Alison Fromme

A survey of children's imaging services has found a twofold variation in radiopharmaceutical doses administered during pediatric nuclear medicine exams. For some radiopharmaceuticals, the reported maximum activities varied by as much as a factor of 10, and minimum activities differed by as much as a factor of 20, suggesting the need for a consensus among nuclear physicians on appropriate doses for young patients. Based a survey of 16 selected procedures at 13 pediatric hospitals in North America, the study from Boston's Children's Hospital found that in general, however, variation was within a factor of 2. The report reveals a need for better tools to guide dosing practices, according to the authors. The report appeared in the June 2008 

"At this time, the majority of radiopharmaceutical package inserts do not provide guidance on pediatric doses," said lead author Dr. S. Ted Treves, chief of nuclear medicine at Children's and a professor of radiology at Harvard Medical School. The survey tracked the minimum and maximum administered activities, the schedule used to determine the appropriate administered activity as a function of patient size, and the corresponding factor applied, such as activity per kilogram or activity per body surface area. The minimum total doses of technetium-99m mercaptoacetyltriglycine (MAG3), a tracer frequently used during renal scintigraphy, ranged from 18.5 to 148 MBq. Activity per kilogram varied from 1.85 to 10.36 MBq and the maximum dose from 111.0 to 370.0 MBq. Overall, the greatest inconsistency was found for levels of minimum total administered activity in newborns and infants."In imaging children, physicians typically base dosages on the patient's body weight, the nature and type of problem being investigated, the equipment available, and their own experience. This has led to the variations in dosage that currently exist," Treves said. The authors speculate that since the survey uncovered differences among premier facilities, variations in the larger nuclear medicine community could be even greater. Treves identified the need for the survey when he was asked to participate in a different multicenter study that prescribed doses much higher than those he normally uses. "I knew there were no standards," he said.The survey confirmed his suspicion that significant variation exists. "We were able to characterize the variation, and this provides an opportunity to stop and think about that," he said. The study has prompted the formation of a workgroup to balance the need for high-quality images with the lowest possible activities and develop guidelines for pediatric radiopharmaceutical dosing. Members of the Pediatric Imaging Council and the Society for Pediatric Radiology who practice nuclear medicine will participate. "This group will examine administered dosages and come up with recommended radiopharmaceutical dosages over the next year." said council president Dr. Michael Gelfand.For more information from the Diagnostic Imaging archives:

Pediatric imagers put dose campaign on the road

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Articles

A survey of children’s imaging services has found a twofold variation in radiopharmaceutical doses administered during pediatric nuclear medicine exams. For some radiopharmaceuticals, the reported maximum activities varied by as much as a factor of 10, and minimum activities differed by as much as a factor of 20, suggesting the need for a consensus among nuclear physicians on appropriate doses for young patients.

Study finds huge variations in pediatric nuclear medicine dosing

Unnecessary surgeries for suspected, but ultimately benign, ovarian tumors could be reduced if ultrasonography is improved, according to a recent report in 

. The study showed that the number of surgeries for suspected cancers was significantly higher after routine ultrasounds compared with ultrasounds performed by sonographers who have more than 10 years of experience. 

Ultrasound is commonly used for preoperative assessment, but diagnostic accuracy varies with operator experience and skill. Dr. Joseph Yazbek and colleagues at Guy's and St Thomas' Hospital NHS Foundation Trust in London conducted a randomized study to determine whether this operator variation led to differences in management of 165 patients with ovarian abnormalities. 

Seventy-seven women at London's regional South-East Gynaecological Cancer Centre received ultrasounds performed by examiners who had more than 10 years of experience in gynecological ultrasonography and were certified teachers of the technique (level III). The remaining 73 patients received ultrasounds performed by technologists trained in gynecological ultrasonography who were certified at level II. 

Of the women who received scans by the level II technologists, 37% underwent major surgical staging procedures, compared with 22% of those who received ultrasounds by level III examiners. 

"We expected a greater reduction in the number of major operative procedures and more minimally invasive procedures in the level III arm of the study," he said. Other studies have shown that level III ultrasonographers can identify cancerous tumors with 95% accuracy."

In this trial, all cancerous tumors among the women were identified, and level III examiners correctly diagnosed the nature of the abnormalities in all but one of the patients. Level II examiners did so in only 52% of the cases.

"Clinicians still do not have a great belief in the ability of ultrasound to accurately predict the nature of ovarian tumors," Yazbek said. "This will happen with time, by training more specialists in gynecological ultrasound and further improving the diagnostic ability of ultrasound scanning to differentiate benign from malignant ovarian tumors."

Few ultrasonographers specialize in gynecology in the U.K. Training more specialists would help improve the accuracy of diagnoses for patients, according to Dr. Yazbek. 

The problem is likely not confined to the U.K.

"In general, ultrasound operator-dependence is well known," said Dr. Leslie Scoutt, chief of the radiology department's ultrasound section at Yale University. Scoutt was not associated with the study. 

experience with gynecological ultrasound were more accurate when

characterizing ovarian masses than less experienced technologists.

For more information from the Diagnostic Imaging archives:

High-quality ultrasound demonstrates measurable effect in ovarian cancer management

Report from SNM: PET/CT excels in management of recurring ovarian cancer

Unnecessary surgeries for suspected, but ultimately benign, ovarian tumors could be reduced if ultrasonography is improved, according to a recent report in The Lancet Oncology. The study showed that the number of surgeries for suspected cancers was significantly higher after routine ultrasounds compared with ultrasounds performed by sonographers who have more than 10 years of experience.

Sonographer experience translates into fewer unnecessary ovarian tumor surgeries

For the first time, researchers have combined functional and anatomic MR imaging to reveal abnormalities in both physiological states in a well-defined subgroup of schizophrenic patients with chronic auditory hallucinations. With the potential to visually pinpoint abnormalities, MRI could prove useful as a diagnostic and follow-up tool to evaluate treatment for people with the disorder, according to lead investigator Dr. Luis Marti-Bonmati, chief of MR at Dr. Peset University Hospital in Valencia, Spain.

Researchers imaged subjects as they listened to a recording of either neutral or emotionally charged words that are frequently heard by psychotic patients with auditory hallucinations. Brain function in the schizophrenic group was marked by an increased hemodynamic response in the temporal lobe. Structurally, gray matter volume in auditory processing regions of these patients was lower than in the controls (Radiology 2007;244:549-556).

Although the researchers expected a relationship between structural and functional aberrations, they were surprised to find so many coinciding areas that followed the same pattern: structural reduction of gray matter volume and functional overactivation. The coinciding areas included large clusters in the left and right middle temporal and left and right superior temporal gyri and smaller areas in the left posterior and right anterior cingular gyri, left inferior opercular frontal gyrus, and right middle occipital gyrus.

Marti-Bonmati suggests that overactivation and corresponding gray matter deficits in the limbic and frontal brain of schizophrenics reflect a dysfunctional emotional response to spoken words.

Schizophrenia is a complex syndrome with a strong genetic basis, yet the phenotypes are poorly understood, according to Fred W. Sabb, Ph.D., a research scientist with the Consortium for Neuropsychiatric Phenomics at the University of California, Los Angeles.

This study represents an important step in examining phenotypic indicators across several dimensions, he said.

"By combining fMRI and structural MRI results, these researchers have been able to localize specific structural deficits and abnormal neural signatures associated with behavior and examine how these are related to symptomatology at the core of the schizophrenia syndrome," Sabb said. "This multidimensional approach represents an exciting new area for neuroimaging, as we look to link phenotypes from genome to syndrome in the study of complex neuropsychiatric disorders."

Auditory delusions show link to voice-processing area

Functional magnetic resonance imaging has helped University of Washington researchers discover that too much connectivity between the language-processing regions of the brains of dyslexic children may contribute to reading disabilities. Follow-up scans produced functional evidence that these abnormal connectivity patterns were mitigated after only three weeks of specialized reading training.

Radiology professor Dr. Todd Richards and neuropsychologist Virginia Berninger, Ph.D., director of the university's Learning Disability Center in Seattle, conducted fMRI on 18 dyslexic children with known reading problems and 21 children who were good readers and spellers. All subjects exhibited normal intelligence and were in the fourth through sixth grades. FMRI was acquired while they performed word tasks, such as deciding whether nonsense words, such as "pleak" and "leeze," could have the same sound. 

The imaging protocol involved a standard fMRI EPI-planar pulse sequence (TR/TE 3000/50 msec) with 21 6-mm-thick slices acquired with a 1-mm gap between each. Data were processed using FSL software from the Oxford (University) Center for Functional Magnetic Resonance Imaging of the Brain in the U.K. FSL software and custom software written by Richards were used to calculate brain correlation values from user-defined seed points. Each functional scan lasted five minutes, 42 seconds.

Baseline scans revealed that compared to normal controls, the dyslexic children exhibited significantly more connectivity between left inferior frontal gyrus seed points and the right inferior frontal gyrus while completing word tasks.

"The results were surprising because we were expecting to see deficits in connectivity, not over-connectivity, in dyslexia," Richards said in an interview. "Some brain regions are too strongly connected functionally in children with dyslexia when they are deciding which sounds go with which letters."

Different areas of the brain must communicate with each other properly in order to decode written language, according to Berninger. The brain center for this communication is like the conductor of an orchestra, she said. The left inferior frontal gyrus may serve as the conductor for language, ensuring that information is shared with the correct timing and in the proper sequence. In people with dyslexia, that conductor is ineffective.

But the trial also demonstrated that the abnormal pattern observed in dyslexic children can be modified. Functional MRI was again performed on the dyslexic children after they participated in three weeks of alphabetic, phonetic, and word recognition training. 

Scans performed after treatment revealed that the amount of connectivity from the left inferior frontal gyrus seed point decreased in the brains of children with dyslexia to become more like the connectivity patterns of the control subjects, suggesting that focused instruction can normalize this aspect of brain activity among dyslexic children.

"We had hints in previous studies that the ability to decode novel words improves when a specific brain region in the right hemisphere decreases in activation," Richards said. "This study suggests that the deactivation may result in a disconnection in time from the comparable region in the left hemisphere, which in turn leads to improved reading. Reading requires sequential as well as simultaneous processes."

The study was reported in the October issue of the 

For more information from the Diagnostic Imaging archive:

Brain imaging focuses on connectivity and activation

Functional MRI snoops out how, why we decide to buy

Schizophrenic patients who hear voices demonstrate abnormalities in voice-processing brain regions

fMRI tests assumptions about behavior and thought

Alison Fromme

Articles

Study finds huge variations in pediatric nuclear medicine dosing

Sonographer experience translates into fewer unnecessary ovarian tumor surgeries

Auditory delusions show link to voice-processing area

fMRI links brain connectivity pattern with reading problems in dyslexic children