The PET Scan, a Chemist’s View

This entry is part 2 of 3 in the series "Radiation" --

Liam had a Positron Emission Tomography (PET) scan on 19Sept2014. For this the radioactive tracer is Fludeoxyglucose (18F) or (18F-FDG) for short. For those of you crazy chemistry people out there (like Jenn and myself), check this out:

a)Fludeoxyglucose b) β+ Decay of a proton emits a positron (and changes Fluorine to Oxygen); Since a positron is the antimatter equivalent of an electron, when it finds the closest electron it will annihilate. The matter will cease to exist, and it will turn into energy in the form of light (gamma rays). The two gamma rays produced each will have 511 keV of energy. c) With a little acid, the product will be glucose and continue through the energy cycle in the cell. Until the radioactive decay, the molecule is stuck. There is no chemistry available to the cell to process the glucose with substituted Fluorine, once the F gets converted to a hydroxyl, the chemistry can proceed as normal (With a heavy, but stable Oxygen atom)

The 18F-FDG looks just like the glucose molecule except for a heavy fluorine in place of the  2′ hydroxyl group.  Since all cells use glucose as a power source, the PET scan exploits the fact that cancer cells require more energy, and they will take up more of the compound than normal cells. The areas of the body emitting large amounts of gamma radiation are likely to have concentrations of cancer cells.

For those of you (and I know who you are) who would like even more information, here are some links that I found helpful when I was coming up to speed on the technique:

Fludeoxyglucose (18F)

Positron Emmision Tomography

A Molecular Imaging Primer: Modalities, Imaging Agents, and Applications (scroll down to figure 13)

Decay scheme of 18F

What does it mean to be Liam’s Shield Bearer?

Liam’s name means Beloved, Courageous Protector.  We remind him every time he goes to sleep because it’s part of his blessing song.  (Each of our kids has a personalized blessing that we sing over them before they go to sleep.  It’s a Harris-thing.)

After learning of Liam’s diagnosis, I kept hearing the words of Nehemiah 1:11 in my head, “I was a cupbearer to the king,” and I realized that what Liam the Protector needed was an army of Shield Bearers–people who would lift up the shield of faith and pray for our son.  It’s a similar image to Aaron and Hur raising up Moses’ weary hands and keeping them steady till sunset  as  Joshua battled the Amalekites in Exodus 17:8-15.  Liam is fighting a battle and needs the shield of faith to be raised on his behalf.

The verse on the bracelets is Ephesians 6:16, “In addition to all this, take up the shield of faith, with which you can extinguish all the flaming arrows of the evil one.”  It’s the ending verse to the Ephesians 6:10-16 Armor of God passage:

10 Finally, be strong in the Lord and in his mighty power. 11 Put on the full armor of God,so that you can take your stand against the devil’s schemes. 12 For our struggle is not against flesh and blood, but against the rulers, against the authorities, against the powers of this dark world and against the spiritual forces of evil in the heavenly realms.13 Therefore put on the full armor of God, so that when the day of evil comes, you may be able to stand your ground, and after you have done everything, to stand. 14 Stand firm then, with the belt of truth buckled around your waist, with the breastplate of righteousness in place, 15 and with your feet fitted with the readiness that comes from the gospel of peace. 16 In addition to all this, take up the shield of faith, with which you can extinguish all the flaming arrows of the evil one.

As you pray for Liam, we encourage you to put on the full armor of God before taking up the shield of faith to pray for our son.

We are so grateful for your prayers and humbled by the number of people who are praying for Liam.  People coast to coast and around the world are praying for our son.  We serve a big God and trust that regardless of the outcome that He will be glorified.

A Stressful Time Back at Home After Round 1

This entry is part 7 of 10 in the series "Liam's Battle" --
A bucket full of Liam's medications

A bucket full of Liam’s medications

The day my son was released from the hospital after his first round of chemo (a 5 day round that with complications led to 22 days in hospital), I came home to find my wife frantically working on Excel with the hustle and bustle of a full house exploding around her. There was a lot going on, but it was clear that what she was doing was important. The kids, who had not seen her in a long time, were siphoned off into another room every time they would show up to hang out with her.

Medicine Delivery Schedule

The Medicine Matrix

What was she doing that was so pressing? She was making a matrix of all of the medications that needed to be administered to Liam.

I found this odd. How many medications had been sent home with him?  Quite a few. When it was broken down on how many doses he is getting a day there are thirty-one.  Thirty-one different things to keep track of. Twenty-nine syringe cleanings. Thirty-one administrations by mouth with differing volume amounts.

As I watched Jenn frantically come to terms with the reality of this situation, i.e. that there were no nurses to administer and keep track of all of the medications that Liam needs, I had the stark revelation that many parents out there must not be able to keep all of this straight.  All that the discharge paperwork said was which medications he was on, the doses per day, and when the last dose was given.

This seems like a poor system.  We have figured it out, but perhaps there is a better way than, “Here you go. Good luck!”

Our experience at Children’s Medical Center has been very positive.  The medical professionals (doctors, nurses, technicians, social worker, child life specialist, music therapists, physical therapists, kitchen staff, janitorial staff, volunteers, etc., etc.) have all been wonderful.  They all created a very safe bubble for Jenn and Liam; however, I think that the transition from the hospital to home has been a little more like the bubble popping than staying in the bubble and floating home on the breeze.

It is good for the two of them to be back home. It has been a wonderful time for me to regain some of the sanity that I had lost, and I enjoy interacting with Liam all of the chances I can get.  When he is home, I get more time with him.

The bubble with all of its iridescent protection returns next Wednesday 21Sept2014 when chemo round 2 starts.

Stem Cells, A Weakened Immune System, and a Dirty House

This entry is part 6 of 10 in the series "Liam's Battle" --
"GCSF Crystal Structure.rsh" by Ramin Herati

“G-CSF Crystal Structure” by Ramin Herati

Liam was allowed to come home for a week before he has to go back in to the hospital for round 2 chemo. Exciting, yes; however, I am forced to look at my home in a different manner.  I have never had to worry about a weakened immune system before.

A typical motto in our house has been, “A few germs will build your immune system.” — You people out there with small kids know what I mean.

A few germs, however,  can be deadly to a little guy that has an impaired immune system.  It is true that after this first round of chemo, his white blood cells are coming back.  But after every successive round of chemo, his immune system will get hammered to the point that it will be close to death (if not dead). So much so, that after the next round of chemo (round 2), they will harvest stem cells from his bone marrow so that they can use them later to reboot his immune system.

The process is pretty neat. They will actually administer a drug (Granulocyte colony-stimulating factor G-CSF) that stimulates the bone marrow to push stem cells out into the peripheral blood.

The collection is performed through a process known as “apheresis.” Blood is drawn and passed into a machine that spins the blood to remove certain stem cells (those identified as “CD34+”), and then the blood is returned to the child. [1]

After the cells have been collected, they will be used during the consolidation phase to give a boost or jump start to the bone marrow.  The autologous (meaning he is his own donor) stem cell transplant will occur under a very strict, positive pressure, wing on the oncology floor.

Having the ability for forward vision, however, only makes me more concerned about what I can do today. While Liam’s immune system is not completely compromised yet, the house as well as the lifestyle of three siblings and a dog have me a bit on edge. What needs to change so that Liam is protected? How do we make it through this time in our life when it seems impossible to keep out external germs while he is at home?

So, the immediate family and myself have spent the day attempting to prepare for Liam’s return to home, albeit for a short while.  We have vacuumed, mopped the floor, washed all of the sheets, removed all that can potentially have germs.  Still, my vision leads me to despair. I know how tiny these bacteria are. I know how my kids will interact with one another.

This problem is beyond me. So, I must keep the cub scout motto in my mind, “Do your best!”  It is all I can do, nothing more.

MetaIodoBenzylGuanidine (mIBG) [update]

This entry is part 1 of 3 in the series "Radiation" --


[Update to the Update: On 24July2015 after his cancer had relapsed, another mIBG scan was performed. This time, the cancer was shown to be mIBG avid]

[Update: On 4Sept2014, during the imaging 123-mIBG, it was determined that Liam’s Neuroblastoma is one of the types that does not take up mIBG. This means that he will be excluded from participation of the 131-mIBG study and we will be performing more chemo treatments]

Let’s not leave out the cool science.  During the course of his treatment Liam will encounter mIBG (MetaIodoBenzylGuanidine).  The first time that he encounters it, should all go well, is this week (~4Sept2014). He will be injected with the chemical so that his Neuroblastoma can be imaged. So, how does it work? It turns out that Neuroblastoma has a strong affinity for this compound in about 85% of cases.[1] In a very high percentage, the Neuroblastoma cells will take this compound up while the normal cells will not. This is called ‘selectivity’. (i.e. the Neuroblastoma soaks this compound up selectively over normal cells).  mIBG in itself, however, doesn’t do anything. It is taken into the cell, and then is excreted from the cell at a later time.  This means that the Neuroblastoma cells are not sensitive to the compound. 

A clever and ingenious pupil of chemistry can already see what to do next.  Swapping out the Iodine atom on this compound with the radioactive version  makes this molecule very useful.


123 Iodine will decay by electron capture to form 123 Tellurium which will then emit a Gamma ray with an energy of 159 keV. This is useful for imaging.  This is like having an x-ray performed, but rather than having an x-ray source shining high energy light through Liam, the light will be generated inside him!  Since this radioactive atom is attached to a compound which is only selective to Neuroblastoma, Gamma rays (like x-rays) will be generated only at the Neuroblastoma sites.  With the correct detector, the Neuroblastoma will light up like a Christmas tree.


If 131 Iodine is used, different results will be observed.  131 Iodine decays in the follow two manners (statistically a 90% Beta(-) Decay and a 10% Gamma decay):

(Beta(-) Decay ~90%) {^{131}_{53}\mathrm{I}} \rightarrow \beta + \bar{\nu_e} + {^{131}_{54}\mathrm{Xe}^*}  + 606 keV 

(Gamma Decay ~10%) {^{131}_{54}\mathrm{Xe}^*}  \rightarrow {^{131}_{54}\mathrm{Xe}} + \gamma  + 364 keV

The Beta(-) decay produces a very energetic electron and an Antineutrino which have a tissue penetration of about 0.6 to 2 mm. This is enough energy to destroy cells. (i.e. a cell sized atomic bomb) So in essence, this gives a pathway for the mIBG, which is very selective to the Neuroblastoma, to blow up the cells (and leave the good cells alone)

This mIBG therapy is typically only given in cases of Nueroblastoma that have relapsed, however, we may be one of the lucky families that gets this treatment as a clinical trial directed at making this part of the standard treatment.  If everything works out well, we will be part of this trial sometime after 5 or 6 chemotherapy treatments.

This mIBG scan being performed this week will only involve 123 Iodine for gamma ray imaging. This will indicate all of the places that the Nueroblastoma has metastasized to. It will be used as a baseline for how he is progressing in his treatment later on.

  1. According to “…Roughly 80-85% of neuroblastomas will absorb MIBG. There are really 2 ways in which MIBG treatment is used. In both methods, the MIBG chemical is attached to an iodine molecule that has been made radioactive. The radioactivity can be either a low-dose or a high-dose…. ”