Postcards From San Francisco — SIR 2012
Vol. 13 No. 4 P. 32
Editor’s Note: This article was produced from press materials and staff press conference coverage at the Society of Interventional Radiology’s (SIR) 37th Annual Scientific Meeting last month in San Francisco.
Reducing Dose in CT-Guided Lung Biopsy
Revising CT protocols from equipment standards can reduce radiation exposure in lung nodule biopsies, according to research presented at SIR’s annual meeting last month.
While there is debate about the actual risk of cumulative exposure from the types of medical imaging that emit radiation, interventional radiologists and other doctors are trying to curb patient dose. CT has been gaining recognition as the most effective imaging technique for lung nodules since it is more sensitive than chest X-rays and other imaging tests.
“Lung nodules are clearly imaged using CT because of the high contrast between normal air-containing lung tissue and higher-density lung nodules,” said Jeremy Collins, MD, an assistant professor of radiology at Northwestern University in Chicago. “CT technologies have come a long way in offering new tools that reduce the per-procedure radiation dose.”
This research protocol adjusted CT imaging parameters to further reduce radiation exposure while maintaining image quality. The new protocol reduces the amount of energy the CT scanner uses to produce images and moderates the current of the X-ray tube to put out a smaller dose during examination.
“All image studies using X-ray technology are going to be associated with a small amount of finite radiation exposure,” Collins said. “Although the jury is still out to some degree, there is general consensus in the community that the radiation dose risk is both linear and additive. Any place where we can reduce the incremental dose for each imaging study is very important because the overall exposure over time can be substantial.”
For the study, researchers implemented the new CT imaging protocol for lung nodule biopsy and then reviewed data from 100 people, one-half of whom underwent CT-guided biopsies prior to the new protocol and one-half after the protocol went into effect. The low-dose protocol led to a 66% drop in radiation dose, and image quality was maintained for all biopsies. “We found that simple modifications to the CT technique used for guidance to perform lung biopsies resulted in a significant dose reduction to individuals treated,” Collins said. “This was possible while maintaining appropriate image quality for interventional radiologists performing biopsy, and fortunately the modification to the scanner technique is simple and can be applied to any existing CT scanner system.”
The lower-dose protocol can be adopted immediately, Collins noted, but physicians need to evaluate each case based on a person’s body size or anatomy that is more difficult to image.
Reducing dose for lung nodule biopsy could prove especially useful if CT screening of smokers becomes more widely used.
“The published early results of a trial using computed tomography to detect lung nodules demonstrated that screening with low-dose CT reduced mortality from lung cancer by 20% compared to screening with chest X-rays alone,” Collins said. “Statistically, many people who undergo screening will have nodules detected with CT and a biopsy may be recommended. We want to minimize the side effects of the biopsy procedure.” ■
Endovascular Aorta Repair Offers Lower Mortality Rates
Endovascular repair of the abdominal aorta is safer than open surgical repair and associated with lower mortality rates, according to data presented at SIR’s annual meeting.
About one-half of the patients who suffer a burst aneurysm in the abdominal aorta don’t make it to the hospital in time for life-saving treatment, which is most likely to be open surgery to repair the blood vessel. In this study, researchers retrospectively compared patients who were treated with open surgery to endovascular repair; the study examined the histories of nearly 39,000 patients. In the United States, 9% of the population over the age of 65 has an abdominal aortic aneurysm, and there are 15,000 deaths per year from their rupturing.
“We found that endovascular aortic repair resulted in significantly fewer hospital deaths after treatment compared to open surgery, and the hospital stay associated with endovascular repair was less than that of open surgery,” said Prasoon Mohan, MD, coauthor of the study.
The researchers reviewed data from the National Inpatient Sample (NIS), a national all-payer database containing information on approximately 8 million hospital encounters per year. The objective was to compare outcomes of all cases of ruptured abdominal aortic aneurysm from 2001 to 2009 that were treated by endovascular repair or open surgery. They found 38,858 individuals who received one of these two treatments. Endovascular repair was used to treat 6,790 patients; 32,069 individuals had open surgery.
The researchers reported that 39.7% of patients who received open surgery died in the hospital compared with 28.2% of patients who received the stent graft. The average length of hospital stay was almost 14 days for surgery patients compared with approximately 11 days for patients who had the endovascular procedure. While 35% of patients were able to go home without requiring further in-patient rehabilitation after endovascular repair, only 22% of open surgery patients were discharged to their homes. Interestingly, regardless of the type of repair, women had worse outcomes compared with men after the procedure.
“Endovascular aortic repair involves less recovery time and fewer discharges to in-patient care facilities, potentially saving insurers, institutions and individuals money,” Mohan said. He added the researchers are working with their hospitals’ institutional review boards and the FDA to develop a prospective trial of the two procedures. ■
New Data on Prostate Embolization for BPH
The Brazilian interventional radiologist pioneering prostatic artery embolization for benign prostatic hyperplasia (BPH) presented new data on the treatment for enlarged prostate at SIR’s annual meeting.
“Having an enlarged prostate is very common in many men over the age of 50, and these new findings provide hope for those who might not be candidates for transurethral resection of the prostate, or TURP, and may allow them to avoid serious complications that sometime result from surgery, such as impotence, retrograde ejaculation, and urinary incontinence. This could mean that more men have a chance at getting their lives back,” said Francisco Cesar Carnevale, MD, PhD, a professor and chief of the interventional radiology section at the Hospital das Clínicas Hospital of the Faculty of Medicine at the University of São Paulo in Brazil.
A man’s prostate can slowly grow larger with age due to a noncancerous process known as BPH. In many men, this enlargement can compress the urethra and cause urination and bladder problems such as dribbling at the end of urinating, an inability to urinate, incomplete emptying of the bladder, incontinence, and having a strong and sudden urge to urinate or a weak urine stream. For these men, symptoms can cause a marked decrease in quality of life, Carnevale said.
“This study looked at results from men who suffered with acute urinary retention due to an enlarged prostate and who were treated,” noted Carnevale, who indicated that prior to embolization, all had medical treatment and urethral catheters and were waiting for surgery. “After the treatment, we assessed quality of life and evaluated how well the urinary system was working. Clinical success was seen in 91% of those treated, and technical success was evident in 75% of those treated.”
Using a tiny 1-mm-diameter microcatheter threaded into the prostate arteries, 12 prostatic artery embolization procedures using resin microspheres as embolizing agents were performed on 11 individuals aged 59 to 78 (average age of 68.5) under local anesthesia. MRI and ultrasound were also used to study the exact anatomy of the prostate.
Carnevale’s subjects had follow-up ranging from 16 to 45 months. At the time of treatment, the men’s prostate volume ranged from 30 to 90 g (the normal male prostate weighs 20 to 25 g); all reported acute urinary retention.
Both ultrasound and MRI revealed an overall 30% volume reduction in the prostate size at final follow-up. Overall clinical improvement in lower urinary tract symptoms at the one-year mark was observed and corroborated by all patients. All those treated also reported a high degree of satisfaction and increased quality of life after the treatment.
“Although these preliminary results are very promising for American men, it must be noted that prostate artery embolization is an extremely advanced embolization procedure requiring rigorous training and a detailed knowledge of the prostate anatomy and surrounding vessels,” said James B. Spies, MD, MPH, FSIR, a professor and chair of the radiology department at Georgetown University Medical Center in Washington, DC.
“More than a quarter of a million men undergo surgery for an enlarged prostate every year, at an estimated annual cost of over $1 billion per year because current therapies including medication just aren’t working for them,” said Ziv J Haskal, MD, FSIR, who traveled to Brazil to learn about the treatment and to begin the process that may bring this treatment to the United States. “I saw firsthand how these men responded to treatment. With the possibility of faster recovery—on an outpatient basis—and with no bladder catheters, reduced symptoms, improved urination, and fewer potential side effects, prostatic artery embolization could signal a bold new change in accepted prostate therapy.” ■
Stomach Embolization Could Be a Weight-Loss Treatment
Using embolic beads to block arteries to the stomach and suppress hunger could someday become a less invasive alternative to weight-loss treatments, according to lab animal research presented at SIR’s annual meeting.
“Currently, there are three clinically viable surgical alternatives for obesity: gastric bypass surgery, gastric pacing, and endoscopic gastric banding. These procedures have varying success rates; they are invasive, require extensive gastric/bowel reconstruction or external devices, and can have significant surgical complications,” said Charles Y. Kim, MD, an assistant professor of radiology at Duke University Medical Center in Durham, North Carolina, and lead investigator on one of the studies.
“Our promising results led us to believe that a minimally invasive interventional radiology treatment called bariatric arterial embolization would allow for precise targeting of a specific portion of a person’s stomach in order to decrease production of ghrelin, a hormone that causes hunger. This treatment could one day be the answer for those who have not been successful with weight loss through diet and exercise,” Kim said.
In lab animal studies, researchers selectively embolized and decreased the blood flow to a very specific part of the stomach, which led to significantly decreased levels of ghrelin in the treated animals. “We found that when ghrelin levels decrease, appetite and hunger also decrease, causing weight loss in the treated animals relative to nontreated animals,” Kim explained. “Bariatric arterial embolization may have a future use in treating obesity in humans by significantly suppressing appetite to achieve weight loss.”
The researchers will continue studies aimed at the reduction and elimination of complications, such as stomach ulcers, and expressed confidence that bariatric arterial embolization is very close to moving toward the clinical trial phase in the United States.
A second study related to the topic tested a new type of X-ray-visible embolic bead for bariatric arterial embolization.
“Until now, clinically available embolic beads have not been visible on X-ray during or after delivery,” explained Clifford R. Weiss, MD, an assistant professor of radiology at Johns Hopkins University School of Medicine in Baltimore. “We developed a new embolic bead that can be seen directly by X-ray imaging and have tested them [in an animal model] in the new bariatric embolization treatment for obesity.”
Typically, embolic beads are mixed with an X-ray-visible contrast agent that shows the beads’ location during infusion, but the beads can’t be tracked after the contrast washes away, Weiss noted.
“By making the beads X-ray visible and using them in tandem with C-arm cone-beam CT—a new way of X-ray imaging that creates 3D pictures—these beads can be tracked both during and after delivery,” Weiss said. “This allows for more precise assessment of ‘on-target’ embolization. Due to the fact that these beads are visible and can be tracked over time, we should be able to assess their long-term presence. If needed, the patient can then be retreated. With the current clinically available beads, it is not possible to determine whether they are intact and functional over time. We recommend further studies to prove the beads’ safety over time and ensure they do not have any unintended effects on the target organs or on the individuals being treated. We believe there are myriad possible applications for these beads, such as treating cancer of the liver or noncancerous uterine masses.” ■