The IMSI method: a Novelty in Assisted Reproduction

Where aggravated male infertility is present, the sole solution is an ICSI procedure: injecting a spermatozoid into the egg cell cytoplasm. The innovative technique of IMSI (injecting a morphologically selected spermatozoid into the egg cell cytoplasm) was developed to boost the procedure’s probability of success. The technique involves monitoring spermatozoa under the very great magnification of some 6600 times, offering the embryologist the opportunity to make detailed visual assessments of important sub cellular organelles. The technique brings to the fore defects that would otherwise not be apparent under standard microscope magnifications of 200 to 400 times. Selecting spermatozoa using IMSI and combining it with ICSI offers a more secure and reliable egg cell fertilisation, boosts the implantation potential of embryos and cuts the risk of spontaneous abortion.

Regardless of the great microscope magnification, selecting spermatozoa for injecting retains a certain degree of subjectivity on the part of the embryologist. To avoid the risk of human error, a special software was developed alongside the powerful microscopy system, making precise analysis and fine selection of the “best” spermatozoa through strict morphological criteria. Thanks to this, spermatozoa thus selected are not only vital but also morphologically sound.


This is the sole automated software for the live assessing of spermatozoal morphology in real time and at microscopic magnifications of over 6600 times. IMSI–STRICT combines the strict morphologic assessment criteria of Tygerberg and Kruger with a very recent method of morphologic assessment of moving spermatozoa organelles, called MSOME (motile sperm organelle morphology examination) and offers software categorisation of spermatozoa by reference to the size and shape of their heads, tails and vacuole numbers.

The Benefits of IMSI–STRICT:

  • Objective spermatozoal classification removes subjectivity in assessments by embryologists, cutting the probability of human error;
  • The analysis is rapid, reducing the time elapsed between spermatozoal processing and their injection into the egg cell (the ICSI procedure);
  • Allows standardised selection of spermatozoa for ICSI procedures;
  • Allows process documentation and data archiving;
  • Allows quality control;
  • Improves embryo quality by boosting the number of embryos which attain the blastocyte stage;
  • Reduces the proportion of embryos with chromosomal anomalies;
  • Boosts the proportion of successful pregnancies;
  • Reduces the proportion of spontaneous abortions.


Indications for IMSI:

  • Male infertility;
  • Teratozoospermia;
  • High degree of spermatozoal DNA fragmentation;
  • Embryos with poor morphological characteristics in prior IVF/ICSI procedures;
  • Spontaneous abortions in the first trimester of pregnancy;
  • A history of unsuccessful in vitro procedures;
  • Sterility for unclear reasons.


The Application of IMSI–STRICT in Bulgaria:

The innovative IMSI–STRICT method was first applied in Bulgaria at the Sofia Hospital of Obstetrics, Gynaecology and Reproductive Medicine.