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Tickers in this article: ACHC IDXX OMED VAR
DELAFIELD, Wis. (Stockpickr) -- Professional traders running mutual funds and hedge funds don't just look at a stock's price moves; they also track big changes in volume activity. Often when above-average volume moves into an equity, it precedes a large spike in volatility.

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Major moves in volume can signal unusual activity, such as insider buying or selling -- or buying or selling by "superinvestors."

Unusual volume can also be a major signal that hedge funds and momentum traders are piling into a stock ahead of a catalyst. These types of traders like to get in well before a large spike, so it's always a smart move to monitor unusual volume. That said, remember to combine trend and price action with unusual volume. Put them all together to help you decipher the next big trend for any stock.

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With that in mind, let's take a look at several stocks rising on unusual volume today.

Varian Medical Systems

Varian Medical Systems (VAR) is a manufacturer of medical devices and software for treating cancer and other medical conditions with radiotherapy, radiosurgery, proton therapy and brachytherapy. This stock closed up 1.5% at $79.24 in Monday's trading session.

Monday's Volume: 1.53 million
Three-Month Average Volume: 773,698
Volume % Change: 97%

From a technical perspective, VAR jumped modestly higher here with above-average volume. This stock has been uptrending strong for the last month, with shares moving higher from its low of $71.98 to its intraday high of $79.34. During that move, shares of VAR have been consistently making higher lows and higher highs, which is bullish technical price action. That move has now pushed shares of VAR within range of triggering a big breakout trade. That trade will hit if VAR manages to take out Monday's high of $79.34 to its 52-week high at $80.66 with high volume.

Traders should now look for long-biased trades in VAR as long as it's trending above some near-term support levels at $77 or at $76 and then once it sustains a move or close above those breakout levels with volume that's near or above 773,698 shares. If that breakout hits soon, then VAR will set up to enter new 52-week-high territory, which is bullish technical price action. Some possible upside targets off that breakout are $85 to $90.