Imaging technology today is providing a far more accurate and insightful glimpse into men’s health than ever before. In particular, state-of-the-art imaging technology is aiding in the screening, diagnosis, and treatment of the three biggest killers of men: lung, prostate, and colon cancers.
But we have good news. According to the National Cancer Institute (NCI of Bethesda, Md), the death rate from lung cancerthe leading killer-continues to decrease among white and black men. Prostate cancer death rates have been declining since 1994, according to the NCI, and colorectal cancer mortality rates have been in steep decline since the mid-1980s.
Modalities for Diagnosis
“CT is and has been the gold standard” for cancer diagnosis and follow up, due to its ease of use, access in the community, and excellent ability to view tumors, according to Sholom Ackelsberg, general manager of global CT and functional imaging research at GE Healthcare (Waukesha, Wis).
Today’s CT scanners provide submillimeter isotropic resolution capabilities, which enable physicians to see an object in any dimension with equal levels of very precise detail, allowing for accurate measurements of any object in the body. GE Healthcare’s LightSpeed VCT scanner, for example, provides 4 cm of anatomic coverage with 0.35-mm isotropic resolution in a single gantry rotation, which means a much shorter breath hold for the patient and, thus, a quicker exam. In illustration, it allows for a noninvasive coronary CT angiogram to be performed in 5 seconds.
“We’ve seen CT become the main imaging tool in just about every radiology practice in the country,” says Doug Ryan, director of the CT business unit at Toshiba American Medical Systems (TAMS of Tustin, Calif).
The use of positron emission tomography (PET) is also very effective in diagnosing tumors. And PET/CT is considered by many to provide unparalleled imaging sensitivity and acquisition flexibility.
“The PET market became very strong within the last 3 years,” explains Karthik Kuppusamy, global manager of functional CT and advanced imaging applications at GE Healthcare. “Three years ago, it was a PET market. Today, it is a PET/CT market. More than 90% of all PET/CT procedures are done for oncology, because PET/CT provides metabolic information, so the physician can begin treatment planning at once.”
Ryan states that PET is primarily used for breast cancer diagnosis, but as PET’s target area grows, it will be used to diagnose tumors in other areas of the body.
Four-dimensional respiratory gating with CT or PET/CT applications is an invaluable tool in accurate tumor targeting and treatment, according to Ackelsberg.
GE Healthcare’s 4-D respiratory gating tool, Advantage 4D, provides functionality that allows physicians to assess motion of tumors and organs, measure the motion, select candidates for gated therapy, and provide dynamic input for both gated and ungated radiation therapy planning.
“The Advantage 4D software enables physicians to monitor breathing through time and match images to the patient’s breathing cycle,” says Wendy Harris, general manager of the oncology division at GE Healthcare. “Together with a linear accelerator, Advantage 4D works to track the tumor and treat it as it’s moving.”
CT and PET/CT both are used in screening, diagnosis, and treatment of lung, prostate, and colorectal cancer.
“CT tells us the anatomical characteristics of the structure-the volume and density of the tumor structure-and the anatomical information, [as in] what organs the tumor is attached to or if the tumor has encroached upon the capsule of the prostate. It helps the physician in deciding the course of treatment,” states Praveen P. Nadkarni, MD, marketing manager of cardiac and preventive care in the CT marketing division at Siemens Medical Solutions (Malvern, Pa). “CT also can guide radiation therapy treatment by telling us exactly where to deliver the radiation dose, and it also can tell us if the treatment has been effective, using a follow-up CT scan to evaluate the change in tumor size posttreatment.”
According to Nadkarni, the ability of state-of-the-art 16- and 64-slice CT to look at submillimeter structures is its key contribution to earlier visualization of cancer. Higher resolution is possible by the latest advances in CT technology, and the newer diagnostic tools that are enabled and enhanced by CT also help improve tumor detection.
The first 4-slice CT scanner was developed in 1998, and it had a resolution of 1 mm for routine applications. Today’s newest CT scanners have a 0.4-mm resolution. CT scanners have evolved rapidly, from 4 to 16 and now to 64 slices per rotation.
“Even a small submillimeter change in resolution can make quite a difference in terms of earlier diagnosis,” Nadkarni explains.
Multi-slice CT technology has helped drive the development of further technological applications for tumor detection, such as colonography and advanced lung analysis software, according to Ackelsberg.
Simulation software aids the physician in actively planning treatment, by using CT or PET/CT scan information to simulate treatment plans.
Virtual Reality
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TAMS Ryan explains that just 5 years ago, a CT exam of the colon took up to 15 minutes; today, advances in CT acquisition mean that the same exam can be done in about 10 seconds. Nodules are characterized more easily, and fewer movements take place in the colon during the exam.
“A colonoscopy is very uncomfortable for the patient. They want to get it done quickly,” Ryan says. “Now we can acquire many more images with CT-and a lot quicker. You can see more of the body or of a particular area in question.”
Vikas Narula, manager of collaboration development at Vital Images (Minneapolis), notes that a tremendous effort within radiology has been to prove the merits of virtual colonography. Today’s CT technology and patient preparation techniques, along with the advantages of advanced visualization software, have helped make CT colonography a more widespread screening technique for detecting colon cancer.
“Now, radiologists can [move] through the colon and get a virtual view, in a minimally invasive manner,” Narula says. “Advances in software technology have improved read time efficiency and accuracy, making CT colonography more attractive and realistic.”
Some still debate whether CT colonography is better than conventional colonoscopy, but according to Narula, “Radiologists know it’s moving in that direction; it’s just a matter of time until CT colonography is routine practice.”
“Multiple facets are involved to ensure complete adoption of the technique,” he continues, “including scientific validation, patient and physician education, and technology standardization. Radiologists can now virtually slice the colon and get a vision of it, all without having to ever penetrate the patient. Increases and advances in software technology have improved speed and access. We can get a few hundred scans from moving a patient only twice.”
Points With Prostate Cancer
Many techniques in imaging today are used for diagnosing and treating prostate cancer, including intensity modulated radiation therapy (IMRT), ultrasound, and brachytherapy.
IMRT is an advanced mode of high-precision radiotherapy that uses computer-controlled X-ray accelerators to deliver exact radiation doses to a malignant tumor or particular areas within the tumor. The radiation dose is designed to conform to the tumor shape by modulating the strength of the radiation beam to focus a higher dose to the tumor, all while minimizing exposure to surrounding tissues. Treatment is carefully planned using 3-D CT images of the patient, along with computerized dose calculations to determine the dose intensity pattern that will best conform to the tumor shape. Several intensity-modulated fields coming from different beam directions combine to produce a radiation dose tailored to the patient that maximizes tumor dose and minimizes exposure to adjacent tissues.
“Today, more imaging tools are available,” says Joe Barden, global oncology manager at Vidar Systems (Herndon, Va). “When you put these advanced imaging modality capabilities with IMRT, it allows you to pinpoint radiation to the tumor and spare healthy tissue. Imaging coupled with IMRT has allowed the treatment process to evolve from having radiation delivered to a very large area to a much smaller target region. Imaging in IMRT allows you to verify the dose delivered against the dose prescription. These image-based targeting and verification processes allow for more accurate information to impact the tumor and mean shorter wait times to measure the patient’s response to treatment. Better treatment management means better outcomes-especially in prostate cancer. With IMRT, success rates can be as high as 95%, no matter when the cancer was diagnosed.”
Because the ratio of normal tissue dose to tumor dose is minimized with the IMRT approach, increased radiation doses can be targeted safely to tumors with fewer side effects, compared to conventional radiotherapy techniques. IMRT also has the potential to reduce treatment toxicity, even when doses are not increased. IMRT allows immediate verification of successful treatment.
Currently, IMRT is being used to treat prostate cancer as well as cancers of the head and neck, breast, thyroid, and lung and in gynecologic, liver and brain tumors, lymphomas, and sarcomas.1 IMRT can provide a high radiation dose to the prostate gland while reducing the dosage that reaches the rectum and bladder. Because IMRT is so accurate, a higher daily dosage is frequently used, compared to regular radiation techniques, so the treatment can be completed in fewer days. IMRT can be used as the sole treatment for prostate cancer, for 6-7 weeks; or 4 weeks of IMRT is combined with high dose rate (HDR) brachytherapy for a state-of-the-art treatment combination.2
Along with diagnosing prostate cancer, ultrasound is commonly used to guide the biopsy, according to Heidi Hricak, MD, chairman of diagnostic radiology at Memorial Sloan-Kettering Cancer Center (New York.)
Urologist John Sislow, MD, agrees, adding that he uses ultrasound at his practice in Walla Walla, Wash. “Ultrasound is more practical and less time consuming than a CT,” he says. “It can be done in the doctor’s office, and it helps pinpoint exactly where to biopsy. Ultrasound can show low-density areas that can be indicative of prostate cancer. The image can be enhanced for a clear picture. Anybody can appreciate a better image-it helps the practitioner diagnose cancer.”
Finally, HDR brachytherapy is sometimes combined with two other separate therapies-moderate dose external beam radiation and short-term hormonal therapy-to be known as “triple-modality therapy.” Studies have shown that adding hormonal therapy to radiation can increase the tumor control rates, notably for Gleason 7 and higher or for prostate-specific antigen (PSA) 10 or higher. Patients with a low-risk prostate cancer might be advised to take a shorter duration of hormone therapy or none at all. Patients with high-risk prostate cancer might be advised to take triple hormone blockade for approximately 15 months.2
HDR brachytherapy can be used for a range of prostate stages, PSA values, and tumor grades. The components and dosages are modified for those with low-, intermediate-, or high-risk prostate cancer. This treatment also can be used for tumors that are too advanced for radical prostatectomy. For early stages, this treatment is an alternative to the radical prostatectomy, but with fewer side effects.2
According to Michael J. Zelefsky, chief of brachytherapy services at Memorial Sloan-Kettering, “3-D IMRT is a new technique that allows radiologists to deliver higher radiation doses, a substantial improvement in brachytherapy. Ultrasound is used during the brachytherapy procedure to place the seeds with precision. Now we have very sophisticated computer programs to capture needle coordinates where the seeds should be for best dose to the gland and minimal dose to the urethra and rectum. [The use of] 3-D IMRT has reduced side effects [of radiation therapy] and improved precision.”
Zelefsky adds that MRI, PET, and other related imaging modalities are being used more and more to monitor treatment effectiveness. These modalities can be very effective tools in localizing active cancer cells, and he believes that they could lead to “supertargeted” therapies.
“CAT, MRI, and PET simulators are now standard in planning and more effectively map out the areas that need to be treated,” he says. “The need for additional therapies very often depends on what we glean from imaging studies.”
Two More Tools
Medical film digitizers convert hard copy X-ray, CT, ultrasound, MRI, and radiation dose films to digital images that are electronically transmitted, viewed, analyzed, and stored. High-quality electronic images help clinicians improve patient care and enhance efficiency in many ways.
Film dosimetry is the practice of using film to measure aspects of radiation delivery, while quality assurance (QA) monitors beam performance. Dose film information is obtained from dosimetry software and merged with images to complete a final analysis of prescription dose versus actual dose.
“The charged coupled device (CCD) detector quantity and quality has advanced from a 4,000 element array to an 8,000 element array in the last 10 years,” explains Vidar Systems’ Barden. “The detector converts digital information from the analog film on the shape and intensity of the beam and scatter from the beam. We have the capability to manage an array with firmware from 0.0 optical density (OD) to 4.0 OD. We’ve gone from 12-bit grayscale data acquisition to 32-bit grayscale data acquisition and to mapping 8-, 12-, and 16-bit grayscale. We now have up to 65,000 shades of gray to measure the dose profile against.”
Advanced radiation therapy treatments use the penumbral region to better treat tumor regions and spare adjacent tissue, instead of just the flat part of the beam. Greater dose accuracy provided by digitizers result in less damage to surrounding tissues and better patient outcomes.
Film-based dosimetry provides radiation physicists and oncologists with high-resolution, reproducible analyses of radiation treatment beams. Dose levels to adjacent tissues can be accurately measured and controlled, resulting in greater confidence in the delivered dose, less damage to surrounding tissue, and better outcomes for patients.
Advanced Visualization Software
Radiologists can be overwhelmed with the volume of images and data presented by diagnostic imaging tools, making it difficult to identify specific cancers. The introduction of multi-slice CT equipment, along with review workstation hardware and software advances, leads many radiologists to use sophisticated 3-D visualization software.
Three-dimensional imaging software is used in clinical diagnosis and therapy planning, enabling users to combine medical images created in different scanning modalities to form a single image with richer diagnostic information. The technology can fuse images from the same or different modalities (eg, CT, MR, and PET), from data sets acquired at different times, or from data sets generated on equipment from different manufacturers. Software-based fusion technology can assess the movement of a patient examined using a combined scanner, such as PET/CT, and comparing images taken at different times, such as before and after treatment. The user can create 2-D and 3-D views of human anatomy and interactively navigate within these images to better visualize and understand internal structures and disease conditions.
CAD systems are another cutting-edge diagnostic tool in lung cancer. The vertical integration of CAD and hardware development results in better integration of software and film digitizer components, lower production costs, and reduced administrative overhead.
Advanced lung analysis software aids in tumor diagnosis by quantifying scars and lesions present on the lungs and tracking them over time. It aids treatment by measuring the volume and number of lesions to see if the treatment is working.
Men: More Health Savvy
“Consumers are becoming more aware of their own health,” says Nadkarni of Siemens. “Now they take their health in their own hands. The Internet, as an educational medium, has been partially responsible for this [transformation]. Also, there is better and more consumer-directed advertising today.
“Plus, physicians now realize that newer technologies can play a role in earlier diagnosis,” he continues. “Earlier diagnosis could equal a reduction in the morbidity and mortality rate.”
Vidar Systems’ Barden believes that improved technology, coupled with a growth in patient education, is responsible for earlier cancer diagnosis and treatment among men.
“Most men don’t like going to the doctor,” he says. “Therefore, the more men know about the heath issues facing them, and the understanding of how new technology can improve their life expectancy and quality, the more willing they will be to make that critical appointment.”
Laura Gater is a contributing writer for Medical Imaging.
References
- ACR/RSNA/RadiologyInfo.com. Intensity-Modulated Radiation Therapy (IMRT). Available at: http://www.radiologyinfo.org/content/therapy/imrt.htm. Accessed July 27, 2004.
- Cancer Treatment Centers of America. HDR Prostate Brachytherapy. Available at: http://www.brachytherapy.com/prost-brachy.html. Accessed July 27, 2004.
Today’ Prostate Cancer Treatments: More Aggressive, Successful
In recent years, doctors have become increasingly willing to treat prostate cancer more aggressively with radiation therapy. As a result, more patients are being cured of their cancer, according to a recent study.1 A 1999 Patterns of Care survey reviewing the records of more than 550 patients from 58 institutions across the United States shows that, in comparison to surveys from 1989 and 1994, radiation oncologists are using higher doses of external beam radiation therapy to treat both earlier stages and more aggressive forms of prostate cancer. In 1999, 45% of prostate cancer patients were treated with higher doses of radiation therapy compared with 3% in both 1989 and 1994. In the study, researchers learned that the results of clinical trials have persuaded many radiation oncologists today to add androgen deprivation therapy to radiation therapy for treating more aggressive or well-established cancers. Further, the use of CT-based treatment planning and conformal radiation therapy for treatment delivery has significantly increased. “This is an important study because it looks at changing trends over many years in the use of radiation therapy for curing prostate cancer in the United States,” says Michael J. Zelefsky, MD, lead author of the study and a radiation oncologist at Memorial Sloan-Kettering Cancer Center (New York). “After careful analysis, we have learned that, in general, more radiation oncologists are applying the results of clinical trials, which have taught us to use higher dose levels of radiation and integrate hormone therapy in conjunction with radiation therapy to achieve more successful outcomes for prostate cancer patients. In short, the trends are demonstrating more precise delivery of high-dose treatment.” -LG Reference
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Coronary Calcium Screening
“The presence of calcium in the coronary arteries, and the amount, are accepted as indicators for coronary artery disease,” notes Roger Schulte, VP of Image Analysis Inc (Columbia, Ky). The company has provided calcium scoring software and calibration phantoms for several National Institutes of Health studies, as well as other scientific studies, that are evaluating whether drugs can reduce calcification in the arteries. Schulte was involved in the early days of coronary calcium scoring development using the Electron Beam CT from Imitron Inc (then of San Francisco) in the late 1980s, when coronary calcium screening was first studied. At that point, it was only a “pipe dream,” he recalls. Cardiologist Arthur Agatston, MD, worked closely with Imitron engineers to develop the quantification of calcium as a quantifiable indicator of coronary artery disease. Agatston published many of the early studies on calcium scoring. With the recent advent of very fast multi-slice CT scanners and respiratory gating, coronary calcium screening capabilities have been distributed widely in the marketplace, and software is becoming more sophisticated. According to Schulte, the new Image Analysis calcium scoring software, for example, is focused on a high degree of automation and includes phantom calibration to aid in measurement precision and improvement in the ability to perform serial exams to monitor calcified plaques over time. -LG |
Coronary calcium has always been suspected to be a marker for coronary artery disease. Today, with faster slice CT scanners, calcium can be detected inside the coronary artery.
QCT Bone Density MeasurementMen with prostate cancer usually have low bone mass as a consequence of the cancer or the treatments. Physicians need to establish a baseline for bone mass after patients are determined to have cancer. Most prostate cancer patients are older and have developed age-related calcifications in their spine and other areas. Other methods of bone-density testing are not able to eliminate the extraneous calcifications and have poor sensitivity compared to quantitative computed tomography (QCT). “If you’re trying to monitor bone-density drug therapy, QCT with 3-D imaging makes it possible to isolate the metabolic bone to see changes, loss, or gain from therapy,” explains Roger Schulte, VP of Image Analysis Inc (Columbia, Ky). “DXA [dual-energy X-ray absorptiometry] lacks some sensitivity because it can’t separate the metabolic part from the structural part of the bone.” Image Analysis introduced the first commercial QCT bone densitometry system in 1984. All CT manufacturers can offer QCT capabilities for most scanners; some companies, like Image Analysis, provide the bone mineral density (BMD) application software. Image Analysis offers a bone densitometry system that provides DXA-like results from calibrated and reformatted 3-D CT images. DXAVIEW Spine includes both cortical and trabecular bone components at multiple regions of interest (ROI). The patient is scanned simultaneously with the calibration phantom from which conventional QCT as well as DXA measurements are possible. The reprocessed image data provide a 2-D projection measurement of bone density, referenced to calcium hydroxyapatite as with conventional DXA. Spinal trabecular bone is generally considered the site of highest sensitivity for BMD measurements, as trabecular bone is the most biologically active site for bone loss or gain. DXAVIEW Hip from Image Analysis uses a CT 3-D volumetric image set to provide DXA-like measurements of the hip. CT images are calculated using calcium hydroxyapatite phantoms as with conventional QCT. The hip is isolated from the surrounding soft tissue and image data are reprojected from 3-D to 2-D space. ROIs are placed on the calibrated 2-D data, and calculations are performed. Conventional DXA has been shown to create BMD inaccuracies in large patients with significant overlying soft tissue. The 3-D data of CT avoids these problems by eliminating the overlying soft tissue before computing BMD values. The entire QCT measurement, including acquisition, automated ROI placement, and generation of the patient report, can be completed in just a few minutes. The exam requires only a lateral localization image and three low-dose CT slices. The software provides analysis with graphical output and clinical report generation. Bone densitometry can then be analyzed at any convenient time. QCT is reimbursed by Medicare as well as by most private insurers. -LG |
