Rigid motion-resolved B 1 + prediction using deep learning for real-time parallel-transmission pulse design

Purpose

Tailored parallel-transmit (pTx) pulses produce uniform excitation profiles at 7 T, but are sensitive to head motion. A potential solution is real-time pulse redesign. A deep learning framework is proposed to estimate pTx B₁⁺ distributions following within-slice motion, which can then be used for tailored pTx pulse redesign.

Methods

Using simulated data, conditional generative adversarial networks were trained to predict B₁⁺ distributions in the head following a displacement. Predictions were made for two virtual body models that were not included in training. Predicted maps were compared with groundtruth (simulated, following motion) B₁⁺ maps. Tailored pTx pulses were designed using B₁⁺ maps at the original position (simulated, no motion) and evaluated using simulated B₁⁺ maps at displaced position (ground-truth maps) to quantify motion-related excitation error. A second pulse was designed using predicted maps (also evaluated on ground-truth maps) to investigate improvement offered by the proposed method.

Results

Predicted B₁⁺ maps corresponded well with ground-truth maps. Error in predicted maps was lower than motion-related error in 99% and 67% of magnitude and phase evaluations, respectively. Worst-case flip-angle normalized RMS error due to motion (76% of target flip angle) was reduced by 59% when pulses were redesigned using predicted maps.

Conclusion

We propose a framework for predicting B₁⁺ maps online with deep neural networks. Predicted maps can then be used for real-time tailored pulse redesign, helping to overcome head motion–related error in pTx.

[Diagnostics of diseases of the optic nerve head in times of artificial intelligence and big data]

Hintergrund

Der Einsatz von künstlicher Intelligenz (KI) ist unter anderem in der automatischen Bildsegmentierung, -analyse und Klassifikation interessant und bereits für verschiedene Bereiche der Augenheilkunde beschrieben.

Fragestellung

Diese Arbeit soll einen Überblick über aktuelle Ansätze und Fortschritte bei der Anwendung von Big Data und KI bei verschiedenen Erkrankungen des Sehnervenkopfes geben.

Material und Methode

Es wurde eine PubMed-Recherche durchgeführt. Gesucht wurde nach Studien, die klinische Fragestellungen mithilfe von Big-Data-Ansätzen beantworteten oder klassische Methoden des maschinellen Lernens bei der Analyse von multimodaler Bildgebung des Sehnervenkopfes verwendeten.

Ergebnisse

Big Data kann bei Volkskrankheiten wie dem Glaukom helfen, klinische Fragestellungen zu beantworten. KI findet sowohl bei der Segmentierung von multimodaler Bildgebung des Sehnervenkopfes als auch bei der Klassifikation von Erkrankungen wie dem Glaukom oder der Stauungspapille auf diesen Bilddaten Anwendung.

Schlussfolgerung

Mithilfe von Big Data und KI können Zusammenhänge besser erkannt und die Diagnostik und Verlaufsbeurteilung von Erkrankungen des Sehnervenkopfes erleichtert oder automatisiert werden. Eine Voraussetzung für die klinische Anwendung ist in Europa die CE-Kennzeichnung als ein Medizinprodukt und in den USA die Zulassung durch die Food and Drug Administration.

["Flipped classroom"-A future concept for student teaching in ophthalmology?]

BACKGROUND

"Flipped classroom" is a didactic teaching concept in which learning contents are prepared by self-study with arranged tools before the classroom session. The concept offers the advantage of a uniform knowledge base for the students at the beginning of the course and also the advantage of a greater theoretical knowledge, which creates more opportunities for practical exercises, application and consolidation in the subsequent joint teaching units. This study describes the establishment and application of such a model in student teaching in ophthalmology and analyzes the student's evaluation.

METHODOLOGY

For the winter term 2018/2019, a new teaching module was designed and established in a cooperation between the department of ophthalmology and the Institute for Education and Study Affairs (IfAS) at the medical faculty of the University of Münster. A uniform training of the lecturers as well as a preparation of the students for the restructuring took place. After the course the evaluation of the students was recorded and evaluated using a standardized online evaluation.

RESULTS

Between the winter semester 2018/2019 and the winter semester 2019/2020, an average of 112.3 ± 4.0 students were taught with the "flipped classroom" model. Of these 93.7% were able to give an assessment. In the previous semesters with the old teaching concept (summer semester 2015 to summer semester 2018), the average number of students was 115.4 ± 15.1 with an assessment rate of 93.3%. The new teaching concept achieved on average a better assessment than the old module.

CONCLUSION

With a "flipped classroom" space and flexibility can be generated for a more individual course preparation and at the same time a higher practical part. Further studies are needed to analyze whether this also enables a sustainable transfer of knowledge.

Impact of integrated multiple image averaging on OCT angiography image quality and quantitative parameters

PURPOSE

Multiple image averaging (MIA) is a new approach to improve OCT angiography (OCTA) imaging. The aim of this work was to analyze the impact of MIA on image quality and quantitative OCTA parameters.

METHODS

Twenty eyes from 20 healthy volunteers (55.65 ± 14.8 years) were prospectively enrolled. Imaging was performed using two commercially available OCTA devices (Canon OCT HS-100, Optovue AngioVue) using a uniform imaging protocol. Each participant had two single scans of the macula (3 × 3mm, Canon and Optovue) as well as five continuous single scan imaging procedures (3 × 3mm each) using the Canon device. Three out of five of these images with highest quality were manually chosen and then automatically processed by the Canon device using MIA. The superficial retinal plexus of the single scans and of MIA images was analyzed with regard to the device' own image quality scores (IQS), peak signal-to-noise ratio (PSNR), the size of the foveolar avascular zone (FAZ), and vessel density (VD). Image acquisition times were recorded. Parameters were compared between the devices and the different imaging protocols.

RESULTS

Average acquisition time was significantly higher for the MIA compared with the single measurements (29.09 ± 10.19 seconds (s) (MIA) vs. 5.56 ± 2.17 s (Canon single scan) vs. 20.28 ± 6.81 s (Optovue) (p < 0.001)). IQS showed no significant differences between the devices and between the recording protocols. PSNR was 12.38 ± 0.20 (Canon single scan), 13.01 ± 0.36 (Canon MIA), and 14.34 ± 0.60 (Optovue) (p < 0.001 between the groups). Mean FAZ area in Canon single scans was 0.29 ± 0.06 mm², 0.27 ± 0.07 mm² using MIA, and 0.27 ± 0.08 mm² using the Optovue device. There was no significant difference between mean FAZ measurements before and after averaging (Canon single scan vs. MIA, p = 0.168). VD of the parafoveal area using MIA was significantly lower compared with both single scans (p < 0.001).

CONCLUSIONS

MIA can improve PSNR, but it also reduces imaging speed and significantly affects VD measurements. Therefore, when comparing OCTA data, the use of uniform imaging protocols is required.

[Spontaneous intraocular hemorrhage under oral anticoagulation : Apixaban in comparison to phenprocoumon]

BACKGROUND

To determine and compare the frequency of intraocular hemorrhage in patients who underwent oral anticoagulation with apixaban or phenprocoumon.

METHODS

A retrospective analysis of patients under oral anticoagulant medication (apixaban or phenprocoumon) seen between January 2015 and June 2015 at the department of ophthalmology, University of Muenster Medical Center was performed. Vitreal or retinal hemorrhage in addition to clinical information including age, gender, best corrected visual acuity, concomitant diseases, concomitant medication and therapy were obtained. Bleeding frequency in both groups was compared using Fisher's exact test.

RESULTS

A total of 172 patients were included with a mean age = 74.0 ± 10.6 years, 57.0% (n = 98) male and 43.0% (n = 74) female. In the phenprocoumon group 147 patients (3.4%, n = 5) developed a retinal or vitreal hemorrhage. In the apxiban group 25 patients (36%, n = 9) developed a retinal or vitreal hemorrhage. There was a significant correlation between the group and bleeding risk (p < 0.001).

CONCLUSION

There was a significant correlation between medication (apixaban vs. phenprocoumon) and bleeding risk in this study population. Further studies with more patients especially in patients with a high risk of hemorhage, age-related macular degeneration (AMD) and proliferative diabetic retinopathy are needed.

Inferior shoulder dislocation after shortening osteotomy of the humerus. A case report

We present a case of a post-surgical complete dislocation after excessive proximal humeral shortening osteotomy performed in a patient operated on for atrophic non-union of a proximal humeral fracture. This complication has not been previously reported.

The dislocation occurred due to extensive laxity of the soft tissue envelope, predominantly the deltoid muscle, as well as rotator cuff tear.

The reconstructive procedurę consisted of vertical duplication of the capsule, reinforcement of the repair with coracoacromial ligament, tenodesis of the long head of the biceps tendon to the conjoined tendon and distal transfer of the deltoid muscle. The repair was reinforced with transarticular Steinmann pins. 15 months after surgery, there is an inferior subdislocation present, with full reduction in active abduction. Patient is pain-free at rest, and pain grade 4 in VAS scale in activity with loading.

Impact of eye-tracking technology on OCT-angiography imaging quality in age-related macular degeneration

OBJECTIVE

To evaluate the impact of eye-tracking (ET) technology on optical coherence tomography angiography (OCT-A) image quality and manifestation of motion artifacts in patients with age-related macular degeneration (AMD).

METHODS

In a prospective trial, multimodal retinal imaging including OCT-A was performed in 30 patients (78.97 ± 9.7 years) affected by different stages of AMD. Central 3 × 3 mm² OCT-A imaging was performed four times consecutively in each patient, twice with active, and twice with inactive ET. Parameters for image evaluation were signal strength index (SSI), variability of foveal vessel density (VD), acquisition time, presence of motion artifacts caused by eye movement (blink lines, displacement) and by software correction of eye movement (quilting, stretch artifacts, vessel doubling). Images were evaluated by two independent readers with subsequent senior reader arbitration for presence of artifacts, and an OCT-A motion artifact score (MAS) was calculated.

RESULTS

Eight patients had early and eight patients had intermediate stages of AMD. Four patients had an atrophic late stage and ten patients an exudative stage of the disease. SSI was 53.55 with inactive and 57.18 with active ET (p = 0.0005). Coefficients of variability of VD between the first and second measurement were 8.9% with inactive and 5.7% with active ET. Mean image acquisition time was 15.97 s (active ET: 22.88 s, p < 0.001). Presence of motion artifacts was significantly higher with inactive ET (mean MAS 3.27 vs. 1.93; p < 0.0001). MAS correlated with AMD disease stage [p = 0.0031 (inactive ET) and p < 0.0001 (active ET)] and with SSI (p = 0.0072 and p = 0.0006).

CONCLUSIONS

In patients with AMD, active ET technology offers an improved image quality in OCT-A imaging regarding presence of motion artifacts at the expense of higher acquisition time.

Performance optimization of ERP-based BCIs using dynamic stopping

Brain-computer interfaces based on event-related potentials face a trade-off between the speed and accuracy of the system, as both depend on the number of iterations. Increasing the number of iterations leads to a higher accuracy but reduces the speed of the system. This trade-off is generally dealt with by finding a fixed number of iterations that give a good result on the calibration data. We show here that this method is sub optimal and increases the performance significantly in only one out of five datasets. Several alternative methods have been described in literature, and we test the generalization of four of them. One method, called rank diff, significantly increased the performance over all datasets. These findings are important, as they show that 1) one should be cautious when reporting the potential performance of a BCI based on post-hoc offline performance curves and 2) simple methods are available that do boost performance.

[Limb-sparing surgical treatment in osteosarcoma]

From 1998 we performed limb-sparing surgery in 6 patients with osteosarcoma. No evidence of disease or local recurrence was noted in any of the patients after a mean follow-up period of 13 months. Age at the time of operation ranged from 8 to 14 years. Wide resection margins were achieved in all patients. The results of functional evaluation according to Enneking were excellent in 5 cases and poor in one. Bony defects created by limb-sparing procedures may be reconstructed by many methods. In growing children, limb-sparing surgery needs special consideration to avoid later limb-length discrepancy and expandable prostheses have been used to anticipate this problem.

[Surgical resection of primary soft-tissue sarcoma of the extremities]

We evaluated 5 patients who had soft tissue sarcoma of the extremity treated by limb sparing surgery. All tumors were adjacent to bone, with no features of infiltration. According to the Surgical Staging System, all tumors were IIB. The mean follow-up was 13 months. To achieve wide resections of the tumors in such cases we recommend resections of the tumor with part of the bone, which is in direct contact with the tumor. Wide resection margins were achieved in all patients and none had local recurrence during the observation period.

[Acetabular roof remodeling after varus derotation osteotomy in congenital hip dysplasia]

The aim of this paper was to evaluate the acetabular roof remodelling process and changes of the Wiberg angle after proximal femur varus drotational osteotomy up to skeletal maturity. The analysis included 33 patients after 48 osteotomies (in 15 patients on both sides). The age at the time of surgery ranged from 1.0 to 9.8 years, mean 4.7 years. Follow-up time ranged from 7.6 to 15.9 years, mean 12.0 years. Statistical analysis showed significant differences in acetabular index, Sharp's angle, acetabular ratio and Wiberg's angle between early post-operative x-rays and radiograms taken at the last follow-up. Comparison not only of the remodelling dynamics, but also final radiological measurements confirm the necessity for surgical of severely dysplastic acetabular roof, especially in older age groups.

[The influence of the amount of variation of cervical-thoracic angle on the hip status and radiological results of the treatment of developmental hip dysplasia by torsion osteotomy]

The aim of this paper was to determine the differences in hip remodeling and final outcomes of hip dysplasia treatment by fixing a certain amount of varus during varus-detorsion osteotomy of the proximal femur. The analysis included 33 children who underwent 48 osteotomies. During final follow-up at skeletal maturity it was found that the amount of varus fixed during the osteotomy influenced significantly femur remodeling and some containment measurements. However it played only slight part in acetabular remodeling. The outcomes at final follow-up proved significantly better in the group in whom a greater amount of varus was fixed.

[Proximal femur remodeling after proximal femur varus-derotational osteotomy in treatment of developmental dysplasia of the hip]

The aim of this paper was to assess proximal femur remodelling after proximal femur varus-derotational osteotomy in treatment of developmental dysplasia of the hip up to skeletal maturity. The analysis included 48 osteotomies performed in 33 children between 1st and 10th year of life. The follow-up period was on average 12 years. Supported by statistical evaluation the analysis showed persistent increase of the neck-shaft angle after proximal femur varus-derotational osteotomy, especially in the younger age groups. It also correlated strongly with the amount of varus fixed at the time of operation. On other hand femoral antetorsion corrected during surgery remained unchanged till skeletal maturity.

Cloning and characterization of secretory tyrosine phosphatases of Mycobacterium tuberculosis

Two genes with sequence homology to those encoding protein tyrosine phosphatases were cloned from genomic DNA of Mycobacterium tuberculosis H(37)Rv. The calculated molecular masses of these two putative tyrosine phosphatases, designated MPtpA and MPtpB, were 17. 5 and 30 kDa, respectively. MPtpA and MPtpB were expressed as glutathione S-transferase fusion proteins in Escherichia coli. The affinity-purified proteins dephosphorylated the phosphotyrosine residue of myelin basic protein (MBP), but they failed to dephosphorylate serine/threonine residues of MBP. The activity of these phosphatases was inhibited by sodium orthovanadate, a specific inhibitor of tyrosine phosphatases, but not by okadaic acid, an inhibitor of serine/threonine phosphatases. Mutations at the catalytic site motif, cysteine 11 of MPtpA and cysteine 160 of MPtpB, abolished enzyme activity. Southern blot analysis revealed that, while mptpA is present in slow-growing mycobacterial species as well as fast-growing saprophytes, mptpB was restricted to members of the M. tuberculosis complex. These phosphatases were present in both whole-cell lysates and culture filtrates of M. tuberculosis, suggesting that these proteins are secreted into the extracellular medium. Since tyrosine phosphatases are essential for the virulence of several pathogenic bacteria, the restricted distribution of mptpB makes it a good candidate for a virulence gene of M. tuberculosis.