P-551 High concordance of the embryonic cell-free DNA with the inner cell mass: impact of blastocyst quality, patient age and mode of fertilization

Study question

Does the embryonic cell-free DNA (cfDNA) in the culture medium represent the chromosomal content of the inner cell mass (ICM)? Which factors impact concordance rates?

Summary answer

There is high ploidy concordance between ICM biopsies and embryonic cfDNA. This value is independent of female age, insemination technique and embryo quality.

What is known already

The existence of embryonic cfDNA in spent blastocyst medium (SBM) has been confirmed in recent studies, opening a new era of possibilities for non-invasive preimplantation genetic testing for aneuploidy (niPGT-A). High concordance rates of cfDNA with trophectoderm (TE) biopsies and with whole blastocysts have been reported. However, the compartment(s) from where this DNA originates remain unclear. Both TE and ICM are potential sources, but, at the moment, the origin of this cfDNA is unknown as well as the mechanisms underlying its secretion into the medium.

Study design, size, duration

We carried out a prospective study to investigate the concordance of cfDNA with the corresponding TE and ICM biopsies. 141 day-6/7 blastocysts were donated for research after written informed consent signature for the project approved by the Ethics Committee. Embryos underwent TE biopsy and SBM collection in the same PGT-A cycle. ICM biopsy in thawed blastocysts was performed after TE biopsy diagnosis. cfDNA, TE and ICM biopsies were analyzed from January 2019 to November 2021.

Participants/materials, setting, methods

Embryos were cultured in routine conditions up to day 4. They were then washed and transferred to a new 10μl culture medium droplet. On day 6, SBM was collected and frozen at -20 °C; and blastocyst biopsy and vitrification were performed. Subsequently, blastocysts were thawed and ICM biopsy was conducted. All samples were analyzed by NGS (Ion ReproSeq PGS kit, ThermoFisher Scientific) and the results were analyzed with customized algorithms for TE, ICM and cfDNA.

Main results and the role of chance

In combination, the three sample types (cfDNA, ICM and TE) were informative in 81.6% of the blastocysts (115/141).

Considering the ICM as the reference, ploidy concordance (i.e. being both euploid or aneuploid) for cfDNA was 86.1% (99/115) and for TE was 89.6% (103/115), without statistical difference. False positive rates were similar for cfDNA and for TE biopsies (6.1% and 9.6%, respectively), and false negative rates were not significantly different, but higher in cfDNA (7.8%) than in TE (0.9%), due to potential contamination with maternal DNA. Ploidy concordance between embryo cfDNA and TE biopsies was 89.6% (103/115).

When the results were stratified by female age (≤37 or > 37 years), insemination technique (ICSI or IVF), blastocyst expansion degree (expanded, hatching or fully hatched), and ICM/TE quality (A or B), the informativity of the cfDNA was very similar between the different groups and ranged from 83.7% to 100%. Nevertheless, there were subtle differences for ICM-cfDNA ploidy concordance. It was slightly increased for the older female age group (88.3% vs 83.6% female age ≤37) as well as for ICSI (89.7% vs 82.5% in IVF) and for ICM quality B (88.4% vs 80.0% for ICM A). None of those differences reached statistical significance.

Limitations, reasons for caution

When stratifying according to the different criteria, the sample size analyzed was too small to draw strong conclusions. Therefore, more studies, with bigger sample size, are needed to replicate the results.

Wider implications of the findings

The embryonic cfDNA released to the culture medium provides information of the overall blastocyst chromosomal constitution, as suggested by the high ploidy concordance rates reported between ICM and cfDNA. This supports the use of niPGT-A as an alternative to other invasive aneuploidy detection methods that require a biopsy.

Trial registration number

ClinicalTrials.gov. ID NCT03520933

P-085 Use of an artificial intelligence tool to assess single-sperm motility variables related to bias preference of ICSI sperm selection practice, normal fertilization, and blastocyst formation

Study question

Which single-sperm WHO motility variables are associated with ICSI sperm selection preference, normal fertilization, and blastocyst formation when assessed by an artificial intelligence platform?

Summary answer

Injected sperm had higher VSL, VAP, and LIN compared with non-injected. Higher STR was associated with fertilization and higher WOB and less HMP with blastulation.

What is known already

Sperm selection for intracytoplasmic sperm injection (ICSI) is key to its success. Currently, the procedure may be subjective although the embryologist selects rapidly from a small population of sperm. There is no consensus on specific motility variables for single-sperm selection.

SiD (IVF 2.0 Limited, UK) software is able to assess all sperm in a visual field and accurately compute the motility variables for each sperm in real-time. SiDTM could help to understand the association between motility variables related to ICSI success and to assess the differences in sperm selection practice between different clinics and operators.

Study design, size, duration

473 ICSI videos and their corresponding outcome were retrospectively analyzed using SiD software and assessed against normal fertilization (2PN), and blastocyst formation (BF), from four fertility clinics in different countries between July 2021 to December 2021. Ethical approval was obtained. This study was non-interventional. The study parameters were defined as sperm that were selected or non-selected, 2PN, and BF.

Participants/materials, setting, methods

Motility variables were computed from ICSI videos for VSL, VCL, LIN, VAP, ALH, WOB, STR as defined by the WHO manual for the examination and processing of human semen; and HMP, a metric associated with sperm-head movements. Injected sperm were manually identified and the injection was visually verified by a senior embryologist. Extracted motility variables were standardized according to each clinic and PVP concentration. Study groups were tested with a two-sided Mann-Whitney U test.

Main results and the role of chance

Video analysis identified 304 selected and 9543 non-selected sperm. 2PN and BF status was known for 302 and 301 injected oocytes respectively (2PN rate: 79%, BF rate: 53%).

Embryologists used VSL, VAP, and LIN as the preferred motility criteria to select sperm (p < 0.001). Using data from all clinics, we found a tendency for STR (p = 0.12) and LIN (p = 0.14) for 2PN and WOB (p = 0.11) and VAP (p = 0.18) for BF.

There was partial consistency on sperm selection criteria amongst clinics: Clinic1 selected VSL, VAP, and LIN as the main variables to select sperm; Clinic2 VSL, WOB, and LIN; Clinic3 VSL, VAP, and VCL; and Clinic4 ALH, VCL, and VAP (p < 0.001).

For Clinic1 higher HMP showed a correlation (p = 0.06, n = 21) to 2PN, while higher WOB (p = 0.12, n = 21) did for BF. Clinic2 showed a limited association to higher STR and 2PN (p = 0.12, n = 120), and a significant association between higher WOB and BF (p < 0.05, n = 120). Clinic3’s data suggested that higher STR was associated with 2PN (p < 0.05, n = 97) and low HMP with BF (p < 0.05, n = 97).

Limitations, reasons for caution

This retrospective study needs to be repeated prospectively with larger numbers in more locations using embryologists with different levels of ICSI experience. Clinical outcome data such as clinical pregnancy, miscarriage, and live birth impact is still required.

Wider implications of the findings

SiD was able to track and extract motility features from single sperm. SiDTM could assist embryologists in real-time to select sperm during ICSI and could be used as a training tool to reduce variability among embryologists.

Trial registration number

RPA-2021-03

Catheter-tracking FOV MR fluoroscopy

Recent improvements in intravascular magnetic resonance imaging techniques mandate an accurate method of monitoring the introduction of MR catheter probes into the vessel of interest. For this purpose, a novel imaging protocol and a display method have been designed. First, a roadmap 3D image data set with standard pulse sequences is obtained using an external imaging coil. Subsequently, using very narrow rectangular-FOV fast-spoiled gradient recalled (SPGR), a movie of the percutaneous placement procedure of an MR catheter probe is acquired at a rate of 7.3 frames/second. In this protocol, the probe is used to transmit RF pulses and receive MR signal. A computer program was written for image unwrapping and for displaying the unwrapped movie frames on the roadmap image. In an alternative protocol, the movie frames in two projection angles were acquired in an interleaved fashion. Frames were unwrapped and combined with a 3D roadmap and displayed on a Silicon Graphics workstation equipped with stereovision goggles. Using these methods, percutaneous catheter placement in a phantom and a dog was examined. In conclusion, a new visualization technique for MR catheter placement is proposed. Combining this technique with high resolution intravascular MRI techniques may result in a very useful diagnostic tool for the evaluation of atherosclerosis and other vessel diseases.

Ultimate intrinsic signal-to-noise ratio in MRI

A method to calculate the ultimate intrinsic signal-to-noise ratio (SNR) in a magnetic resonance experiment for a point inside an arbitrarily shaped object is presented. The ultimate intrinsic SNR is determined by body noise. A solution is obtained by optimizing the electromagnetic field to minimize total power deposition while maintaining a constant right-hand circularly polarized component of the magnetic field at the point of interest. A numerical approximation for the optimal field is found by assuming a superposition of a large number of plane waves. This simulation allowed estimation of the ultimate intrinsic SNR attainable in a human torso model. The performance of six coil configurations was evaluated by comparing the SNR of images obtained by the coils with the ultimate values. In addition, the behavior of ultimate intrinsic SNR was investigated as a function of main field strength. It was found that the ultimate intrinsic SNR increases better than linearly with the main magnetic field up to 10 T for our model. It was observed that for field strengths of 4 T or higher, focusing is required to reach the ultimate intrinsic SNR.

Intravascular magnetic resonance imaging of aortic atherosclerotic plaque composition

Magnetic resonance imaging (MRI) may be an excellent tool to define atherosclerotic plaque composition, but surface MRI (SMRI) suffers from a low signal-to-noise ratio and low resolution of arterial images. Intravascular MRI (IVMRI) represents a potential solution for acquiring high-quality in vivo images of atherosclerotic plaques. Isolated segments of 11 thoracic human aortas obtained at autopsy were imaged by IVMRI using an intravascular receiver catheter coil designed and built at our institution. Images obtained by IVMRI were compared with corresponding images obtained by SMRI and with histopathological aortic cross sections. The intensity of intimal thickness and plaque components was graded by IVMRI and histopathology using a score of 1 for mild, 2 for moderate, and 3 for severe intensity. IVMRI had an agreement of 75% with histopathology in fibrous cap grading (37.5% expected, kappa = 0.60, P < 0.001) and of 74% in necrotic core grading (39% expected, kappa = 0.57, P < 0.001). Intraplaque calcification was correctly graded by IVMRI in six of the eight plaques in which histopathology recognized calcium. The analysis of intimal thickness showed 80% agreement between IVMRI and histopathology (52% expected, kappa = 0.59, P < 0.001). IVMRI image features were similar to those of SMRI. In addition, IVMRI accurately determined atherosclerotic plaque size in comparison with histopathology and SMRI (slope = 1.25 cm2, r = 0.99, P < 0.001 for luminal area by IVMRI vs histopathology; slope = 0.97 cm2, r = 0.996, P < 0.001 for luminal area by IVMRI vs SMRI). IVMRI has the potential to provide important prognostic information in patients with atherosclerosis because of its ability to accurately assess both plaque composition and size.

Intravascular magnetic resonance imaging using a loopless catheter antenna

Recently, intravascular catheter probes have been developed to increase signal-to-noise ratio (SNR) for MR imaging of blood vessels. Miniaturization of these catheter probes without degrading their performances is very critical in imaging small vessels such as coronary arteries. Catheter coils have a loop incorporated in their structure and have limitations in physical dimensions and electromagnetic properties. The use of a loopless intravascular catheter antenna is proposed to overcome these problems. The catheter antenna is essentially a dipole, which makes a very thin diameter possible, and its electronic circuitry can be placed outside the blood vessels without performance degradation. The theoretical foundation for the design and operation of the catheter antenna is presented. Several catheter antennae, as small as 1.5 French, were constructed and tested on phantoms and rabbits with great success. The catheter antenna has a simple structure and is easy to design, implement, and operate.

High resolution intravascular MRI and MRS by using a catheter receiver coil

Potentially important diagnostic information about atherosclerosis can be obtained by using magnetic resonance imaging and spectroscopy techniques. Because critical vessels such as the aorta, coronary arteries, and renal arteries are not near the surface of the body, surface coils are not adequate to increase the data quality to desired levels. A few catheter MR receiver coil designs have been proposed for imaging the walls of large blood vessels such as the aorta. These coils have limited longitudinal coverage and they are too thick to be placed into small vessels. A flexible, long and narrow receiver coil that can be placed on the tip of a catheter and will enable multi-slice high resolution imaging of small vessels has been developed. The authors describe the theory of the coil design technique, derive formulae for the signal-to-noise ratio characteristics of the coil, and show examples of high resolution cross-sectional images from isolated human aortas acquired by using this catheter coil. In addition, high resolution in vivo rabbit aorta images were obtained as well as a set of spatially resolved chemical shift spectra from a dog circumflex coronary artery.