Trans-spectral impedance (T-scan) imaging has been developed over the last decade and has been shown to be a safe and effective technique when used as an adjunct to mammography. The T-scan system was granted US Food and Drug Administration (FDA) pre-market approval (PMA) on April 19, 1999. The T-scan system is the first totally new imaging method to receive FDA approval since magnetic resonance imaging was approved in 1984. The T-scan system (TransScan Tscan-2000) is ISO 9001 (International Standards Organization) certified and has received the CE Mark, the "Conformit� Europe�ne" certification of the European Commission to allow products to be sold in Europe.
T-scan impedance imaging of the breast is generally safe, painless, and unlike x-ray and nuclear medicine imaging, the T-scan does not use radiation. Impedance imaging is also non-invasive, meaning no incision and no injection is needed for the study. The T-scan FDA evaluation process took two years (the original submission was made in 1997); noteworthy since magnetic resonance imaging took four years to gain FDA approval after initial submission in the early 1980s. T-scan imaging has been used clinically in Israel since the 1980s.
The T-scan system underwent a lengthy clinical trial process prior to gaining FDA approval. Clinical trial data for the FDA submission was gathered at seven locations including four hospitals in the United States, and hospitals in France, Israel and Italy:
- Allegheny Hospital, Pittsburgh, Pennsylvania, USA
- Elisha Hospital, Haifa, Israel (Orah Laver-Moskovitz, MD)
- Faulkner Hospital, Boston, Massachusetts, USA (Norman Sadowsky, MD)
- Hadassah Hospital, Mt. Scopus, Jerusalem, Israel (Scott Fields, MD)
- Pistoia Hospital, Pistoia, Italy (Giancarlo Piperno, MD)
- Sinai Women's Health Center, Detroit, Michigan, USA (Michele Rossman, MD, Edward Philips, MD)
- University of Massachusetts Medical Center, Worcester, Massachusetts, USA (Carl D'Orsi, MD)
There is also a TransScan installed at Chilton Hospital in New Jersey (Rena Wagner, MD) that has been operating under an Internal Review Board (IRB).
Click here for a clinical example of T-scan.
The TransScan system underwent a rigorous clinical trial process. A double-blinded study was performed to demonstrate that electrical impedance scanning (EIS) detects cancer and can adjunctively improve diagnostic accuracy. The study was comprised of 504 biopsy cases and 264 screening cases. For each case, the examiner was blinded as to the results of all other tests and a standard, non-targeted frontal full breast EIS was performed, without knowledge of whether there was a lesion or its location. Corresponding four view mammographic examinations were read blindly and then read in adjunctive combination with EIS.
Table 1: Improvement of Diagnostic Accuracy with Adjunctive EIS (2)
| Mammogram | EIS | Adjunctive | p-value | |
| Sensitivity | 82% | 69% | 86% | < 0.1 |
| Specificity | 39% | 45% | 51% | < 0.0001 |
| PPV | 43% | 42% | 49% | < 0.01 |
| NPV | 80% | 78% | 87% | < 0.01 |
PPV = positive predictive value, NPV = negative predictive value
Double Blind Study Results: Improved accuracy in diagnosing breast cancer with adjunctive EIS (T-scan) is shown in Table 1.
Conclusion of Double Blind Study: This study demonstrated that EIS (T-scan) detects cancer and that mammography with adjunctive EIS is more sensitive and specific than mammography alone.
Targeted Study Of EIS: A targeted study of EIS was also performed to determine the accuracy of EIS alone, directed to a specific lesion (abnormality) as intended in clinical use. The EIS was targeted to the lesion and scored positive if a focal brightness from increased conductivity or capacitance values was noted in the vicinity of the lesion. 704 lesions (583 from Elisha Hospital, Haifa; 74 from Hadassah Hospital, Jerusalem and 47 from Pistoia Hospital, Pistoia) were biopsied.
Results Targeted Study Of EIS: EIS findings were correlated against histology and summarized in table 2.
Table 2: Accuracy of Targeted EIS (3)
|
Malignant |
No. | TP | FN | Sensitivity |
| IDC | 119 | 98 | 21 | 82% |
| DCIS | 45 | 33 | 12 | 73% |
| Other | 20 | 18 | 2 | 90% |
| Total | 184 | 149 | 35 | 81% |
|
Benign |
No. | TN | FP | Specificity |
| FCC | 106 | 81 | 25 | 76% |
| FA | 67 | 44 | 23 | 66% |
| HA | 35 | 19 | 16 | 54% |
| AH | 124 | 90 | 34 | 73% |
| mixed/other | 188 | 115 | 73 | 73% |
| Total | 520 | 349 | 171 | 71% |
Abbreviation
Key:
FCC = fibrocystic changes, FA = fibroadenoma, HA = hyperplasia, AH = atypical hyperplasia
IDC = invasive ductal carcinoma, DCIS = ductal carcinoma in situ
When used in conjunction with mammography in multicenter clinical trials, T-scan adjunctive diagnosis increased the sensitivity of mammography from 82% to 86% (in a general population from 80% to 90%) and the specificity from 55% to 77%. In other words, mammography and T-scanning together we able to identify 90% of cancerous abnormalities and determine the specific type of abnormality 77% of the time. Combining T-scan with mammography is projected to provide a 99% negative predictive value (doctors will be able to accurately predict that the patient does not have cancer 99% of the time). (4) The belief is that the T-scan will help improve patient compliance with guidelines for mammography by providing a non-invasive, adjunctive tool to increase the accuracy of breast cancer diagnosis and decrease the number of unnecessary biopsies.
Click here for a clinical example of T-scan.
