around the embryo region of interest. Another in-
sightful research that uses deep learning for automat-
ing assessment of human embryos in IVF treatment
is reported in (Lockhart, 2018). Three tasks were the
focus of this work: blastocyst grading, cell detection
and counting, and embryo stage classification and on-
set detection. For the latter task, the proposed model
incorporates temporal learning over the TLI sequence
and automatically detects three classes, namely cleav-
age, morula, and blastocyst stage onsets. In order to
detect stage transitions, two image sequence batches
are fed in parallel, in pairwise learning, through two
separate CNNs, which are based on VGG16 architec-
tures pre-trained on the ImageNet dataset with three
final convolution layers fine-tuned. Fully connected
layers from each classifier are concatenated and used
to predict whether the input images fed through each
branch were at the same stage. Synergic loss from this
binary output is backpropagated through both classi-
fier branches. Stage transitions predictions are then
refined using temporal context in an LSTM layer sep-
arately for each synergic branch.
Gomez et al. (Gomez et al., 2022) worked on the
automatic annotation of the 16 embryo development
phases. In addition to providing a fully annotated
dataset composed of 704 time-lapse videos, authors
applied ResNet, ResNet-LSTM and ResNet3D mod-
els to automatically annotate the stage development
phases. The evaluation results showning the superi-
ority of ResNet-LSTM and ResNet-3D over ResNet,
prove the importance of using the temporal informa-
tion in the automatic annotation process. However,
predicting the 16 classes of embryonic development
is prone to numerous challenges, primarily due to
the extensive computational requirements necessary
for training DL models on more than 300k images,
which demand high-performance GPUs. Fukunaga et
al. (Fukunaga et al., 2020) proposed an automated
pronuclei determination system based on few amount
of supervised data. In their paper, authors proposed
a framework of four stages. First, images are pre-
processed to detect and focus on the embryo area us-
ing a circular Hough mask. Then, images are passed
for main processing to two CNNs, both composed of
two convolution layers and two fully connected lay-
ers. The first model detects the outline around pronu-
clei and passes these outline images to the second
CNN, which gives a probability distribution of the
number of pronuclei (0PN, 1PN, 2PN). Finally, pre-
dictions are postprocessed through a Hidden Markov
model, while setting conditions for the change in the
number of pronuclei over time. Thus, the change of
the number of pronuclei, if occurred (the state can re-
main unchanged), is only valid from 0PN to either
1PN or 2PN and from 1PN to 2PN. This integration
of time-series information resulted in improvement of
performance in sensitivity, however the accuracy re-
mains relatively low. To the best of our knowledge,
this workb (Fukunaga et al., 2020) is the only exist-
ing reference that deals with detecting and determin-
ing pronuclei number in IVF embryos.
In this work, we aim to automate the annotation
process of the early stages of embryonic development,
from Polar Body appearance (tPB2) to just before
the first cell division (t2). We create a deep learn-
ing model that analyzes the TLI incubator’s sequences
of embryonic development and annotates tPN, de-
fined as the time at which fertilization status is con-
firmed, immediately before the time fading of pronu-
clei (tPNf) (Ciray et al., 2014).
3 METHODOLOGY
3.1 Dataset
The dataset used in this work is a collection of 352
videos of unique embryos exported from a private TLI
IVF Incubator manufactured by Esco Medical
R
. The
frames of each video are time-lapse embryo images
taken every five minutes, starting shortly after fertil-
ization. Each video contains between 600 and 1400
frames in gray scale with a resolution of 1280 × 720
pixels.
An experienced biologist notes the start and end
time of each phase of the embryo’s development.
Each image of each video has therefore a class, which
corresponds to the phase seen in the image. The an-
notations follow the same convention used by Gomez
et al. (Gomez et al., 2022) and academic guidelines
(Ciray et al., 2014). There are, in general, 16 annota-
tions corresponding to 16 different instants of embryo
evolution. Here, as we are only interested in detect-
ing two key instants, namely tPB2 and tPN, we only
consider the following phases:
• tPB2: time of appearance of second polar body
• tPNa: time of pronuclei appearance
• tPNf: time of pronuclei fading
• t2: time of first cell division marks the end of
pronuclear phase
The stage tPN, which is defined as the time at which
fertilization status is confirmed, is calculated from
tPNa and tPNf (Ciray et al., 2014). We received the
annotation in Excel sheets generated by the software
of the TLI incubator, which we had to parse to extract
useful information.
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