FDG-PET imaging in hematological malignancies.

The majority of aggressive lymphomas is characterized by an up regulated glycolytic activity, which enables the visualization by F-18 FDG-PET/CT. One-stop hybrid FDG-PET/CT combines the functional and morphologic information, outperforming both, CT and FDG-PET as separate imaging modalities. This has resulted in several recommendations using FDG-PET/CT for staging, restaging, monitoring during therapy, and assessment of treatment response as well as identification of malignant transformation. FDG-PET/CT may obviate the need for a bone marrow biopsy in patients with Hodgkin's lymphoma and diffuse large B cell lymphoma. FDG-PET/CT response assessment is recommended for FDG-avid lymphomas, whereas CT-based response evaluation remains important in lymphomas with low or variable FDG avidity. The treatment induced change in metabolic activity allows for assessment of response after completion of therapy as well as prediction of outcome early during therapy. The five-point scale Deauville Criteria allows the assessment of treatment response based on visual FDG-PET analysis. Although the use of FDG-PET/CT for prediction of therapeutic response is promising it should only be conducted in the context of clinical trials. Surveillance FDG-PET/CT after complete remission is discouraged due to the relative high number of false-positive findings, which in turn may result in further unnecessary investigations. Future directions include the use of new PET tracers such as F-18 fluorothymidine (FLT), a surrogate biomarker of cellular proliferation and Ga-68 CXCR4, a chemokine receptor imaging biomarker as well as innovative digital PET/CT and PET/MRI techniques.

Qualitative and quantitative performance of ¹8F-FDG-PET/MRI versus ¹8F-FDG-PET/CT in patients with head and neck cancer.

BACKGROUND AND PURPOSE: MR imaging and PET/CT are integrated in the work-up of head and neck cancer patients. The hybrid imaging technology (18)F-FDG-PET/MR imaging combining morphological and functional information might be attractive in this patient population. The aim of the study was to compare whole-body (18)F-FDG-PET/MR imaging and (18)F-FDG-PET/CT in patients with head and neck cancer, both qualitatively in terms of lymph node and distant metastases detection and quantitatively in terms of standardized uptake values measured in (18)F-FDG-avid lesions. MATERIALS AND METHODS: Fourteen patients with head and neck cancer underwent both whole-body PET/CT and PET/MR imaging after a single injection of (18)F-FDG. Two groups of readers counted the number of lesions on PET/CT and PET/MR imaging scans. A consensus reading was performed in those cases in which the groups disagreed. Quantitative standardized uptake value measurements were performed by placing spheric ROIs over the lesions in 3 different planes. Weighted and unweighted κ statistics, correlation analysis, and the Wilcoxon signed rank test were used for statistical analysis. RESULTS: κ statistics for the number of head and neck lesion lesions counted (pooled across regions) revealed interreader agreement between groups 1 and 2 of 0.47 and 0.56, respectively. Intrareader agreement was 0.67 and 0.63. The consensus reading provided an intrareader agreement of 0.63. For the presence or absence of metastasis, interreader agreement was 0.85 and 0.70. The consensus reading provided an intrareader agreement of 0.72. The correlations between the maximum standardized uptake value in (18)F-FDG-PET/MR imaging and (18)F-FDG-PET/CT for primary tumors and lymph node and metastatic lesions were very high (Spearman r = 1.00, 0.93, and 0.92, respectively). CONCLUSIONS: In patients with head and neck cancer, (18)F-FDG-PET/MR imaging and (18)F-FDG-PET/CT provide comparable results in the detection of lymph node and distant metastases. Standardized uptake values derived from (18)F-FDG-PET/MR imaging can be used reliably in this patient population.

N staging of lung cancer patients with PET/MRI using a three-segment model attenuation correction algorithm: initial experience.

OBJECTIVES: Evaluate the performance of PET/MRI at tissue interfaces with different attenuation values for detecting lymph node (LN) metastases and for accurately measuring maximum standardised uptake values (SUVmax) in lung cancer patients. MATERIALS AND METHOD: Eleven patients underwent PET/CT and PET/MRI for staging, restaging or follow-up of suspected or known lung cancer. Four experienced readers determined the N stage of the patients for each imaging method in a randomised blinded way. Concerning metastases, SUVmax of FDG-avid LNs were measured in PET/CT and PET/MRI in all patients. A standard of reference was created with a fifth experienced independent reader in combination with a chart review. Results were analysed to determine interobserver agreement, SUVmax correlation between CT and MRI (three-segment model) attenuation correction and diagnostic performance of the two techniques. RESULTS: Overall interobserver agreement was high (κ = 0.86) for PET/CT and substantial (κ = 0.70) for PET/MRI. SUVmax showed strong positive correlation (Spearman's correlation coefficient = 0.93, P < 0.001) between the two techniques. Diagnostic performance of PET/MRI was slightly inferior to that of PET/CT, without statistical significance (P > 0.05). CONCLUSIONS: PET/MRI using three-segment model attenuation correction for LN staging in lung cancer shows a strong parallel to PET/CT in terms of SUVmax, interobserver agreement and diagnostic performance. KEY POINTS: •F18-FDG PET/MRI shows similar performance to F18-FDG PET/CT in lung cancer N staging. •PET/MRI has substantial interobserver agreement in N staging. •A three-segment model attenuation correction is reliable for assessing the mediastinum.

Single photon emission computerized tomography with capromab pendetide plus computerized tomography image set co-registration independently predicts biochemical failure.

PURPOSE: We evaluate the usefulness of pretreatment (111)Indium capromab pendetide (ProstaScint) planar imaging (immunoscintigraphy) plus single photon emission tomography co-registration with computerized tomography scans to detect occult metastatic disease and predict for biochemical failure, in a cohort of patients with a clinical diagnosis of localized adenocarcinoma of the prostate referred for primary radiotherapy. MATERIALS AND METHODS: Patients were followed after radiotherapy for evidence of biochemical failure using 2 criteria of prostate specific antigen clinical nadir +2 ng/ml and American Society for Therapeutic Radiology and Oncology Consensus definitions. Median followup was 58.8 months (mean 64.8). Clinical risk factors defined 3 risk groups of high (51), intermediate (72) and low (116). RESULTS: Overall biochemical failure was 18.3% vs 11.8% by the 2-BFC at 8-year actuarial analysis with 58.8 months median followup. By the CN +2 definition the control date for the cohort is 34.8 months. Pretreatment SPECT/CT suggested prostate cancer metastasis (22), seminal vesicle extension (20) and organ confined disease (197). Biochemical failure in patients having extra-periprostatic metastatic prostate cancer, seminal vesicle extension and organ confined disease uptake on SPECT/CT was 43.2%, 16.0% vs 14.7% (p = 0.0006); and 33.3%, 15.0% vs 8.7% (p = 0.0017) by the 2-BFC, respectively. Cox multiple regression analysis demonstrated that a finding of extra-periprostatic metastatic prostate on SPECT/CT significantly predicted a 4.2-fold greater risk (p = 0.0012) and a 4.5-fold greater risk (p = 0.0011) of failure by the 2-BFC than organ confined disease adjusting for treatment and risk group. CONCLUSIONS: Unconfirmed findings of extra-periprostatic metastatic prostate cancer on SPECT/CT immunoscintigraphy independently and significantly predicted an increased risk of biochemical failure in patients presenting for radiotherapy with a clinical diagnosis of localized prostate cancer.

Positive emission tomography for evaluating a complete clinical response in patients with ovarian or peritoneal carcinoma: correlation with second-look laparotomy.

OBJECTIVE: Positive emission tomography (PET) provides a novel means of imaging malignancies. The following study was undertaken to evaluate the predictive value of PET in determining a pathologic complete response in patients with advanced ovarian or peritoneal carcinoma who had a complete clinical response following primary chemotherapy. METHODS: Twenty-two patients with advanced-stage ovarian (N = 17) or peritoneal (N = 5) carcinoma who had achieved complete clinical and radiologic remission and normal CA-125 level after six cycles of chemotherapy and who had consented to a second look laparotomy procedure were studied. All patients received platinum based therapy and all but one patient, treated elsewhere, received paclitaxel in combination with platinum. Following IV administration of 20 mCi [(18)F]fluorodeoxyglucose (FDG), the entire abdomen and pelvis were scanned. Various technical modifications including bladder activity dilution, intravenous hydration with diuretic therapy, and mechanical bowel preparations, were used to reduce background activity. Second-look laparotomy findings were classified as negative, macroscopically positive if a biopsy of a suspicious area was histologically positive, or microscopically positive if only a nonsuspicious area was histologically positive. The effect of patient preparation prior to PET imaging was evaluated. RESULTS: Persistent disease was found in 13 of the 22 patients (59%). Only one of nine sites with macroscopic and none of four with microscopic disease were accurately predicted. The sensitivity was only 10% and the specificity 42%. Intravenous hydration, diuretic therapy, and bowel preparation did not improve the results. CONCLUSIONS: These results suggest that despite technical modifications the sensitivity of PET before second-look laparotomy for small-volume persistent disease is low.

Functional evaluation of arteriovenous malformations.

Detailed knowledge of the angioarchitecture of arteriovenous malformations (AVMs) is necessary in determining the optimal timing and method of treatment of these challenging lesions. Many techniques are available for studying the functionality of surrounding cortical structures of AVMs. These include the use of positron emission tomography, functional magnetic resonance imaging, magnetoencephalography, and direct provocative testing of cortical function. The use of these methods to determine flow dynamics and tissue perfusion is also reviewed. These techniques are discussed in the present study, and their judicious utilization will enhance the safety of AVM therapy.

Empleo del tomógrafo PET para detectar metástasis linfáticas en pacientes con cáncer prostático: técnica actualizada y aumento en la precisión / The use of PET scanning to detect lymphatic metastases in patients with prostate cancer: updated technique and increased accuracy

Objetivos: El tomógrafo PET (positron emission tomography) fue utilizado en un estudio que hemos realizado para evaluar a pacientes con cácer prostático que eran candidatos a terapia curativa definitiva y a pacientes en los que terapias anteriores habían fracasado. Informamos nuestra experiencia inicial. Métodos: Cincuenta y nueve pacientes con cáncer prostático fueron evaluados con el tomógrafo PET. Los pacientes del grupo 1 (n=22) eran candidatos a terapia definitiva. Estos pacientes fueron sometidos a tomografía PET una semana antes de la linfadenectomía y los resultasos fueron comparados con la histología de los ganglios linfáticos pélvicos. Los pacientes del grupo 2 (n=37) habían fracasado en terapias anteriores y fueron sometidos a tomografía PET para detectar la presencia y ubicación recurrente o enfermedades metastásicas. Resultados: El grado de efectividad general de la tomografía PET en detectar metástasis linfáticas en pacientes que eran candidatos a terapia curativa (grupo 1) fue de 21/22 (95 por ciento) con una sensibilidad del 67 por ciento y unas especificidad del 100 por cien. En los pacientes en los que habían fracasado terapias anteriores (grupo 2), los sitios de recurrencia o enfermedades metastásicas incluían las fosas prostáticas, el esqueleto óseo y los ganglios inguinales, obturadores, periaórticos e ilíacos. Veinte pacientes (54 por ciento) mostraron un escaneo PET anormal y el antígeno específico prostático sérico medio (PSA) para pacientes con una examen positivo no fue significativamente distinto del de aquellos con escaneo normal /media 7,2 vs. 4,3 mg/dl: p=0,4). Conclusiones: La tomografía PET demuestra ser una promesa para ayudar a catalogar estadios en pacientes con cáncer prostáticos. Aun cuando nuestro estudio es limitado debido al bajo número de pacientes en el grupo 1 que padecen metástasis linfáticas, nuestros resultados son prometedores. La investigación posterior está garantizada

Empleo del tomógrafo PET para detectar metástasis linfáticas en pacientes con cáncer prostático: técnica actualizada y aumento en la precisión / The use of PET scanning to detect lymphatic metastases in patients with prostate cancer: updated technique and increased accuracy

Objetivos: El tomógrafo PET (positron emission tomography) fue utilizado en un estudio que hemos realizado para evaluar a pacientes con cácer prostático que eran candidatos a terapia curativa definitiva y a pacientes en los que terapias anteriores habían fracasado. Informamos nuestra experiencia inicial. Métodos: Cincuenta y nueve pacientes con cáncer prostático fueron evaluados con el tomógrafo PET. Los pacientes del grupo 1 (n=22) eran candidatos a terapia definitiva. Estos pacientes fueron sometidos a tomografía PET una semana antes de la linfadenectomía y los resultasos fueron comparados con la histología de los ganglios linfáticos pélvicos. Los pacientes del grupo 2 (n=37) habían fracasado en terapias anteriores y fueron sometidos a tomografía PET para detectar la presencia y ubicación recurrente o enfermedades metastásicas. Resultados: El grado de efectividad general de la tomografía PET en detectar metástasis linfáticas en pacientes que eran candidatos a terapia curativa (grupo 1) fue de 21/22 (95 por ciento) con una sensibilidad del 67 por ciento y unas especificidad del 100 por cien. En los pacientes en los que habían fracasado terapias anteriores (grupo 2), los sitios de recurrencia o enfermedades metastásicas incluían las fosas prostáticas, el esqueleto óseo y los ganglios inguinales, obturadores, periaórticos e ilíacos. Veinte pacientes (54 por ciento) mostraron un escaneo PET anormal y el antígeno específico prostático sérico medio (PSA) para pacientes con una examen positivo no fue significativamente distinto del de aquellos con escaneo normal /media 7,2 vs. 4,3 mg/dl: p=0,4). Conclusiones: La tomografía PET demuestra ser una promesa para ayudar a catalogar estadios en pacientes con cáncer prostáticos. Aun cuando nuestro estudio es limitado debido al bajo número de pacientes en el grupo 1 que padecen metástasis linfáticas, nuestros resultados son prometedores. La investigación posterior está garantizada(AU)

Multicenter ProstaScint imaging findings in 2154 patients with prostate cancer. The ProstaScint Imaging Centers.

OBJECTIVES: To report the results of a retrospective study of 2290 ProstaScint scans of 2154 patients with prostate carcinoma done at 15 institutions. METHODS: The results were analyzed by logistic regression after stratification of the patients into four groups: group 1, newly diagnosed; group 2, after radical prostatectomy with a rising prostate-specific antigen (PSA) level; group 3, after radiation therapy with a rising PSA level; and group 4, after hormonal therapy. RESULTS: The PSA level and ProstaScint scans positive in the prostate bed (P <0.001) and for pelvic metastases (P <0.001), but not for extrapelvic metastases, correlated significantly in group 1 patients. In group 2, the association for detecting fossa recurrence was weaker (P = 0.033) and was insignificant for pelvic and extrapelvic metastases. Patients in group 3 also exhibited a weak PSA-ProstaScint association for detecting fossa recurrence (P = 0.038), and was insignificant for pelvic and extrapelvic metastases. No significant PSA-ProstaScint correlation was found in patients in group 4 for fossa recurrence, pelvic or extrapelvic metastases. The distribution of positive ProstaScint results among the prostate/prostate bed, pelvic nodes, and extrapelvic nodes was nearly equal for all groups, except that a significantly greater percentage of extrapelvic metastases was found in the hormonal group (group 4). The ProstaScint results were independent of the Gleason score for 260 patients before and 285 patients after therapy. CONCLUSIONS: The results of this study underscore the complementary diagnostic value of ProstaScint to PSA level and Gleason score as an independent indicator of prostate cancer recurrence and metastases and in identifying extrapelvic metastases in both newly diagnosed and recurrent prostate cancer.

24. The Fusion of Anatomic and Physiologic Tomographic Images to Enhance Accurate Interpretation.

Purpose: Dedicated PET-(fluorine-18)-fluorodeoxyglucose (FDG) studies were interpreted with the corresponding anatomic images (MR or CT) using image fusion display to improve spatial accuracy for the interpreter and the referring physician.Methods: The image-fusion display system was designed in-house and allows manual alignment and display of one image volume as an overlay on the other which has improved accurate correlation of physiological and anatomical information for more than 50 patient studies.Results: A case of a patient with left foot recurrent melanoma is presented for which the PET scan showed a large focus of activity just lateral to the urinary bladder. Image fusion confirmed that the PET focus corresponded to an abnormal lymph node on the follow-up CT scan. In a case of bladder carcinoma which included bladder augmentation, altered surgical anatomy rendered interpretation of the FDG-PET images difficult. The fusion with the patient's CT scan allowed evaluation of the altered physiology due to the altered surgical anatomy which permitted accurate image interpretation. In a case of pelvic lymphoma, the FDG-PET scan showed intense activity adjacent to the acetabulum and possibly within it. Image fusion allowed accurate localization of the patient's primary lesion with the additional benefit of showing activity extending into the adjacent bone.Conclusion: Image fusion of tomographic, anatomic and physiologic information permits accurate lesion localization including separation of soft tissue from bone. The image-fusion technique facilitates image-guided biopsy by providing accurate anatomic localization.

Positron emission tomography for evaluating para-aortic nodal metastasis in locally advanced cervical cancer before surgical staging: a surgicopathologic study.

PURPOSE: Positron emission tomographic (PET) scanning provides a novel means of imaging malignancies. This prospective study was undertaken to evaluate PET scanning in detecting para-aortic nodal metastasis in patients with locally advanced cervical carcinoma and no evidence of extrapelvic disease before planned surgical staging lymphadenectomy. MATERIALS AND METHODS: After 20 mCi of 2-[18F]fluoro-2-deoxy-D-glucose (FDG) were administered intravenously, the abdomen and pelvis were scanned. Continuous bladder irrigation was used to reduce artifact. Patients were classified by the presence or absence of FDG uptake in the primary tumor and in pelvic or para-aortic nodes. Para-aortic node metastases were classified as present or absent according to a standardized staging procedure. Pelvic node metastases were similarly classified in a subset of patients who underwent pelvic node resection. RESULTS: Thirty-two patients with stage IIB (n = 6), IIIB (n = 24), and IVA (n = 2) tumors were studied. Fluorodeoxyglucose was taken up by 91% of the cervical tumors. Six of eight patients with positive para-aortic node metastasis had PET scan evidence of para-aortic nodal metastasis. One of the two false-negatives had only one microscopic focus of metastatic cancer. In the para-aortic nodes, PET scanning had a sensitivity of 75%, a specificity of 92%, a positive predictive value of 75%, and a negative predictive value of 92%. Fluorodeoxyglucose para-aortic nodal uptake conferred a relative risk of 9.0 (95% confidence interval, 2.3 to 36.0) for para-aortic nodal metastasis. All 10 of 17 patients with metastasis were predicted by PET scanning (P < .001); five of these patients had abnormalities on computed tomographic scans. CONCLUSION: Cervical cancers have a high avidity for FDG. The use of PET-FDG scanning accurately predicts both the presence and absence of pelvic and para-aortic nodal metastatic disease.

The role of fluorodeoxyglucose and positron emission tomography in the evaluation of pancreatic disease.

BACKGROUND: The difficulties involved in the timely and accurate diagnosis of pancreatic disease are well known. The usual imaging modalities usually identify abnormalities but may not always differentiate malignancy from other condition such as scar tissue or chronic inflammation. The purpose of our study was to determine if fluorodeoxyglucose positron emission tomography (FDG PET) can accurately diagnose pancreatic disease. METHODS: The records of 15 patients presenting with pancreatic disease were retrospectively reviewed. The diagnosis suspected by imaging modalities was compared with the final tissue diagnosis. Two patients were excluded because no tissue was obtained. RESULTS: Adenocarcinoma was diagnosed in 9 patients. A mass consistent with this diagnosis was seen in 8 of 9, 6 of 9, 6 of 8, and 5 of 5 patients by PET, computed tomography (CT), endoscopic retrograde cholangiopancreatography (ERCP), and endoscopic ultrasound (EUS), respectively. Chronic pancreatitis (CP) was diagnosed in 2 patients. The unique appearance on FDG PET made the diagnosis in both these patients. Both patients with CP were thought to have a malignancy by CT and EUS and 1 of 2 by ERCP. Neuroendocrine tumors were diagnosed in 2 other patients. One of 2 was seen by FDG PET and both by CT. CONCLUSIONS: FDG PET can accurately differentiate a pancreatic adenocarcinoma from chronic pancreatitis in a patient with a suspicious pancreatic mass. Thus, FDG PET may help in establishing a diagnosis and subsequently managing a patient with pancreatic disease.

Elimination of artifactual accumulation of FDG in PET imaging of colorectal cancer.

BACKGROUND: Positron emission tomography (PET) with fluorine-18 labeled deoxyglucose (FDG) can detect tumor recurrences in surgical patients that are otherwise difficult to assess by CT, as well as distant metastases and small malignant nodes that are not identified by other imaging modalities. However, the evaluation of such malignancy is complicated by urinary and colonic concentrations of FDG. Methods and examples of the elimination of artifactual accumulation of FDG in PET imaging of the abdomen and pelvis are presented. METHODS: Elimination of artifactual accumulation requires patient preparation that begins with cleansing of the colon using an isosmotic solution taken the evening prior to examination. Approximately 500 MBq of F-18 FDG is intravenously administered upon arrival at the PET facility and then the patient is hydrated. After administration of furosemide, a Foley catheter with a drainage bag is placed and the patient is then scanned. Just prior to scanning over the pelvis, normal saline is delivered retrogradely into the urinary bladder. At the end of scanning, the patient voids and repeated pelvic images are obtained. RESULTS: These routines yield a clean scanning field. Lesions that will generally be missed because they are obscured by FDG accumulations along the colon or in the kidneys, ureters, or bladder are better visualized and identified with greater confidence. Artifacts that lead to misinterpretation also are reduced. CONCLUSION: Elimination of artifactual accumulation of FDG in the colon and urinary system is essential if primary cancer, associated adenopathy, or subtle recurrences are to be evaluated in FDG PET imaging of the abdomen and pelvis.

Technical improvements in fluorine-18-FDG PET imaging of the abdomen and pelvis.

UNLABELLED: PET tumor imaging of the abdomen and pelvis is prone to artifacts due to urinary tract activity. A new technique has been developed to reduce such artifacts and enhance study interpretation. METHODS: Thirty minutes after the injection of 18F-FDG, 500 cc 0.45% NaCl were administered intravenously over 30 min and a Foley catheter was placed in the bladder. At the start of imaging (60 min post-injection), furosemide was given (0.3 mg/kg). Prior to imaging the pelvis, the urinary catheter was clamped and saline was introduced retrograde into the bladder until full. RESULTS: This technique has been used successfully in more than 130 patients, resulting in a marked improvement in study quality and tumor detection. CONCLUSION: Hydration and administration of furosemide, along with placement of a Foley catheter in the bladder, have proven effective in eliminating image artifacts originating from the kidneys, ureters and bladder. Backfilling the bladder also provides a well-defined anatomic landmark for study interpretation.

Axillary lymph node metastases: screening with [F-18]2-deoxy-2-fluoro-D-glucose (FDG) PET.

PURPOSE: To evaluate [fluorine-18]2-deoxy-2-fluoro-D-glucose (FDG) positron emission tomography (PET) of the axilla as a screening test for detecting regional spread of breast cancer. MATERIALS AND METHODS: High-dose FDG PET of the axilla was successfully performed in 50 patients (age range, 36-79 years) with breast cancer before 52 axillary lymph node dissections. Two additional patients had scans that were uninterpretable because of intense myocardial activity that obscured the axilla. RESULTS: The sensitivity and negative predictive value were both 95%, the specificity was 66%, and the overall accuracy was 77%. The only false-negative PET scan was obtained in the largest patient, who had a low-quality scan. CONCLUSION: Patients with negative PET scans had such a low risk for axillary lymph node metastases that axillary dissection was not warranted. Patients with positive PET scans required dissection to confirm the presence and determine the number of positive lymph nodes. Had this algorithm been used to select patients for dissection, approximately $120,000 in charges ($2,300 per patient) would have been saved and 22 patients would have been spared the morbidity of axillary lymph node dissection. Within this study population, PET scans of the axilla were interpreted with sufficient sensitivity for PET to serve as a cost-effective screening test for axillary lymph node metastases.

Radiation dose to the bladder wall from 2-[18F]fluoro-2-deoxy-D-glucose in adult humans.

Accurate determination of the radiation dose to the bladder wall from 2-[18F]fluoro-2-deoxy-D-glucose (2-[18F]FDG) is important because the bladder is the critical organ in radiotracer studies using 2-[18F]FDG. The radiation dose to the bladder wall from injected 2-[18F]FDG was estimated using both a dynamic bladder model and the conventional MIRD model. The dynamic model takes into account the excretion rate, the varying size of the bladder, the volume at injection, and an estimated bladder time activity curve. Our data from 302 adult subjects in a five-year period indicate that when the bladder is large at the time of injection, the dose to the bladder is greatly reduced. The absorbed dose of the bladder based on the dynamic model for an initial volume of 450 ml is 0.16 +/- 0.06 rad/mCi, while that for an initial volume of 200 ml is calculated to be 0.37 +/- 0.18 rad/mCi. The MIRD model estimates an average value of 0.35 +/- 0.16 rad/mCi for the 302 cases.