Patent Number: 
Section: claims

1. A radiation-shielding assembly for holding a container, the assembly comprising:a body comprising radiation shielding material and at least partially defining a cavity having first and second opposite ends and an axis extending between the first and second ends; anda spacer adapted to be at least partially received in the cavity, the spacer being selectively adjustable to change a space between a container support surface in the cavity and the first end of the cavity for use in positioning containers of different heights in a substantially similar location relative to the first end of the cavity, the spacer being slidable along the axis of the cavity to adjust the space between the support surface and the first end of the cavity. 2. The assembly of claim 1, wherein the support surface is defined by a radiation shielding element adapted to limit escape of radiation through the second end of the cavity. 3. The assembly of claim 1, wherein the spacer is adapted to move the support surface along the axis of the cavity upon rotation of the spacer. 4. The assembly of claim 3 further comprising:a detent adapted for being fixed relative to the body, wherein the spacer has a helical channel defined therein, the detent being received in the channel. 5. The assembly of claim 4 wherein the helical channel is a first helical channel, the spacer having a second helical channel therein, the first channel being adapted for use with a first container and the second channel being adapted for use with a second container, the first container having a different height than the second container, the assembly being adapted to permit selective movement of the detent between the first and second helical channels. 6. The assembly of claim 4 wherein a plurality of recesses are formed in a bottom of the helical channel, and wherein the detent is adapted for selective engagement with the recesses for indexed movement of the spacer relative to the detent. 7. The assembly of claim 1, wherein the body defines an opening at the second end of the cavity, the assembly further comprising a base releasably secured to the body at the second end of the cavity, the base defining a receptacle that adjoins the opening when the base is secured to the body, the spacer being adapted to be at least partially received in the receptacle, a detent of the spacer being mounted on the base so that the detent is substantially fixed relative to the body when the base is secured to the body. 8. The assembly of claim 1 wherein the spacer has a plurality of markings thereon corresponding to the different heights of the containers, the markings being positioned relative to a viewing window of the assembly so that a marking indicating a particular height of a container in the cavity is in registration with the window when the spacer is adjusted to make the space between the support surface thereof and the first end of the cavity substantially correspond to a height of the container of that particular height. 9. A method of using a radiation-shielding assembly, the method comprising:disposing an adjustable spacer of a radiation-shielding assembly a first distance from an open end of a cavity defined in the radiation-shielding assembly to define a first volume for holding a container; andmoving the spacer along an axis of the cavity to dispose the spacer a second distance from the open end of the cavity to define a second volume for holding a container, the second distance being different than the first distance and the second volume being different from the first volume. 10. The method of claim 9 further comprising releasably locking the spacer in position relative to the cavity. 11. The method of claim 9, wherein the moving comprises rotating the spacer relative to at least another portion of assembly. 12. The method of claim 9, wherein the assembly comprises a detent and defines a channel in which the detent is disposed, wherein the moving comprises moving at least one of the detent and the channel relative to the other of the detent and the channel. 13. The method of claim 9, further comprising:placing a first container of a first height in the cavity prior to the moving;removing the first container from the cavity prior to the moving; andplacing a second container of a second height different from the first height in the cavity subsequent to the moving. 14. The method of claim 9, wherein the moving comprises moving the spacer from a first indexed position to a second indexed position.