About selective echography in some eye diseases

Diagnostic A-Scan of Choroidal Melanoma: Automated Quantification of Parameters

Aim

To develop an automated algorithm to quantify ultrasonographic A-scan parameters of choroidal melanoma.

Methods

The study included 100 consecutive patients with a clinical diagnosis of choroidal melanoma. Ultrasonographic A-scans (8 MHz, 1,550 m/s, tissue sensitivity = 67 dB) were performed by standard techniques. We created and then utilized a MATLAB® script to generate four quantifiable A-scan parameters: (1) tumor height (mm), (2) the number of internal reflectivity peaks (numerical value), (3) median internal reflectivity (%), and (4) angle κ (°).

Results

There were small (≤2.5 mm, n = 32), medium (2.6-10.0 mm, n = 53), and large (> 10.0 mm, n = 14) tumors. The mean number of internal reflectivity peaks counted between the two tumor boundary spikes (surface and base) was 10.0 (σ = 8.7, range 1-37). The median value of the internal reflectivity peaks for all cases varied from 19.8 to 99.5 (mean = 68.3, σ = 20.5). A statistically significant correlation was observed between the tumor height categories and each of the three A-scan parameters: the number of internal reflectivity peaks (ρ = 0.90, p < 0.01), median internal reflectivity (ρ = -0.63, p < 0.01), and a positive angle κ (ρ = -0.32, p = 0.03).

Conclusions

An automated algorithm can provide quantifiable A-scan parameters for choroidal melanoma.

Echographic classification of intraocular tumours. A 15-year retrospective analysis

The data on echographic routine diagnosis of intraocular tumours (prominence equal to, or larger than 2 mm) during the years 1976-1990 in the authors' department, were analyzed by multivariate statistical methods, using the final diagnosis either from pathology after enucleation or from the confirmed clinical diagnosis. The material consisted of melanomas (n = 325), metastases (n = 44), haemangiomas (n = 19) and other intraocular tumours (n = 16). The best set of echographic parameters in descending order of significance was: reflectivity (A-mode), choroidal excavation (B-mode), shape (B-mode), and regularity (A/B mode). Echographic differentiation by computer analysis of data on the three main kinds of tumours (melanoma/metastasis/haemangioma) separate from all the remaining tumours was expressed by the correct fraction: melanoma 89%, metastasis 80% and haemangioma 97%. The clinical echographic classification for these cases was 89%, 93% and 99.5%, respectively. The simultaneous differentiation between the three classes was found to yield a correct fraction of 85% by computer statistics and 95% by routine echography. The results of the present study might be used for prospective classification through the use of the parameter 'knowledge base' contained in the statistical classification procedure.

The history of ultrasound techniques in ophthalmology

The history of 50 years of applications of ultrasound in ophthalmology is described. This period started in 1938 with a study of the possible effects of high intensity ultrasound on eyes. The measurement of biological effects for the assessment of potential hazards characterizes the first decades. More recently, the therapeutic use of ultrasound by hyperthermia has gained much interest in ophthalmology. Further topics are: the measurement of acoustic characteristics of ocular tissues; the biometry of the eye ball, the results of which are used to calculate the optical power of artificial lens implants; the development of diagnostic instruments in various parts of the world; and ultrasonic tissue characterization for the differential diagnosis of pathology. The final topic is concerned with some recent developments which present a look into the future.

[An equidensometric method for objective evaluation of ultrasonic b-scan pictures (author's transl)]

An equidensometric procedure is presented for achieving objective evaluation of ultrasonic B-scan pictures. Using special film (Agfacontour film) it is possible to select and show individually areas of equal brightness appearing on the B-scan, so called "equidensites". This can be done by colouring each area differently or by using a system of symbols. There is a description of the way in which the Agfacontour film works and is processed. Clinical evidence can be provided to prove the equidensometric evaluation of ultrasonic B-pictures of the eye can offer a considerable amount of additional information.