Radioactivité médicale
P.108-109
ACTIVITÉ D'EXPLORATION
1Radioactivité médicale
1
Depuis sa découverte à la fin du XIXe siècle, la radioactivité a été mise à profit dans le domaine médical, notamment pour le traitement de différentes formes de cancers. Pour autant, son utilisation n’est pas sans danger.
➜ Quels sont les risques liés à la radioactivité ?
Objectifs
- Citer des applications dans le domaine médical.
- Déterminer les isotopes radioactifs d’un élément à partir d’un diagramme (, ).
Frise interactive
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Doc. 1Histoire de la radioactivité
Doc. 1
La découverte de la radioactivité a permis de faire de nombreuses avancées dans le domaine médical avec l’apparition des premières radiographies et des traitements par radiothérapie.
Eras
Évènements
- 1893 - : <span data-content-md-theme="pc-pink" data-content-md-tag="color" data-temp-content-md-index="2629638" class="sc-gxMtzJ fxZxQb lls-viewer-color"><strong data-content-md-tag="b" data-temp-content-md-index="2629637" class="sc-dfVpRl HpwYT lls-viewer-b">Découverte des rayons X</strong> par W. Röntgen (Prix Nobel 1901).</span> |
- 1896 - : <span data-content-md-theme="pc-blue2" data-content-md-tag="color" data-temp-content-md-index="2629640" class="sc-gxMtzJ iNCwuo lls-viewer-color"><strong data-content-md-tag="b" data-temp-content-md-index="2629639" class="sc-dfVpRl jNZScH lls-viewer-b">Mise en évidence des rayons uraniques</strong> par H. Becquerel (Prix Nobel 1903).</span> |
- 1898 - : <span data-content-md-theme="pc-orange" data-content-md-tag="color" data-temp-content-md-index="2629642" class="sc-gxMtzJ drKSQl lls-viewer-color"><strong data-content-md-tag="b" data-temp-content-md-index="2629641" class="sc-dfVpRl coHjUA lls-viewer-b">Découverte du radium et du polonium</strong> par M. Curie (Prix Nobel 1903) et P. Curie (Prix Nobel 1903).</span> |
- 1901 - : <span data-content-md-theme="pc-red" data-content-md-tag="color" data-temp-content-md-index="2629648" class="sc-gxMtzJ AGNCD lls-viewer-color"><strong data-content-md-tag="b" data-temp-content-md-index="2629644" class="sc-dfVpRl jyQAWn lls-viewer-b">Curiethérapie et émission <span data-content-md-tag="math" data-temp-content-md-index="2629643" data-content-md-katex="\alpha" class="sc-cmTdod kmzvxb lls-viewer-math" contenteditable="false"><span><span class="katex"><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.43056em;vertical-align:0em;"></span><span class="mord mathnormal" style="margin-right:0.0037em;">α</span></span></span></span></span></span></strong><br data-content-md-tag="br" data-temp-content-md-index="2629645"/> L’atome se scinde en un noyau d’hélium et un atome plus léger.<br data-content-md-tag="br" data-temp-content-md-index="2629646"/> <span data-content-md-tag="math" data-temp-content-md-index="2629647" data-content-md-katex="^A_Z\text{X} \rightarrow \ ^{A-4}_{Z-2}\text{Y} + \ ^4_2\text{He}" class="sc-cmTdod kmzvxb lls-viewer-math" contenteditable="false"><span><span class="katex"><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:1.1166619999999998em;vertical-align:-0.275331em;"></span><span class="mord"><span></span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.8413309999999999em;"><span style="top:-2.424669em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mathnormal mtight" style="margin-right:0.07153em;">Z</span></span></span><span style="top:-3.063em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mathnormal mtight">A</span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.275331em;"><span></span></span></span></span></span></span><span class="mord text"><span class="mord">X</span></span><span class="mspace" style="margin-right:0.2777777777777778em;"></span><span class="mrel">→</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span></span><span class="base"><span class="strut" style="height:1.233324em;vertical-align:-0.351862em;"></span><span class="mord"><span class="mspace"> </span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.881462em;"><span style="top:-2.406469em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight"><span class="mord mathnormal mtight" style="margin-right:0.07153em;">Z</span><span class="mbin mtight">−</span><span class="mord mtight">2</span></span></span></span><span style="top:-3.1031310000000003em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight"><span class="mord mathnormal mtight">A</span><span class="mbin mtight">−</span><span class="mord mtight">4</span></span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.351862em;"><span></span></span></span></span></span></span><span class="mord text"><span class="mord">Y</span></span><span class="mspace" style="margin-right:0.2222222222222222em;"></span><span class="mbin">+</span><span class="mspace" style="margin-right:0.2222222222222222em;"></span></span><span class="base"><span class="strut" style="height:1.0622159999999998em;vertical-align:-0.24810799999999997em;"></span><span class="mord"><span class="mspace"> </span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.8141079999999999em;"><span style="top:-2.4518920000000004em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight">2</span></span></span><span style="top:-3.063em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight">4</span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.24810799999999997em;"><span></span></span></span></span></span></span><span class="mord text"><span class="mord">He</span></span></span></span></span></span></span></span> |
- 1937 - : <span data-content-md-theme="pc-purple1" data-content-md-tag="color" data-temp-content-md-index="2629650" class="sc-gxMtzJ jxpZiW lls-viewer-color"><strong data-content-md-tag="b" data-temp-content-md-index="2629649" class="sc-dfVpRl bBjChV lls-viewer-b">Interdiction du radium non thérapeutique.</strong></span> |
- 1950 - : <span data-content-md-theme="pc-green3" data-content-md-tag="color" data-temp-content-md-index="2629656" class="sc-gxMtzJ iOggoG lls-viewer-color"><strong data-content-md-tag="b" data-temp-content-md-index="2629652" class="sc-dfVpRl iqYlc lls-viewer-b">Tomographie et émission <span data-content-md-tag="math" data-temp-content-md-index="2629651" data-content-md-katex="\beta ^+" class="sc-cmTdod kmzvxb lls-viewer-math" contenteditable="false"><span><span class="katex"><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.9657709999999999em;vertical-align:-0.19444em;"></span><span class="mord"><span class="mord mathnormal" style="margin-right:0.05278em;">β</span><span class="msupsub"><span class="vlist-t"><span class="vlist-r"><span class="vlist" style="height:0.771331em;"><span style="top:-3.063em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mbin mtight">+</span></span></span></span></span></span></span></span></span></span></span></span></span></strong><br data-content-md-tag="br" data-temp-content-md-index="2629653"/> L’atome se scinde en un atome fils et une particule chargée positivement : un positon.<br data-content-md-tag="br" data-temp-content-md-index="2629654"/> <span data-content-md-tag="math" data-temp-content-md-index="2629655" data-content-md-katex="^A_Z\text{X} \rightarrow \ ^{\quad A}_{Z-1}\text{Y} + \ ^0_1\text{e}^+" class="sc-cmTdod kmzvxb lls-viewer-math" contenteditable="false"><span><span class="katex"><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:1.1166619999999998em;vertical-align:-0.275331em;"></span><span class="mord"><span></span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.8413309999999999em;"><span style="top:-2.424669em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mathnormal mtight" style="margin-right:0.07153em;">Z</span></span></span><span style="top:-3.063em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mathnormal mtight">A</span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.275331em;"><span></span></span></span></span></span></span><span class="mord text"><span class="mord">X</span></span><span class="mspace" style="margin-right:0.2777777777777778em;"></span><span class="mrel">→</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span></span><span class="base"><span class="strut" style="height:1.174993em;vertical-align:-0.333662em;"></span><span class="mord"><span class="mspace"> </span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.8413309999999999em;"><span style="top:-2.424669em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight"><span class="mord mathnormal mtight" style="margin-right:0.07153em;">Z</span><span class="mbin mtight">−</span><span class="mord mtight">1</span></span></span></span><span style="top:-3.063em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight"><span class="mspace mtight" style="margin-right:1.4285714285714286em;"></span><span class="mord mathnormal mtight">A</span></span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.333662em;"><span></span></span></span></span></span></span><span class="mord text"><span class="mord">Y</span></span><span class="mspace" style="margin-right:0.2222222222222222em;"></span><span class="mbin">+</span><span class="mspace" style="margin-right:0.2222222222222222em;"></span></span><span class="base"><span class="strut" style="height:1.0622159999999998em;vertical-align:-0.24810799999999997em;"></span><span class="mord"><span class="mspace"> </span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.8141079999999999em;"><span style="top:-2.4518920000000004em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight">1</span></span></span><span style="top:-3.063em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight">0</span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.24810799999999997em;"><span></span></span></span></span></span></span><span class="mord"><span class="mord text"><span class="mord">e</span></span><span class="msupsub"><span class="vlist-t"><span class="vlist-r"><span class="vlist" style="height:0.771331em;"><span style="top:-3.063em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mbin mtight">+</span></span></span></span></span></span></span></span></span></span></span></span></span></span> |
- 1951 - : <span data-content-md-theme="svt-pink1" data-content-md-tag="color" data-temp-content-md-index="2629662" class="sc-gxMtzJ dAAVmS lls-viewer-color"><strong data-content-md-tag="b" data-temp-content-md-index="2629658" class="sc-dfVpRl cKBHXI lls-viewer-b">Scintigraphie et émission <span data-content-md-tag="math" data-temp-content-md-index="2629657" data-content-md-katex="\beta ^-" class="sc-cmTdod kmzvxb lls-viewer-math" contenteditable="false"><span><span class="katex"><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.9657709999999999em;vertical-align:-0.19444em;"></span><span class="mord"><span class="mord mathnormal" style="margin-right:0.05278em;">β</span><span class="msupsub"><span class="vlist-t"><span class="vlist-r"><span class="vlist" style="height:0.771331em;"><span style="top:-3.063em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mbin mtight">−</span></span></span></span></span></span></span></span></span></span></span></span></span></strong><br data-content-md-tag="br" data-temp-content-md-index="2629659"/> L’atome se scinde en un atome fils et une particule chargée négativement : un électron. <br data-content-md-tag="br" data-temp-content-md-index="2629660"/> <span data-content-md-tag="math" data-temp-content-md-index="2629661" data-content-md-katex="^A_Z\text{X} \rightarrow \ ^{\quad A}_{Z+1}\text{Y} + ^{\enspace 0}_{-1}\text{e}^-" class="sc-cmTdod kmzvxb lls-viewer-math" contenteditable="false"><span><span class="katex"><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:1.1166619999999998em;vertical-align:-0.275331em;"></span><span class="mord"><span></span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.8413309999999999em;"><span style="top:-2.424669em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mathnormal mtight" style="margin-right:0.07153em;">Z</span></span></span><span style="top:-3.063em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mathnormal mtight">A</span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.275331em;"><span></span></span></span></span></span></span><span class="mord text"><span class="mord">X</span></span><span class="mspace" style="margin-right:0.2777777777777778em;"></span><span class="mrel">→</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span></span><span class="base"><span class="strut" style="height:1.174993em;vertical-align:-0.333662em;"></span><span class="mord"><span class="mspace"> </span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.8413309999999999em;"><span style="top:-2.424669em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight"><span class="mord mathnormal mtight" style="margin-right:0.07153em;">Z</span><span class="mbin mtight">+</span><span class="mord mtight">1</span></span></span></span><span style="top:-3.063em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight"><span class="mspace mtight" style="margin-right:1.4285714285714286em;"></span><span class="mord mathnormal mtight">A</span></span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.333662em;"><span></span></span></span></span></span></span><span class="mord text"><span class="mord">Y</span></span><span class="mspace" style="margin-right:0.2222222222222222em;"></span><span class="mbin"><span class="mbin">+</span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.8141079999999998em;"><span style="top:-2.451892em;margin-left:0em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight"><span class="mord mtight">−</span><span class="mord mtight">1</span></span></span></span><span style="top:-3.063em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight"><span class="mspace mtight" style="margin-right:0.7142857142857143em;"></span><span class="mord mtight">0</span></span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.30643899999999996em;"><span></span></span></span></span></span></span><span class="mspace" style="margin-right:0.2222222222222222em;"></span></span><span class="base"><span class="strut" style="height:0.771331em;vertical-align:0em;"></span><span class="mord"><span class="mord text"><span class="mord">e</span></span><span class="msupsub"><span class="vlist-t"><span class="vlist-r"><span class="vlist" style="height:0.771331em;"><span style="top:-3.063em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mbin mtight">−</span></span></span></span></span></span></span></span></span></span></span></span></span></span> |
- 1951 - : <span data-content-md-theme="svt-pink1" data-content-md-tag="color" data-temp-content-md-index="2629668" class="sc-gxMtzJ dAAVmS lls-viewer-color"><strong data-content-md-tag="b" data-temp-content-md-index="2629664" class="sc-dfVpRl cKBHXI lls-viewer-b">Émission <span data-content-md-tag="math" data-temp-content-md-index="2629663" data-content-md-katex="\gamma" class="sc-cmTdod kmzvxb lls-viewer-math" contenteditable="false"><span><span class="katex"><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.625em;vertical-align:-0.19444em;"></span><span class="mord mathnormal" style="margin-right:0.05556em;">γ</span></span></span></span></span></span></strong><br data-content-md-tag="br" data-temp-content-md-index="2629665"/> Un noyau excité redescend vers un niveau d’énergie plus stable en émettant un photon.<br data-content-md-tag="br" data-temp-content-md-index="2629666"/> <span data-content-md-tag="math" data-temp-content-md-index="2629667" data-content-md-katex="^A_Z\text{Y}* \rightarrow \ ^A_Z\text{Y} + \gamma" class="sc-cmTdod kmzvxb lls-viewer-math" contenteditable="false"><span><span class="katex"><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:1.1166619999999998em;vertical-align:-0.275331em;"></span><span class="mord"><span></span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.8413309999999999em;"><span style="top:-2.424669em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mathnormal mtight" style="margin-right:0.07153em;">Z</span></span></span><span style="top:-3.063em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mathnormal mtight">A</span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.275331em;"><span></span></span></span></span></span></span><span class="mord text"><span class="mord">Y</span></span><span class="mord">∗</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span><span class="mrel">→</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span></span><span class="base"><span class="strut" style="height:1.1166619999999998em;vertical-align:-0.275331em;"></span><span class="mord"><span class="mspace"> </span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.8413309999999999em;"><span style="top:-2.424669em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mathnormal mtight" style="margin-right:0.07153em;">Z</span></span></span><span style="top:-3.063em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mathnormal mtight">A</span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.275331em;"><span></span></span></span></span></span></span><span class="mord text"><span class="mord">Y</span></span><span class="mspace" style="margin-right:0.2222222222222222em;"></span><span class="mbin">+</span><span class="mspace" style="margin-right:0.2222222222222222em;"></span></span><span class="base"><span class="strut" style="height:0.625em;vertical-align:-0.19444em;"></span><span class="mord mathnormal" style="margin-right:0.05556em;">γ</span></span></span></span></span></span></span> |
- 1976 - : <span data-content-md-theme="pc-dark-blue" data-content-md-tag="color" data-temp-content-md-index="2629670" class="sc-gxMtzJ cKtwyM lls-viewer-color"><strong data-content-md-tag="b" data-temp-content-md-index="2629669" class="sc-dfVpRl cHjTEa lls-viewer-b">Interdiction du radium thérapeutique,</strong> remplacé par l’iridium et le césium. </span> |
Supplément numérique
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Doc. 2Diagramme (, ) de Segrè
Doc. 2
On répertorie actuellement 118 éléments chimiques et 287 noyaux stables pour près de 2 800 noyaux radioactifs que l’on peut représenter sur le diagramme de Segrè avec en abscisse le numéro atomique et en ordonnée le nombre de neutrons .
Supplément numérique
Cliquez ici pour découvir un diagramme (, ) de Segrè animé, afin d’observer la structure atomique de chaque isotope et de découvrir leur stabilité ou types d’émissions.
Doc. 3Radioprotection
Doc. 3
Doc. 4Exposition à la radioactivité
Doc. 4
L’exposition à la radioactivité naturellement présente dans l’air et dans l’alimentation est quasi-permanente. Elle peut varier en fonction de la zone géographique.
Une exposition ponctuelle est également possible lors d’examens médicaux ou de voyages en transports aériens, par exemple, avec des doses radioactives parfois importantes.
Ces différentes expositions peuvent entraîner des problèmes de santé à plus ou moins long terme.
Une exposition ponctuelle est également possible lors d’examens médicaux ou de voyages en transports aériens, par exemple, avec des doses radioactives parfois importantes.
Ces différentes expositions peuvent entraîner des problèmes de santé à plus ou moins long terme.
Compétences
✔ RAI/MOD : Modéliser
une transformation
✔ RAI/ANA : Utiliser et interpréter des documents
✔ RAI/ANA : Utiliser et interpréter des documents
Questions
1. Proposer une explication au fait que le radium non thérapeutique ait finalement été interdit.
2. Identifier la zone du diagramme (, ) correspondant à chaque type d’émission et citer la ou les particules en excès dans chaque cas.
3. Dans le milieu médical, le carbone 11 est utilisé pour la tomographie, l’iode 131 pour la scintigraphie et le radium 226 pour la radiothérapie. À l’aide d’une classification périodique, écrire les équations des désintégrations associées.
4. Préciser à quoi servent les protections dans les salles de radiothérapie.
2. Identifier la zone du diagramme (, ) correspondant à chaque type d’émission et citer la ou les particules en excès dans chaque cas.
3. Dans le milieu médical, le carbone 11 est utilisé pour la tomographie, l’iode 131 pour la scintigraphie et le radium 226 pour la radiothérapie. À l’aide d’une classification périodique, écrire les équations des désintégrations associées.
4. Préciser à quoi servent les protections dans les salles de radiothérapie.
Synthèse de l'activité
Lister les risques encourus en cas d’exposition lors d’une radiographie.