ICS 11.120.01  
 
Reference number  
DRS 478 : 2021  
© RSB 2021  
  
 RWANDA 
STANDARD  DRS  
478 
 
First edition  
2021 -mm-dd 
 
Medical u ltrasound gel  — Specification  
   
DRS 478 : 2021  
©RSB 2 021 - All rights reserved                  ii 
 In order to match with technological development and to keep continuous progress in industries, 
standards are subject to periodic review. Users shall ascertain that they are in possession of the latest 
edition  
 
 
 
 
 
 
 
 
© RSB 2021  
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized 
in any form or by any means, electronic or mechanical, including photocopying and microfilm, without 
prior written permission from R SB. 
Requests for permission to reprodu ce this document should be addressed to : 
Rwanda Standards  Board  
P.O Box 7099 Kigali -Rwanda  
KK 15 Rd, 49  
Tel. +250 788303492  
Toll Free: 3250  
E-mail: info@rsb.gov.rw  
Website: www.rsb.gov.rw  
ePortal: www.portal.rsb.gov.rw   DRS 478 : 2021  
iii                ©RSB 2021  - All rights reserved  
 Contents  Page 
1 Scope  ................................ ................................ ................................ ................................ ......................  1 
2 Normative references  ................................ ................................ ................................ ............................  1 
3 Terms and definitions  ................................ ................................ ................................ ...........................  1 
4 Requirem ents ................................ ................................ ................................ ................................ .........  2 
4.1 General requirements  ................................ ................................ ................................ ...........................  2 
4.2 Specific requirements  ................................ ................................ ................................ ...........................  2 
5 Packaging and labelling ................................ ................................ ................................ ........................  3 
5.1 Pack aging  ................................ ................................ ................................ ................................ ...............  3 
5.2 Labelling  ................................ ................................ ................................ ................................ .................  3 
6 Sampling  ................................ ................................ ................................ ................................ ................  4 
Annex  A (normative)  Ste rility test  ................................ ................................ ................................ ....................  5 
A.1 Introduction  ................................ ................................ ................................ ................................ ............  5 
A.2 Fluid thioglycollate medium  ................................ ................................ ................................ .................  5 
A.3 Alternative  ................................ ................................ ................................ ................................ ..............  6 
A.4 Soya -bean case in digest medium  ................................ ................................ ................................ ........  6 
A.5 Sterility  ................................ ................................ ................................ ................................ ...................  7 
Annex  B (normative)  Sampling  ................................ ................................ ................................ ........................  8 
B.1 General requirements of sampling  ................................ ................................ ................................ ...... 8 
B.2 Sampling of packages ................................ ................................ ................................ ...........................  8 
 DRS 478 : 2021  
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 Foreword   
Rwanda Standard s are prepared  by Technical Committees and approved by R wanda Standards Board (RSB) 
Board  of Directors in  accordance with the procedures of RSB, in compliance with Annex 3 of the WTO/TBT 
agreement on the preparation, adoption and application of standards.  
The main task o f technical committees is to prepare national standards.  Final Draft Rwanda S tandards 
adopted by Technical committ ees are ratified  by me mbers of RSB Board of Director s for publication and 
gazettment as Rwanda Standards.  
DRS 478  was prepared by Technical Co mmittee RSB/TC 015, Pharmaceutical Products  
In the preparation of this standard, reference was made to the following standard:  
US 2129 : Medical Ultrasound gel — Specification  
The assistance de rived from the above source is hereby acknowledged with thanks.  
Committee membership  
The following organizations were represented on the Technical Committee on Pharmaceutical Products  
(RSB/TC 015) in the preparation of this standard.  
Healthcare Pharmacy  
HORIZON/SOPYRWA  
IKIREZI Products  
National Pharmacy Council (NPC)  
Rwanda Food and Drugs Authority (FDA)  
Rwanda Forensic Laboratory (RFL)  
Rwanda Inspectorate, Competition and Consumer Protection Authority (RICA)  
Rwanda Medical Supply Ltd  
Rwanda Social Security Agency (RSSB)  
University of Rwanda/College of Medicine and Pha rmacy Sciences (UR/CMPS)  
University of Rwanda/College of Sciences and Technology (UR/CST)  DRS 478 : 2021  
v                ©RSB 2021  - All rights reserved  
 University of Rwanda/College of Education (UR/CE)  
Rwanda  Standards Board  (RSB) – Secretariat  DRS 478 : 2021  
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 Introduction   
Ultrasound gel or a coupling agent utilizes a basic physics principle where sound waves tend to carry very well 
through an aqueous or watery medium. When applied to the surface of the patient’s skin, the ultrasound gel 
acts as a coupling medium and enhances the transmission of ultrasonic sound waves from th e skins surface 
to the head of the ultrasound transducer. Ultrasound gel serves as a lubricant and improves the acoustic 
transmission of sound waves to the create the image for the sonographer to examine on the monitor.  
 
 DRS 478 : 2021  
1                ©RSB 2021  - All rights reserved  
 Medical ultrasound gel  — Specification  
1 Scope   
This Draft Rwanda Standard specifies requirements, sampling and test methods for medical ultrasound gels.  
2 Normative references   
The following documents are referred to in the text in such a way that some or all of  their content constitutes 
requirements of this document.  For dated references, only the edition  cited appl ies. For undated references, 
the latest edition of the referenced document (including any amendments) applies.  
RS EAS 847 -17: 2017 , Cosmetic industry  — Analytical methods —Part 17: Determination of pH  
ISO 21149 , Enumeration and detection of aerobic mesophilic bacteria  
ISO 21150, Cosmetics -- Microbiology -- Detection of Escherichia coli   
US 1847:2017, Standard Test Methods for Specific Gravity, Apparent, of Liquid Industrial Chemicals  
ISO 3104:1994, Petroleum products - Transparent and opaque liquid s - Determination of kinematic viscosity 
and calculation of dynamic viscosity   
ISO 22718, Cosmetics -- Microbiology -- Detection of Staphylococcus aureus   
ISO 22717, Cosmetics -- Microbiology -- Detection of Pseudomonas aeruginosa   
ISO 10993 -1:2003, Biolog ical evaluation of medical devices — Part 1: Evaluation and testing  
3 Terms and definitions   
For the purposes of this standard, the follow ing terms and definitions  apply . 
3.1 
medical ultrasound gel  
conductive medium that enables air free bond between the skin/mucus linings of cavities and the probe or 
transducer, letting the waves transmit directly to the tissues beneath and to the parts that need to be imaged.   
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 3.2 
bacteriostatic  
capable of inhibiting the growth or reproduction of bacteria.  
3.3 
transducer  
a device that converts energy from one form to another.  
4 Requirements  
4.1 General requirements  
4.1.1  The medical ultrasound gel shall be a clear viscous gel, free from any foreign matter, sediments and 
air bubbles.  
4.1.2  The medical ultrasound gel shall be odourless, bacteriostatic and non -irritating when tested in 
accordance ISO 10993 -1. 
4.1.3  The medical ultrasound gel shall be free from formaldehyde, soluble in water, non -staining and shall 
not damage transducers.  
4.1.4  The sterile medical ultrasound gel shall be tested in accordance with Annex A.  
4.2 Specific requirements  
4.2.1  The medical ultrasound gel shall conform to the requirements specified in table 1 when tested in 
accordance with the test methods prescribed therein.  
Table 1 – Specific requirements f or medical ultrasound gel  
S/N Parameters  Requirements  Test methods  
1 pH (neat)  6.5 – 7.5 RS EAS 847 -17 
2 Density at 23 °C, g/cm3 0.683 – 1.283  US 1847  
3 Viscosity, Centipoise, min.  10,000  ISO 3104  
4.2.2  The medical ultrasound gel shall comply with the heavy metal limits given in Table 2 when tested in 
accordance with the test methods specified therein.  
Table 2 – Heavy metal limits for medical ultrasound gel  
S/N Parameters  Maximum limitsa Test methods  
1 Lead as Pb, mg/kg.  10.0 
EAS 847 -16 2 Arsenic as As, mg/kg. 2.0 
3 Mercury as Hg, mg/kg.  2.0 
a The total amount of heavy metals as lead, arsenic and mercury, in combination in the finished product shall not exceed 10 m g/kg DRS 478 : 2021  
3                ©RSB 2021  - All rights reserved  
 4.2.3 The medical ultrasound gel shall comply with the microbiological limits given in table 3 when tested in 
accordance with the test methods specified therein.  
Table 3 – Microbiological limits  for medical ultrasound gel  
S/N Parameters  Requirements  Test methods  
1 Total viable count for aerobic 
mesophilic microorganisms, 
CFU/g or CFU/ml, max.  1 000  ISO 21149  
2 Pseudomonas aeruginosa 
Not detectable in 1 ml or 
1 g of the product  ISO 22717  
3 Staphylococcus aureus  ISO 22718  
4 Candida albicans  ISO 18416  
5 Packaging and labelling  
5.1 Packaging  
The medical ultrasound gel shall be packaged in suitable containers to ensure stability and prevent 
contamination of the product during of transportation, handling and storage.  
5.2 Labelling  
The package shall be legibly and indelibly marked with the following information  in any of the three lang uages 
officially accepted in the Republic of Rwanda namely: Kinyarwanda, French and English : 
a) Manufacturer’s name and physical address;  
b) Product name as “Medical ultrasound gel”;  
c) Batch/lot number;  
d) List of ingredients;  
e) Net content;  
f) Manufacture and expiry date s; 
g) Country of origin;  
h) Storage instructions;  
i) Warning/precautions.  
j) For the sterile, indicate the word “sterile”   
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 6 Sampling  
Sampling shall be done in accordance with annex B.  
 DRS 478 : 2021  
5                ©RSB 2021  - All rights reserved  
 Annex  A 
(normative)  
 
Sterility test  
A.1 Introduction  
The following culture media have been found to be suitable for the test for sterility. Fluid thioglycollate medium 
is primarily intended for the culture of anaerobic bacteria; however, it will also detect aerobic bacteria. Soya -
bean casein digest medium is suitable for the culture of both fung i and aerobic bacteria.  
A.2 Fluid thioglycollate medium  
L-Cystine                0.5 g  
Agar                 0.75 g  
Sodium chloride               2.5 g  
Glucose monohydrate/anhydrous           5.5 g/5.0 g  
Yeast extract (water -soluble)            5.0 g  
Pancreatic digest of casein             15.0 g  
Sodium thioglycollate, or             0.5 g  
Thioglycollic acid               0.3 mL  
Resazurin sodium solution (1g/L of resazurin sodium) freshly prepared   1.0 mL  
Water                 1000 mL  
pH after sterilization              7.1 ± 0.2 
A.2.1  Mix the L -cystine, agar, sodium chloride, glucose, water -soluble yeast extract and pancreatic digest 
of casein with the water R and heat until solution is effected.  
A.2.2  Dissolve the sodium thioglycollate or thioglycollic acid in the s olution and, if necessary, add 1 M 
sodium hydroxide so that, after sterilisation, the solution will have a pH of 7.1 ± 0.2. If filtration is necessary, 
heat the solution again without boiling and filter while hot through moistened filter paper.  
A.2.3  Add t he resazurin sodium solution, mix and place the medium in suitable vessels which provide a 
ratio of surface to depth of medium such that not more than the upper half of the medium has undergone a  
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 colour change indicative of oxygen uptake at the end of the incubation period. Sterilise using a validated 
process. If the medium is stored, store at a temperature between 2 °C and 25 °C in a sterile, airtight container.  
A.2.4  If more than the upper one -third of the medium has acquired a pink colour, the medium may  be 
restored once by heating the containers in a water -bath or in free - flowing steam until the pink colour 
disappears and cooling quickly, taking care to prevent the introduction of non -sterile air into the container. Do 
not use the medium for a longer st orage period than has been validated. Fluid thioglycollate medium is to be 
incubated at 30 -35 °C.  
A.2.5  For products containing a mercurial preservative that cannot be tested by the membrane -filtration 
method, fluid thioglycollate medium incubated at 20 -25 °C may be used instead of soya -bean casein digest 
medium provided that it has been validated as described in growth promotion test.  
A.3 Alternative  
Where prescribed or justified and authorized, the following alternative thioglycollate medium may be used. 
Prep are a mixture having the same composition as that of the fluid thioglycollate medium, but omitting the 
agar and the resazurin sodium solution, sterilise as directed above. The pH after sterilisation is 7.1 ± 0.2. Heat 
in a water -bath prior to use and incub ate at 30 -35 °C under anaerobic conditions.  
A.4 Soya -bean casein digest medium  
Pancreatic digest of casein                 17.0 g  
Papaic digest of soya -bean meal               3.0 g  
Sodium chloride                   5.0 g  
Dipotassium hydrogen phosphate               2.5 g  
Glucose monohydrate/anhydrous               2.5 g/2.3 g  
Water R                     1000 mL  
pH after sterilization                  7.3 ± 0.2  
A.4.1  Dissolve the solids in water R, warming slightly to effect solution. Cool the solution to room 
temperature. Add 1 M sodium hydroxide, if necessary, so that after sterilisation the solution will have a pH of 
7.3 ± 0.2.  
A.4.2  Filter, if necessary, to clarify, distribute into suitable vessels and sterilise using a validated process. 
Store at a temperat ure between 2 °C and 25 °C in a sterile well -closed container, unless it is intended for 
immediate use. Do not use the medium for a longer storage period than has been validated. Soya -bean 
casein digest medium is to be incubated at 20 -25 °C. The media used  comply with the following tests, carried 
out before or in parallel with the test on the product to be examined.  DRS 478 : 2021  
7                ©RSB 2021  - All rights reserved  
 A.5 Sterility  
Incubate portions of the media for 14 days. No growth of micro -organisms occurs.  
 
   
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 Annex  B 
(normative)  
 
Sampling  
B.1 General requirements of sa mpling  
B.1.1  In drawing, preparing, storing and handling samples, the following precautions and directions shall be 
observed.  
B.1.2  Samples shall be taken in a protected place not exposed to damp air, dust or Soot . 
B.1.3  The sampling instrument shall be cl ean and dry.  
B.1.4  The samples, the material being sampled, the sampling instrument and the containers for samples 
shall be protected from adventitious contamination.  
B.1.5  The samples shall be placed in clean and dry glass containers. The sample containers shall be of a 
size such that they are almost completely filled by the sample.  
B.1.6  Each container shall be sealed air -tight after filling and marked with full details of sampling, batch or 
code number, name of manufacturer, and other important particulars of the consignment.  
B.1.7  The samples shall be stored in such a. manner that the temperature of the material does not vary 
unduly from the normal temperature and they are protected from light.  
B.1.8  Sampling shall be done by a person agreed to between the purchaser and the supplier, and in the 
presence of the purchaser or his representative and the supplier or his representatives.  
B.2 Sampling of packages  
B.2.1  General – The sampling procedure for packages shall consist essentially in selecting and drawing, a 
sufficient number of unit packs.  
Lot – In a single consignment, all the packages containing medical ultrasound gel of the same type and form, 
representing the same batch of manufacture, shall constitute a lot. If the consignment consists of pack ages 
containing medical ultrasound gel of different types or forms or batches of manufacture, then the packages 
containing products of the same type, form and batch of manufacture shall be grouped together; each group 
shall constitute a separate lot.  
Scale  of sampling – For ascertaining the conformity of a lot to the requirements prescribed in the 
specifications for individual medical ultrasound gel and toilet goods, tests shall be carried out on each lot 
separately. The number (n) of packages to be selecte d for drawing the samples shall depend on the size (N) 
of the lot in accordance with Table B.1.  DRS 478 : 2021  
9                ©RSB 2021  - All rights reserved  
 Table B.1 – Scale of sampling for packages  
Number of packages in the 
lot (N)  Number of packages to be 
selected (n)  
Up to 3  Each container  
4 to 50  3 
51 to 150 4 
151 to 300  5 
301 to 500  6 
501 and above  7 
The packages shall be selected at random and to ensure random and to ensure randomness of selection, 
random number tables shall be used. In case such tables are not available, the following procedure may be 
adopted: ‘Starting from any package, count all the packages in one order as 1,2,3 . . . . . . . . . up to r and so 
on, where r is the integral part of N/n. Every rth package thus counted shall be withdrawn to give a sample for 
purposes of test.   
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 Bibliography  
[1]  
 
 DRS 478 : 2021  
 
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