Mapping of magnetic resonance imaging's transverse relaxation time at low signal-to-noise ratio using Bloch simulations and principal component analysis image denoising.

High-resolution mapping of magnetic resonance imaging (MRI)'s transverse relaxation time (T2 ) can benefit many clinical applications by offering improved anatomic details, enhancing the ability to probe tissues' microarchitecture, and facilitating the identification of early pathology. Increasing spatial resolutions, however, decreases data's signal-to-noise ratio (SNR), particularly at clinical scan times. This impairs imaging quality, and the accuracy of subsequent radiological interpretation. Recently, principal component analysis (PCA) was employed for denoising diffusion-weighted MR images and was shown to be effective for improving parameter estimation in multiexponential relaxometry. This study combines the Marchenko-Pastur PCA (MP-PCA) signal model with the echo modulation curve (EMC) algorithm for denoising multiecho spin-echo (MESE) MRI data and improving the precision of EMC-generated single T2 relaxation maps. The denoising technique was validated on simulations, phantom scans, and in vivo brain and knee data. MESE scans were performed on a 3-T Siemens scanner. The acquired images were denoised using the MP-PCA algorithm and were then provided as input for the EMC T2 -fitting algorithm. Quantitative analysis of the denoising quality included comparing the standard deviation and coefficient of variation of T2 values, along with gold standard SNR estimation of the phantom scans. The presented denoising technique shows an increase in T2 maps' precision and SNR, while successfully preserving the morphological features of the tissue. Employing MP-PCA denoising as a preprocessing step decreases the noise-related variability of T2 maps produced by the EMC algorithm and thus increases their precision. The proposed method can be useful for a wide range of clinical applications by facilitating earlier detection of pathologies and improving the accuracy of patients' follow-up.

Gas forming infection of the spine: a systematic and narrative review.

PURPOSE: Gas forming infection (GFI) of the spine is a rapidly progressive and potentially life-threatening infection. It can be a consequence of aetiologies such as Emphysematous Osteomyelitis (EOM), Necrotizing Fasciitis (NF), and Gas-containing Spinal Epidural Abscess (Gas-containing SEA). This review aims to summarize the characteristics of these subtypes of GFI, describing their aetiology, diagnosis, management, and prognosis. METHODS: PubMed, Embase, Web of Science and the Cochrane Database were systematically searched for studies reporting on gas forming infections of the spine or a known subtype. Cases of post-operative and iatrogenic spinal infection were excluded. RESULTS: The literature review revealed 35 studies reporting on 28 cases of EOM, three cases of NF involving the spine and seven cases of Gas-containing SEA. Thirty studies reporting on 32 cases of GFI were available for data analysis. The mean age of the patients was 60.9 years and a concomitant diagnosis of diabetes mellitus was reported in 57.5% of patients infected. Fever and back pain were the most common presenting symptoms. The lumbar spine was the most commonly affected spinal segment. Mortality from EOM, NF and Gas-containing SEA were 34.8, 100 and 28.5%, respectively. DISCUSSION: Gas forming infection of the spine is a rare condition with an extremely poor prognosis, requiring early and aggressive surgical treatment. A multi-disciplinary approach is necessary for management. Nonetheless, even in cases of early recognition and optimal management, multisystem failure may still occur, and mortality rates remain high due to the aggressive nature of this infection. LEVEL OF EVIDENCE: Systematic review of level IV studies.

Femur fractures and hemorrhagic shock: Implications for point of injury treatment.

BACKGROUND: Femur shaft fractures (FSF) are perceived as potentially life-threatening injuries due to significant blood loss. However, these injuries are rarely the sole cause of hemorrhagic shock. Clinical practice guidelines for the prehospital management of FSF are inconsistent, especially concerning the use and timing of traction splinting which is postulated to reduce bleeding. We sought to understand the association between FSF and shock, and identify risk factors for shock among casualties with FSF. METHODS: This is a retrospective analysis of trauma casualties treated by Israeli Defense Forces (IDF) medical teams between the years 2000-2020 and suffering from isolated FSF. Prehospital data from the IDF-Medical Corps Trauma Registry was merged with hospitalization data from the Israeli National Trauma Registry. Isolated FSF was analyzed by excluding casualties with an Injury Severity Score ≥ 16 and an Abbreviated Injury Scale ≥ 3 in other anatomical regions. Shock was defined as systolic blood pressure ≤ 90 mmHg and/or heart rate ≥ 130 beats per minute. A case series review was performed for casualties in shock with isolated FSF injuries. Multivariable logistic regression was performed to assess for injury characteristics associated with shock. RESULTS: During the study period, we identified 213 patients with FSF (4.9%) of which 129 were isolated injuries. Overall, 9.9% and 26.3% of casualties had concurrent thoracic and abdominal injuries, respectively. Most FSF were due to motor vehicle accidents (60.1%) and shock was present in 17.1%. In isolated FSF patients, gunshot and explosive injury mechanisms were prevalent (65.0%) with severe shock being present in 8.5%. Open fractures were present in 72.7% of isolated FSF patients in shock. Open FSF injuries were characterized by prehospital bleeding which was difficult to control. In a multivariable logistic regression model, severe concomitant injuries were associated with increased odds of shock. CONCLUSIONS: Shock rarely presents when FSF is the primary injury. Such casualties predominantly suffer from open FSF which may present as difficult to control thigh bleeding. Our findings do not support urgent prehospital leg traction splinting which may result in delayed evacuation to definitive care. Casualties with shock and FSF should be investigated for other sources of bleeding. Leg traction splinting should be reserved for suspected FSF injuries with shock or persistent thigh bleeding.

T2 Mapping Values in Postmeniscectomy Knee Articular Cartilage after Running: Early Signs of Osteoarthritis?

Loading on the joints during running may have a deleterious effect on post-partial meniscectomy knee cartilage, leading to osteoarthritis. Utilizing T2-mapping measurements before and after running may enable the observation of changes in the articular cartilage of the postmeniscectomy knees compared with healthy knees. After medial partial meniscectomy, 12 volunteers underwent magnetic resonance imaging (MRI) of the both knees, before and immediately after 30 minutes of running. Quantitative assessment of articular cartilage was performed using a T2-mapping technique. In the medial compartment of the operated knees, significantly lower T2 values were found in anterior tibial plateau (pre- vs. postrun: 33.85 vs. 30.45 ms; p = 0.003) and central tibial plateau (33.33 vs. 30.63 ms; p = 0.007). Similar differences were found in lateral regions of central femur (post- vs. prerun: 35.86 vs. 40.35 ms; p = 0.015), posterior femur (34.89 vs. 37.73 ms; p = 0.001), and anterior tibia (24.66 vs. 28.70 ms, p = 0.0004). In lateral compartment, postrun values were significantly lower in operated compared with healthy knees, in central femur (34.89 vs. 37.59 ms; p = 0.043), posterior femoral (36.88 vs. 39.36 ms; p = 0.017), anterior tibia (24.66 vs. 30.20 ms; p = 0.009), and posterior tibia (28.84 vs. 33.17 ms; p = 0.006). No statistical difference was found while comparing postrun to prerun healthy knees. Lower T2 values were found in operated knees after 30 minutes of running. These changes were seen in medial and lateral compartments. We suspect that running may subject the articular cartilage to excessive loads in the post-partial meniscectomy knee, loads that in healthy knee do not cause any changes.

Post-Run T2 Mapping Changes in Knees of Adolescent Basketball Players.

OBJECTIVE: While articular cartilage defects are common incidental findings among adult athletes, the effect of running on the cartilage of adolescent athletes have rarely been assessed. This study aims to assess the variations in the articular cartilage of the knees in healthy adolescent basketball players using quantitative T2 MRI (magnetic resonance imaging). DESIGN: Fifteen adolescent basketball players were recruited (13.8 ± 0.5 years old). Girls were excluded to avoid potential gender-related confounding effects. Players underwent a pre-run MRI scan of both knees. All participants performed a 30-minute run on a treadmill. Within 15 minutes after completion of their run, players underwent a second, post-run MRI scan. Quantitative T2 maps were generated using the echo modulation curve (EMC) algorithm. Pre-run scans and post-run scans were compared using paired t test. RESULTS: Participants finished their 30-minute run with a mean running distance of 5.77 ± 0.42 km. Pre-run scans analysis found statistically significant (P < 0.05) changes in 3 regions of the knee lateral compartment representing the cartilaginous tissue. No differences were found in the knee medial compartment. Post-run analysis showed lower T2 values in the medial compartment compared to the pre-run scans in several weight-bearing regions: femoral condyle central (pre/post mean values of 33.9/32.2 ms, P = 0.020); femoral condyle posterior (38.1/36.8 ms, P = 0.038); and tibial plateau posterior (34.1/31.0 ms, P < 0.001). The lateral regions did not show any significant changes. CONCLUSIONS: Running leads to microstructural changes in the articular cartilage in several weight-bearing areas of the medial compartment, both in the femoral and the tibial cartilage.

Delayed Penetration of the Thoracic Aorta by Pedicle Screws: A Case Report of Screws Left As-Is.

STUDY DESIGN: A case report. OBJECTIVE: Presentation of a patient diagnosed with perforation of the aorta by pedicle screws at levels T6 and T9 2 years after spinal fusion, who was advised no intervention. Review of other reported cases that did not undergo excision of the penetrating screws. SUMMARY OF BACKGROUND DATA: More than 30 cases of aortic penetration by pedicle screws were described. Gradual penetration of the screws into the aorta rarely causes symptoms other than backache. However, only two cases were treated conservatively. METHODS: A 65-year-old female patient underwent spinal decompression and T5-T10 posterior fusion following a spinal abscess. Two years and 8 months postoperatively, she underwent a computed tomography scan for suspicion of spinal hardware infection, which showed T6 and T10 screws penetrating the thoracic aorta. RESULTS: Due to high morbidity, the patient was not offered an operation for screw excision. CONCLUSION: This case report adds to the only two previous reports of patients who did not undergo revision of pedicle screws penetrating thoracic aorta. LEVEL OF EVIDENCE: 5.