Long, Zaiyang

Abstract Objective . The use of Feraheme (ferumoxytol) as a contrast agent in MR-guided focused ultrasound (MRgFUS) tumor ablations could enhance treatment safety and efficacy by improving vascular visualization through strong T1 and T2 shortening effects. However, Feraheme impact on MR thermometry and tissue heating is unclear. This study evaluates the feasibility of incorporating Feraheme into MRgFUS by assessing its impact on MR imaging contrast, MR thermometry, and thermal response in tissue-mimicking phantoms. Approach . Tissue-mimicking phantoms with 0 (baseline), 0.25, and 0.5 mM Feraheme concentrations were prepared using a validated recipe. Acoustic attenuation was measured with a commercial diagnostic ultrasound scanner. MR imaging at 1.5 T was performed to assess gradient-recalled-echo (GRE)-based thermometry signal-to-noise-ratio (SNR), relaxation rates, and relaxivities. MRgFUS system integrated with 1.5 T MRI was used to perform multiple sonications in the phantoms. Temperature elevations and focal heating areas were quantified from proton resonance frequency (PRF) shift thermometry. Experiments were repeated three times over the period of eight-weeks. Separately, temperature-dependent nuclear magnetic resonance (NMR) spectroscopy was performed at 3.0 T in saline-diluted Feraheme phantoms (0, 0.25, 0.5, and 1.0 mM) to assess the influence of Feraheme concentration on PRF coefficients used in MR thermometry. Main results . Phantoms showed nuclear relaxation times ( T 1: 1178.1 ± 77.8, T 2: 103.21 ± 2.45 ms) and attenuation coefficients (0.34–0.36 dB cm −1 MHz −1 ) within expected biological tissue ranges. Relaxivities demonstrated a strong linear dependence on Feraheme concentration ( r 1: 17.5 ± 0.2, r 2: 209.2 ± 2.6 s −1 mM −1 ). Relative to baseline (0 mM) phantom, the SNR of GRE-based thermometry increased by 12.6% at 0.25 mM and decreased by 27.1% at 0.5 mM. Sonications in Feraheme-containing phantoms resulted in statistically higher temperature elevations ( p < 0.001 ) although no statistically significant difference was observed between 0.25 and 0.5 mM. All NMR measurements demonstrated stable, linear PRF temperature dependence ( R 2 = 0.996–0.999), with PRF coefficients (between −0.0074 and −0.0082 ppm °C −1 ). The resulting thermometry bias was small and predictable (+0.67 and +1.73 per 20 °C at 3.0 T for 0.25 and 0.5 mM). Significance . These findings demonstrate that MR thermometry remains feasible at moderate Feraheme concentrations and support its potential use to enhance visualization of critical vasculature near targeted tissues during MRgFUS.

Elevated intratumoral interstitial fluid pressure (IFP) can negatively impact the efficacy of neoadjuvant chemotherapy (NAC) of breast cancer. This study aims to predict breast cancer pathological complete response (pCR) to NAC based on IFP measures by 3-D subharmonic-aided pressure estimation (SHAPE). SHAPE uses the inverse linear relationship between hydrostatic pressure and subharmonic signal magnitude from intravascular ultrasound contrast agents. Thirty-eight breast cancer patients undergoing NAC from three clinical sites were enrolled for this study. SHAPE data were collected for each subject at 0%, 10%, and 30% of NAC completion using a Logiq E9 system (GE HeathCare) equipped with an RSP6-16D probe. The contrast agent used was Definity (Lantheus Medical Imaging). The subharmonic signal gradients between tumor and adjacent normal tissue were calculated and compared with patient pathological response outcome using t-test and receiver operating characteristic (ROC) curve analysis. Pressure gradients between pCR (15 patients) and non-pCR (23 patients) groups were significantly different at 0 (p = 0.02), 10 (p = 0.03), and 30% (p = 0.0003) completion of NAC. Area under the curve values of 0.69, 0.77, and 0.86 were achieved at 0%, 10%, and 30% of NAC completion, respectively. Overall, SHAPE pressure gradients may aid prediction of NAC pathological response in breast cancer patients.

Abstract Background The IEC exposure index (EI), deviation index (DI), and target exposure index (EI T ), represent critical standardized metrics for the evaluation of exposure and quality in radiographic imaging. Purpose This work develops and validates a systematic procedure to estimate the EI T for eight of the most common radiography imaging protocols utilizing automatic exposure control (AEC) from measurements acquired under reference conditions. Methods A model was developed to define the relationship between a systems AEC logic, and an estimation of the EI under flat‐field conditions (EIFFC). Separately, clinical data and acquisition protocol information for resultant EI during patient studies were also collected for the eight protocols studied: Chest posteroanterior (PA), Chest lateral, Abdomen anteroposterior (AP), Pelvis AP, L‐Spine AP, C‐Spine AP, T‐Spine AP, and Ribs AP. Data were collected from 41 x‐ray units spanning seven institutions. For each protocol on each unit the EIFFC was computed based on the acquisition protocol, as well as median EI from clinical exams to produce a scaling factor (SF). Kruskal–Wallis statistical tests were used to compare SF's between vendors and AEC cell configurations. Results SFs for eight radiographic imaging protocols have been produced per vendor and per AEC cell selection. A workflow has been established for end‐users to follow to apply these SFs to flat‐field measurements taken at their own locations to establish local EI T . Conclusions The study results show that in seven of the eight imaging protocols, the SFs for most units included in the study report SFs within 1 DI (± 25%) of their respective final vendor reported SF (218/228). The ribs protocol is the exception to this finding (n = 26). SFs have high utility for establishing EI T values on individual x‐ray units and normalizing EI value distributions for quality assurance purposes.

Objectives Uniformity artifacts caused by defective transducer elements or scanner malfunctions degrade diagnostic image quality. Traditional quality control (QC) methods, such as phantom testing and visual or quantitative image analysis, can be labor‐intensive and limited in test frequency. This study aims to develop a deep learning framework to detect uniformity artifacts and complement traditional QC. Methods Clinical median images were generated by aggregating co‐registered grayscale ultrasound images acquired by each transducer and computing median intensity values across the image stack. A pretrained ResNet‐18 model was fine‐tuned on a dataset consisting of clinical median images from linear and curvilinear transducers. The dataset was divided into training, validation, and testing subsets, ensuring no overlap between training and test transducers. To assess generalizability, the model was also evaluated on an independent test set of 396 phantom‐validated images from linear and curvilinear transducers. Results The model achieved 100% accuracy on the first dataset's test set. On the independent test set, it attained 87.4% accuracy with high sensitivity (0.84) and specificity (0.88), demonstrating robust generalization. Occlusion sensitivity maps confirmed the model's attention to uniformity artifact regions. Conclusion The deep learning framework using clinical median images demonstrated robust performance across several linear and curvilinear transducer models. It could be integrated into the clinical QC workflow by automating artifact detection in an effective and timely manner. In our practice, it can flag median images classified as artifact‐present, reducing human review time by approximately 80% while preserving detection accuracy.

This slide presentation uses real-world examples from diverse modern systems to categorize digital radiographic artifacts by likely cause and outlines investigation and mitigation strategies to improve troubleshooting, artifact prevention, and patient care.

Objectives Periodic quality control (QC) testing of ultrasound (US) imaging systems is essential to ensure and maintain image quality and safety. The study aims to analyze QC findings from medical physics annual surveys of modern clinical US systems in a multi‐institutional survey. Methods QC results from annual surveys between 2018 and 2021 were retrospectively collected from 12 medical physicists from 11 institutions or consulting companies (hereafter referred to as sites). QC tests were classified as scanner‐ and transducer‐related tests, where scanner‐related tests also included evaluation of diagnostic workstation display monitors and routine QC programs if applicable. Test methodology and pass/fail criteria were established by each site. QC findings were defined as results requiring follow‐up action by service engineers, vendors, or other personnel. The percentage of annual findings was calculated for each site and averaged across the years of data contributed. Furthermore, findings across all sites were aggregated for an overall analysis. Results QC data from a total of 1069 scanner tests and 4542 transducer tests were collected. The average annual percentage of scanner‐related findings varied from 0 to 40.8% among all sites (first quartile 8.7%, median 18.2%, and third quartile 34.1%), while that of transducer‐related findings ranged between 0.5% and 19.9% (first quartile 3.9%, median 7.2%, and third quartile 14.5%). For scanner‐related tests, the top 3 categories of findings were associated with physical and mechanical integrity (171 findings, 74.7%), quantitative testing of the scanner display monitor (40 findings, 17.5%), and scanner port creating artifacts (10 findings, 4.4%). The top 3 findings for transducers related to uniformity and artifact (227 findings, 79.9%), physical and mechanical integrity (44 findings, 15.5%), and sensitivity in fundamental mode (9 findings, 3.2%). Conclusions Medical physics annual surveys revealed considerable actionable findings of modern US systems, which inform the status of current US QC practices in the United States and may guide future standardization and recommendation of QC tests.

Abstract Osteoarthritis of the knee is a common cause of pain, functional disability, and reduced quality of life in the elderly. Despite its prevalence, there are limited currently available noninvasive treatment options. MRI-guided focused ultrasound (MRgFUS) is a noninvasive thermal ablation method which is used in a spectrum of musculoskeletal conditions. It is FDA approved for the treatment of painful bone metastases and osteoid osteoma, and has been considered for the treatment of other painful conditions such as osteoarthritis. The purpose of this case report is to describe the use of MRgFUS for the treatment of osteoarthritic knee pain in a 72-year-old male. The patient led an active lifestyle, however suffered significant limitations due to lateral knee pain with jogging and walking down the stairs. MRgFUS ablation treatment was performed to the lateral knee, targeting the periosteum in the patients’ area of pain. Following treatment, he experienced considerable reduction in his activity limiting symptoms with a duration of at least 6 months. Similar pain reduction was observed in two small series of MRgFUS treatment of knee pain from Japan. It is important for radiologists to be aware of MRgFUS as an innovative ablation modality. MRgFUS appears promising as a safe, non-invasive treatment option for temporary relief of knee pain. This may be particularly valuable for patients who are unwilling or unable to undergo total knee arthroplasty.

Abstract Objective To evaluate the safety and tolerability of MRI-guided focused ultrasound (MRgFUS) for the treatment of facet joint–mediated pain in human subjects for whom conventional treatment had failed. Secondarily, to evaluate effectiveness of the procedure. Methods Consecutive patients who underwent MRgFUS at our institution were retrospectively identified. Chart review was performed to obtain relevant clinical and technical data. All patients had chronic low back pain and positive comparative medial branch blocks. Results Twenty-six MRgFUS treatments in 20 patients were included. Mean sonication energy was 1436.6 Joules. The procedure was technically successful in all patients. Of the treated patients, 29.6% experienced short-term worsening of low back pain immediately after the procedure, all by 1–4 points on a 0–10 scale. One patient (3.8%) reported temporary worsening of preexisting radicular symptoms after the procedure. Of 21 treatments with clinical follow-up of at least 3 months available, 12 (57.1%) had &gt;3 months’ pain relief, 2 (10%) had &lt;3 months’ benefit, 6 (30%) reported no benefit, and 1 (5%) patient was lost to follow-up. In patients who reported at least some benefit with prior conventional radiofrequency ablation, 8/10 (80%) benefited from the MRgFUS procedure. Conclusion The present study demonstrates that MRgFUS ablation of the lumbar facet joints is a safe and tolerable procedure in human subjects and could provide another option for patients for whom radiofrequency ablation had failed. More than half of all patients received significant durable pain relief, which jumped to 80% for patients who had experienced at least some benefit from prior radiofrequency ablations.

AbstractThe well‐referenced structural shielding design NCRP Report No. 147 uses workload information based on self‐reported film‐screen data from the AAPM Task Group 9 survey. The aim of this study was to assess the clinical workload distributions of modern digital radiography (DR) systems in general hospital and pediatric‐only practices. A retrospective analysis of DR imaging data on four radiographic systems in a hospital practice and two radiographic systems in a pediatric practice, through a custom clinical DICOM header analytics program. A total of 203, 294 exposures from the general hospital practice and 25,415 from the pediatric practice from 2019 and 2021 were included. Values for kVp, mAs, and detector type (wall bucky, table bucky, or free detector) were extracted. For each exam, mAs was accumulated in a kVp histogram with bins 5 kVp wide and further parsed by detector type. Total workload was calculated by summing all exposures, then normalized by the number of patients. The median (25th and 75th percentile) workload in the hospital practice was 0.43 (0.22, 1.13) mA‐min per patient, while the average was 1.36 ± 3.08. Pediatric data yielded a median (25th and 75th percentile) of 0.10 (0.05, 0.23) and an average of 0.29 ± 0.69 mA‐min per patient. Mean number of patients per week was 230 adult and 57 pediatric. Hospital workload data is approximately 44% less than the NCRP Report No. 147 value.