PET/CT in Evolution
PET/CT technology is fairly mature. Hybrid scanners are best known for their utility in accurate staging in certain types of cancers, including lung, liver, breast and prostate. Yet, medicine is just beginning to scratch the surface of PET/CT’s potential.
The newest options, such as Siemens Medical Solutions Biograph with TrueV extended field of view option, improve on their predecessors and open the door to new clinical applications, improved patient care and increased efficiency.
Next generation PET/CT: Under the microscope
Karolinska University Hospital/Institute in Stockholm, Sweden, started the PET/CT deployment process in 2002. After securing funding in 2004, Prof. Stig A. Larsson, PhD, head of department of nuclear medicine, and his colleagues began evaluating various options.
“It was difficult,” admits Larsson, “as our county hospital was the first in Sweden to invest in PET/CT technology.” Ultimately, the Swedish pioneer selected Siemens Biograph with TrueV. The decision boiled down to a few factors, says Larsson. The hospital already owned two Siemens PET scanners (ECAT Exact and ECAT 31), so investing in its PET/CT sibling offered a degree of consistency and familiarity for both radiologists and technical staff. In addition, Karolinska University Hospital wanted to pair PET with 64-slice CT as the combination delivers the benefits of both PET scanning and 64-slice CT technology. That end-goal narrowed the field to a single vendor.
The final factor, says Larsson, is the increased axial field of view on the Siemens Biograph with TrueV. “A conventional PET scanner includes three detector rings, which create an axial field of view of approximately 16 cm,” Larsson explains. “Biograph with TrueV adds a fourth detector ring, which increases the axial length to 21.5 cm. It is quite an improvement.”
The system delivers benefits on multiple fronts; it is more efficient, accurate and cost-effective than other PET/CT scanners. For starters, the larger field of view not only translates into a 30 percent increase in sensitivity, but also a reduction of bed positions from seven to five in whole-body PET/CT scans. Spatial resolution is similar to other scanners, but each scan entails more counts to create a more accurate image with less noise. In fact, the wider axial field translates into a 78 percent increase in count rate performance.
“Since deploying PET/CT, some surgeons do not operate until a PET/CT study with 18FDG [fluorodeoxyglucose] is performed,” says Larsson. The technology has shown to be particularly helpful in lung cancer and liver transplant cases.
Take for example a surgical lung cancer case. If the tumor has metastasized outside of the lungs, the patient is seldom a surgical candidate. Conventional imaging, however, does not provide a clear guidance. “Biograph with TrueV is much more accurate,” Larsson says. “Surgeons are more sure of what they see, and whether or not the tumor has metastasized beyond the lungs. They are better able to determine appropriate treatment, which means better patient outcomes.”
In addition to providing improved clinical images, the system offers new levels of efficiency. For example, a conventional 2D axial PET whole-body scan with a 10 cm field of view can take an hour or longer. A three-detector ring PET/CT scanner reduces the scan time to 15 to 20 minutes. Biograph True V delivers additional improvements by cutting scan time to 10 to 15 minutes.
Karolinksa University Hospital/Institute is capitalizing on the reductions in scan time by increasing patient throughput. “When we first started PET/CT scanning in May 2006, we scheduled four to five patients a day on the three ring, 16 cm field-of-view system. When we upgraded to the fourth ring, we increased the patient load to 10 to 12 patients daily,” explains Larsson. The hospital aims to increase throughput again by beginning FDG injections at 8:30 am rather than 10 am. “We’ll easily be able to run 15 to 16 patients each day.” In addition, the shorter scan time delivers additional image-quality benefits, says Larsson, as patients are much less likely to move during a 15-minute scan than they are during a one-hour study.
The faster throughput benefits both patients and the bottom line, says Larsson. Patients have shorter wait times, which can accelerate the care cycle. And Karolinska increases its revenue via the additional patient load.
Another plus associated with Siemens Biograph PET/CT is the solid engineering behind the scanner. “Usually new systems have bugs in the software and higher than normal downtime,” Larsson says, “but we’ve had very few problems with this solution.” The lack of downtime has allowed the site to build momentum in PET/CT imaging as radiologists and technologists build their skills and exploit the capabilities of the system.
Setting the stage for optimal deployment
PET/CT does bring significant results and benefits; however, it requires some adjustments, particularly in the area of staffing. “It’s important to realize that PET/CT takes some time to interpret,” notes Larsson. Karolinska Institute/Hospital ensured high-quality, timely turn-around by adding a second nuclear medicine physician to its staff, and Larsson expects to hire a third specialist in the next year.
Staffing considerations extend beyond physicians. Karolinska also hired two new technologists to staff its PET/CT scanner. Larsson cautions, “It can be challenging to find techs experienced in both CT and nuclear medicine.” In fact, the hospital’s new techs both came from a CT environment and lacked nuclear medicine experience. The solution, however, was fairly simple. Karolinska sent the new techs to two training courses to bring them up to speed with PET/CT technology.
Future directions
Karolinska University Hospital/Institute remains in the early stages of PET/CT scanning and anticipates additional gains as physicians better understand the capabilities of the Biograph with TrueV.
One area of intense interest is gated respiratory and cardiac studies. Larsson and his colleagues are investigating the utility of the system in gated exams. “It is reasonable to predict that the scans will be quite useful,” notes Larsson. Once again, he credits the extended-field-of-view capabilities for the improvement. “The technologist can extend the field as the lung tumor moves, so that the field always covers the tumor.” The improved coverage, in turn, helps radiation oncologists better define the target and confine treatment to the tumor.
Larsson foresees PET/CT opening other doors as well. For example, the combination of 64-slice CT with the increased sensitivity enabled by the larger field of view is expected to improve results in cardiac studies — for instance by dynamic studies using 11C-acetate. Another option is dynamic studies of the lungs and liver. PET/CT could be used in place of SPECT to determine energy metabolism and other biochemical mechanisms in various organs. A very interesting approach would be to test a variety of some specific substances for tumor imaging to evaluate the pathological nature of the tumor tissue.
The newest options, such as Siemens Medical Solutions Biograph with TrueV extended field of view option, improve on their predecessors and open the door to new clinical applications, improved patient care and increased efficiency.
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| Acquired on the Biograph 16-slice PET•CT system, this image shows a male patient with rising PSA-values following treatment for prostatic cancer. The CT-image (left) does not show any suspicious findings. The FDG-PET image (center) shows two metastases. The overlaid PET/CT image (right) shows the exact location of the metastases (arrows) in the abdomen. |
Next generation PET/CT: Under the microscope
Karolinska University Hospital/Institute in Stockholm, Sweden, started the PET/CT deployment process in 2002. After securing funding in 2004, Prof. Stig A. Larsson, PhD, head of department of nuclear medicine, and his colleagues began evaluating various options.
“It was difficult,” admits Larsson, “as our county hospital was the first in Sweden to invest in PET/CT technology.” Ultimately, the Swedish pioneer selected Siemens Biograph with TrueV. The decision boiled down to a few factors, says Larsson. The hospital already owned two Siemens PET scanners (ECAT Exact and ECAT 31), so investing in its PET/CT sibling offered a degree of consistency and familiarity for both radiologists and technical staff. In addition, Karolinska University Hospital wanted to pair PET with 64-slice CT as the combination delivers the benefits of both PET scanning and 64-slice CT technology. That end-goal narrowed the field to a single vendor.
The final factor, says Larsson, is the increased axial field of view on the Siemens Biograph with TrueV. “A conventional PET scanner includes three detector rings, which create an axial field of view of approximately 16 cm,” Larsson explains. “Biograph with TrueV adds a fourth detector ring, which increases the axial length to 21.5 cm. It is quite an improvement.”
The system delivers benefits on multiple fronts; it is more efficient, accurate and cost-effective than other PET/CT scanners. For starters, the larger field of view not only translates into a 30 percent increase in sensitivity, but also a reduction of bed positions from seven to five in whole-body PET/CT scans. Spatial resolution is similar to other scanners, but each scan entails more counts to create a more accurate image with less noise. In fact, the wider axial field translates into a 78 percent increase in count rate performance.
“Since deploying PET/CT, some surgeons do not operate until a PET/CT study with 18FDG [fluorodeoxyglucose] is performed,” says Larsson. The technology has shown to be particularly helpful in lung cancer and liver transplant cases.
Take for example a surgical lung cancer case. If the tumor has metastasized outside of the lungs, the patient is seldom a surgical candidate. Conventional imaging, however, does not provide a clear guidance. “Biograph with TrueV is much more accurate,” Larsson says. “Surgeons are more sure of what they see, and whether or not the tumor has metastasized beyond the lungs. They are better able to determine appropriate treatment, which means better patient outcomes.”
In addition to providing improved clinical images, the system offers new levels of efficiency. For example, a conventional 2D axial PET whole-body scan with a 10 cm field of view can take an hour or longer. A three-detector ring PET/CT scanner reduces the scan time to 15 to 20 minutes. Biograph True V delivers additional improvements by cutting scan time to 10 to 15 minutes.
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| Biograph 16-slice PET•CT system |
The faster throughput benefits both patients and the bottom line, says Larsson. Patients have shorter wait times, which can accelerate the care cycle. And Karolinska increases its revenue via the additional patient load.
Another plus associated with Siemens Biograph PET/CT is the solid engineering behind the scanner. “Usually new systems have bugs in the software and higher than normal downtime,” Larsson says, “but we’ve had very few problems with this solution.” The lack of downtime has allowed the site to build momentum in PET/CT imaging as radiologists and technologists build their skills and exploit the capabilities of the system.
Setting the stage for optimal deployment
PET/CT does bring significant results and benefits; however, it requires some adjustments, particularly in the area of staffing. “It’s important to realize that PET/CT takes some time to interpret,” notes Larsson. Karolinska Institute/Hospital ensured high-quality, timely turn-around by adding a second nuclear medicine physician to its staff, and Larsson expects to hire a third specialist in the next year.
Staffing considerations extend beyond physicians. Karolinska also hired two new technologists to staff its PET/CT scanner. Larsson cautions, “It can be challenging to find techs experienced in both CT and nuclear medicine.” In fact, the hospital’s new techs both came from a CT environment and lacked nuclear medicine experience. The solution, however, was fairly simple. Karolinska sent the new techs to two training courses to bring them up to speed with PET/CT technology.
Future directions
Karolinska University Hospital/Institute remains in the early stages of PET/CT scanning and anticipates additional gains as physicians better understand the capabilities of the Biograph with TrueV.
One area of intense interest is gated respiratory and cardiac studies. Larsson and his colleagues are investigating the utility of the system in gated exams. “It is reasonable to predict that the scans will be quite useful,” notes Larsson. Once again, he credits the extended-field-of-view capabilities for the improvement. “The technologist can extend the field as the lung tumor moves, so that the field always covers the tumor.” The improved coverage, in turn, helps radiation oncologists better define the target and confine treatment to the tumor.
Larsson foresees PET/CT opening other doors as well. For example, the combination of 64-slice CT with the increased sensitivity enabled by the larger field of view is expected to improve results in cardiac studies — for instance by dynamic studies using 11C-acetate. Another option is dynamic studies of the lungs and liver. PET/CT could be used in place of SPECT to determine energy metabolism and other biochemical mechanisms in various organs. A very interesting approach would be to test a variety of some specific substances for tumor imaging to evaluate the pathological nature of the tumor tissue.
| ADDITIONAL RESOURCES Read more on Siemens PET/CT |