Is More Pb the Answer in a Changing Medical Environment?

1. Is More Pb the Answer in a Changing Medical Environment? Presented by Dawn Banghart, CHP Stanford University

2. Has a doctor ever told you … • We will only do 4 PET/CT studies per day. Maximum. • We will replace the simulator with a PET/CT and will only use it for overflow studies. Its primary use will be after-hours research. • There will never be a PET/CT in this room, just a CT. Really.

3. You are leaving for vacation and get this phone call … • We are purchasing a new, self-shielded, portable intraoperative electron linear accelerator therapy unit. It will be located in our existing OR suite. Does it need any additional shielding?

4. Control panels Chief Tech’s Office Current gamma camera locations It’s Monday. You are getting this Physician’s Email … • We are considering replacing our 3 GE gamma cameras with 3 new cameras, each one having a low-dose CT option. If we replace them, can we still put all three cameras in the same open room? We need a response by Thursday. • The room layout:

5. Introduction • A rapidly changing medical environment includes upgraded diagnostic machines such as • Mobile CT and Therapy units • Increasing PET/CT demands • On-site cyclotrons and facility retrofits • Shielding calculations and considerations are made against the backdrop of • Budget issues • Project timelines • Existing space • Pressures to increase patient load.

6. Topics to be covered • This presentation will: • Summarize the changing landscape of Stanford University’s medical machines and facilities in the past 10 years. • Share and discuss specific shielding projects (the good, the bad and the ugly). • Focus mainly on PET patients and diagnostic machines with the exception of one exotic therapy machine. Tomorrow Today

7. Stanford CTs: A Snapshot10 years Ago and Now 12 total 5 total

8. What’s in the pipeline 18 More!

9. Additional growth measures: • Portable C-arms • 3 in 1997 • 17 in 2007 • Cyclotron Installation (completed in late 2005) Consider increases as more PET/CTs come online.

10. PET/CT Patient load increasesPositron Emitters can’t be ignored • We have • Observed significant patient study increases. • Learned that doctors are not the best resource when considering their changing future. • They consistently underestimate patient workloads. • F-18, while not a machine, with a 4 mm half-value layer, is a walking concern in our waiting rooms and for our doctors and technicians.

11. PET/CT Shielding Calc tools: • Site Evaluation: • Use of adjacent spaces (including above and below injection room and uptake room). • Get architectural drawings as soon as you learn about the project. • We find that obtaining drawings can take weeks and often the needed information (e.g., cross-sections) needs to be requested repeatedly • Spreadsheets are our friend! • AAPM Task Group 108: PET and PET/CT Shielding Requirements includes guidance on: • Decay correction for dose integration period). • Patient F-18 shielding

12. PET Patient Basics – • PET patients use positron emitters (emits 511 KeV photon) • The patient associated dose rate depends on: • Number of patients/week • Procedure time • Uptake time: 1 hour • Scanning time: 0.5 hour • Administered activity • 10 - 20 mCi • Note: Minimal facility shielding is required where clinics have large rooms (greater than 3 meters) Comparison between F-18 and the Tc99m “workhorse”

13. As described by the Stanford Hospital Nuclear Medicine Chief Tech: When we first began, we did up to six patient's a day with one tech. We currently schedule 12-15 patient's a day with one scanner and two techs. As described by the VA Palo Alto Nuclear Medicine Chief Tech: Started operations with new machine May 7, 2006. Began with 4 patients per day now doing 7. We were dosing one per hour, but since June 07, we are “batching” one patient every 30 minutes in the morning. PET Patient workload increases

14. PET Patient Load Increase Patients Per Day

15. Is Stanford’s experience common?What the experts have observed: • “Clinical imaging exams in the US increased almost 600 percent from 1980 to 2006. In the past, natural background radiation was the leading source of human exposure; that has been displaced by diagnostic imaging procedures.” • “This is an absolutely sentinel event, a wake-up call,” said Fred Mettler, principle investigator for the study by the NCRP. “Medical exposure now dwarfs that of all other sources.” Reference: With Rise in Radiation Exposure, Experts Urge Caution on Tests NYT, By RONI CARYN RABIN Published: June 19, 2007

16. Revise the background pie or does more Pb help?

17. Whose doing our work? • Stanford approaches increasing shielding calculation demands in several ways: • Hire one additional health physicist • John Kwofie! • Use the manufacturer to do the bulk of the calculations – then we review and verify • Hire a contractor to do the big projects • The new radiation oncology department • The new nuclear medicine suite • The cyclotron

18. Waiting Area Hot Lab Office First ExampleVA facility new PET/CT machine • Shielded injection and patient waiting room not designed because “patient workload was to be <4 per day.” Workload now 7/day. • Part-time nurse’s dosimeter indicated unusual monthly high exposures (averaging 270 mrem per/month) over 7 months. • Work environment analysis showed the office she’d moved into in August 2006 was next to patient waiting area. When not worn, her lab coat hung on the door facing patient area. • Measured dose rates up to 4 mrem/hr when patients sit near office. • 3 months of monitoring waiting area indicates exposures of 300 mrem/month.

19. Desk Patient Desk Our VA Pb recommendations – • The good news: • After giving our nurse an EPD we found that her actual dose (several mrem/day) was far lower than what her badge was exposed to. • The bad news: • They now want to put two people into this small office. • Recommendations: • Shield the room and convert it into the PET patient injection and waiting area instead of an office. • Shield the wall facing the patient waiting room and remove the door. • Move PET patients to shielded alcove leading to PET/CT room. (The doctor liked this idea.) • Bottom Line: More Pb

20. Second Example - The Mobetron The case of the mobile therapy accelerator • What is it? A mobile electron beam accelerator designed for Intraoperative Radiation Therapy (IORT). • Design minimizes radiation leakage and facilitates IORT treatments in non-shielded operating rooms. • When not in use, treatment head locks horizontally, reducing gantry height enabling doorway and elevators access. • Electron beam energies: • 4 MeV • 6 MeV • 9 MeV • 12 MeV

21. Stanford’s Intended Use • The Mobetron weighs 700 lbs. • Console and high voltage power supply separate • We will house it in one (maybe two) operating room(s). • The SU Hospital OR room has a storage room with a window. We will permanently set up the console area in that room. • The patient bed needs to be moved and aligned with the Mobetron (this will have it’s own challenges for the nursing staff).

22. Mobetron shielding considerations • Mobetron gantry rotates +/-45 degrees from the vertical. A beamstopper tracks the rotation and intercepts patient scatter. • Because the Mobetron is mobile, can be used in more than one OR. • Self-shielding limits stray x-ray radiation to <2 mrem at a distance of 3 m from the patient (for a delivered 2000 rad electron beam dose at 50 cm SSD). • Shielding calculation assumptions: • 3 patients/week and 150/year • QA's to be done in off hours • If more studies desired, shorter or lower energy procedures can be scheduled.

23. Overhead view of OR room

24. Mobetron beam side viewNote Angle limitations

25. Mobetron Calculations:Occupancy assumed to be 1 for adjacent rooms; ¼ for the hallway.

26. Mobetron Pb conclusions: • At this time no Pb appears to be required however occupancy information needs to be obtained for the room below the OR. • Administratively limit studies (patients/week and 150/year – or energetically set limits). • Perform QA the night before. • Procedures need to be developed for OR staff that describes • Room access limitations • Study limitations

27. Third Example: The Portable CereTom • Intended for x-ray CT applications for anatomy that can be imaged in a 25cm field of view • Primarily head and neck • Think: Emergency Department or Oakland Raiders • The Raiders now scan players and diagnose head trauma during games

28. CereTom information • CereTom is a high resolution • 80 KvP • 8 row • 25cm field of view • Uses dry sealed batteries which power system while unplugged • Has necessary safety features such as • Emergency stop switch • X-ray indicators • Interlocks • Patient alignment laser • Has retractable caster wheels so the system can be moved “easily” to different locations.

29. Stanford’s intended use • To be used by the Lucile Packard Children’s Hospital for: • Head scans • Infant abdominal scans (Eventually) • Ideal for children too sick to bring to the emergency department. • Sick children require tremendous support for transport (consider IVs, monitors, etc.) • The CereTom enables quick decisions and timely interventions.

30. CereTom radiation scatter Dosage lines in mR/sec. Overall exposure varies depending on scan times. 45° angle is area of highest exposure

31. CereTom Pb considerations • If the CereTom is rolled into preemie unit what are the exposures to nearby beds? • Dose per scan at 1 meter ranges from 1 to 6 mrem depending on scan parameters • Conclusions: • Provide lead curtains or lead impregnated plastic screens that can extend along the side of the bed to shield the 45° angle exposures • Drape nearby incubators with lead aprons • Challenges: • Ensure visibility of patient is not hampered • Ensure console setup not on 45° angle • Ensure administrative controls are practiced

32. The Tale of Two TrailersFourth Example

33. Trailers are a packaged unit • Advantage, they come pre-shielded, but shielding must be confirmed by survey. • The GE CT mobile unit has fencing to protect it from vehicles (dose rates outside = background). • PET/CT trailer dose rates are ~ 1 mrem/hr near the injection room and: • Has plumbing • Combined hot lab/injection room

34. Trailer Pb Considerations • Our experience so far has been that these mobile facilities are convenient to use and do not require additional Pb. • Cautions: • Park these trailers in areas where there is low occupancy. • Survey exterior to the injection room while occupied by a patient to ensure dose rates are less than 2 mrem in any one hour. • If dose rates exceed 2 mrem in any one hour consider fencing.

35. Final Example – VA Room with 3 Cameras • Our current project: Calculate exposure impact to technicians when 3 gamma cameras replaced Hawkeye CTs. • Note control panel and computer work station locations

36. Control panels Chief Tech’s Office Current gamma camera locations The VA Camera Room • Control panel areas and works stations are the most vulnerable to radiation from the head of the CT. • Calculations show that control panels areas, if directly behind the CT head will receive 20 mrem/week if technicians stayed in the control panel area throughout the whole study.

37. Chief Tech’s Office Current gamma camera locations VA Room with 3 Cameras – Conclusions • The Chief technologist has stated that technicians will not stay in the control panel area. They will move around the room. • Decision: • Remove and limit computer work stations behind the CTs. • Shift console areas • Install portable Pb shields around control panel area. Control panels

38. What are the hurdles to good shielding?

39. Expense • We prefer to design conservatively • Use consistent lead thickness on each wall to minimize errors • Where possible plan for future (assume eventual CT to PET/CT conversions) • Assume patient workload increase. • But Pb is expensive! Dollars/pound per year

40. What’s up with Pb? • By Jan. 6 of this year, Money Week reported that lead prices were up 40 percent for the year (!!). • Market conditions are driven by China. The Chinese, (leading exporters of lead) have: • Decreased their exports • Added a 10 percent tax on lead • Now use more lead in their own manufacturing processes. • The US has five lead mines in: Missouri, Alaska, Idaho, Montana, and Washington.

41. What manufacturing processes are we competing with? • Automobile/truck lead-acid battery industry are the principal users of lead (83%). • 11% of lead used in ammunition; casting material; sheets (including radiation shielding), pipes, cable covering, solder, and oxides for glass, ceramics, pigments, and chemicals. • The balance used for uninterruptible power-supply equipment for computer and telecommunications networks and hospitals, and, ballast and counter weights!

42. What are other hurdles? • Time • They may have end of year money to use or a company may be donating a machine and a “hot” offer may cool off. • Get comfortable with and use that spreadsheet. • Space • Retrofitting rooms and replacing older less energetic machines with newer more energetic machines: • A simulator room becomes a PET/CT room • Find out what Pb may already exist in the walls (This may also be a challenge).

43. To Conclude … • Is More Pb the Answer in a Changing Medical Environment? • At Stanford we found that for: • PET patients and PET/CTs the answer is always yes. • Portable units like the Mobetron, CereTom administrative controls can work. • Trailers – no – but survey to confirm • Machine replacements into existing rooms – usually, but: • The more space the better • Look at existing Pb and determine if it is adequate

44. Thank you! • Questions?