{IMAGERIGHT:http://www.massdevice.com/sites/default/wp-content/uploads/checkup/090922_index1.gif}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 from its most recent quarterly report and each Friday’s closing share price.

The Massachusetts index for the week ended Sept. 18 closed at 5.2, down a tick compared with the prior week. Since Jan. 1, when we began tracking these companies, the index has risen 17.2 percent.

The Minnesota index for the week ended Sept. 18 closed at 3.5, down 1.1 percent compared with the prior week. Since Jan. 1, when we began tracking these companies, the index has risen 19.5 percent.

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The California index for the week ended Sept. 18 closed at 6.6, up 2.6 percent compared with the prior week. Since Jan. 1, when we began tracking these companies, the index has risen 54.8 percent.

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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):

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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 Sept.18:

The 10 biggest gainers:

1. Intraop Medical Corp. (CA): 250% (open $0.02; close $0.07)
2. Imaging3 Inc. (CA): 157.1% (open $0.14; close $0.36)
3. Acusphere Inc. (MA): 36.4% (open $0.11; close $0.15)
4. Enteromedics Inc. (MN): 33.1% (open $3.63; close $4.83)
5. Thermage Inc. (Solta Medical Inc.) (CA): 31.9% (open $1.63; close $2.15)
6. Pressure BioSciences Inc. (MA): 25% (open $1.48; close $1.85)
7. Hypertension Diagnostics Inc. (MN): 25% (open $0.12; close $0.15)
8. Pro-Dex Inc. (CA): 20% (open $0.50; close $0.60)
9. NMT Medical Inc. (MA): 19.9% (open $1.81; close $2.17)
10. Trimedyne Inc. (CA): 16.7% (open $0.36; close $0.42)

Sources: Google Finance and Yahoo! Finance.

And the 10 biggest losers:

1. Quick-Med Technologies Inc. (MA): -34% (open $1.00; close $0.66)
2. Optical Sensors Inc. (Vasamed) (MN): -33.3% (open $0.15; close $0.10)
3. World Heart Inc. (CA): -20.7% (open $4.49; close $3.56)
4. Bruker Corp. (MA): -10.2% (open $10.72; close $9.63)
5. AdvanSource Biomaterials Corp. (MA): -8.8% (open $0.34; close $0.31)
6. Osmetech (MA): -8.8% (open $2.50; close $2.28)
7. Hansen Medical Inc. (CA): -7.9% (open $3.40; close $3.13)
8. Uroplasty Inc. (MN): -7.6% (open $0.79; close $0.73)
9. Oculus Innovative Sciences Inc. (Micromed) (CA): -6.9% (open $2.88; close $2.68)
10. Cytori Therapeutics Inc. (CA): -6.8% (open $3.81; close $3.55)

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.