Estimated radiation exposure and cancer risk from CT and PET/CT scans in patients with lymphoma

Cumulative radiation exposure from radiological imaging in patients with Hodgkin and diffuse large b-cell lymphoma not submitted to radiotherapy

OBJECTIVE

To assess the cumulated exposure to radiation due to imaging in Hodgkin (HL) and diffuse large B-cell (DLBCL) lymphoma patients who were not submitted to radiotherapy.

METHODS

The study population included 51 and 83 adult patients with HL and DLBCL, with a follow-up duration >1 year. The cumulated exposure was expressed using patient-specific data as cumulated effective dose (CED).

RESULTS

Fifty-one HL patients (median age 47 years) were followed for a median of 3.5 years. The median total CED per subject was 104 mSv. CT and PET/CT examinations accounted for 75 and 25% of the total CED, respectively. 26 patients (49%) had a total CED ≥ 100 mSv and the maximum CED was 302 mSv. Eighty-three DLBCL patients (median age 66 years) were followed for a median of 3.7 years. The median total CED per subject over the study period was 134 mSv. CT and PET/CT for 86% and 13% of the total CED, respectively. 56 patients (67%) had a total CED ≥100 mSv. The maximum CED was 557 mSv.

CONCLUSION

Our study demonstrated the large number of imaging procedures performed for patients with lymphoma. Overall, 61% of the patients accrued a CED ≥ 100 mSv. Imaging policies were only in a partial agreement with current international guidelines.

ADVANCES IN KNOWLEDGE

The cumulated exposure radiation exposure may be of concern in HL patients and the contribution of CT procedures to the total CED is significant. The standardisation of clinical guidelines for managing patients with lymphoma is warranted.

CANCER RISK ESTIMATION FOR PATIENTS UNDERGOING WHOLE-BODY PET/CT SCANS

The objective of this paper was to compute the effective dose, as well as the lifetime attributable risk (LAR) of cancer related to whole-body positron emission tomography (PET)/computed tomography (CT) scan for 193 adult patients. The mean effective dose for all patients from a single PET/CT scan was 20.6 mSv. For males aged 40 y, a single PET/CT scan is associated with a LAR of cancer incidence of 0.169%. This risk increased to 0.85% if an annual surveillance protocol for 5 y was performed. For female patients aged 40 y, the LAR of cancer mortality increased from 0.126 to 0.63% if an annual surveillance protocol for 5 y was performed. Since PET/CT scans are associated with a high dose and a risk of developing cancer, it was important to balance the advantages and risks before conducting any scans. This is especially important for younger patients and those who are overweight.

Fully automated image quality evaluation on patient CT: Multi-vendor and multi-reconstruction study

While the recent advancements of computed tomography (CT) technology have contributed in reducing radiation dose and image noise, an objective evaluation of image quality in patient scans has not yet been established. In this study, we present a patient-specific CT image quality evaluation method that includes fully automated measurements of noise level, structure sharpness, and alteration of structure. This study used the CT images of 120 patients from four different CT scanners reconstructed with three types of algorithm: filtered back projection (FBP), vendor-specific iterative reconstruction (IR), and a vendor-agnostic deep learning model (DLM, ClariCT.AI, ClariPi Inc.). The structure coherence feature (SCF) was used to divide an image into the homogeneous (RH) and structure edge (RS) regions, which in turn were used to localize the regions of interests (ROIs) for subsequent analysis of image quality indices. The noise level was calculated by averaging the standard deviations from five randomly selected ROIs on RH, and the mean SCFs on RS was used to estimate the structure sharpness. The structure alteration was defined by the standard deviation ratio between RS and RH on the subtraction image between FBP and IR or DLM, in which lower structure alterations indicate successful noise reduction without degradation of structure details. The estimated structure sharpness showed a high correlation of 0.793 with manually measured edge slopes. Compared to FBP, IR and DLM showed 34.38% and 51.30% noise reduction, 2.87% and 0.59% lower structure sharpness, and 2.20% and -12.03% structure alteration, respectively, on an average. DLM showed statistically superior performance to IR in all three image quality metrics. This study is expected to contribute to enhance the CT protocol optimization process by allowing a high throughput and quantitative image quality evaluation during the introduction or adjustment of lower-dose CT protocol into routine practice.

Patients undergoing multiple 18F-FDG PET/CT exams: Assessment of frequency, dose and disease classification

OBJECTIVE

To analyse the frequency, demographics, primary disease and cumulative effective dose of patients undergoing two or more 18F-FDG PET/CT examinations in a year.

METHODS

In a retrospective study performed at a tertiary-care hospital, patients who underwent ≥2 18F-FDG PET/CT scans in a calendar year were identified for two consecutive years. The CT radiation dose was calculated using dose-length-product and sex-specific conversion factors. The primary malignancy of patients was retrieved from electronic medical records.

RESULTS

10,714 18F-FDG PET/CT exams were performed for 6,831 unique patients in 2 years, yielding an average of 1.6 exams per patient. The maximum number of 18F-FDG PET/CT examinations any patient underwent in a single year was seven. 20.9% patients had ≥2 18F-FDG PET/CT exams in any single year. Thirty nine percent patients in the cohort were below 60 years age. The median dose for 18F-FDG PET/CT examination was 25.1 mSv and maximum value reaching 1.7 to 2.9 times the median value. Cumulative effective dose (CED) was≥100 mSv in 12-13% of the patients. The cumulative dose for both years combined demonstrated the 25th percentile, 50th percentile and 75th percentile as well as the mean to be over 100 mSv, with the 25th percentile being 109 mSv. The dominant primary malignancies contributing to serial 18F-FDG PET/CTs in decreasing frequency were melanoma, non-Hodgkin's lymphoma (NHL), gastrointestinal cancer, breast cancer and Hodgkin's lymphoma.

CONCLUSIONS

A sizeable number of patients undergo≥2 18F-FDG PET/CT exams with one out of every eight patients receiving cumulative dose≥100 mSv and that includes patients with long-life expectancy.

ADVANCES IN KNOWLEDGE

The study found that one of five patients had≥2 18F-FDG PET/CT exams in a calendar year, one of four patients in two years and one of eight patients received cumulative dose≥100 mSv. Top malignancies associated with serial imaging in decreasing order of frequency included melanoma, non-Hodgkin's lymphoma (NHL), gastrointestinal cancer, breast cancer and Hodgkin's lymphoma.

Cumulative radiation doses due to nuclear medicine examinations: a systematic review

OBJECTIVES

To systematically review the published data regarding the cumulative exposure to radiation in selected cohorts of adults or paediatric patients due to diagnostic nuclear medicine examinations.

METHODS

We conducted PubMed/Medline searches of peer-reviewed papers on cumulated effective dose (CED) from diagnostic nuclear medicine procedures published between 01 January 2010 until 31 January 2021. Studies were considered eligible if the contribution of nuclear medicine examinations to total CED was >10%. Studies reporting cumulative doses in a single episode of care or in a limited time (≤1 year) were excluded. The main outcomes for which data were sought were the CED accrued by patients, the period in which the CED was accrued, the percentage of patients with CED > 100 mSv and the percentage contribution due to nuclear medicine procedures to the overall CED.

RESULTS

The studies included in the synthesis were 18 which enrolled a total of 1,76,371 patients. Eleven (1,757 patients), three (1,74,079 patients) and four (535 patients) were related to oncological, cardiologic and transplanted patients, respectively. All the studies were retrospective; some of the source materials referred to small number of patients and some of the patients were followed for a short time. Not many studies accurately quantified the contribution of nuclear medicine procedures to the overall radiation exposure due to medical imaging. Finally, most of the studies covered an observation period which extended mainly in the 2000-2010 decade.

CONCLUSIONS

There is a need of prospective, multicentric studies enrolling a greater number of patients, followed for longer period in selected groups of patients to fully capture the cumulative exposure to radiation in these settings.

ADVANCES IN KNOWLEDGE

This systematic review allows to identify selected group of patients with a specific health status in which the cumulated exposure to radiation may be of concern and where the contribution of nuclear medicine procedures to the total CED is significant.

Imaging Surveillance of Limited-stage Classic Hodgkin Lymphoma Patients After PET-CT-documented First Remission

INTRODUCTION

Early stage Hodgkin lymphoma (ESHL) is highly curable; however, 10% to 15% of patients experience relapse. We examined the utilization of follow-up imaging for patients with ESHL who achieved a metabolic complete response after upfront therapy.

MATERIALS AND METHODS

The records of adult patients treated at a single institution between 2003 and 2014 were reviewed. Positron emission tomography-computed tomography (PET-CT) and CT scan frequency was quantified during the 2 years following treatment and subsequent visits beyond 2 years.

RESULTS

The study cohort contained 179 patients. The median age was 31 years; bulky disease was present in 30%. ABVD (doxorubicin, bleomycin, vinblastine, and dacarbazine) or AVD (doxorubicin, vinblastine, and dacarbazine) was given in 97%; 75% received radiation therapy. At a median follow-up of 6.9 years, the 5-year progression-free and overall survival rates were 93.7% and 98.1%, respectively. Relapse occurred in 5% (n = 9) of patients at a median of 9.1 months (range, 4.6-27.2 months) from therapy. Two patients presented with symptoms prompting imaging in follow-up. Within 2 years after therapy, 376 PET-CT scans and 3325 CT scans were performed, yielding an average of 2.1 PET-CTs and 18.6 CTs per patient. Of the initial 179 patients, 113 had follow-up conducted beyond 2 years post-therapy; an average of 2.7 PET-CTs and 33.2 CTs were performed. In the 2-year post-therapy period, 463 scans were performed per relapse detected.

CONCLUSION

In this cohort of patients with ESHL who responded completely to frontline therapy, the relapse rate was low. Routine imaging surveillance lacks clinical benefit in this patient population.

Cumulative exposure to ionising radiation from diagnostic imaging tests: a 12-year follow-up population-based analysis in Spain

OBJECTIVES

To calculate each patient's cumulative radiation exposure and the recurrent tests during a 12-year study period, according to sex and age, in routine practice.

DESIGN

Retrospective cohort study.

SETTING

A general hospital with a catchment population of 224 751 people, in the Southeast of Spain.

PARTICIPANTS

Population belonged to the catchment area of that hospital in 2007. We collected all consecutive diagnostic imaging tests undergone by this population until 31 December 2018. We excluded: imaging tests that did not involve radiation exposure.

MAIN OUTCOME MEASURES

The cumulative effective dose and the recurrent imaging tests by sex and age at entry of study.

RESULTS

Of the 224 751 people, 154 520 (68.8%) underwent an imaging test. The population had 1 335 752 imaging tests during the period of study: 1 110 077 (83.0%) plain radiography; 156 848 (11.8%) CT; 63 157 (4.8%) fluoroscopy and 5670 (0.4%) interventional radiography. 25.4% of the patients who had a CT, underwent five or more CTs (5.4% in the 0-20 years age group). The median total cumulative effective dose was 2.10 mSv (maximum 3980.30) and 16.30 mSv (maximum 1419.30 mSv) if we considered only doses associated with CT. Women received more effective dose than men (median 2.38 vs median 1.90, p<0.001). A total of 7142 (4.6%) patients received more than 50 mSv, with differences in men and women (p<0.001) and 2.5% of the patients in the 0-20 years age group, if we considered only doses associated with CT.

CONCLUSIONS

Nearly 5% of patients received doses higher than 50 mSv during the 12-year period of study and 2.5% of the patients in the 0-20 years age group, if we considered only doses associated with CT. The rate of recurrent examinations was high, especially in older patients, but also relevant in the 0-20 years age group.

EFFECTIVE RADIATION DOSE OF 18F-FDG PET/CT: HOW MUCH DOES DIAGNOSTIC CT CONTRIBUTE?

The aim was to estimate the effective doses associated with different types of scanning protocols and how much the diagnostic computed tomography (DCT) scan contributed to the total dose of the dual-modality positron emission tomography/computed tomography (PET/CT) examinations. The results showed that an average radiation dose of 8.19 ± 0.83 mSv and 13.44 ± 5.14 mSv for the PET and CT components, respectively, resulting in a total dose of 21.64 ± 5.20 mSv. Approximately 92.7% (980 of 1057) of the patients underwent additional DCT protocols. The DCT protocols contributed 42% of the overall effective radiation doses, which was larger than the percentage contributed by the PET component (38%) and LCT protocols (20%). Reducing the diagnostic area of the DCT scans that patients undergo and decreasing the use of chest-abdomen-pelvis (CAP), abdomen-pelvis (AP) and chest DCT protocols, especially the CAP protocol, will be helpful in decreasing the effective radiation doses of PET/CT scan.

Monitoring clinical outcomes in aggressive B-cell lymphoma: From imaging studies to circulating tumor DNA

Recent guidelines have de-emphasized the role of routine surveillance computed tomography (CT) scans for diffuse large B-cell lymphoma (DLBCL) patients who achieve a complete response to front-line therapy. This shift in practice recommendations was prompted by retrospective studies that failed to demonstrate clear clinical utility for surveillance CT in unselected DLBCL patients. Controversy remains, however, over the role of routine surveillance CT in the highest risk patients for treatment failure who would remain candidates for aggressive salvage therapies. Novel high-throughput sequencing methods can non-invasively monitor tumor-specific DNA in the blood and offers clear advantages designed to overcome fundamental limitations of CT scans. This review will discuss the current controversies surrounding monitoring clinical outcomes in aggressive B-cell lymphomas, with a specific emphasis on DLBCL. Fundamental limitations of imaging scans will be addressed and the potential of monitoring circulating tumor DNA as an adjunct or replacement for CT scans will be discussed.

Estimation of lifetime attributable risks (LARs) of cancer associated with abdominopelvic radiotherapy treatment planning computed tomography (CT) simulations

PURPOSE

The present study attempts to calculate organ-absorbed and effective doses for cancer patients to estimate the possible cancer induction and cancer mortality risks resulting from 64-slice abdominopelvic computed tomography (CT) simulations for radiotherapy treatment planning (RTTP).

MATERIAL AND METHODS

A group of 70 patients, who underwent 64-slice abdominopelvic CT scan for RTTP, voluntarily participated in the present study. To calculate organ and effective doses in a standard phantom of 70 kg, the collected dosimetric parameters were used with the ImPACT CT Patient Dosimetry Calculator. Patient-specific organ dose and effective dose were calculated by applying related correction factors. For the estimation of lifetime attributable risks (LARs) of cancer incidence and cancer-related mortality, doses in radiosensitive organs were converted to risks based on the data published in Biological Effects of Ionizing Radiation VII (BEIR VII).

RESULTS

The mean ± standard deviation (SD) of the effective dose for males and females were 13.87 ± 2.37 mSv (range: 9.25-18.82 mSv) and 13.04 ± 3.42 mSv (range: 6.99-18.37 mSv), respectively. The mean ± SD of LAR of cancer incidence was 35.34 ± 13.82 cases in males and 34.49 ± 9.63 cases in females per 100,000 persons. The LAR of cancer mortality had the mean ± SD value of 15.38 ± 4.25 and 16.72 ± 3.87 cases per 100,000 persons in males and females respectively.

CONCLUSION

Increase in the LAR of cancer occurrence and mortality due to abdominopelvic treatment planning CT simulation is noticeable and should be considered.

Modular cervical plate system for adjacent segment disease

BACKGROUND

Adjacent-level disease after anterior cervical discectomy and fusion (ACDF) occurs in a significant proportion of patients and frequently requires revision operation. Methods using traditional plates typically require removal of the plate with anecdotally increased operative-time and morbidity. We review our experience in treating symptomatic adjacent-segment disease using both traditional plate removal and modular-plate system which allows for add-on plate components rather than removal of the entire plate.

METHODS

Authors compared 64 patients with revision surgery using modular-plate system for adjacent-segment disease compared to 2-cohorts: 1) patients with traditional plate-removal; and 2) patients with no prior plate. Clinical data included demographics, original surgery, presentation, current surgery, use of modular system, need for preoperative computed-topography, operative-time, blood loss, hospital stay, complications, length of dysphagia, neck disability index and time-until-fusion.

RESULTS

Modular cervical plate system was utilized to prevent exposure and removal of the entire plate. The terminal portion of the plate was exposed and the distal module was removed. Following the discectomy/arthrodesis, a module-plate extension was added onto the previous plate for extension of the prior instrumentation. Preoperative planning computed-topography was required in 26% of plate-removal and 17% of modular-plate cases. Revision surgery with no prior plate had reduced operative-time (77.0±18.1 min) when compared with plate removal (103.8±46.2 min; P<0.01). Blood-loss was lower for modular-plate system (38.3±20.4 mL) and no prior plate (38.4±12.6 mL) versus plate removal (78.2±65.9 mL, P<0.01). Hospital stay was similar for all groups. No complications were experienced with modular-plate revision but plate removal and revision after no prior plate carried 7.7% and 10.5% complication rates, respectively. There was a trend towards lower dysphagia and neck disability index with modular-plate revision.

CONCLUSIONS

Use of modular cervical plate system allows for extension of a plate and reduces morbidity when treating adjacent-segment disease.

Utility of Routine Surveillance Imaging for Hodgkin Disease following Autologous Transplant: Experiences from a Single Institution

BACKGROUND

Surveillance scans performed after autologous stem cell transplant (auto-HCT) for patients with Hodgkin disease (HD) have no proven survival benefit.

METHODS

We studied survival differences among patients with HD after auto-HCT whose recurrences were detected on clinical history and exam, versus those detected on routine surveillance scan.

RESULTS

Among the 98 patients with HD that underwent auto-HCT from 2000 to 2014 at our institution, 30 relapsed, of which 21 were detected radiologically and 9 clinically. There were no statistically significant differences in patient characteristics between the 2 groups. The median time to progression was 118 days for the clinical cohort and 284 days for the radiological cohort (p = 0.05). Median overall survival (OS) was 728 days for the clinical cohort, and was not reached for the radiological cohort (p = 0.02).

DISCUSSION

In our review, most patients with HD after auto-HCT were diagnosed radiologically. Patients whose relapse was diagnosed clinically were likely to be detected earlier and have a shorter OS. Patients with aggressive disease may be detected when clinically relevant, regardless of scanning. Routine scanning may not be necessary in the majority of patients with HD following auto-HCT.

Utility of routine surveillance imaging for diffuse large B-cell lymphoma post autologous transplant: A single center experience

Surveillance scans after autologous stem cell transplant (auto-HCT) for patients with relapsed/refractory (RR) diffuse large B Cell lymphoma (DLBCL) have no proven survival benefit. We studied survival differences among patients with RR DLBCL post auto-HCT whose recurrences were detected clinically versus with routine surveillance imaging. Among the 139 patients with RR DLBCL that underwent auto-HCT from 2000 to 2014 at our institution, 37 relapsed: 21 clinical and 16 radiological. The median time to progression was 167 days for the clinical cohort and 565 days for the radiological cohort (p = 0.03), and median overall survival (OS) was 587 days and not reached, respectively (p = 0.006). Most patients with relapsed DLBCL after auto-HCT were diagnosed clinically and were likely to be detected earlier and have a shorter OS. Relapse in patients with aggressive disease will likely be detected when clinically apparent, and the outcome of these patients is independent of the way the relapse is diagnosed. Thus, universal scanning after auto-HCT appears to have little benefit.

Inter-Observer Agreement of Whole-Body Computed Tomography in Staging and Response Assessment in Lymphoma: The Lugano Classification

Background

To assess inter-observer agreement of whole-body computed tomography (WBCT) in staging and response assessment in lymphoma according to the Lugano classification.

Material/Methods

Retrospective analysis was conducted of 115 consecutive patients with lymphomas (45 females, 70 males; mean age of 46 years). Patients underwent WBCT with a 64 multi-detector CT device for staging and response assessment after a complete course of chemotherapy. Image analysis was performed by 2 reviewers according to the Lugano classification for staging and response assessment.

Results

The overall inter-observer agreement of WBCT in staging of lymphoma was excellent (k=0.90, percent agreement=94.9%). There was an excellent inter-observer agreement for stage I (k=0.93, percent agreement=96.4%), stage II (k=0.90, percent agreement=94.8%), stage III (k=0.89, percent agreement=94.6%) and stage IV (k=0.88, percent agreement=94%). The overall inter-observer agreement in response assessment after a completer course of treatment was excellent (k=0.91, percent agreement=95.8%). There was an excellent inter-observer agreement in progressive disease (k=0.94, percent agreement=97.1%), stable disease (k=0.90, percent agreement=95%), partial response (k=0.96, percent agreement=98.1%) and complete response (k=0.87, Percent agreement=93.3%).

Conclusions

We concluded that WBCT is a reliable and reproducible imaging modality for staging and treatment assessment in lymphoma according to the Lugano classification.

Surveillance Scans in Lymphoma: Friend or Foe?

OPINION STATEMENT

Advancements in the treatment of lymphoma over the last few decades have allowed more patients to achieve a remission after the completion of therapy. Due to the improvement in response rates, methods to detect recurrence early and accurately during follow-up, especially in patients with potential curable aggressive lymphomas, are a key. Observation has always involved close clinical follow-up with the use of physical exams and routine labs, but rapid changes in technology have allowed CT scans, PET scans, and MRIs to become an integral part of managing patients with lymphoma. While the utility of scans in initial staging and immediately after completion of therapy is well established, the use of these imaging modalities for monitoring recurrence in lymphoma patients is still controversial. Patient advocacy groups and other regulatory committees have questioned the frequency and in some cases even the need for these tests in patients without evidence of active disease given the concern for radiation-associated health risks. Additionally, the extent to which this form of testing impacts the psyche of our patients is not completely known. Given the numerous questions raised about the benefits, safety, and cost-effectiveness of CT imaging, firm guidelines are needed at this time in standard practice and within our clinical trials to limit the use of surveillance imaging. Such efforts are expected to improve the utility of these scans in asymptomatic patients, reduce healthcare costs, and reduce patient exposure to radiation.

Evaluation of 2 diuretic 18fluorine-fluorodeoxyglucose positron emission tomography/computed tomography imaging protocols for intrapelvic cancer

BACKGROUND

18F-Fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) plays an important part in the oncological evaluation of the abdomen and pelvis, but the interpretation and quantification is often hampered by intense physiological urinary activity. We evaluate 2 different diuretic imaging protocols by comparing intensity of urinary activity and we look at the impact of multiple variables on the final urinary activity.

METHODS

Comparative analysis of 102 patients (median age: 64) having intrapelvic carcinoma. After full body acquisition, 58 patients were administered 20 mg of furosemide 90 min post injection of FDG (P90). For 44 patients, 20 mg of furosemide was administered 30 min post injection of FDG (P30). Comparisons between groups were performed using the Mann-Whitney Test and χ2. The BMI, creatinine, clearance, age, injected activity, diuretic protocol, gender and glycemia were evaluated with multivariate analysis for their impact on the final urinary activity.

RESULTS

Concerning the comparison of the urinary activity we observe a significant difference (P=0.0029) between P90 and P30 for the SUVmax (median 4.3 [range 1.6: 17.7] vs. 6.0 [range 2.9: 15.1]), and for the SUVmean (P<0.001) (median 2.4 [range 1.1; 9.9] vs. 3.8 [range 2.0; 10.1]). For 2 patients of P30, the acquisition was interrupted because the patient needed to void. Multivariate analysis shows that creatinine and creatinine clearance do not have a significant independent impact on the final bladder activity.

CONCLUSIONS

By comparing the 2 diuretic imaging protocols, we found a significant lower urinary activity for the P90 protocol and the regression decision tree shows that the P90 protocol is mostly superior. The P30 protocol, which seems to be less well tolerated, is adequate in the group of patients with an injected activity of less than 240 MBq and older than 65 years, if P90 is not feasible. For most patients with injected activity ≥240 MBq or BMI of ≥25 and a glycemia >120 mg/dL, a significant amount of residual urinary activity remains for both protocols.

Estimated cumulative radiation dose received by diagnostic imaging during staging and treatment of operable Ewing sarcoma 2005-2012

BACKGROUND

Patients with Ewing sarcoma are subject to various diagnostic procedures that incur exposure to ionising radiation.

OBJECTIVE

To estimate the radiation doses received from all radiologic and nuclear imaging episodes during diagnosis and treatment, and to determine whether ¹⁸F-fluorodeoxyglucose positron emission tomography - computed tomography (¹⁸F-FDG PET-CT) is a major contributor of radiation.

MATERIALS AND METHODS

Twenty Ewing sarcoma patients diagnosed in Norway in 2005-2012 met the inclusion criteria (age <30 years, operable disease, uncomplicated chemotherapy and surgery, no metastasis or residual disease within a year of diagnosis). Radiation doses from all imaging during the first year were calculated for each patient.

RESULTS

The mean estimated cumulative radiation dose for all patients was 34 mSv (range: 6-70), radiography accounting for 3 mSv (range: 0.2-12), CT for 13 mSv (range: 2-28) and nuclear medicine for 18 mSv (range: 2-47). For the patients examined with PET-CT, the mean estimated cumulative effective dose was 38 mSv, of which PET-CT accounted for 14 mSv (37%).

CONCLUSION

There was large variation in number and type of examinations performed and also in estimated cumulative radiation dose. The mean radiation dose for patients examined with PET-CT was 23% higher than for patients not examined with PET-CT.

An overview of CEST MRI for non-MR physicists

The search for novel image contrasts has been a major driving force in the magnetic resonance (MR) research community, in order to gain further information on the body’s physiological and pathological conditions.

Chemical exchange saturation transfer (CEST) is a novel MR technique that enables imaging certain compounds at concentrations that are too low to impact the contrast of standard MR imaging and too low to directly be detected in MRS at typical water imaging resolution. For this to be possible, the target compound must be capable of exchanging protons with the surrounding water molecules. This property can be exploited to cause a continuous buildup of magnetic saturation of water, leading to greatly enhanced sensitivity.

The goal of the present review is to introduce the basic principles of CEST imaging to the general molecular imaging community. Special focus has been given to the comparison of state-of-the-art CEST methods reported in the literature with their positron emission tomography (PET) counterparts.

CT restaging of testicular germ cell tumors: The incidence of isolated pelvic metastases

PURPOSE

We determined the incidence of isolated pelvic metastases at restaging computed tomography (CT) in patients with testicular germ cell tumors to consider if imaging the pelvis could be omitted.

METHODS

After receiving IRB approval for this HIPAA-compliant retrospective study, medical records of 560 men (mean age 32.8) with 583 testicular germ cell tumors who underwent 3683 restaging CT scans of the abdomen and pelvis were reviewed to determine the proportion of patients with metastatic disease in the pelvis alone, as verified by histology or by resolution after therapy. Chi-square statistical analysis tested the association between factors currently thought to predispose patients to pelvic metastases. Patients were also categorized by clinical stage, tumor histology, and initial treatment.

RESULTS

Isolated pelvic metastases were detected in nine (1.6%) of 560 men. Neither bulky abdominal disease (p=0.85) nor extratesticular invasion by the primary tumor (p=0.37) were statistically significant in predicting which patients were more likely to have isolated pelvic metastases. Among the nine patients with isolated pelvic recurrence, only three (0.7%) of 408 men with no known pelvic disease at initial staging and no tumor marker elevation at restaging had isolated pelvic metastases. Isolated pelvic recurrence was not statistically different when analyzed by initial stage and treatment.

CONCLUSION

The incidence of isolated pelvic metastases in testicular germ cell tumors at restaging CT is low, but no group of patients was found to be without risk. Therefore, given the small, if any, risk of radiation-induced harm, the decision about whether to include routine pelvic CT in surveillance protocols should be individualized.

Role of computed tomography on large B-cell non-Hodgkin's lymphoma follow-up and the risk of radiation-induced neoplasm: A retrospective cohort study

INTRODUCTION

To evaluate the role of surveillance computed tomography (CT) in detection of tumor relapse after complete remission for large-cell lymphoma and to estimate the cancer risk related to those examinations.

MATERIALS AND METHODS

We retrospectively identified the cases of large-cell lymphoma diagnosed at our institution during a fifteen years period. We extracted from charts the information needed. Agreement between clinical and radiological evaluation for relapse detection was determined with index kappa and McNemar tests. We analysed the surveillance CT examinations performed to the patients in complete remission with no recurrence during the follow-up period and we estimated the life attributable risk (LAR) of radiation-induced cancer above base line using the approach of the Biological Effects of Ionizing Radiation (BEIR) VII.

RESULTS

184 patients with biopsy confirmed large-cell lymphoma were included. Complete remission was attained in 125 patients. After a median follow-up of 93.73 months, 97 of them remain in remission. Relapse was confirmed in 28 patients; only 3 of them were asymptomatic. Kappa and McNemar analyses revealed good agreement for diagnosis of recurrence and significant difference for exclusion of relapse. Patients in remission received a median of 6 surveillance CT examinations. Fifty-seven patients had total cumulative doses greater than 100mSv. The mean increase in estimated radiation-induced cancer risk was 0.5%.

CONCLUSION

Our results suggest that periodic CT examinations have a limited role in detecting relapse in large-cell lymphoma as the clinical surveillance dictates the patient management.

Assessment of the Role of Different Imaging Modalities with Emphasis on Fdg Pet/Ct in the Management of Well Differentiated Thyroid Cancer (WDTC)

BACKGROUND

Positron emission tomography/computed tomography is suggested to have a role in detection of iodine negative recurrence in well differentiated thyroid cancer. The aim of this study is to identify role of different imaging modalities in the management of well differentiated thyroid cancer.

METHODS

We reviewed 900 well differentiated thyroid cancer patients after post-thyroidectomy who underwent recombinant human thyroid stimulating hormone stimulated Sodium Iodide I 131 imaging. Out of 900 patients, 74 had positron emission tomography/computed tomography. Multivariate analysis was performed by controlling positron emission tomography/computed tomography, Sodium Iodide I 131 scan, neck ultrasonography, age, sex, primary tumor size, stage, histology, thyroglobulin. Patients were grouped according to results of Sodium Iodide I 131 scan and positron emission tomography/computed tomography.

RESULTS

Positron emission tomography/computed tomography was positive in 23 of 74 patients. The sensitivity for positron emission tomography was 11/11(100%), the specificity was 51/63 (81.0%), the positive predictive value was 11/23 (47.8%), and the negative predictive value was 51/51 (100%). The sensitivity for the neck ultrasonography was 4/8 (50%), the specificity was 53/60 (88.3%), positive predictive value was 4/11 (36.4%), and negative predictive value was 53/57 (93.0%). 50% of patients who had Sodium Iodide I 131 negative scan and positive positron emission tomography/computed tomography had a change in management. Thirty-six percent with positive neck ultrasonography had a change in management. Out of 11 recurrences, 6 had distant metastatic disease, and 5/11 had regional nodal disease. Neck ultrasonography showed nodal metastasis in 4/5 (80%).

CONCLUSION

Positron emission tomography/computed tomography altered management in the presence of a high thyroglobulin level and a negative Sodium Iodide I 131 scan. Neck ultrasonography should be the first line of imaging with rising thyroglobulin levels. Positron emission tomography/computed tomography should be considered for cases with high thyroglobulin levels and normal neck ultrasonography to look for distant metastatic disease.

Rethinking clinical response and outcome assessment in a biologic age

Standardized response criteria for lymphoma are critical for the evaluation of new therapies. Widely adopted recommendations, most recently the Lugano classification, have been developed primarily for assessment of conventional chemotherapeutic regimens. More recently, several classes of drugs, including immunomodulatory agents, B cell receptor pathway targeting kinases, and checkpoint (PD-1, PDL-1) inhibitors have demonstrated impressive activity in a broad range of histologies. However, they may be associated with features during treatment suggestive of progressive disease despite clinical benefit. Immune response criteria have been proposed for solid tumors, and a modification is needed to be more applicable to lymphomas. Following treatment, conservative use of imaging is recommended based on clinical indications. As newer targeted agents with unique mechanisms of action are developed, current response and follow-up criteria must be made sufficiently flexible for optimal evaluation.

MRI-Guided Percutaneous Biopsy of Mediastinal Masses Using a Large Bore Magnet: Technical Feasibility

OBJECTIVE

To evaluate the diagnostic accuracy and safety of magnetic resonance imaging (MRI)-guided percutaneous biopsy of mediastinal masses performed using a wide-bore high-field scanner.

MATERIALS AND METHODS

This is a retrospective study of 16 consecutive patients (8 male, 8 female; mean age 74 years) who underwent MRI-guided core needle biopsy of a mediastinal mass between February 2010 and January 2014. Size and location of lesion, approach taken, time for needle placement, overall duration of procedure, and post-procedural complications were evaluated. Technical success rates and correlation with surgical pathology (where available) were assessed.

RESULTS

Target lesions were located in the anterior (n = 13), middle (n = 2), and posterior mediastinum (n = 1), respectively. Mean size was 7.2 cm (range 3.6-11 cm). Average time for needle placement was 9.4 min (range 3-18 min); average duration of entire procedure was 42 min (range 27-62 min). 2-5 core samples were obtained from each lesion (mean 2.6). Technical success rate was 100%, with specimens successfully obtained in all 16 patients. There were no immediate complications. Histopathology revealed malignancy in 12 cases (4 of which were surgically confirmed), benign lesions in 3 cases (1 of which was false negative following surgical resection), and one inconclusive specimen (treated as inaccurate since repeat CT-guided biopsy demonstrated thymic hyperplasia). Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy in our study were 92.3, 100, 100, 66.7, and 87.5%, respectively.

CONCLUSION

MRI-guided mediastinal biopsy is a safe procedure with high diagnostic accuracy, which may offer a non-ionizing alternative to CT guidance.

Evaluating Positron Emission Tomography Use in Differentiated Thyroid Cancer

BACKGROUND

Using the Surveillance, Epidemiology, and End Results-Medicare database, a substantial increase was found in the use of positron emission tomography (PET) scans after 2004 in differentiated thyroid cancer (DTC) patients. The reason for the increased utilization of the PET scan was not clear based on available the data. Therefore, the indications for and outcomes of PET scans performed at an academic institution were evaluated.

METHODS

A retrospective cohort study was performed of DTC patients who underwent surgery at the University of Michigan Health System from 2006 to 2011. After identifying patients who underwent a PET scan, indications, rate of positive PET scans, and impact on management were evaluated. For positive scans, the location of disease was characterized, and presence of disease on other imaging was determined.

RESULTS

Of the 585 patients in the cohort, 111 (19%) patients had 200 PET scans performed for evaluation of DTC. Indications for PET scan included: elevated thyroglobulin and negative radioiodine scan in 52 scans (26.0%), thyroglobulin antibodies in 13 scans (6.5%), rising thyroglobulin in 18 scans (9.0%), evaluation of abnormality on other imaging in 22 scans (11.0%), evaluation of extent of disease in 33 scans (16.5%), follow-up of previous scan in 57 scans (28.5%), other indications in two scans (1.0%), and unclear indications in three scans (1.5%). The PET scan was positive in 124 studies (62.0%); positivity was identified in the thyroid bed on 25 scans, cervical or mediastinal lymph nodes on 105 scans, lung on 28 scans, bone on four scans, and other areas on 14 scans. Therapy following PET scan was surgery in 66 cases (33.0%), chemotherapy or radiation in 23 cases (11.5%), observation in 110 cases (55.0%), and palliative care in one case (0.5%). Disease was identifiable on other imaging in 66% of cases. PET scan results changed management in 59 cases (29.5%).

CONCLUSIONS

In this academic medical center, the PET scan was utilized in 19% of patients. Indications for the PET scan included conventional indications, such as elevated thyroglobulin with noniodine avid disease, and more controversial uses, such as evaluation of extent of disease or abnormalities on other imaging tests. PET scan results changed management in about 30% of cases.

Very low utility of surveillance imaging in early-stage classic Hodgkin lymphoma treated with a combination of doxorubicin, bleomycin, vinblastine, and dacarbazine and radiation therapy

BACKGROUND

This study evaluated the need for surveillance imaging in early-stage classic Hodgkin lymphoma (cHL) after planned combined-modality therapy (CMT).

METHODS

Primary early-stage cHL patients who underwent CMT were included. Positron emission tomography (PET)/computed tomography (CT), CT, or both were performed at the initial staging, during or after chemotherapy, and for at least 2 years during follow-up. Imaging studies and medical records were reviewed to determine if and when relapse had occurred. Radiation doses and costs were also calculated from follow-up imaging.

RESULTS

The study included 78 patients with a median follow-up of 46 months; 85% of the patients had stage II disease (32% with bulky disease). Four of 77 interim PET scans were positive; none of these patients relapsed during follow-up, which ranged from 24 to 80 months. After a total of 466 follow-up imaging studies (91% with CT and 9% with PET/CT), no cHL relapse was detected. Eleven abnormal findings were noted on surveillance imaging: 9 were false-positives, and 2 were second primary malignancies. The average cumulative dose per patient from follow-up imaging was 107 mSv, which translated into an estimated lifetime excess cancer risk of 0.5%; the estimated total costs were $296,817 according to Medicare reimbursements.

CONCLUSIONS

Surveillance imaging with either CT or PET/CT can be omitted safely for early-stage cHL treated with a combination of doxorubicin, bleomycin, vinblastine, and dacarbazine and radiation therapy because the risk of relapse is extremely low. This observation also applies to patients with bulky disease. The elimination of surveillance imaging will also reduce healthcare expenses and cumulative radiation doses in these predominantly young patients.