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Objective Establish a radiologist-run consultation clinic to review breast density and supplemental screening exams (SSEs) directly with patients in response to breast density reporting laws. Methods Breast radiologists opened and staffed a clinic for formal patient consultations regarding breast density and SSEs. An IRB-approved questionnaire assessed patient knowledge of breast density, SSEs, and encounter satisfaction. Comparative statistical analyses were performed on knowledge-based questions. Results From February 2019 to February 2021, 294 reimbursable consultations were performed with 215 patients completing pre- and post-consultation questionnaires (survey response rate, 73%). Median patient age was 58 years (range, 34–86 years) and 9% (19/210) had a personal history of breast cancer. An increase in patient knowledge of breast density and SSEs was observed as follows: breast density categories (9% correct pre-consultation (20/215), 86% correct post-consultation (185/215), P Conclusion A consultation clinic staffed by breast radiologists focused on breast density and supplemental breast cancer screening can provide personalized patient counseling, engage patients in shared decision making, assist referring clinicians, and support high quality patient-centered care.

In routine clinical practice, contrast-enhanced mammography (CEM) examinations identify enhancing findings seen only on subtraction images that have no low-energy mammographic or sonographic correlate. The purpose of this study is to report the frequency and malignancy rates of enhancing findings seen only on subtraction images in a tertiary care breast imaging practice.Consecutive review of CEM exams from December 2015 to May 2020. Chi square tests were used to determine associations between cancer diagnosis and clinical characteristics of enhancing findings seen only on subtraction images, P .05 indicating a statistically significant difference.Four percent (100/2464) of CEM examinations identified 108 enhancing findings seen only on subtraction images. Twenty of those CEM enhancing findings were directly managed as a multifocal disease. Of those further evaluated with MR, 23% (19/78) with associated MR correlates were treated surgically as presumed multicentric or multifocal disease following multidisciplinary review. The remaining 76% (59/78) of enhancing findings were seen only on subtraction images, these included: 20% (12/59) and downgraded to benign on MR 80% (47/59) with suspicious findings which underwent MR vacuum assisted breast biopsy yielding: 26% (12/47) malignancy, 9% (4/47) high risk, and 66% (31/47) benign diagnoses.Enhancing findings seen on subtraction only CEM images are seen in 4% of cases in clinical practice. MR correlation can help characterize CEM findings to: (1) avoid unnecessary biopsy for benign findings, and (2) guide tissue sampling or empiric surgical planning for suspicious findings.

Objective Evaluate women’s anxiety and experience undergoing screening mammography during the COVID-19 pandemic. Methods An IRB-approved anonymous survey was administered to women receiving screening mammography across six sites in the U.S. and Singapore from October 7, 2020, to March 11, 2021. Using a 1–5 Likert scale, women rated their pre- and post-visit anxiety regarding having their mammogram during the COVID-19 pandemic, importance of observed COVID-19 precautions, and personal risk factors for breast cancer and severe COVID-19 illness. Post-visit change in anxiety was evaluated. Multivariable logistic regression was used to test associations of pre-visit anxiety with breast cancer and COVID-19 risk factors. Results In total, 1086 women completed the survey. Of these, 59% (630/1061) had >1 breast cancer risk factor; 27% (282/1060) had >1 COVID-19 risk factors. Forty-two percent (445/1065) experienced pre-visit anxiety. Pre-visit anxiety was independently associated with risk factors for severe COVID-19 (OR for >2 vs 0 risk factors: 2.04, 95% confidence interval [CI]: 1.11–3.76) and breast cancer (OR for >2 vs 0 risk factors: 1.71, 95% CI: 1.17–2.50), after adjusting for age and site. Twenty-six percent (272/1065) of women reported post-visit anxiety, an absolute 16% decrease from pre-visit anxiety (95% CI: 14%–19%, P Conclusion Pre-visit anxiety was associated with COVID-19 or breast cancer risk factors and declined significantly after screening mammography. Provider masking and physical distancing were rated the most important precautions implemented by imaging clinics.

Objective and Rationale: To investigate the utility of screening Contrast Enhanced Mammography (CEM) imaging as a supplemental screening tool in women at elevated risk for breast cancer. Materials and Methods: This prospective, single institution, IRB approved observational study was conducted in asymptomatic women 35 years of age or older who were deemed at elevated risk of breast cancer, defined as IBIS v.8.0 lifetime risk of breast cancer score >15% or a prior personal history of breast cancer. Enrollment started in January 2019 and is on-going. An interim data analysis was performed. Women were invited to undergo supplemental CEM screening within 180 days of negative (BI-RADS 1 or 2) conventional 2D/3D screening mammography (MG). Patients with prior screening MBI, ultrasound or MR imaging within 12 months were excluded from study participation. Outcome measures were supplemental cancer detection rates, sensitivity, specificity, positive predictive value, and negative predictive value of CEM, along with their 95% confidence intervals, as well as the biologic profiles of MG-occult, CEM detected cancers. Results: A total of 351 women were enrolled in this prospective study over a 20-month period. To date, we have 1 year follow up on 106 cases with negative follow-up MG. Average age of the participants was 56 years ± 9.44 (standard deviation); 11 patients had screening 2D MG, 333 had combined 3-D and 2-D screening MG; 309 dense and 37 non-dense breasts based on ACR BI-RADS categories. CEM depicted 8 additional breast cancers (table 1), which were otherwise MG occult, for an overall supplemental cancer detection rate of 22.7 per 1000 patients, 95% CI (9.9, 44.3). 1 false negative cancer on CEM imaging which was further detected on MR imaging only. Biopsy revealed 16 benign changes (16/28=57%), 4 high-risk lesions (4/28=14%), and 8 breast cancers (8/28=29%) (table 2). CEM imaging screening offered high specificity (0.942, 95% CI (0.917, 0.967), high NPV 0.997, 95% CI (0.991, 1.000) and moderate PPV (0.286, 95% CI (0.118, 0.453) and sensitivity (0.889, 95% CI (0.684, 1.000)). Size of CEM detected cancers ranged from 7 to 57 mm. Conclusion: This pilot trial demonstrates a supplemental cancer detection rate of 22.7 per 1000 during prevalence round of CEM screening in women at an elevated risk for breast cancer. These initial results are comparable to results reported for high-risk surveillance MR imaging. Larger, multi-institutional high-risk CEM trials are needed for those patients who are not otherwise undergoing regular supplemental surveillance MR imaging. Citation Format: Bhavika K. Patel, Victor Pizzitola, Donald Northfelt, Karen Anderson, Marina Giurescu, Gina Mazza, Roxanne Lorans, William Eversman, Richard Sharpe, Juliana Kling, Denise Millstine, Ernst Brenda, Patricia Cronin, Heidi Apsey, Jennifer Palmieri, Barbara Pockaj, Michele Halyard. Supplemental contrast enhanced mammography screening of women with elevated risk of breast cancer [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS2-41.

Background: Contrast-enhanced mammography (CEM) is an emerging breast imaging technique utilizing iodinated contrast to highlight areas of neovascularity. The role of CEM in patients with breast implants has not yet been characterized. We report our clinical experience of CEM in patients with breast augmentation surgery to better understand the potential diagnostic utility and limitations of CEM in the setting of breast implants. Materials and Methods: A HIPPA compliant, IRB exempt single-institution review of prospective CEM cases who had “breast implants” in their report between 01/2015 and 03/2020. Medical records were reviewed to supplement database information. Results: Forty-six patients were included with a mean age of 52 years (range 33-72). Clinical indications included: high risk research screen 3 (6%), diagnostic evaluation for abnormal imaging 24 (52%), further evaluation of newly diagnosed breast cancer 12 (26%) or assessment of neoadjuvant treatment response 7 (15%). Thirty patients had malignant lesions. Histology was invasive ductal carcinoma (90%), invasive lobular carcinoma (7%), and ductal carcinoma in situ (3%). CEM identified the index cancer and extent of disease in 28/30 (93%) of malignant cases. In two patients (7%), the malignant lesion was not included in the field-of-view due to its location. One of these lesions was a far medial mass within the breast which was detected by ultrasound alone. The other false negative CEM was a palpable axillary mass negative on both mammogram (MG) and MRI but seen by ultrasound. Twenty-three (50%) underwent additional breast MRI of which 20 had an already diagnosed cancer. the findings on CEM were concordant with MR imaging for the index lesion in 19/20 (95%) cases (kappa=0.86; p Six additional lesions were found by CEM and confirmed by MRI. Of these lesions, 33% were found to be malignant and changed the surgical procedure. Four were only seen on CEM (no MRI comparison was available) and 75% were found to be malignant. One was only seen on MRI and was benign. One additional lesion was only seen as an asymmetry on MG without CEM or MRI correlate. This was benign on both the biopsy and surgical pathology. Conclusions: CEM appears to be a valuable breast imaging modality for diagnostic evaluations and surgical staging, including patients with breast implants. Due to technical artifacts and positioning limitations for posterior lesions, we recommend performing CEM with implant displaced views. Breast centers that use CEM, should be aware of field of view as a potential limitation when evaluating extent of disease in patients with breast augmentation. Citation Format: Molly Carnahan, Barbara Pockaj, Victor Pizzitola, Marina Giurescu, Roxanne Lorans, William Eversman, Richard Sharpe, Patricia Cronin, Donald Northfelt, Karen Anderson, Brenda Ernst, Bhavika Patel. Experience of contrast-enhanced mammography in patients with breast augmentation surgery [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS3-23.

Background Upstaging from DCIS to invasive ductal carcinoma varies widely from 0 to 59%. We aim to identify risk factors associated with upstaging in all DCIS patients and based on specific surgical intervention. Methods Patients with a pre-operative diagnosis of DCIS undergoing BCT or mastectomy were reviewed. Multivariable analysis was performed to identify risk factors for upstaging. Results In total, 623 patients had a preoperative diagnosis of DCIS. Upstaging occurred in 74 patients (12%) overall. There was no difference in upstaging rates between mastectomy and BCT (11% v 14% p = 0.27). Sentinel lymph node biopsy was positive in 4/212 patients (1%). Multivariable analysis revealed suspicion of microinvasion (OR 5.7 95%CI2.2–14.9), surgeon suspicion of invasive disease (OR 2.7, 95% CI 1.2–6.4) and larger size/multicentric/extensive tumor (OR 1.9 95% CI 1.1–3.4) increase risk of upstaging. Conclusions Suspicion of microinvasion, surgeon suspicion, and tumor size can be used to help guide the use of sentinel lymph node biopsy. For patients without these high risk characteristics, it is hard to justify the use of concurrent SLN biopsy for patients who undergo BCT.

Objectives Studies have shown that having a baseline mammogram, the first screening mammogram, available for comparison at the time of interpreting a subsequent mammogram significantly decreases the potential of a false-positive examination. Our aim was to evaluate knowledge of and perception about the significance of baseline mammograms in those women undergoing screening mammography. Materials and Methods A cross-sectional prospective survey study was conducted in women without a history of breast cancer presenting for their screening mammogram. Respondents were surveyed anonymously between March and April 2017. The questionnaire was developed by primary care providers and radiologists and pretested for readability and clarity. Results In all, 401 women (87% white, 93% educated beyond high school) completed surveys in which 77% of women reported having yearly mammograms, 31% reported having a history of an abnormal mammogram, and 45% had not heard the term baseline mammogram. Of those who had heard the term, the most commonly reported source was their primary care provider (31%). Although 74% chose the correct definition of a baseline mammogram, 67% did not think that a baseline mammogram was important for decreasing associated cost, time, and discomfort due to the number of mammograms incorrectly read as abnormal. Conclusion In a group of educated women who routinely get mammograms, almost one-half had not heard the term baseline mammogram. Furthermore, most women did not think baseline mammography was important for decreasing associated cost, time, and discomfort due to mammograms incorrectly read as abnormal. This study suggests that efforts to improve women’s understanding of baseline mammograms and their importance are warranted, with greatest opportunity for health care providers and radiologists.

In 17 women with newly diagnosed breast cancer who underwent contrast-enhanced mammography (CEM) and MRI, both modalities were found to be concordant for the index cancer. In six of the 17 women, CEM showed an additional lesion that was confirmed by MRI. Of these six additional lesions, three were multifocal, one was multicentric, and two were contralateral; two of the six were malignant. MRI did not identify any additional cancers that were not identified on CEM. CEM may have a role in women with breast augmentation and either a contraindication or limited access to MRI.

As experience and aptitude in digital breast tomosynthesis (DBT) have increased, radiologists are seeing more areas of architectural distortion (AD) on DBT images compared with standard 2D mammograms. The purpose of this study is to report our experience using tomosynthesis-guided vacuum-assisted biopsies (VABs) for ADs that were occult at 2D mammography and ultrasound and to analyze the positive predictive value for malignancy.We performed a retrospective review of 34 DBT-detected ADs that were occult at mammography and ultrasound.We found a positive predictive value of 26% (nine malignancies in 34 lesions). Eight of the malignancies were invasive and one was ductal carcinoma in situ. The invasive cancers were grade 1 (4/8; 50%), grade 2 (2/8; 25%), or grade 3 (1/8; 13%); information about one invasive cancer was not available. The mean size of the invasive cancers at pathologic examination was 7.5 mm (range, 6-30 mm).Tomosynthesis-guided VAB is a feasible method to sample ADs that are occult at 2D mammography and ultrasound. Tomosynthesis-guided VAB is a minimally invasive method that detected a significant number of carcinomas, most of which were grade 1 cancers. Further studies are needed.

Analysis of joint fluid remains a key factor in the diagnosis of periprosthetic infection. Recent reports have shown that neutrophils in infected joint fluid release esterase, an enzyme that is a reliable marker for infection. Testing for leukocyte esterase is routinely done in the analysis of urine for the presence of urinary tract infection, by a simple “dipstick” method. We report our experience with this technique in the evaluation of patients suspected of having septic arthritis or periprosthetic joint infection (PJI) by comparing results of leukocyte esterase positivity with confirmed joint infection as defined by the American Academy of Orthopaedic Surgeons (AAOS). We retrospectively reviewed leukocyte esterase test results performed on synovial fluid aspirated from 57 patients with prosthetic (52) and native (5) joints. Patients either presented with unexplained painful arthroplasties, routine testing of PROSTALAC (PROSthesis with Antibiotic-Loaded Acrylic Cement) orthopedic implants, or clinical suspicion of periprosthetic infection or septic arthritis. Synovial fluid was percutaneously aspirated using a standard technique. The patient age range was 31–91 years with a mean age of 69.1 years, consisting of 30 women (52.6 %) and 27 men (47.4 %). The “gold standard” for the presence or absence of infection at our institution and in the study group was based on the most recent recommendations of the AAOS. Positive culture remained the “gold standard” for native joint infection. Of the total 57 joints aspirated and included in the study, 20 (35.1 %) were read as positive (2+) on the leukocyte test strip and 37 (64.9 %) were read as negative (negative, trace, or 1+). PJI was diagnosed in 19 patients and native joint septic arthritis was identified in one patient. Sensitivities were excellent at 100 % with no false negatives in the entire cohort. There was one false positive in the periprosthetic group yielding a specificity, positive predictive value and negative predictive value of 97, 95, and 100 %, respectively. The results for the native joints showed markedly less specificity and positive predictive value at 50 and 33 %; however, its negative predictive value remained at 100 %. Our test results confirm that the leukocyte esterase test can accurately detect PJI and that it can be used as a part of the traditional PJI workup. In the assessment of native joints, its high negative predictive value suggests that it is a valuable tool in excluding native joint septic arthritis.

The purpose of this article is to discuss facilitators of and barriers to future implementation of contrast-enhanced mammography (CEM) in the United States.CEM provides low-energy 2D mammographic images analogous to digital mammography and contrast-enhanced recombined images that allow assessment of neovascularity similar to that offered by MRI. The utilization of CEM in the United States is currently low but could increase rapidly given the many potential indications for its clinical use.

Percutaneous synovial biopsy has recently been reported to have a high diagnostic value in the preoperative identification of periprosthetic infection of the hip. We report our experience with this technique in the evaluation of patients undergoing revision hip arthroplasty, comparing results of preoperative synovial biopsy with joint aspiration in identifying an infected hip arthroplasty by bacteriological analysis. We retrospectively reviewed the results of the 110 most recent revision hip arthroplasties in which preoperative synovial biopsy and joint aspiration were both performed. Revision surgery for these patients occurred during the period from September 2005 to March 2012. Using this study group, results from preoperative cultures were compared with preoperative laboratory studies and the results of intraoperative cultures. Synovial aspiration was done using an 18- or 20-gauge spinal needle. Synovial biopsy was done coaxially following aspiration using a 22-gauge Chiba needle or 21-gauge Sure-Cut needle. Standard microbiological analysis was performed on preoperative synovial fluid aspirate and synovial biopsy. Intraoperative tissue biopsy bacteriological analysis results at surgical revision were accepted as the “gold standard” for the presence or absence of infection. Seventeen of 110 (15 %) of patients had intraoperative culture-positive periprosthetic infection. Of these 17 cases, there were ten cases where either the synovial fluid aspiration and/or the synovial biopsy were true positive (sensitivity of 59 %, specificity of 100 %, positive predictive value of 100 % and accuracy of 94 %). There were seven cases where aspiration and biopsy results were both falsely negative, but no false-positive results. Similar results were found for synovial fluid aspiration alone. The results of synovial biopsy alone resulted in the identification of seven infected joints with no false-positive result (sensitivity of 41 %, specificity of 100 %, positive predictive value of 100 %, and accuracy of 91 %). Standard microbiological analyses performed on percutaneous synovial biopsy specimen during the preoperative evaluation of patients undergoing revision hip arthroplasty did not improve detection of culture-positive periprosthetic infection as compared to synovial fluid aspiration alone.

Contrast-enhanced digital mammography (CEDM) is the only imaging modality that provides both (a) a high-resolution, low-energy image comparable to that of digital mammography and (b) a contrast-enhanced image similar to that of magnetic resonance imaging. We report the initial 208 CEDM examinations performed for various clinical indications and provide illustrative case examples. Given its success in recent studies and our experience of CEDM primarily as a diagnostic adjunct, CEDM can potentially improve breast cancer detection by combining the low-cost conclusions of screening mammography with the high sensitivity of magnetic resonance imaging.

Invasive lobular cancer (ILC) of the breast is difficult to diagnose clinically and radiologically. It is hoped that preoperative magnetic resonance imaging (MRI) can improve evaluation of extent of disease.Patients diagnosed with ILC at a single institution from 2001 to 2008 who underwent clinical breast examination (CBE), mammography, ultrasound, and MRI were studied retrospectively. Concordance between tumor size on imaging/CBE and pathologic size was defined as size within ± 0.5 cm. Pearson correlation coefficients (R) were calculated for each modality. Local recurrence and re-excision rates were compared with those patients with ILC who did not undergo preoperative MRI.Seventy patients with ILC had all imaging modalities, including CBE, performed preoperatively. The sensitivity for detection of ILC by MRI was 99%. MRI-based tumor size was concordant with pathologic tumor size in 56% of tumors. MRI overestimated tumor size by0.5 cm in 31% of tumors. Correlation of tumor size on imaging with final pathology was better for MRI (R = 0.75) than for mammography (R = 0.65), CBE (R = 0.63), or ultrasound (R = 0.45, all P0.01). Preoperative MRI was associated with lower reoperation rates for close/positive margins (P0.05).For ILC, MRI has better sensitivity of detection and correlation with tumor size at pathology than CBE, mammography, or ultrasound. However, 31% of cases are overestimated by MRI, and correlation remains only at 0.75. The select use of MRI for preoperative estimation of tumor size in ILC is supported by our data, but the need for improvement and refinement of imaging remains.

To describe the cortical tangential approach to ultrasonographically (US) guided renal transplant biopsy and evaluate its efficacy in obtaining sufficient cortical tissue.This HIPAA-compliant retrospective study was exempted from review by the institutional review board. Informed consent was not required. The number of core biopsy samples, glomeruli, and small arteries obtained during 294 consecutive US-guided renal transplant biopsies in 254 patients (134 men, 120 women; age range, 19-79 years; mean age, 52.2 years) in one department between June 1 and December 31, 2008, were recorded, along with any ensuing complications. Procedural success was assessed according to Banff 97 criteria.There were 1.2 +/- 0.4 (standard deviation) biopsy core samples taken per case by 11 radiologists using the cortical tangential approach. In 290 cases, biopsy results showed 21.7 +/- 10.1 glomeruli and 5.0 +/- 2.8 small arteries. Two hundred seventy-six (95%) cases were adequate or minimal according to Banff 97 assessment criteria. Of the 14 inadequate cases (5%), six were lacking only one glomerulus to achieve minimal status. Only one biopsy core sample was taken in all 14 inadequate cases and in 233 successful cases (success rate, 85%). None of the 43 cases with two or more biopsy core samples taken were inadequate (success rate, 100%). Two patients (0.7%) had a hemorrhagic complication requiring transfusion, and another four patients (1.4%) experienced a minor self-limiting complication.The cortical tangential approach can be used by a cohort of radiologists to achieve 95% or higher collective success in obtaining cortical tissue during renal transplant biopsy, with few complications. The success rate is higher, without increased complications, when more than one core specimen is taken.

To re-assess the accuracy of chemical shift imaging in diagnosing indeterminate bone marrow lesions as benign or malignant. We retrospectively reviewed our experience with MR imaging of the pelvis to assess the accuracy of chemical shift imaging in distinguishing benign from malignant bone lesions. Two musculoskeletal radiologists retrospectively reviewed all osseous lesions biopsied since 2006, when chemical shift imaging was added to our routine pelvic imaging protocol. Study inclusion criteria required (1) MR imaging of an indeterminate bone marrow lesion about the pelvis and (2) subsequent histologic confirmation. The study group included 50 patients (29 male, 21 female) with an average age of 67 years (range, 41–89 years). MR imaging results were evaluated using biopsy results as the “gold standard.” There were 27 malignant and 23 benign lesions. Chemical shift imaging using an opposed-phase signal loss criteria of less than 20 % to indicate a malignant lesion, correctly diagnosed 27/27 malignant lesions and 14/23 benign lesions, yielding a 100 % sensitivity, 61 % specificity, 75 % PPV, 100 % NPV, and 82 % accuracy. The area under the receiver operator characteristic (ROC) curve was 0.88. The inter-rater and intra-rater agreement K values were both 1.0. Chemical shift imaging is a useful adjunct MR technique to characterize focal and diffuse marrow abnormalities on routine non-contrast pelvic imaging. It is highly sensitive in identifying malignant disease. Despite its lower specificity, the need for biopsy could be eliminated in more than 60 % of patients with benign disease.

Breast cancer screening recommendations are in flux. We reviewed the methods of detecting newly diagnosed breast neoplasms at our institution. A retrospective review of patients stratified by age was performed to compare mammography with self- (SBE) and clinical (CBE) breast examination methods of cancer detection from 2005 to 2009. We identified 782 patients. Patients aged

6 Background: Traditional screening mammography (MG) enables early detection of breast cancer and therefore results in decreased mortality. Mammography, however, is an imperfect tool and limited by an overall sensitivity of 75-85%. Specificity is limited as well resulting in many false-positive examinations and unnecessary follow-up examinations. The recent development of contrast-enhanced digital mammography (CEDM) has made the usage of IV contrast enhancement with mammography a possibility. CEDM is an angiographic technique that uses digital subtraction, which removes the normal mammary gland on images in order to detect breast tumors and visualize their vascularity. The literature is promising with regard to CEDM as studies have found that CEDM achieves increased sensitivity without reductions in specificity in comparison to MG, US and/or MRI. Methods: In this multi-reader study we compared the diagnostic accuracy of CEDM as an adjunct to MG/US in patients with suspicious findings (BI-RADS 4). The study population included 31 patients who were imaged with CEDM prior to their scheduled US or stereotactic-guided biopsy. We compared the relative performance of MG/US alone versus MG/US/CEDM in determining the probability of malignancy. Histology served as the gold standard. Results: See table below. Conclusions: The addition of CEDM to the workup of suspected lesions on MG and/or US preliminarily decreases the number of false-positive MG thereby with potential to reduce cost and unnecessary patient harm. [Table: see text]

OBJECTIVES: Intramuscular injection is a commonly used route of parenteral drug administration. We studied the fat vs muscle location, the depth of calcified buttock granulomas, and the thickness of subcutaneous fat. Data were assessed with respect to the length of a needle commonly used in intramuscular buttock injections. DESIGN: Three hundred thirty-eight sequential pelvic computed tomographic scans were studied. Subcutaneous fat thickness was measured for each patient at the upper outer quadrant of the buttock. The location and depth of each calcified granuloma were also recorded. SETTING: Tertiary care academic teaching hospital. RESULTS: One hundred sixty-four calcified granulomas were found in 67 patients. One hundred fifty-two of these granulomas were in fat and 12 were in muscle; this was statistically significant using a single-sample binomial distribution (P < .001;95% confidence interval, 0.04 to 0.13). The mean (+/- SD) subcutaneous fat thickness at the upper outer quadrant of the buttock was 5.0 +/- 1.9 cm, with female patients having a mean subcutaneous fat thickness of 5.7 +/- 1.8 cm vs 4.4 +/- 1.7 cm for male patients. CONCLUSIONS: The finding that buttock subcutaneous fat thickness exceeds the length of the most commonly used needle for intramuscular buttock injection (3.8 cm), together with the preponderance of calcified granulomas found in the fat of female patients, suggests that the currently used injection technique may not be therapeutically optimal. We suggest that longer needles be used for intramuscular buttock injections in adults.