMRI TLBF agreement was modest, with significant baseline FAIR ASL liver perfusion and tissue T1 differences in rodents with advanced cirrhosis compared with controls. Following inflammatory stress, differences in hepatic perfusion response were detected between cirrhotic/control animals, but liver T1 was unaffected. Findings underline the potential of FAIR ASL in the assessment of vasoactive treatments for patients with chronic liver disease and inflammation.