Scan Artist

Most of us have had a panoramic X-ray. Unlike intraoral radiography procedures, panoramic scans don’t have a propensity for causing patients to gag; instead, they capture an image of the oral cavity and adjacent structures extraorally as the sensor circumnavigates the patient’s head. The result is a two-dimensional image of the teeth, jaws, sinuses and temporomandibular joints. But watch your step when it comes to terminology.

This type of radiography, often called a “pan” for short, is also known by an assortment of misleading names — a fact that shouldn’t be lost on savvy sales pros who wish to be taken seriously. Probably the most egregious — and most widespread — radiographical faux pas is to refer to a panoramic X-ray unit as the “panorex.” This is like using the brand name “Kleenex” in reference to all sorts of facial tissues. Panorex is a trademarked name for a machine introduced in North America in 1959. Why does this matter?

“If you want to see a radiologist cringe, call every panoramic view a ‘Panorex,'” cautions Edwin T. Parks, DMD, MS, a professor of oral pathology, medicine and radiology at Indiana University School of Dentistry in Indianapolis. “The only true Panorex,” he explains, “was manufactured by SS White and is no longer available. It had a white spot right down the middle of it, because it would take half of the pan, then move the patient over and take the other half.”

PAN, CEPH OR CONE?

Cone beam computed tomography (CBCT) is the ultimate option in the so-called three-in-one units that typically start with a base panoramic model that can either be ordered or upgraded with cephalometric and/or CBCT capabilities. The latter renders three-dimensional images that, when compared to pans, would seem to be a clear winner in diagnostic utility. And some offices have switched over to this technology whole hog, using it in numerous applications. Three-dimensional radiography can capture tremendous amounts of information that lead to more accurate diagnoses — so why not just go with CBCT imaging?

Edwin T. Parks, DMD, MS, a professor of oral pathology, medicine and radiology at Indiana University School of Dentistry in Indianapolis, explains that the biggest reason is resolution. “With CBCT, taking a scan of the area that you would take in a panoramic view, you may get 1.5 to 2 line pairs per mm resolution,” he says. “But with a digital pan you’ll get 10 to 11 line pairs per mm resolution. So there’s a huge difference between the two.”

Line pairs is a measure of resolution, sort of like counting pixels or dots per inch — and the higher the number, the better the resolution. So, according to Parks, even if you had a CBCT, for a whole jaw shot — showing both maxilla and mandible — taking a pan is the better option.

In addition, he points out that a CBCT machine is about three to four times more expensive and three-dimensional scans emit more radiation than a digital panoramic scan. “In fact,” he reports, “the radiation dosage from a CBCT is about 10 to 30 times the amount of a digital pan. So there’s a significant difference in dose.”

Older panoramic units, still used in many offices, require film, a darkroom and beaucoup chemicals. Digital panoramic systems began to appear in the mid-1990s, however — and have become widely available in the last 10 years. And most clinicians agree this is a good thing. Says the American Dental Association’s Give Kids a Smile program co-founder Jeffrey B. Dalin, DDS, who operates a general practice in St. Louis, “The change to a panoramic digital format has to be the most significant advancement in this field over the past few decades. The quality of the images has improved exponentially.”

In addition, Parks points out that office efficiency is much greater because a staff member isn’t tied up in the darkroom processing filmbased X-rays. “Staff efficiency is usually where you make your dollars,” he notes, adding that with direct digital imaging (as opposed to photostimulable phosphor plate-based indirect digital radiography or film units), the results are immediate. “This means if the image is going south, you can stop right then and there,” says Parks. “You don’t have to complete the image, process it and then find out that something’s wrong.” This kind of instantaneous feedback not only saves time, he asserts, but if it also reduces the need for retakes, it can help minimize cumulative radiation dosage.

PLACES PLEASE

Of course, correct positioning is critical to obtaining clear, diagnostically accurate panoramic images. If the patient is not lined up properly for the scan, the image will distort. Positioning is made easier through the use of a bite guide, chin rest, head supports, handgrips, placement markings and an alignment beam. Many units allow adjustments with the push of a button. Standard placement usually incorporates the Frankfort horizontal plane and midsagittal vertical plane views. Positioning may be slightly different for bitewing shots. Once the patient — outfitted with a protective lead apron and thyroid collar — is in position for image acquisition, the process takes just seconds.

As Paul Feuerstein, DMD, an adjunct professor at Boston’s Tufts University School of Dental Medicine and a Billerica, Massachusettsbased general practitioner, who lectures and writes about digital technology, explains, “The direct digital pan has a sensor, similar to an intraoral digital X-ray sensor, only larger. The machine sends out a beam in one path, capturing information as it circles the patient’s head.”

 

Direct digital imaging captures images via vertical, fan-shaped beams and sensors. They’re connected to a computer that processes the images automatically. By comparison, indirect digital units require the use of photostimulable phosphor plates (more commonly known as PSPs) that, like film cassettes, are inserted into the machine. The plate stores the exposed image, which is extracted once the scan is finished. But whereas film-based pans are developed in a darkroom, PSPs are “read” by laser scanners, resulting in diagnostic-quality radiographs that can be manipulated via software like any digital image.

Digital panoramic unit designs vary according to manufacturer, but common features include the ability to capture various arch shapes, as well as curvilinear images of jaw cross sections, maxillary sinuses and the temporomandibular joints. And one of the more recent developments is the ability to take panoramic bitewings, as well.

LIST THE ADVANTAGES

Feuerstein points out that the advantages of digital panoramic radiography go much further than improved resolution over film. “The method of capture eliminates the blank/overlap area in the middle,” he notes. “You also can zoom in and digitally enhance areas on the digital image and, of course, share images and duplicate them more easily.”

POINT of SALE

  • DIGITAL PANORAMIC RADIOGRAPHY

  • Digital panoramic radiography is quick and comfortable for patients, with the added bonus of requiring a lower dosage of radiation than film.
  • Panoramic systems offer a visual perspective not readily available from conventional intraoral radiography, and this can boost diagnostic utility.
  • Elminating the need for darkrooms, chemicals and developing chores helps save time and money, and is also better for the environment.
  • Many newer digital panoramic radiography units can be upgraded to provide cephalometric and three-dimensional cone beam computed tomography images.
  • Film-based panoramic units can sometimes be upgraded to either indirect or direct digital imaging via retrofitting, and this may represent a worthwhile entry point into the digital milieu.
Dalin, who has been involved with digital radiography since 1998, is in lock step with Feuerstein. “We have the ability to enhance the images,” he reports, “and some units generate instant on-screen images, allowing rapid diagnoses.” He also notes that, compared to film, the sensitivity of digital radiography allows the use of lower doses of radiation when exposing images. “In addition, digital pans are a boon to patient education and case acceptance,” he says. “What’s more, they eliminate the need for a darkroom, chemicals and film, and make it easy to share images with other dentists and third-party payers. It saves money in the long run.”

Parks explains that pans benefit patients in whom clinicians need to see a large area all at the same time, such as in trauma cases or simply for patient ease and the opportunity to see more area. “For example,” he says, “someone comes in saying they have a toothache on the upper right, but they’re not sure which tooth it is. So you take a panoramic and not only can you see the teeth but you can see the sinus — and it could very well be the sinus that’s the problem. With a pan you can see more information than you can with a standard, intraoral periapical X-ray.”

Feuerstein adds that digital pans of children expose them to less radiation than analog panoramic scans, and can easily provide developmental information. “Being that it’s extraoral,” he says, “the child doesn’t have to struggle with film, PSPs or sensors, which can be difficult to tolerate in some cases. Many adult patients who don’t do well with intraoral radiography find that pans are a comfortable option.”

MAKE THE LEAP

For clients with analog radiography units, retrofitting may provide a way to move into the digital world while still using a familiar piece of equipment. Retrofit kits are available to convert certain analog machines to digital technology. Retrofitting of older machines can easily be done with the use of PSPs in place of film. And some systems can also convert film to a digital format. According to Feuerstein and others, this can be a simple and cost-effective way for clinicians to get started in digital radiography.

In some cases, hardware retrofits may be an option — but with retrofits costing more than $10,000, buying a new pan is probably a better strategy, says Feuerstein. “One other idea is getting a digital scanner,” he suggests. “This kind of unit will scan any film and digitally enhance it.”

Many of today’s digital panoramic machines are designed to allow field upgrading. For instance, clinicians can purchase new digital pan units as “three-in-ones.” This means that while they are laying out cash for basic pan units, as their practices or needs grow, cephalometric and, eventually, threedimensional cone beam computed tomography capability can be added.

“Some practices have already gone to digital intraoral sensors and might be interested in getting a digital pan,” notes Feuerstein, adding, “If an office currently has an analog pan and uses it, the digital pan is a step up. Since some models cost less than $25,000, it’s an upgrade worth considering.”

Your clinical clients should also be aware that there are costs involved in going digital that extend beyond the radiographic unit purchase, including software and the need to add monitors or computer stations in operatories. But, says Dalin, “There are countless ways to realize a return on the investment. Besides time savings and the elimination of darkrooms and film-processing chemicals, retakes are instantaneous. Multiple images are often needed during an endodontic appointment, and as much as 20 minutes or more can be saved by doing things digitally.” In addition, he notes that dentists can use this technology to easily check the fit of indirect restorations, saving money by avoiding remakes. “And for periodontics,” he adds, “co-diagnosis and patient education are easier with an enlarged image appearing on a monitor, as opposed to holding up a piece of film. And finally, if patients are able to visualize what practitioners are discussing with them, it will lead to higher rates of treatment acceptance and, ultimately, happier patients.”

So, according to our experts, digital panoramic radiography is no scam, and adopting this technology can only up your customers’ games by improving patient care and elevating the bottom line. The trick is to help them take the leap into the sometimes scary waters of the digital age. But that’s where knowledgeable sales pros come in as they help transform their clients from digital scan phobics to digital scan artists.

TERMS TO LEARN

  • Bitewing X-rays: Typically, images of the crowns of both maxillary and mandibular posterior teeth
  • Direct Digital Radiography: Images captured on digital sensors that can be viewed instantly on a computer monitor
  • Frankfort Horizontal Plane: Also called “eye-ear plane,” this is an imaging perspective in which the uppermost portion of the external ear canal is aligned with the low point on the lower orbital margin
  • Indirect Digital Radiography: Digital systems using photostimulable phosphor plates (often known by the acronym PSP); these must be exposed and then scanned to obtain images for viewing
  • Line Pairs Per MM (lp/mm): A term describing image resolution, it refers to one black line next to one white space. Like dots per inch (dpi), the higher the value, the better the image resolution
  • Midsagittal Plane: Also called the “median plane,” this imaging perspective results in images in which a vertical, longitudinal plane divides the head into right and left halves

BONUS WEB CONTENT : SENSOR SPEAK

When you start wading into the waters of digital radiography, you start hearing a few acronyms being bandied about: CCD, CMOS and PSP. These are the technologies that allow digital radiography to happen.Though called “sensors,” charge-coupled devices (CCD) and complementary metal oxide semiconductors (CMOS) are actually solid-state image receptors and are used in direct intraoral or extraoral radiography. This technology allows immediate viewing of acquired images via a computer monitor that is connected to the pan unit. 

Photostimulable phosphor plates (PSP) are plates endowed with phosphor particles that capture and store images. This technology is known as indirect digital radiography because the exposed PSP has to be scanned before a digital image can be viewed on a monitor.

For digital panoramic radiography, these are the go-to technologies, with CCD or CMOS seen on newer machines and PSP technology often accommodating retrofits of film based-units.

BONUS WEB CONTENT : FUTURE OF DENTAL RADIOGRAPHY

Right now, dental professionals are striving toward digital workflows, especially when it comes to radiography. “In the near future,” says St. Louis-based general practitioner Jeffrey Dalin, DDS, “we will see units become more affordable, and dentists are already finding more uses for the current technologies.”But what about developments in other kinds of technologies that can lay out the inner landscape of the oral cavity? “I have heard about sonic or ultrasonic technology coming into play in the future,” says Dalin. “This might eventually allow us to eliminate the use of radiation.” 

Edwin T. Parks, DMD, MS, of the Indiana University School of Dentistry in Indianapolis, is skeptical about how soon this might happen. “I think a lot of the caries detection programs that are available will become more user friendly and more accurate with time. And these technologies don’t require X-radiation. But in terms of something that’s totally new, I think it’s going to be some time before we replace the X-ray image — I’m not aware of anything on the horizon that can compete.”

BONUS WEB CONTENT : SELECTION CRITERIA

According to Parks, panoramic radiography isn’t done for every patient, with clinicians following parameters for radiography set forth in “The Selection of Patients for Dental Radiographic Examinations,” a collaborative effort involving the U.S. Food and Drug Administration, American Dental Association and other groups. “With selection criteria the way they’re written now, you pretty much have to answer the question: ‘Why am I taking this?’” he advises. “And if you can’t come up with a reason other than ‘because insurance pays for it,’ it’s probably not a good thing to do. And the latest iteration of the selection criteria states that you should not look for occult pathology. In other words, you shouldn’t take the image on the offhand chance that you might find something. You must have a specific reason.”
MENTOR August 2013, 4(8): 14–16, 18–19.

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