TissueDB/Tissues/Tumor
Solid tumors are abnormal masses of tissue characterised by increased cellular density and firmness compared to surrounding tissue. They may arise from epithelial, mesenchymal, or connective tissues and often present as discrete, palpable lesions within subcutaneous or deeper tissue planes. Breast lesions are abnormal masses within breast tissue, and ultrasound-guided core-needle biopsy "is an essential diagnostic tool for the evaluation of breast lesions".[1] In simulation a tumour is almost never modelled on its own: it is a discrete inclusion of one material held inside a block of a second material standing in for the healthy tissue around it, and the training value comes from telling the two apart — by ultrasound, by MR contrast, or by what comes back inside a biopsy needle.[2][1]
Materials
| Material | Visual | Tactile | Simulator | Notes |
|---|---|---|---|---|
| Polyacrylamide (PAA) with bovine serum albumin | A 2 cm transparent sphere is the tumour, hung on a thread in the centre of a 6 × 6 × 6 cm cuboid of the surrounding-tissue material. The formulation is 6.65% w/v acrylamide, 0.35% w/v bis-acrylamide, 2% w/v bovine serum albumin, 6% v/v glycerol and 1.1% w/v silicon dioxide in a 0.2 M citrate buffer held at pH 4.5. The albumin is what makes it a tumour rather than a lump: it coagulates from transparent to cream-white above 55 °C, and the buffer is there to bring that threshold down from the protein's natural 70 °C into the 50–60 °C range of thermal injury to soft tissue, so the ablated volume becomes visible to the naked eye. Density 1.076 ± 0.011 g/cm³, propagation speed 1616 ± 7 m/s at 2.7 MHz.[2] | |||
| Agar with silica dioxide (the healthy tissue around the tumour) | 6% w/v agar + 4% w/v silica dioxide, poured around the suspended sphere and cooled to 45 °C first so it does not coagulate the protein inside it. This is the opaque option: it gives strong MR contrast against the tumour sphere but you cannot see into it. Density 1.060 ± 0.012 g/cm³, propagation speed 1537 ± 6 m/s at 2.7 MHz.[2] | |||
| Polyacrylamide (the healthy tissue around the tumour) | 7% w/v PAA with 2% w/v bovine serum albumin and no silicon dioxide — the same recipe as the sphere minus the contrast agent. The whole block is then transparent, so the coagulated focal spot can be watched forming without an MRI scanner. Leaving the silicon dioxide out of the surround is what preserves the contrast between the two.[2] | |||
| Green olives in black-ink agar | For breast lesions the whole tumour is a table olive. Several green olives float inside a "round pie" of black-ink coloured agar-agar gel; under ultrasound they are the lesions, and "presence of olive material inside the biopsy needle confirmed a correct biopsy" — the model marks its own success.[1] A second published model puts a green pea inside a pimento olive and embeds it in a turkey breast, so that a radiotracer injected into the pea makes an occult lesion for radio-guided localisation.[3] |
Things to Look Out For
Reading the phantom as an anatomical breast. The agar-and-olives model teaches finding and hitting a lesion, nothing else. Its own authors list first among the study's limitations that "the training phantom made of agar-agar does not realistically resemble the human breast". It is a target field, not a breast.[1]
Expecting a second run out of it. The same limitation list says the phantom "can only be used for one training session", and the authors note that the alternatives they were avoiding — cadaver and turkey-breast models — are single use as well.[1]
Treating the colour change as the ablation boundary. In the albumin phantom the protein starts coagulating just above 55 °C and is only fully coagulated, cream-white, at about 65 °C. The visible white volume is therefore a threshold crossing, not an isotherm, and the edge of what you can see is not the edge of the thermal dose.[2]
Handling the tumour material before it has set. Acrylamide is neurotoxic before polymerisation and the source requires a fume hood and safety equipment for the whole preparation; it is safe to handle only after polymerisation is complete. The exothermic reaction is also enough to spoil the phantom — the filled moulds go straight into sealed bags at about 4 °C for at least 30 minutes "to avoid premature coagulation of the thermally sensitive BSA protein".[2]
- Breast — the surrounding tissue in the breast-lesion models; Breast Lesions redirects to this page
- Adipose Tissue — common surrounding tissue
- Skin — overlying structure in cutaneous and subcutaneous tumors
- Fascia — boundary structure for deep tumors
- Muscle — deep tumor plane
Simulation Requirements
| Domain | Requirements |
|---|---|
| Visual | Two different answers, and the choice is a design decision. An opaque agar surround gives no view in, so the lesion is found only on the scanner. A transparent polyacrylamide surround lets a coagulating focal spot be watched turning from clear to cream-white "with 'naked eyes' without the necessity of using advance equipment and techniques such as MRI and MR-Thermometry". For the ultrasound-biopsy model the visual requirement is simply that the lesion shows against the background: green olives in black-ink agar, imaged before and after the needle pass.[2][1] |
| Tactile | Not characterised in either source. Both report density, propagation speed, attenuation and MR relaxation, and neither reports a stiffness, indentation or palpation measurement — so although "increased cellular density and firmness compared to surrounding tissue" is what defines a solid tumour clinically, neither paper sets a measured firmness target for a tumour phantom. What they do set is a needle-feel requirement: the biopsy is judged correct by what the needle brings back, not by what it felt like going in.[1] |
References
[edit source]- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 Schmidt G, Gerlinger C, Endrikat J, Gabriel L, Müller C, Baus S, Volk T, Findeklee S, Solomayer EF, Hamza A, Ströder R. Teaching breast ultrasound skills including core-needle biopsies on a phantom enhances undergraduate student's knowledge and learning satisfaction. Archives of Gynecology and Obstetrics 2021;304(1):197–202. DOI: 10.1007/s00404-021-06016-8. PMID 33728537. PMC PMC8164585.
- ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 Sofokleous P, Damianou C. High-quality agar and polyacrylamide tumor-mimicking phantom models for magnetic resonance-guided focused ultrasound applications. Journal of Medical Ultrasound 2023;32(2):121–133. DOI: 10.4103/jmu.jmu_68_23. PMID 38882616. PMC PMC11175378.
- ↑ Aydogan F, Mallory MA, Tukenmez M, Sagara Y, Ozturk E, Ince Y, Celik V, Akca T, Golshan M. A low cost training phantom model for radio-guided localization techniques in occult breast lesions. Journal of Surgical Oncology 2015;112(4):449–451. DOI: 10.1002/jso.23984. PMID 26250621. Abstract consulted.