Tissue-mimicking phantom for prostate cancer brachytherapy

1. A phantom for prostate cancer brachytherapy comprising:

(a) a prostate tissue phantom having a shape of a real prostate gland, the prostate tissue phantom comprising a polyvinyl alcohol cryogel having undergone 3-5 freeze-thaw cycles and having 10-20% w/w polyvinyl alcohol in a solvent, 4-8% w/w oil and an amount of acoustic scattering particles to ultrasonically distinguish the prostate tissue phantom from its surroundings;

(b) a perineal tissue phantom surrounding the prostate tissue phantom, the perineal tissue phantom comprising a polyvinyl alcohol cryogel having undergone 1-2 freeze-thaw cycles and having 10-20% w/w polyvinyl alcohol in a solvent, 4-8% w/w oil and an amount of acoustic scattering particles to ultrasonically distinguish the perineal tissue phantom from its surroundings;

(c) a skin tissue phantom separating all or part of the perineal tissue phantom from an outside environment, the skin tissue phantom comprising a polyvinyl alcohol cryogel having undergone at least 6 freeze-thaw cycles and having 15-25% w/w polyvinyl alcohol in a solvent; and,

(d) an enclosure for containing the prostate tissue phantom, the perineal tissue phantom and the skin tissue phantom.

2. The phantom for prostate cancer brachytherapy according to claim 1 , further comprising a urethra tissue phantom in an anatomically correct position with respect to the prostate tissue phantom.

3. The phantom for prostate cancer brachytherapy according to claim 2 , wherein the urethra tissue phantom comprises a polyvinyl alcohol cryogel having undergone at least 5 freeze-thaw cycles and having 10-20% w/w polyvinyl alcohol in a solvent and 5-20% w/w acoustic scattering particles.

4. The phantom for prostate cancer brachytherapy according to claim 3 , wherein the urethra tissue phantom comprises a polyvinyl alcohol cryogel having undergone at least 6 freeze-thaw cycles having 15% w/w polyvinyl alcohol, and 9% w/w cellulosic acoustic scattering particles.

5. The phantom for prostate cancer brachytherapy according to claim 1 , wherein the solvents comprise water.

6. The phantom for prostate cancer brachytherapy according to claim 1 , wherein the oils comprise castor oil or mineral oil.

7. The phantom for prostate cancer brachytherapy according to claim 1 , wherein the polyvinyl alcohol cryogel of the prostate tissue phantom underwent 4 freeze-thaw cycles and has 0.1-1% w/w acoustic scattering particles and the polyvinyl alcohol cryogel of the perineal tissue phantom underwent 1 freeze-thaw cycle and has 2-10% w/w acoustic scattering particles.

8. The phantom for prostate cancer brachytherapy according to claims 1 , wherein

the polyvinyl alcohol cryogel of the prostate tissue phantom underwent 4 freeze-thaw cycles and has 15% w/w polyvinyl alcohol, 6% w/w castor oil and 0.5 wt % cellulosic acoustic scattering particles,

the polyvinyl alcohol cryogel of the perineal tissue phantom underwent 1 freeze-thaw cycle and has 15% w/w polyvinyl alcohol, 6% w/w castor oil and 3% w/w cellulosic acoustic scattering particles, and

the polyvinyl alcohol cryogel of the skin tissue phantom has 20% w/w polyvinyl alcohol.

9. The phantom for prostate cancer brachytherapy according to claim 1 , wherein one or more of the tissue phantoms comprises a biocide.

10. A prostate tissue phantom having a shape of a real prostate gland, the prostate tissue phantom comprising a polyvinyl alcohol cryogel having undergone 3-5 freeze-thaw cycles and having 10-20% w/w polyvinyl alcohol in a solvent, 4-8% w/w oil and 0.1-1% w/w acoustic scattering particles, weights based on total weight of the cryogel.

11. The prostate tissue phantom according to claim 10 having undergone 4 freeze-thaw cycles and having 15% w/w polyvinyl alcohol in water, 6% w/w castor oil or mineral oil and 0.5% w/w cellulosic acoustic scattering particles.

12. A perineal tissue phantom comprising a polyvinyl alcohol cryogel having undergone 1-2 freeze-thaw cycles and having 10-20% w/w polyvinyl alcohol in a solvent, 4-8% w/w oil and 2-10% w/w acoustic scattering particles, weights based on total weight of the cryogel.

13. The perineal tissue phantom according to claim 12 having undergone 1 freeze-thaw cycle and having 15% w/w polyvinyl alcohol in water, 6% w/w castor oil or mineral oil and 3% w/w cellulosic acoustic scattering particles.

14. A skin tissue phantom comprising a polyvinyl alcohol cryogel having undergone at least 6 freeze-thaw cycles and having 15-25% w/w polyvinyl alcohol in a solvent.

15. The skin tissue phantom according to claim 14 having 20% w/w polyvinyl alcohol in water.

16. A method of producing a phantom for prostate cancer brachytherapy comprising:

(a) providing an enclosure;

(b) positioning a polyvinyl alcohol cryogel-based skin tissue phantom in the enclosure over an area through which a brachytherapy needle can be inserted;

(c) positioning a polyvinyl alcohol cryogel-based prostate tissue phantom in the enclosure in correct anatomical orientation to the skin tissue phantom and a transrectal ultrasound for a brachytherapy procedure;

(d) introducing a polyvinyl alcohol solution into the enclosure to surround the prostate tissue phantom; and,

(e) subjecting the enclosure and its contents to at least one freeze-thaw cycle to create a polyvinyl alcohol cryogel-based perineal phantom from the polyvinyl alcohol solution.