Fiducial Markers For Prostate Cancer

Rebuttal: Brent C Parker Phd

Gold Anchor fiducial marker implantation in prostate

My colleague has made a number of arguments against the use of fiducial markers, and I will address them sequentially.

Surgical risks: The results of Loh et al. were based on retrospective self-reported data from patients. It is possible that the results are biased based on the demographics of the responding patients. Moman et al. reported a urosepsis rate of only 0.2% in 914 patients with either transrectal or transperineal implantation of fiducials.

Not all patients are candidates: While there may be a subset of patients who are not candidates for FMs, this does not address the efficacy of FMs in patient setup. FMs still provide intrafraction target motion information not readily available with CBCT.

Seed migration: Kumar et al. demonstrated an average FM migration < 1 mm. Their results indicated that a margin of 13 mm would account for the vast majority of variations in seed position. Additionally, a large migration of a single seed would be readily apparent in imaging review and that seed could be eliminated from consideration in the image guidance process.

Errors due to edema: Kumar et al. demonstrated that prostate volume showed an average change of 1.4% between FM implant day and 1 week after FM placement. Waiting 1 week after FM placement to simulate the patient would minimize any effects due to edema or inflammation.

To 7 Days Before Your Procedure

You may need to stop taking some of your usual medications before your surgery. Examples include anticoagulants, aspirin, medications that contain aspirin, and vitamin E. Follow your healthcare providers instructions.

You can read about medications that contain aspirin and vitamin E in the resource Common Medications Containing Aspirin, Other Nonsteroidal Anti-inflammatory Drugs , or Vitamin E.

Using Fiducial Markers To Aid In Prostate Cancer Radiation Treatment

The safety and scientific validity of this study is the responsibility of the study sponsor and investigators. Listing a study does not mean it has been evaluated by the U.S. Federal Government. Read our disclaimer for details.

First Posted : May 26, 2003Last Update Posted : April 23, 2018

Study Details

To effectively treat prostate cancer, doctors need an accurate view of the prostate gland during radiation therapy. To help improve this view, doctors may insert gold markers called fiducials into the prostate by placing hollow gold needles through the rectum and moving a fiducial through each needle. The purpose of the study is to determine whether an MRI scan can help doctors improve their placement of these needles.

Prior to their participation in this study, patients will undergo the following evaluations: a physical exam, blood work, urine tests, and, if appropriate, an MRI or bone scan.

Condition or disease

Phase 1

Patients with contraindications to MRI:

Information from the National Library of Medicine

To learn more about this study, you or your doctor may contact the study research staff using the contact information provided by the sponsor.

What Are The Limitations Of Fiducial Markers

Fiducial markers are inert elements that typically do not react with the body or result in any imaging artifacts. They typically do not set off airport scanners. There is a small risk that fiducial markers may be misplaced during placement or may migrate to other areas potentially causing adverse events. This risk is very rare.

Fiducial Marker Seeds For Prostate Cancer Treatment

Safe To Use In Almost Any Inner Organ Gold Anchor

Post author
May 13, 2019

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Relationship Between Film Density And Absolute Dose And Dose Distribution Behind Markers

In the present study, the relationships between the film density and absolute dose at different depths within a fixed SOBP were found to be linear and each linear function in Figure was derived using the least squares method, the gradients of which were 0.146, 0.141, and 0.139, respectively. It can be assumed that the relationship of the dose with the film density is expressed by one linear function regardless of the depth. The mean value of all gradients was used to derive the dose perturbation from the film densities independent of depth.

FIGURE 2

The value of 95th percentile is used to derive the PTV margin. In Osaka HIMAK, Contour is set to 3 mm,, Positioning is set to 1 mm, Sys Range is set to 1 mm, and Stopping Power is derived by multiplying the depth to the target by 3.5%, assuming that the depth is 200 mm. The margins of bsPTV and PTVevlwere calculated using Equation . As shown in Table , the required margins of bsPTV and PTVevl were 8.0, 7.0, 7.0, and 8.0, 5.0, 5.0 mm in LR, SI, and AP directions, respectively.

Other Applications Of Electronic Portal Imaging Devices

The use of EPIDs for detecting radio-opaque fiducial markers implanted in or near a tumor, particularly in the prostate, has received increasing attention as a means of correcting errors in target position from internal organ motion.26

Another application is to verify intensity-modulated treatment fields delivered with an MLC. With present algorithms, this is usually accomplished by irradiation of a flat phantom before actual treatment.29 The images of the subfields composing the intensity-modulated field are summed in the computer to obtain a 2-D intensity pattern , which is compared with the intended pattern from the treatment planning system. Other uses of EPIDs include transit dosimetry to measure the accuracy of dose delivery during treatment, and in accelerator quality-assurance procedures.30,31

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What Is The Procedure

An ultrasound probe is covered in gel and inserted into your back passage to create an image of the prostate, allowing the seeds to be inserted into the different areas of the prostate with great accuracy.

Three marker seeds will then be placed within the prostate through ultrasound based needle guidance. The seeds are NOT placed through the rectum, but through the skin on the outside of your body between the scrotum and the rectum . There may also be a brief, sharp pain as the needle is inserted into the prostate gland.

Gel And Fm Stability Over Time

Transperineal implantation procedure of Gold Anchor fiducial markers in prostate

Monitoring the position of individual FMs over a 4week period on repeat CT scans revealed only sub-millimetre movements of the FM relative to the cube exterior and each other. This indicated that the use of edible gelatine in our study of FM was reliable for preserving the setup of fiducial markers . Detailed results from this study can be found in Additional file : Figure S2 and Additional file : Table ST1).

How Should I Prepare

Prior to your procedure, your blood may be tested to determine how well your kidneys are functioning and whether your blood clots normally.

You should report to your doctor all medications that you are taking, including herbal supplements, and if you have any allergies, especially to local anesthetic medications, general anesthesia or to contrast materials containing iodine . Your physician may advise you to stop taking aspirin, nonsteroidal anti-inflammatory drugs or blood thinners for a specified period of time before your procedure.

Also inform your doctor about recent illnesses or other medical conditions.

Women should always inform their physician and x-ray technologist if there is any possibility that they are pregnant. Many imaging tests are not performed during pregnancy so as not to expose the fetus to radiation. If an x-ray is necessary, precautions will be taken to minimize radiation exposure to the baby. See the Safety page for more information about pregnancy and x-rays.

You will receive specific instructions on how to prepare, including any changes that need to be made to your regular medication schedule. Other than medications, you may be instructed to not eat or drink anything for several hours before your procedure.

You may be asked to remove some or all of your clothes and to wear a gown during the exam. You may also be asked to remove jewelry, eye glasses and any metal objects or clothing that might interfere with the x-ray images.

Number And Types Of Fiducial Markers

FMs exist in a variety of shapes, sizes and materials and are commercially available from a variety of vendors. Gold markers are by far most frequently used for prostate IGRT. This is due to the fact that they are widely available and are visible using MV or kV image guidance. The basic specification for an FM includes radio-opacity for a given imaging modality , that they are readily available and that they are not prohibitively expensive.

This review elicited only one study specifically comparing types of markers. Fonteyne et al investigated five different gold FMs. They observed a better correlation between automatic CBCT image-matching results and manual match results for the largest FM, which was 20mm×0.75mm, than for smaller FMs, suggesting that larger markers may result in more consistent setup data when comparing automatic and manual alignment. However, they also state the largest FM resulted in increased image artefact. Artefact created by FMs on CT and CBCT is one of the main disadvantages of using gold or entirely metallic markers and may add to the degree of uncertainty associated with contouring and matching the prostate and may also result in inaccurate treatment planning. One study suggests that platinum is superior to gold in terms of its visibility on MRI and therefore preferable as an aid for CT/MRI registration. This would have the disadvantage of being more expensive than gold.

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Technical And Treatment Outcomes

The first report of EUS-guided fiducial marker placement was published in 2006 by Pishvaian and colleagues, who successfully deployed fiducial markers in six of seven patients with pancreatic cancer who underwent radiation therapy.31 Later, Varadarajulu and colleagues confirmed the feasibility and safety of EUS-guided fiducial marker placement for the delivery of intensity-modulated radiotherapy .32 Two recent reports have described the utility of fiducials for fluoroscopy-aided intraoperative localization of small pancreatic tumors.35,36 In both reports, the fiducials could be placed successfully without complications and with good operative outcomes.

Ziad F. Issa MD, … Douglas P. Zipes MD, in, 2019

What Will I Experience During And After The Procedure

You will feel a slight pin prick when the needle is inserted into your vein for the intravenous line and when the local anesthetic is injected. Most of the sensation is at the skin incision site when it is anesthetized using local anesthetic.

You may feel some pressure when the pre-loaded needle is inserted, and the area of the needle insertion may possibly feel sore for a few days. If you have significant pain, your doctor may prescribe pain relief medication.

Aftercare instructions vary. However, you generally may remove your bandage one day after the procedure, and you may bathe or shower as normal.

Complete A Health Care Proxy Form

If you havent already completed a Health Care Proxy form, we recommend you complete one now. If youve already completed one or have any other advance directives, bring them to your next appointment.

A health care proxy is a legal document that identifies the person who will speak for you if you cant communicate for yourself. The person you identify is called your health care agent.

Talk with your healthcare provider if youre interested in completing a health care proxy. You can also read the resources Advance Care Planning and How to Be a Health Care Agent for information about health care proxies, other advance directives, and being a health care agent.

Fiducial Markers In Image

US Oncological Disease

Abstract:

Overview

Fiducial markers are emerging as a standard tool for image-guided radiotherapy . The markers are implantable devices designed to act as reliable surrogates for imaging anatomic structures of interest. Fiducial marker techniques were originally developed in the preconformal radiotherapy era for positional verification of tissues that were not easily visualized using portal X-ray film imaging for patient alignment. Soft tissue structures that were relatively mobile could be more readily seen when radio-opaque seeds or wires were implanted in or near organs of interest. However, since comparatively large margins around target volumes were used, dose delivery limitations overshadowed imaging accuracy. In addition, routine and efficient online implementation of patient set-up error analysis and patient repositioning was problematic in the past.

Article:

As a practical matter, improved dose delivery precision necessitates a higher degree of accuracy in targeting the tumor and aligning the patient so as to reproducibly confirm that the tumor is in the same place in 3-D space as the prescribed conformal dose distribution throughout therapy . However, since even small geometric deviations from the treatment plan may result in substantial changes in dose distribution,2 margin reduction must be matched with IGRT techniques lest margin reduction result in poorer clinical outcomes.3

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Quantitative Evaluation Of Fms Visibility And Associated Artefacts

For volumetric X-ray scans , a region of interest for each marker was defined as the box containing 3 FM with 3mm isotropic inner margin . Air bubbles were also removed from this ROI. Using high resolution segments, the FMs in each box were contoured using the Eclipse treatment planning system using the automatic thresholding tool. The maximum HU threshold defining the FM was set as the highest HU value inside box ROI. The minimum value for the threshold was determined in Eclipse by manually adjusting the window level to view the FM only. This way an approximate low threshold value was obtained for each marker. Contouring was performed on CT scans with 0.625mm slice thickness and then transferred to other datasets with different slice thicknesses .

To quantitatively evaluate the visibility of the FM, the contrast-to-noise ratio was also calculated . For each FM, the mean HU and standard deviation were compared to background and standard deviation . The background HU values were determined from the two boxes with gel only . CNR for each FM was then calculated using the equation:

The higher the CNR the more visible the object .

To quantify the severity of streak artefact, firstly an artefact volume was defined for each FM by subtracting the FM structure from the box ROI and this artefact volume was then used in the analysis. Similar to the analysis by Huang et al. , streak artefact index was calculated for each ROI. The SI is defined as

About Fiducial Markers And Rectal Spacers

Prostate Cancer Radiation Fiducial Marker and SpaceOAR Gel Procedure ABS Virtual Reality (360 VR)

Fiducial markers are tiny metal objects . They help your healthcare providers line up the beams of radiation and make sure your radiation therapy is delivered exactly the same way each time. This helps them target the tumor and avoid your nearby healthy tissue. The fiducial markers will stay in your prostate after your treatment.

Youll get a rectal spacer called SpaceOAR hydrogel. It is a gel thats placed between your prostate and rectum to move your rectum away from your prostate. This protects your rectum from radiation and reduces some side effects of radiation therapy. The rectal spacer will stay in place for 3 months. Then, itll be absorbed by your body and come out in your urine.

Work in a hospital or nursing home.

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Arrange For Someone To Take You Home

You must have a responsible care partner take you home after your procedure. A responsible care partner is someone who can help you get home safely and report concerns to your healthcare providers, if needed. Make sure to plan this before the day of your procedure.

If you dont have a responsible care partner to take you home, call one of the agencies below. Theyll send someone to go home with you. Theres usually a charge for this service, and youll need to provide transportation. Its OK to use a taxi or car service, but you must still have a responsible care partner with you.

Agencies in New York