IEC (International Electronic Commissioning) is the world’s leading organization that prepares and publishes International Standards for all electrical, electronic and related technologies.  Wherever you find electricity and electronics, you find the IEC supporting safety and performance, the environment, electrical energy efficiency and renewable energies.  The IEC also manages conformity assessment systems that certify that equipment, systems or components conform to its International Standards.

Out of the four components (the couch, jaws, collimator and gantry), we cover the couch and the gantry in this post and will discuss the jaws and the collimator in next post.

The answer is 4.5 cm.

The answer is 998.5 cm.

The answer is 8.5 cm.

The answer is 994.5 cm.

The answer is 79 cm.

The answer is 55 cm.

The answer is 25 degrees.

The answer is 105 degrees.

Couch: Vertical Movement
The couch vertical is at 8.5 cm. You need to move the table 4 cm upward toward the ceiling. At what do you set the new vertical position of the table from outside the treatment room: 12.5 cm or 4.5 cm?
Click on this link for the answer. Depending on your screen resolution, you may have to scroll up to see the answer window.
The couch vertical is at 2.5 cm. You need to move the table 4 cm upward toward the ceiling. At what do you set the vertical position of the table from outside the treatment room: 6.5, -1.5 or 998.5 cm?
Click on this link for the answer.
Tip: Table vertical position is at 0 degrees at iso-center. Moving the couch toward the floor down from iso-center, the number increases on this coordinate axes. If you move the couch toward the ceiling up from iso-center, the number decreases from 1000.

Couch: Lateral Movement
The couch lateral position is at 4.5 cm. You need to move the table 4 cm toward the right of the gantry if you face the gantry. What do you set the new lateral position of the table from outside the treatment room: 8.5 cm or -8.5 cm?
Click on this link for the answer.
The couch lateral position is at 2.5 cm. You need to move the table 8 cm toward left of the gantry if you face the gantry. What do you set the new lateral position of the table from outside the treatment room: -5.5 cm or 994.5 cm?
Click on this link for the answer.
Tip: Table lateral position is at 0 degrees at iso-center. When moving the couch toward the right (facing the gantry) from iso-center, the number increases on this coordinate axes. If you move the couch toward left (facing the gantry) from iso-center, the number decreases from 1000.

Couch: Longitudinal Movement
The couch longitudinal is at 55 cm. You need to move the couch 24 cm toward the gantry. What do you set the new longitudinal position of the table from outside the treatment room: 79 cm or 31 cm?
Click on this link for the answer.
The couch longitudinal is at 105 cm. You need to move the couch 50 cm away from the gantry. What do you set the new longitudinal position of the table from outside the treatment room: -55 cm or 55 cm?
Click on this link for the answer.
Tip: Table longitudinal Position increases if the couch moves towards the gantry and decreases if the couch moves away from the gantry.

Gantry
The gantry is at 115 degrees. You need to move gantry 90 CCW. What do you set the position of the gantry from outside the treatment room: -25, 25, 205, or 335 degrees.
Click on this link for the answer.
The gantry is at 15 degrees. You need to move gantry 90 CW. What do you set the position of the gantry from outside the treatment room: -75, 105, or 255 degrees.
Click on this link for the answer.
Tip: The gantry on the Varian IEC 601-2-1 scale is at 0 degrees when the gantry is up at vertical position. The degree increases as gantry rotates CW. It goes to 90 degrees when the gantry is to the right (facing the gantry), to 180 degree when gantry is down at vertical position, to 270 degree when gantry is to the left (facing the gantry) and increases as it rotates CW to 359.9 and then 0 degree up at vertical position. Reversely, the angle decreases as gantry rotates CCW.

References:

Staffing in radiation oncology practices has always been plagued with administrative issues. The process of radiation therapy consists of a series of steps and often involves a number of different individuals. Each practice should establish a staffing program consistent with patient care, administrative, research and other responsibilities. It is recognized that talent, training and work preferences may vary from individual to individual; therefore, it is appropriate to factor these aspects into a staffing program. Since the 1980′s many organizations have published benchmarks for radiation therapy staffing. Among these organizations are AAPM, ACR, ACRO, AAMD, ASRT and a few private market research institutions. These reports provide benchmarks for the staffing of not only medical physicists, but also dosimetrists, radiation therapists, and nurses. It is worth noting that some of these reports were generated before computer information system technology became a part of radiation treatment systems. We believe that development of benchmarks for staffing in radiation therapy practices is very important and directly affects the quality of patient care and safety. Until we finalize this study, here are some recent staffing levels in radiation therapy practices as published by the ACR for the purpose of radiation oncology program accreditation.

According to the ACR, for accreditation purposes “the facility’s staffing levels for radiation oncologists, physicists, radiation therapists and dosimetrists are compared to the accredited facility averages and averages for the facility’s stratum as defined in the following table. The table allows facilities to identify personnel and equipment utilization issues. Staffing recommendations may be part of the final report; however, variations from these levels generally do not result in withholding of accreditation unless inadequate staffing levels result in non-compliance with ACR Practice Guidelines and Technical Standards and/or compromise patient safety.”

We will post more articles on this topic in a timely fashion and encourage our readers to send us their thoughts and comments on this issue.

“Self assessment is a process by which an organization evaluates its compliance with external regulatory requirement and commitments and with its own internal radiation safety program requirements. It is a proactive component of an effective management plan for a radiation safety program. This report will cover the types of assessments, their purposes, and the processes for conducting them. It will discuss the frequency, the program areas to be assessed, the documentation, and the follow-up of assessments. The report will also discuss guidance for the scheduling and resolution of corrective actions.”

The report provides information and guidance on the following topics:

- Definition and purposes of self assessment;

- Types of self assessment (i.e., performance based, risk based, compliance based, task, process and program level, formal and informal);

- Responsibilities for establishing self-assessment programs including upper management, line management, the radiation safety committee, radiation safety program personnel including the radiation safety manager or radiation safety officer, and the workers;

-Self assessment program planning for an institution, including determining the purpose and type of self assessment, selecting the program elements to be assessed, allocating the necessary resources, and developing a self assessment program review plan;

- Qualification and selection of individuals performing the self assessments;

- Self assessment methods and techniques including evaluation of radiation safety program survey and monitoring results, workplace observations, interviews, document reviews, checklists, review of metrics, and questionnaires;

- Types of deficiencies that can be identified in the self-assessment process, ranging from the minor ones that are most likely to be found to those that are more serious;

- Identification of noteworthy practices;

- Planning an individual self assessment including the program elements to be assessed, the schedule for performing the self assessment, and the types of self assessment to be used;

- Conducting the self assessment including the entrance meeting, performing the assessment activities, daily team conferences, upper management briefings, exit meeting, and documentation;

- Documenting the self assessment including writing reports, report approval, communicating the results, and legal consideration; and

- Developing corrective-action plans including tracking and resolution of corrective actions and reviewing the effectiveness of the corrective-action program.

In a recent newsletter of the Health Physics Society (Volume XXXVIII Number 4 April 2010), it was noted that David Myers, an HPS member, worked on NCRP Report 162.  In the newsletter, he provides more information about the latest report and its importance to the radiation safety programs of all institutions. The report can be purchased through the NCRP web site for $50 or $40 in pdf format.

Streak artifacts in CT images are generated in conventional CT when implanted objects of high atomic number exist in the patient. The artifact and image degradation associated with the kilovoltage (kV) CT imaging in the presence of high atomic number material greatly hinders the ability to delineate tumors and certain organs, particularly in the treatment planning of a prostate patient with hip prostheses. Such a situation, therefore, precludes precise dose calculation. There are several techniques reported that, if used, can minimize such artifacts, thereby enhancing image visualization for the delineation of tumor and other organs.

1- Charmley et al. (1) suggested that the use of CT-MR image registration to define target volumes in pelvic radiotherapy in the presence of bilateral hip replacements could facilitate target definition of prostate patient with hip replacements. However, a number of factors were found to affect image quality and/or the accuracy of target definition. The standard MR couch, different from a CT or linac treatment couch, might result in different patient positions, and the presence of the metallic implants may create significant distortion.

2- Yazdia M. (2) suggested an adaptive approach to metal artifact reduction in helical computed tomography for radiation therapy planning. At that time, they may require manual image post-processing and most CT scanners available in radiation oncology department are not equipped with these features.

3- The artifact image and degradation associated with the kilovoltage (kV) CT imaging in the presence of high atomic number material is greatly reduced with Megavoltage Cone Beam Computed tomography (MV-CBCT). MV-CBCT has been used in image-guided radiotherapy (IGRT) to correct patient setup immediately before treatment. Hansen et al (3) used this technique to treat paraspinous tumors in the presence of orthopedic hardware. It allows rapid acquisition of 3D images that can be registered with the planning CT with millimeter precision and enhance image visualization by exploiting the predominantly Compton scattering of high-energy photons delivered in the MV-CBCT system. Aubin et al. (4) of the Department of Radiation Oncology at UCSF did a study with the support of Siemens Oncology Care systems on the use of Megavoltage Cone Beam CT to complement CT for target definition in pelvic radiotherapy in the presence of hip replacement. They found the MV-CBCT image could be used to clearly visualize the hip prostheses and provide sufficient soft-tissue contrast to help delineate the prostate, bladder and rectum. The artifacts on the kV CT obscure the border between the prostate and anterior wall of the rectum and the interface between the prostate base and the bladder neck. However, the MV-CBCT images were particularly useful to help delineate these structures as well as the lateral extension of the prostate in the axial plane, the seminal vesicles and the lymph nodes. Also, normal anatomy such as pelvic bones, penile bulb, bladder, femoral heads, rectum and small bowel can be delineated with higher accuracy as well. They evaluate this technique for seven patients. For each patient, the MV-CBCT images were imported into the treatment planning system and registered with the original CT using body anatomy contoured on each image set. The target volumes and organs at risk for prostate treatment were contoured using both the CT and the MV-CBCT for single hip replacement, and using only the MV-CBCT for bi-lateral hip prostheses. For the full article, click on: http://bjr.birjournals.org/cgi/reprint/79/947/918

The following two figures taken from Aubin M. at el (4) show the difference between conventional CT and MV-CBCT images:

1. Chamley N. et al. The use of CT-MR image registration to define target volumes in pelvic radiotherapy in the presence of bilateral hip replacements. BJR 2005; 78:634-636.
2. Yazdia M. et al. An adaptive approach to metal artifact reduction in helical computed tomography for radiation therapy planning: experimental and clinical studies. Int. J. Radiation Oncol Biol Physics 2005; 62(4): 1224-1231.
3. Hansen, E.K. et al. Image guided radiotherapy using Megavoltage Cone-Beam Computer Tomography for treatment of paraspinous tumors in the presence of orthopedic hardware. Int. J. Radiation Oncol Biol Physics 2006; 66(2): 323-326.
4. Aubin M. at el. Use of Megavoltage Cone-Beam CT to complement CT for target definition in pelvic radiotherapy in the presence of hip replacement. Short Communication: British Journal of Radiology 2006.

The internet is strewn with information that is helpful in prepping; the resources are scattered through the Web and take time to find. One site worth bookmarking provides lecture notes on several physics topics listed in the Initial Certification Study Guide as well as a few practice questions. Another site with lecture notes on relevant topics is the course site for Diagnostic Radiology Imaging Physics at UW. More practice question can be found here and here (though at this site, you will have to register to access the free tests).

Your main allies will be your own lecture notes and good prep books. While cross-referencing is always helpful, the following texts have been helpful to other students who took the ABR Part 1 Physics exam in the past. The first is “Review of Radiologic Physics” by Walter Huda. The book is 272 pages with over 500 practice questions, and the material covered is high-yield. The next two texts are pricey, but serve as good reference texts to have in your possession. They are “The Essential Physics of Medical Imaging” by Bushberg et al and “Medical Imaging Physics” by William Hendee and E. Russell Ritenour. We have also heard that reviewing Raphex exam questions is also key in preparing. There are still a few copies of the very old exams available for purchase on Amazon.com. You can also find copies of recent exams for free on the Web: Raphex 2006 Questions and Answers, Raphex 1998 Questions, Raphex 1997 Questions and the Raphex 1997 Answers.

Last, but certainly not least, talk to people who have taken the exam within the last few years. They will be able to tell you what the ABR has been stressing on the exam these days. Ask them how they prepped and what they found to be useful. Start early, and with the resources listed above in addition to those you locate on your own, you should be well-prepared to tackle Part 1 with ease and success.

Right now, the site supports three categories: For Sale, Wanted and Services–all with subcategories of their own. As items are listed (or per your suggestions), these categories may grow or change, as necessary. MDPhysics is a great venue to post notices whether you are selling or in need of new or used physics equipment, books, CDs (or any other media), etc, as our site draws a large audience of medical physicists and medical physics students everyday. Please feel free to share the announcement of the new medical physics classifieds portion of the site with your classmates and colleagues.

Also, stay tuned, as we are also working on another novel functionality for the site, which will hopefully be ready to go live this summer.

P_pol = Abs [(M⁺_raw - M^-_raw)/2M_raw]
M⁺_raw is the reading when positive charge is collected and M^-_raw is the reading when negative charge is collected

There may be some ambiguity when first encountering this equation as to which reading one should use for the M_raw value in the denominator. There are quite a few possibilities, but only one correct answer. So, which reading do you use for M_raw in the denominator?

1- The average of M⁺_raw and M^-_raw
2- The larger value of M⁺_raw and M^-_raw
3- The smaller value of M⁺_raw and M^-_raw
4- Either M⁺_raw or M^-_raw can be selected
5- None of the above

Click here for the answer

The 1950s marked the first use of Sr-90/Y-90 sources for treating wedge-shaped benign ophthalmic lesions. Because of the long (~28.8 years) half-life of Sr-90, many of these ophthalmic applicators are still in use today. The US NRC now requires that the long lived radioactive sources have accredited calibration traceable to the NIST dose to water standard established in 1978 by Pruitt¹ and revised by Soares² in 1991.

Several different units have been used to describe source input of Sr-90/Y-90. Soares described these units and the historical progression of these values³:
1- Roentgen Equivalent Beta (reb)
2- Roentgen Equivalent Physical (rep)
3- Rad
4- Gy

So, what exactly is a “reb”? A reb is equal to “the amount of beta radiation that would produce ionization per unit mass in air equivalent to that produced by 1 R of photons.”⁴

Soares suggested using the conversion factors 0.0093 and 0.00982 (Gy/reb) to convert reb to Gy. For derivation of these conversion factors see Reference 3. According a to recent paper published in Medical Physics by the University of Wisconsin Accredited Dosimetry Laboratory (UWADCL), mCi (1 mCi = 37 MBq) is also used to describe nearly all planar Sr-90 sources⁴. Though for most applicators, these values represent estimated nominal contained activity rather than precisely known or determined values.

If a Sr-90 source is described with reb rather than nominal activity in mCi, one way to find out the activity in mCi is to calibrate the source at an Accredited Dosimetry Calibration Laboratory (ADCL), such as UWADCL, in Gy/sec. Then the activity can be estimated in mCi by using the conversion coefficients derived by Soares to convert reb to Gy¹.

For more information see the following references:
1- J. S. Pruitt. “Calibration of beta-particle-emitting ophthalmic applicators.” NBC special publication No. 250-9, 1978.
2-C. G. Soares. “Comparison of NIST and manufacturer calibration of Sr90+Y90 ophthalmic applicators.” Med. Phys. 22, 1487-1493 (1995).
3- C. G. Soares. “Calibration of ophthalmic applicators at NIST: A revised approach.” Med. Phys. (18), 787-793 (1991).
4- Shannon M. Holmes, John A. Micka, and Larry DeWerd. “Ophthalmic applicators: A review of calibration following the change to SI units.” Med. Phys. 36 (5), 1473-1477, May 2009.

Those who are thinking of switching to medical physics, however, should not give up, as there are certainly ways to transition to the field. And, of course, where there’s a will, there’s a way. I am unable to publish the email we received, since it included a lot of personal specifics. Instead, I am publishing our response to the individual who contacted us with the hope that  it will help others who are in the same boat:

First, I have to tell you that if this was 30-40 years ago, you could switch from your current background to the medical physics profession with great ease. Many well-known medical physicists (including some of the ”greats” of our profession) who made seminal contributions to our field entered “medical physics” with backgrounds similar to yours. Back then, there were only a few academic programs in medical physics, such as Wayne State University (which dates back to the early 70′s), that offered a degree specifically in medical physics. If you had a Ph.D. in physics or a closely-related field (including engineering), you could switch to a career in medical physics by simply getting a job as a medical physicist in a hospital and working under the supervision of a physicist. Alternatively, you could complete a two-year fellowship program at a big cancer institution such as MD Anderson or Memorial Sloan-Kettering. In the late 80′s/early 90′s, more schools started offering degree programs in medical physics. As these programs started growing in number so did the demand for their graduates. Some job and fellowship descriptions started requiring applicants to have graduated from a medical physics program (and these days some have started requiring/giving preference to applicants who have graduated from a CAMPEP-accredited medical physics program).

The fact is, these days, the option to immediately get a job as a medical physicist with a physics degree after graduation is practically obsolete. Even most those with a degree in medical physics do not immediately obtain a job after graduation without any type of post-graduate training (such as a residency or fellowship). This leaves the other option, which is the route most taken: complete post-graduate training, such as a post-doc or residency. The problem is that most of the opportunities are limited to those who have completed a degree program or had graduate training specifically in medical physics. Medical physics residencies and fellowships are highly competitive these days, and as you said in your letter, candidates with medical physics degrees (especially from a CAMPEP-accredited program) have an edge. However, with your background, if you have strong recommendation letters and a compelling essay stating your enthusiasm and reasons for pursuing medical physics, I believe you have a chance to be accepted into a program. I wouldn’t say that it’s a lost cause by any means. What you must concentrate on is articulating the reason for your switch to medical physics. Your intentions should be clear and should be a natural extension of your background, experiences and interest. You must also look at your (what these days is considered a non-traditional) background as an asset rather than a liability. Try to leverage your background and experiences: you bring a lot to the table, but more importantly, you bring a lot to the table that the traditional medical physics Ph.D. does not. You have a chance to offer a different perspective (skill sets, experiences) to any program, which is always a plus in admissions. All these, however, must be articulated–no one reading your application is just going to assume all of this.

That said, you did not mention what particular branch of medical physics you are interested in. From your background, I believe that your odds of getting into a fellowship program in diagnostic physics are much higher rather than a fellowship program in therapeutic physics. Of course, you should pursue your own personal interest at the end of the day; however, you could best leverage your past educational and research experience as a diagnostic medical physicist as opposed to a therapeutic physicist. It is worth mentioning that there are a few residencies/training programs in diagnostic medical physics that do not require a degree in medical physics. Currently, for example, Mayo Clinic is accepting applications for a residency that may be a great fit for you: “The Department of Radiology, Mayo Clinic, Rochester, Minnesota, is offering a clinical medical physics training program focusing on imaging for diagnosis and image-guided interventional procedures … Candidates should possess a recent doctoral degree in medical physics, physics or engineering.” Notice that the program is not restricted to those with only a medical physics doctorate. When applying to residency programs, keep in mind that in 2012 you must have graduated from a CAMPEP-accredited medical physics degree program OR completed a CAMPEP-accredited medical physics residency to be qualified to sit for the boards (ABR certification). In 2014, the rules become such that you must have completed a CAMPEP-accredited medical physics residency to be qualified to sit for the boards (ABR certification).

A last option also exists, which is to pursue a masters degree in medical physics. I have known several experienced Ph.D. scientists/physicists who switched to medical physics by going through a degree program and finishing a masters degree in medical physics. With your background, I believe you would have no problem gaining admissions to an MS program. While plowing out an extra 2 years of schooling may not be the most attractive option, it is your safest bet in terms of then being admitted to a residency program and (if you get an MS at a CAMPEP-accredited program) being certain you will be qualified for ABR certification when 2012 rolls around.

(This is a good time to ask yourself: do you want to work clinically as a medical physicist or do you see yourself doing research as a medical physicist? If you have no desire to work clinically, then you do not need to concern yourself with graduating from accredited programs. So long as you complete a residency or post-doc, you would be able to do research as a medical physicist without the need to sit for the ABR certification exam.)

I will assume that you do want to work clinically. So, in terms of making your application stronger, you may want to consider shadowing a medical physicist at a university hospital. Are there any hospitals associated with your university? Volunteering at a hospital is a good first step, but the most valuable clinical experience you will receive is being able to gain knowledge of the daily duties of a medical physicist. Also, while not a requirement, a strong letter of support from a medical physicist would be beneficial to your application.

Lastly, you mentioned you have been taking pre-med classes. Do not limit yourself to pre-med courses, which are mostly basic science classes (organic chemistry, biology, general chemistry+labs). Take an anatomy class, which while not a pre-med course, is indispensable for a physicist working clinically. I would suggest taking a look at the coursework at medical physics programs and trying to find equivalent or similar courses at your university (or another university nearby):
http://medicalphysics.duke.edu/files/MP-courses-040509.pdf,
http://www.uth.tmc.edu/gsbs/programs/medphys/courses.htm,
http://www.medphysics.wisc.edu/medphys_docs/courses.html

I hope this gives you some ideas in your decision making. I think you are taking some good steps, and I do believe your background will ultimately make you a better medical physicist. I personally believe that if you have a passion for what you are doing and work hard for it, you can achieve anything you want.

If anyone has any additional or supplemental advice for this individual or others looking to switch paths to medical physics, please feel free to share your thoughts by leaving a comment at the bottom of the post.