Interobserver and intraobserver variability of measurements of uveal melanomas using standardised echography

Abstract

Aim: To report on the intraindividual and interindividual variability of tumour size (height and base diameter) measurements using standardised echography in a masked prospective study. Methods: 20 consecutive eyes of 20 patients were examined on four different visits by three experienced examiners using standardised echography. As common in standardised echography, tumour height was evaluated with A-scan technique, while transverse and longitudinal base diameter were calculated with B-scan. Results: Tumour height measurements using A-scan were more accurate than base diameter measurements using B-scan. The standard deviation for tumour height over all visits/measurements was 0.18 mm (A-scan), 0.79 mm for transverse, and 0.69 mm for longitudinal base diameters (B-scan). The interclass correlation coefficient (ICC) was much higher for tumour height measurements with A-scan (0.7735 for three examiners on one visit) than for transverse (0.6563) or longitudinal (0.4522) base diameter measurements with B-scan techniques. Conclusions: A-scan techniques for tumour height measurements provide very reproducible results with little intraindividual and interobserver variability. As B-scan techniques for tumour base evaluation are less accurate they should be used for topographic and morphological examinations. S everal approaches in the management of uveal melanoma exist, mainly depending on the size of the tumour. [1][2][3][4][5][6] In the past 20 years an increasing percentage of patients has been treated with globe preserving therapies. Thus, it is important to have reliable parameters indicating whether the treated lesions decrease in size over time or remain unchanged. In addition, most ophthalmo-oncologists prefer to follow small melanocytic lesions until tumour growth is observed before a treatment is initiated. In these cases standardised A-scan echography is the most commonly used technique for biometry of the eye. It is also essential to establish the diagnosis of uveal melanoma using specific criteria. 7Standardised echography was introduced in the 1960s by Ossoinig for the purpose of ophthalmic tissue differentiation. The term standardised echography refers to a special examination technique which is based on the use of a standardised A-scan instrument especially developed for tissue differentiation. It is complemented by a real time contact B-scan. [8][9][10][11][12] Standardised A-scan is characterised by special signal processing through defined parameters, the so called "internal standardisation" which is provided by the manufacturer (narrowband receiver, special S-shaped type of amplification with a well defined dynamic range, high frequency filtering, etc]. 13 The "external standardisation" is performed by the examiner and includes the ascertainment of the "tissue sensitivity setting," which is optimal for tissue diagnosis. 14 However, besides specially designed equipment, the term standardised echography also implies a standardisation of the A-scan and B-scan examination of the globe and orbit. Meanwhile...

“Melanoma inhibitory activity” (MIA): a promising serological tumour marker in metastatic uveal melanoma

“…Furthermore, we performed standardized A-scan echography to measure the maximum tumour height, as described by Ossoinig et al [22]. In previous studies we had identified tumour height measurements using A-scan (ultrasound B-scan-S V-plus, Memory Card Version S 2.07, all by Biovision/Schwind, Kleinostheim, Germany, now HaagStreit, Clermont-Ferrand, France) to be the most accurate echographic parameter obtainable [13]. The patients were referred to a tumour specialist to be screened for metastatic disease by liver ultrasound and liver enzyme tests (alkaline phosphatase, AST, ALT, bilirubin) as well as chest X-ray.…”

Does the Imaging Method Have an Influence on the Measured Tumor Height in Ruthenium Plaque Therapy of Uveal Melanoma?

“…In temporal lesions and peripheral tumors, US values differed more from CT/MRI values than in nasal or central tumors. This can be explained by an angular distortion of the US measurements when scanning cannot be done orthogonally to the sclera, which is not discussed by Haritoglou et al [4], where one-dimensional A-scan measurements are described as being more precise than 2-D B-scans.…”

“…CT and MRI can reproduce position information to an accuracy of ± 1-2 mm in neurosurgical stereotactic localization [9] and in stereotactic radiosurgery [15]. The interobserver variability of US has been described as 0.6 mm (2 SD [standard deviations]) [4].…”

“…The accuracy of measurements of tumor size is as important for ruthenium plaque therapy as an exact patient positioning is for external-beam therapy [3,18] and stereotactic irradiation [12]. The standard imaging method for measuring tumor height and diameter in uveal melanoma is ultrasound (US), which is routinely used in the initial diagnostic work-up [4]. The most frequently used alternative method is magnetic resonance imaging (MRI) [22].…”

Imaging the intraocular tumor

“…The primary advantage of A-Scan ultrasonography when measuring the thickness of a choroidal tumor is the technique's ability to precisely identify the location of and distance between the anterior tumor margin and the sclera using quantitative spikes of echogenicity [29]. However, obtaining this information accurately is time-consuming and technically difficult.…”