Our Weekly Checkup takes the temperature of the medical device industry’s three largest U.S. clusters: Massachusetts, California and Minnesota.

The MassDevice Indices are weighted according to market capitalization, based on the number of shares outstanding for each company and each Friday’s closing share price.

The Massachusetts index for the week ended Jan. 7, 2011, closed at 6.04, down 1.3 percent compared with the prior week. Since Jan. 1, 2009, when we began tracking these companies, the index has risen 36.2 percent.

The Minnesota index for the week ended Jan. 7, 2011, closed at 3.51, down 5.9 percent compared with the prior week. Since Jan. 1, 2009, when we began tracking these companies, the index has risen 18.9 percent.

The California index for the week ended Jan. 7, 2011, closed at 8.49, up 0.3 percent compared with the prior week. Since Jan. 1, 2009, when we began tracking these companies, the index has risen 100.0 percent.

We also create a composite index of the three regional indices and compare it with four other indices (the S&P 500, the Dow Jones Industrial Average, the Dow’s IHI medical devices index and the NASDAQ exchange):

The Weekly Checkup also compares Monday morning’s opening share prices with their value when the markets close Friday afternoon to calculate the biggest gainers and losers.

Here are the 20 firms that posted the biggest share price gains and losses during the week ended Jan. 7, 2011,:

The 10 biggest gainers:

1. Imaging3 Inc. : 18.59% (open $0.16; close $0.19)
2. Iridex Corp. : 7.16% (open $3.77; close $4.04)
3. Cytori Therapeutics Inc. : 5.61% (open $5.53; close $5.84)
4. Uroplasty Inc. : 4.83% (open $4.35; close $4.56)
5. Biomerica Inc. : 3.70% (open $0.41; close $0.42)
6. WuXi PharmaTech: 3.70% (open $16.76; close $17.38)
7. Conceptus Inc. : 3.66% (open $12.83; close $13.30)
8. Cardica Inc. : 3.33% (open $4.51; close $4.66)
9. Labspace (Alexandria Real Estate Equities): 3.33% (open $73.08; close $75.51)
10. Psychemedics Corp.: 2.78% (open $8.27; close $8.50)

Sources: Google Finance and Yahoo! Finance.

And the 10 biggest losers:

1. NMT Medical Inc.: -21.54% (open $0.65; close $0.51)
2. Biopure Corp.: -16.67% (open $0.01; close $0.01)
3. Patient Safety Technologies Inc. : -8.48% (open $0.93; close $0.85)
4. Biolase Technology Inc. : -7.14% (open $1.68; close $1.56)
5. Cambridge Heart Inc.: -5.13% (open $0.39; close $0.37)
6. Endologix Inc. : -5.04% (open $6.94; close $6.59)
7. Oculus Innovative Sciences Inc. (Micromed): -5.00% (open $2.00; close $1.90)
8. icad Inc.: -4.05% (open $1.48; close $1.42)
9. Caliper Life Sciences: -3.75% (open $5.86; close $5.64)
10. Digirad Corp. : -3.64% (open $2.20; close $2.12)

Sources: Google Finance and Yahoo! Finance.

Disclaimer: MassDevice.com’s rankings do not reflect an opinion of companies’ health, prospects or viability. They are intended to provide a snapshot of publicly traded medical device companies and in no way constitute a recommendation to buy or sell any particular security, portfolio of securities, transaction or investment strategy.