What Are the Indications for PET and PET/CT?

Patient Presentation
A pediatrician overheard one of her residents trying to arrange sedation for a toddler with cancer for a positron emission tomography test (PET). To her it seemed like PET had come up several times during clinical care recently. She commented that she didn’t know the indications for PET since it wasn’t something she would order. A search of the literature found several articles mainly for oncological indications. She reviewed the articles and learned more about the pros, cons and limitations of PET.

Discussion
Positron emission tomography test (PET) and PET/CT that combines PET with computed tomography (CT) was first begun in the 1950s. In 2000 it was the TIME magazine invention of the year. PET gives functional, metabolic data about the human body. When combined with CT’s anatomical, structural data, PET/CT can give both data types concurrently.

PET uses radioactive tracers linked to metabolites. One of the most common tracers is 18F-fluorodeoxyglucose (FDG), a glucose metabolite. Since FDG contains glucose, there will be background tracer uptake particularly in the skeletal muscle, brain, thymus, brown fat, heart, and gastrointestinal track. The tracer is excreted by the kidneys but not reabsorbed, so increased background may be seen in the urinary system. Increasing filtration along with bladder emptying helps to minimize this problem.

The primary indications for PET and PET/CT in pediatrics are for malignancies (see below), but PET and PET/CT are not specific for cancer. PET resolution for malignant lesions is about 10 mm, and PET/CT is about 5 mm. Smaller, slow-growing and well-differentiated tumors have less tracer uptake which can cause a false-negative reading. Other physical problems such as increased test background, increased normal muscle activity, inflammation and infection, may lead to false-positive PET readings too.

Learning Point
PET and PET/CT in adults is mainly used in malignanicies, especially lymphoma, but other indications such as pulmonary infections, rheumatological disorders, and neurosurgical planning for epilepsy treatment have been explored.

Indications and use for PET and PET/CT for pediatric malignancies includes:

  • Bone tumors – staging, prognosis, and treatment response
  • Brain tumors – prognosis, recurrent disease detection, and planning surgical interventions
  • Endocrine tumors – staging
  • Hepatoblastoma – prognosis, recurrent disease detection
  • Lymphomas – staging, restaging, treatment response and recurrent disease detection
  • Sarcomas of the soft-tissue – staging, treatment response, recurrent disease detection
  • Neuroblastoma – staging

One review in 2009 summarized its findings by saying “In paediatric oncology patients, clinical applications of PET/CT including staging, monitoring therapy and therapy planning in lymphomas, soft-tissue and osseous sarcomas, and neuroblastoma. In other entities, PET/CT may be of diagnostic value but the literature is limited.”
Another review in 2010 said, “PET and PET/CT appear to be excellent noninvasive imaging modalities for the management of most of the pediatric cancers except leukemia.” They go on to state that due to their high radiation exposure, PET/CT should be limited to certain applications mainly in lymphoma and certain sarcomas.

Questions for Further Discussion
1. Is PET and PET/CT available in your country??
2. What other nuclear medicine tests are used for malignancy management and what are their indications?

Related Cases

To Learn More
To view pediatric review articles on this topic from the past year check PubMed.

Evidence-based medicine information on this topic can be found at SearchingPediatrics.com, the National Guideline Clearinghouse and the Cochrane Database of Systematic Reviews.

Information prescriptions for patients can be found at MedlinePlus for these topics: Nuclear Scans and Cancer in Children.

To view current news articles on this topic check Google News.

To view images related to this topic check Google Images.

Brody AS, Frush DP, Huda W, Brent RL. Radiation Risk to Children From Computed Tomography. Pediatrics 2007;120;677.
Kumar R, Shandal V, Shamim SA, Halanaik D, Malhotra A. Clinical applications of PET and PET/CT in pediatric malignancies. Expert Rev Anticancer Ther. 2010 May;10(5):755-68.

Franzius C, Juergens KU. PET/CT in paediatric oncology: indications and pitfalls. Pediatr Radiol. 2009 Jun;39 Suppl 3:446-9.

Andersen JB, Mortensen J, Bech BH, Hojgaard L, Borgwardt L. First experiences from Copenhagen with paediatric single photon emission computed tomography/computed tomography. Nucl Med Commun. 2011 May;32(5):356-62.

Wikipedia. Positron emission tomography. http://pediatrics.aappublications.org/cgi/reprint/120/3/677.pdf. (rev. 5/12/2011, cited 5/16/2011)

ACGME Competencies Highlighted by Case

  • Medical Knowledge
    10. An investigatory and analytic thinking approach to the clinical situation is demonstrated.

  • Practice Based Learning and Improvement
    12. Evidence from scientific studies related to the patients’ health problems is located, appraised and assimilated.
    13. Information about other populations of patients, especially the larger population from which this patient is drawn, is obtained and used.
    14. Knowledge of study designs and statistical methods to appraisal clinical studies and other information on diagnostic and therapeutic effectiveness is applied.
    15. Information technology to manage information, access on-line medical information and support the healthcare professional’s own education is used.

    Author

    Donna M. D’Alessandro, MD
    Professor of Pediatrics, University of Iowa Children’s Hospital

  • There are Bugs in the House!

    Patient Presentation
    A 2-year-old female came to clinic for her health supervision visit. The parents were concerned that she had difficulties sleeping at night with late initiation of sleep and multiple awakenings. The social history found a young couple who were living with relatives who also took care of the child while they worked. The household had a large extended family with multiple people coming and going throughout the day and night. The parents noted that the household had many cockroaches and although they themselves had tried to keep their room clean, they often saw cockroaches even during the day. The family said that they did not see nor suspect any bed bugs in their or the patient’s beds. Social services had been working with the parents and felt that they had limited economic means but that the child was not being neglected and that the parents should be commended for everything they had tried to do for the child.

    The pertinent physical exam showed a healthy female with normal development and growth parameters in the 50-75%. Her examination was normal. The diagnosis of a healthy female living in a cockroach infested house and poor sleep hygiene was made. The resident physician discussed the importance of good sleep hygiene, particularly consistency. She told the parents that it was difficult given the situation. The parents said that they and one grandparent usually were the night caretakers and they would try to be more consistent with bedtime. She also gave the family some handouts about how to help clean up the household. The parents were doubtful that they would get any help from the relatives but said they would try. The attending physician had thought that cockroaches might be crawling on the child at night contributing to the poor sleep. The resident recommended that netting might be placed over the crib or mattress and tucked in to try to prevent this problem. The family thought that this was something they could do and were going to try.

    Discussion
    Pests are just that: Pests. They are bothersome, annoying, and irritating. They can be dangerous or non-dangerous.

    Cockroaches are common insects that infest homes. Cockroach body parts and feces can be allergens for certain people. Cockroaches themselves do not directly infect humans with disease through saliva/blood etc., but they carry infectious organisms on their bodies. As cockroaches move in, around, along and through almost anything, they may transmit these organisms to humans through infected food and water, etc. that cockroaches have contacted.

    Cockroaches need food, water and shelter. They generally like carbohydrates so anything that is starch-based is roach food including any paper, wallpaper paste, envelope glue, and soap bars (which often contain carbohydrates). Cockroaches are usually active at night, so daytime sightings usually means a high population of insects which have overrun their shelter. During the day, cockroaches may be found hiding clustered together under, around, or even in the walls of appliances, walls, baseboard crevices, cupboards, pantries and especially around sinks. Shelter is in small cracks, crevices and especially in paper items such as boxes, wastepaper etc.. Given that paper items are often stored with garbage, also often near a water supply, its not surprising that kitchens and bathrooms are common cockroach infestation locations.

    Learning Point
    Cockroach prevention and cleanup includes:

    • Start where the infestation is the highest and work outward from there. Kitchens and bathrooms are often highly infested.
    • Eliminate cracks and crevices with caulk, paint and weatherstripping where possible, especially around pipes, sinks, cupboards, shelving, etc.. Wide cracks are not attractive to roaches, so increasing the width to 1″ in a freestanding cabinet may help eliminate the problem too.
    • Eliminate paper – move boxes, paper and other shelter items to an outside garbage area if possible.
    • Eliminate food – cover and store food in airtight containers. Clean up countertops, sinks, food containers, and garbage areas.
      Clean all countertops and sweep floor and counter tops from crumbs. Clean cupboards of crumbs and frequently wipe out those cupboards with items that may be spilled (bread, cereal) or that have spills (jam jars).

    • Eliminate water – keep plumbing in good working order, eliminate drips and wipe up spills.
    • Separate food, water and shelter sources as much as possible, i.e. frequently remove garbage, move paper items outside the house, wipe up water and other spills quickly.
    • Try using baits or traps before using pesticidal sprays.
      Limit pesticides spray to the infested area and avoid spraying in food preparation or storage areas. Spot spray as much as possible.

    Questions for Further Discussion
    1. Do bedbugs transmit diseases to humans?
    2. How can bedbugs be eliminated?
    3. How should pesticides be appropriately used for insect control?

    Related Cases

    To Learn More
    To view pediatric review articles on this topic from the past year check PubMed.

    Evidence-based medicine information on this topic can be found at SearchingPediatrics.com, the National Guideline Clearinghouse and the Cochrane Database of Systematic Reviews.

    Information prescriptions for patients can be found at MedlinePlus for these topics: Allergy and Pesticides.

    To view current news articles on this topic check Google News.

    To view images related to this topic check Google Images.

    Environmental Protection Agency. IPM for Cockroaches in Schools. Available from the Internet at http://www.epa.gov/pesticides/ipm/schoolipm/chap-6.pdf (rev. 3/1997, cited 5/13/2011).

    Environmental Protection Agency. Cockroaches. Available from the Internet at http://www.epa.gov/agingepa/solutions/08cockroaches.htm (rev. 5/26/2010, cited 5/13/2011).

    Piper GL, Antonelli AL. Cockroaches Identification, Biology, and Control. Available from the Internet at http://cru.cahe.wsu.edu/CEPublications/pnw0186/pnw0186.html (cited 5/13/2011).

    ACGME Competencies Highlighted by Case

  • Patient Care
    1. When interacting with patients and their families, the health care professional communicates effectively and demonstrates caring and respectful behaviors.
    2. Essential and accurate information about the patients’ is gathered.
    3. Informed decisions about diagnostic and therapeutic interventions based on patient information and preferences, up-to-date scientific evidence, and clinical judgment is made.
    4. Patient management plans are developed and carried out.
    5. Patients and their families are counseled and educated.
    8. Health care services aimed at preventing health problems or maintaining health are provided.
    9. Patient-focused care is provided by working with health care professionals, including those from other disciplines.

  • Medical Knowledge
    10. An investigatory and analytic thinking approach to the clinical situation is demonstrated.
    11. Basic and clinically supportive sciences appropriate to their discipline are known and applied.

  • Practice Based Learning and Improvement
    13. Information about other populations of patients, especially the larger population from which this patient is drawn, is obtained and used.
    16. Learning of students and other health care professionals is facilitated.

  • Interpersonal and Communication Skills
    17. A therapeutic and ethically sound relationship with patients is created and sustained.
    19. The health professional works effectively with others as a member or leader of a health care team or other professional group.

  • Professionalism
    20. Respect, compassion, and integrity; a responsiveness to the needs of patients and society that supercedes self-interest; accountability to patients, society, and the profession; and a commitment to excellence and on-going professional development are demonstrated.
    22. Sensitivity and responsiveness to patients’ culture, age, gender, and disabilities are demonstrated.

    Author

    Donna M. D’Alessandro, MD
    Professor of Pediatrics, University of Iowa Children’s Hospital

  • What are the New Recommendations for Rabies Vaccine Treatment?

    Patient Presentation
    A 19-year-old male came to clinic because of a possible bat bite. He lived in a home with 4 other college students, and a bat was found in his bedroom while he was studying. He caught the bat in his T-shirt and let it go outside. He was not wearing gloves. He said he might have been bitten but wasn’t sure, but he had washed his hands thoroughly afterwards and had discarded the T-shirt in the garbage. He had gone to work overnight and when he returned his roommates said they had found 4 other bats in the house. They were all going to the emergency room to be evaluated. The past medical history was non-contributory. He had not received rabies vaccine in the past and was current with his immunizations.

    The pertinent physical exam showed a healthy male with normal vital signs. He had several scratches on his hands that he stated were from his cat and from working outside. None looked infected. The rest of his examination was negative. The diagnosis of significant bat exposure with possible rabies exposure was made. It had been many hours since the exposure and he had washed his hands several times but the physician did decide to thoroughly wash his hands with providine-iodine as it may help and wouldn’t hurt the patient to do it. As there was no obvious bite mark, human rabies immunoglobulin was not injected into a wound but was given in one arm. He was also given the initial rabies vaccination and return appointments for 3 more doses. The patient said that the landlord had been contacted and was going to have the house checked and the bats eliminated before he was going to return to living in it.

    Discussion
    Rabies is an important zoonosis worldwide which causes progressive encephalomyelitis and a high fatality rate. About 55,000 people worldwide die annually. In the US, about 1-3 cases occur annually, but 20-30,000 people receive post-exposure prophylaxis (PEP) for rabies. Importantly, “PEP has never failed in the United States since the introduction of modern cell-derived vaccines in the 1970s.”

    Any mammal is susceptible to rabies virus. While domesticated dogs are an important reservoir internationally, in the US other terrestrial mammals are more important with geographical differences. The most important animals are coyotes, fox, raccoon, and skunk. Mongoose is also important in Puerto Rico. Bats are also important reservoirs. From 2000-2007, 17 of 20 rabies cases that occurred in the US were from bats.

    Rabies transmission from bats “… can occur from minor, seemingly unimportant, or unrecognized bites from bats.” Therefore contact should be minimized. PEP is considered for people who had significant contact, were known to be bitten or were in a room and might be unaware that the bat touched them or bit them. Examples would be a sleeping person or a child who was unattended and is now found to have a bat in the room. If the bat can be safely collected then it can be tested for rabies. If the bat is available for testing and is negative, then PEP is not indicated or can be stopped. If the bat is not available then PEP is given.

    Learning Point
    Treatment for rabies exposure includes wound cleansing with copious amounts of soap and water. Virucidal agents such as povidine-iodine should be used for wound irrigation if available. If the patient is previously unimmunized with rabies vaccine, human rabies immune globulin (20IU/kg weight) is infiltrated into and around the wound if at all possible. If not possible to give the entire dose in this location any remaining immune globulin is given as an injection intramuscularly. In a separate location, and in a separate syringe, rabies vaccine is also given. Approved locations for rabies vaccine is the deltoid area for adults and older children, and anteriolateral thigh for young children. The gluteal area is never used for rabies vaccine administration.

    In 2011, the American Academy of Pediatrics updated their policy statement for rabies prevention. All previous recommendations were unchanged, except for previously unvaccinated immunocompetent people. Four doses of vaccine are now recommended to be given on day 0, 3, 7 and 14. Day 0 is the day dose 1 of vaccine is given. Before this recommendation, 5 doses of vaccine were administered.

    Questions for Further Discussion
    1. What are the rabies treatment recommendations for previously vaccinated individuals?
    2. What PEP is recommended for people with occupational exposure such as veterinarians, animal control officers and roofers?

    Related Cases

    To Learn More
    To view pediatric review articles on this topic from the past year check PubMed.

    Evidence-based medicine information on this topic can be found at SearchingPediatrics.com, the National Guideline Clearinghouse and the Cochrane Database of Systematic Reviews.

    Information prescriptions for patients can be found at MedlinePlus for these topics: Rabies and Animal Bites.

    To view current news articles on this topic check Google News.

    To view images related to this topic check Google Images.

    MMWR. Compendium of Animal Rabies Prevention and Control, 2008, National Association of State Public Health Veterinarians, Inc. (NASPHV), April 18, 2008 / 57(RR02);1-9. Available from the Internet at http://www.cdc.gov/mmwr/preview/mmwrhtml/rr5702a1.htm (rev. 4/18/2008, cited 4/25/2011).

    Centers for Disease Control. Bats. Available from the Internet at http://www.cdc.gov/rabies/exposure/animals/bats.html (rev. 3/22/2010, cited 4/29/2011).

    Centers for Disease Control. Wildlife Reservoir for Rabies. Available from the Internet at http://www.cdc.gov/rabies/exposure/animals/wildlife_reservoirs.html (rev. 11/29/2010, cited 4/25/2011).

    Committee on Infectious Diseases. Rabies-prevention policy update: new reduced-dose schedule. Pediatrics. 2011 Apr;127(4):785-7.

    ACGME Competencies Highlighted by Case

  • Patient Care
    1. When interacting with patients and their families, the health care professional communicates effectively and demonstrates caring and respectful behaviors.
    2. Essential and accurate information about the patients’ is gathered.
    3. Informed decisions about diagnostic and therapeutic interventions based on patient information and preferences, up-to-date scientific evidence, and clinical judgment is made.
    4. Patient management plans are developed and carried out.
    5. Patients and their families are counseled and educated.
    7. All medical and invasive procedures considered essential for the area of practice are competently performed.
    8. Health care services aimed at preventing health problems or maintaining health are provided.

  • Medical Knowledge
    10. An investigatory and analytic thinking approach to the clinical situation is demonstrated.
    11. Basic and clinically supportive sciences appropriate to their discipline are known and applied.

  • Systems Based Practice
    24. Cost-effective health care and resource allocation that does not compromise quality of care is practiced.
    26. Partnering with health care managers and health care providers to assess, coordinate, and improve health care and how these activities can affect system performance are known.

    Author

    Donna M. D’Alessandro, MD
    Professor of Pediatrics, University of Iowa Children’s Hospital

  • How Effective Is Intralesional Candida Antigen for Treatment of Warts?

    Patient Presentation
    A 12-year-old male came to clinic for retreatment of his plantar warts. He had been treated with cryotherapy and salicylic acid 3 months previously. The mother said that she thought they had healed, but 2 days ago she noticed that they had returned. The boy had no pain and said that he thought it was okay as long as they didn’t hurt. The past medical history was non-contributory.

    The pertinent physical exam showed a healthy male with growth parameters in the 10-25%. On his ball of his right foot he had a 5-6 mm lesion and on the great toe had a 4-5 mm lesion. Both had a verrucous pattern with pinpoint hemorrhages. The bottom of the lesions could be palpated. The diagnosis of recurrent plantar warts was made. Cryotherapy was used again, with an appointment for re-freezing in 2-3 weeks. During the interval, salicylic acid use daily was advised. The physician also told the mother that if this treatment didn’t work, that he would refer the patient to dermatology for intralesional candida antigen immunotherapy.

    Discussion
    Veruccae plantaris or plantar warts are caused by Human papillomavirus which causes benign epidermal tumors that often have a cauliflower pattern on the foot that may be elevated or flush with the surrounding skin. Lesions may resemble caluses but the normal footprint pattern is disrupted. The lesions often have pinpoint hemorrhages that appear as black dots. In an immunocompetent individual, the lesions usually have spontaneous resolution within 2 years but the infection may spread to create additional lesions. The lesions may also cause pain or discomfort because of their size or location.

    Plantar warts are often difficult to treat. Treatments include keratolytics (e.g. salicylic acid or tricholoacetamic acid), cryotherapy with liquid nitrogen, electrodesiccation, or direct surgical removal. Suffocation by duct tape and plastic have also been used. Immunotherapy with candida, mumps or trichophytin antigens have been used more recently. These are felt to induce a local and distant immunoresponse that destroys the lesions.

    Learning Point
    Overall intralesional candida antigen therapy appears to be effective.
    A retrospective chart review in 2008 found:

    • For warts – of 55 patients with followup, 48 (87%) had complete resolution after an average of 3.5 monthly injections and another 3 (5.5%) patients had partial clearing after an average of 3 injections.
    • For molluscum contagiosum (caused by a pox virus) – of 25 patients with followup, 14 (56%) had complete resolution after an average of 3 monthly injections and another 7 (28%) had partial clearing after an average of 4 injections.

    This study had a large dropout rate though (for warts 67% and for molluscum 47%).

    In another small study of 18 patients, 11 completed the study and 9 (82%) had complete resolution and 1 (9%)had partial resolution, with a median of 4 every 3-week injections. Also, 6 of 9 patients (67%) with additional warts at distant locations had resolution of those warts.

    Questions for Further Discussion
    1. What is the cost of intralesional treatment with Candida antigen?
    2. How effective is mumps or trichophytin antigen intralesional treatment of plantar warts?
    3. How is intralesional candida antigen given?
    4. How are plantar warts spread?

    Related Cases

    To Learn More
    To view pediatric review articles on this topic from the past year check PubMed.

    Evidence-based medicine information on this topic can be found at SearchingPediatrics.com, the National Guideline Clearinghouse and the Cochrane Database of Systematic Reviews.

    Information prescriptions for patients can be found at MedlinePlus for these topics: Warts and Human Papillomavirus.

    To view current news articles on this topic check Google News.

    To view images related to this topic check Google Images.

    Maronn M, Salm C, Lyon V, Galbraith S. One-year experience with candida antigen immunotherapy for warts and molluscum. Pediatr Dermatol. 2008 Mar-Apr;25(2):189-92.

    Kim KH, Horn TD, Pharis J, Kincannon J, Jones R, O’Bryan K, Myers J, Nakagawa M. Phase 1 clinical trial of intralesional injection of Candida antigen for the treatment of warts. Arch Dermatol. 2010 Dec;146(12):1431-3

    ACGME Competencies Highlighted by Case

  • Patient Care
    1. When interacting with patients and their families, the health care professional communicates effectively and demonstrates caring and respectful behaviors.
    2. Essential and accurate information about the patients’ is gathered.
    3. Informed decisions about diagnostic and therapeutic interventions based on patient information and preferences, up-to-date scientific evidence, and clinical judgment is made.
    4. Patient management plans are developed and carried out.
    7. All medical and invasive procedures considered essential for the area of practice are competently performed.
    8. Health care services aimed at preventing health problems or maintaining health are provided.

  • Medical Knowledge
    10. An investigatory and analytic thinking approach to the clinical situation is demonstrated.
    11. Basic and clinically supportive sciences appropriate to their discipline are known and applied.

  • Systems Based Practice
    23. Differing types of medical practice and delivery systems including methods of controlling health care costs and allocating resources are known.

    Author

    Donna M. D’Alessandro, MD
    Professor of Pediatrics, University of Iowa Children’s Hospital